Merge tag 'OTP-21.2' into sverker/map-from-ks-vs-bug

32 files changed, 5243 insertions, 5350 deletions

diff --git a/erts/emulator/sys/common/erl_check_io.c b/erts/emulator/sys/common/erl_check_io.c
index 44a77f3ea5..c681fa481f 100644
--- a/erts/emulator/sys/common/erl_check_io.c
+++ b/erts/emulator/sys/common/erl_check_io.c
@@ -1,7 +1,7 @@
 /*
  * %CopyrightBegin%
  * 
- * Copyright Ericsson AB 2006-2016. All Rights Reserved.
+ * Copyright Ericsson AB 2006-2018. All Rights Reserved.
  * 
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -29,7 +29,6 @@
 #endif
 
 #define ERL_CHECK_IO_C__
-#define ERTS_WANT_BREAK_HANDLING
 #ifndef WANT_NONBLOCKING
 #  define WANT_NONBLOCKING
 #endif
@@ -38,79 +37,107 @@
 #include "erl_port.h"
 #include "erl_check_io.h"
 #include "erl_thr_progress.h"
+#include "erl_bif_unique.h"
 #include "dtrace-wrapper.h"
 #include "lttng-wrapper.h"
 #define ERTS_WANT_TIMER_WHEEL_API
 #include "erl_time.h"
 
+#if 0
+#define DEBUG_PRINT(FMT, ...) erts_printf(FMT "\r\n", ##__VA_ARGS__)
+#define DEBUG_PRINT_FD(FMT, STATE, ...)                                 \
+    DEBUG_PRINT("%d: " FMT " (ev=%s, ac=%s, flg=%s)",                   \
+                (STATE) ? (STATE)->fd : (ErtsSysFdType)-1, ##__VA_ARGS__, \
+                ev2str((STATE) ? (STATE)->events : ERTS_POLL_EV_NONE),  \
+                ev2str((STATE) ? (STATE)->active_events : ERTS_POLL_EV_NONE), \
+                (STATE) ? flag2str((STATE)->flags) : ERTS_EV_FLAG_CLEAR)
+#define DEBUG_PRINT_MODE
+#else
+#define DEBUG_PRINT(...)
+#endif
+
+#ifndef DEBUG_PRINT_FD
+#define DEBUG_PRINT_FD(...)
+#endif
+
 #ifndef ERTS_SYS_CONTINOUS_FD_NUMBERS
 #  include "safe_hash.h"
 #  define DRV_EV_STATE_HTAB_SIZE 1024
 #endif
 
-typedef char EventStateType;
-#define ERTS_EV_TYPE_NONE     ((EventStateType) 0)
-#define ERTS_EV_TYPE_DRV_SEL  ((EventStateType) 1) /* driver_select */
-#define ERTS_EV_TYPE_DRV_EV   ((EventStateType) 2) /* driver_event */
-#define ERTS_EV_TYPE_STOP_USE ((EventStateType) 3) /* pending stop_select */
-
-typedef char EventStateFlags;
-#define ERTS_EV_FLAG_USED         ((EventStateFlags) 1)   /* ERL_DRV_USE has been turned on */
-#define ERTS_EV_FLAG_DEFER_IN_EV  ((EventStateFlags) 2)
-#define ERTS_EV_FLAG_DEFER_OUT_EV ((EventStateFlags) 4)
-
-#ifdef DEBUG
-#  define ERTS_ACTIVE_FD_INC 2
+typedef enum {
+    ERTS_EV_TYPE_NONE     = 0,
+    ERTS_EV_TYPE_DRV_SEL  = 1, /* driver_select */
+    ERTS_EV_TYPE_STOP_USE = 2, /* pending stop_select */
+    ERTS_EV_TYPE_NIF      = 3, /* enif_select */
+    ERTS_EV_TYPE_STOP_NIF = 4  /* pending nif stop */
+} EventStateType;
+
+typedef enum {
+    ERTS_EV_FLAG_CLEAR         = 0,
+    ERTS_EV_FLAG_USED          = 1,   /* ERL_DRV_USE has been turned on */
+#if ERTS_POLL_USE_SCHEDULER_POLLING
+    ERTS_EV_FLAG_SCHEDULER     = 2,   /* Set when the fd has been migrated
+                                         to scheduler pollset */
+    ERTS_EV_FLAG_IN_SCHEDULER  = 4,   /* Set when the fd is currently in
+                                         scheduler pollset */
 #else
-#  define ERTS_ACTIVE_FD_INC 128
+    ERTS_EV_FLAG_SCHEDULER     = ERTS_EV_FLAG_CLEAR,
+    ERTS_EV_FLAG_IN_SCHEDULER  = ERTS_EV_FLAG_CLEAR,
 #endif
-
-#define ERTS_CHECK_IO_POLL_RES_LEN 512
-
-#if defined(ERTS_KERNEL_POLL_VERSION)
-#  define ERTS_CIO_EXPORT(FUNC) FUNC ## _kp
-#elif defined(ERTS_NO_KERNEL_POLL_VERSION)
-#  define ERTS_CIO_EXPORT(FUNC) FUNC ## _nkp
+#ifdef ERTS_POLL_USE_FALLBACK
+    ERTS_EV_FLAG_FALLBACK      = 8,   /* Set when kernel poll rejected fd
+                                         and it was put in the nkp version */
 #else
-#  define ERTS_CIO_EXPORT(FUNC) FUNC
-#endif
+    ERTS_EV_FLAG_FALLBACK      = ERTS_EV_FLAG_CLEAR,
+#endif
+
+    /* Combinations */
+    ERTS_EV_FLAG_USED_FALLBACK = ERTS_EV_FLAG_USED | ERTS_EV_FLAG_FALLBACK,
+    ERTS_EV_FLAG_USED_SCHEDULER = ERTS_EV_FLAG_USED | ERTS_EV_FLAG_SCHEDULER,
+    ERTS_EV_FLAG_USED_IN_SCHEDULER = ERTS_EV_FLAG_USED | ERTS_EV_FLAG_SCHEDULER | ERTS_EV_FLAG_IN_SCHEDULER,
+    ERTS_EV_FLAG_UNUSED_SCHEDULER = ERTS_EV_FLAG_SCHEDULER,
+    ERTS_EV_FLAG_UNUSED_IN_SCHEDULER = ERTS_EV_FLAG_SCHEDULER | ERTS_EV_FLAG_IN_SCHEDULER
+} EventStateFlags;
+
+#define flag2str(flags)                                                 \
+    ((flags) == ERTS_EV_FLAG_CLEAR ? "CLEAR" :                          \
+     ((flags) == ERTS_EV_FLAG_USED ? "USED" :                           \
+      ((flags) == ERTS_EV_FLAG_FALLBACK ? "FLBK" :                      \
+       ((flags) == ERTS_EV_FLAG_USED_FALLBACK ? "USED|FLBK" :           \
+        ((flags) == ERTS_EV_FLAG_USED_SCHEDULER ? "USED|SCHD" :         \
+         ((flags) == ERTS_EV_FLAG_UNUSED_SCHEDULER ? "SCHD" :           \
+          ((flags) == ERTS_EV_FLAG_USED_IN_SCHEDULER ? "USED|IN_SCHD" : \
+           ((flags) == ERTS_EV_FLAG_UNUSED_IN_SCHEDULER ? "IN_SCHD" :   \
+            "ERROR"))))))))
+
+/* How many events that can be handled at once by one erts_poll_wait call */
+#define ERTS_CHECK_IO_POLL_RES_LEN 512
 
-#define ERTS_CIO_HAVE_DRV_EVENT \
-  (ERTS_POLL_USE_POLL && !ERTS_POLL_USE_KERNEL_POLL)
+/* Each I/O Poll Thread has one ErtsPollThread each. The ps field
+   can point to either a private ErtsPollSet or a shared one.
+   At the moment only kqueue and epoll pollsets can be
+   shared across threads.
+*/
+typedef struct erts_poll_thread
+{
+    ErtsPollSet *ps;
+    ErtsPollResFd *pollres;
+    ErtsThrPrgrData *tpd;
+    int pollres_len;
+} ErtsPollThread;
 
-#define ERTS_CIO_POLL_CTL	ERTS_POLL_EXPORT(erts_poll_control)
-#define ERTS_CIO_POLL_CTLV	ERTS_POLL_EXPORT(erts_poll_controlv)
-#define ERTS_CIO_POLL_WAIT	ERTS_POLL_EXPORT(erts_poll_wait)
-#ifdef ERTS_POLL_NEED_ASYNC_INTERRUPT_SUPPORT
-#define ERTS_CIO_POLL_AS_INTR 	ERTS_POLL_EXPORT(erts_poll_async_sig_interrupt)
+/* pollsetv contains pointers to the ErtsPollSets that are in use.
+ * Which pollset to use is determined by hashing the fd.
+ */
+static ErtsPollSet **pollsetv;
+static ErtsPollThread *psiv;
+#if ERTS_POLL_USE_FALLBACK
+static ErtsPollSet *flbk_pollset;
+#endif
+#if ERTS_POLL_USE_SCHEDULER_POLLING
+static ErtsPollSet *sched_pollset;
 #endif
-#define ERTS_CIO_POLL_INTR 	ERTS_POLL_EXPORT(erts_poll_interrupt)
-#define ERTS_CIO_POLL_INTR_TMD	ERTS_POLL_EXPORT(erts_poll_interrupt_timed)
-#define ERTS_CIO_NEW_POLLSET 	ERTS_POLL_EXPORT(erts_poll_create_pollset)
-#define ERTS_CIO_FREE_POLLSET	ERTS_POLL_EXPORT(erts_poll_destroy_pollset)
-#define ERTS_CIO_POLL_MAX_FDS	ERTS_POLL_EXPORT(erts_poll_max_fds)
-#define ERTS_CIO_POLL_INIT	ERTS_POLL_EXPORT(erts_poll_init)
-#define ERTS_CIO_POLL_INFO	ERTS_POLL_EXPORT(erts_poll_info)
-
-#define GET_FD(fd) fd
-
-static struct pollset_info
-{
-    ErtsPollSet ps;
-    erts_smp_atomic_t in_poll_wait;        /* set while doing poll */
-    struct {
-	int six; /* start index */
-	int eix; /* end index */
-	erts_smp_atomic32_t no;
-	int size;
-	ErtsSysFdType *array;
-    } active_fd;
-#ifdef ERTS_SMP
-    struct removed_fd* removed_list;       /* list of deselected fd's*/
-    erts_smp_spinlock_t removed_list_lock;
-#endif
-}pollset;
-#define NUM_OF_POLLSETS 1
 
 typedef struct {
 #ifndef ERTS_SYS_CONTINOUS_FD_NUMBERS
@@ -119,147 +146,223 @@ typedef struct {
     ErtsSysFdType fd;
     struct {
 	ErtsDrvSelectDataState *select;   /* ERTS_EV_TYPE_DRV_SEL */
-#if ERTS_CIO_HAVE_DRV_EVENT
-	ErtsDrvEventDataState *event;     /* ERTS_EV_TYPE_DRV_EV */
-#endif
-	erts_driver_t* drv_ptr;           /* ERTS_EV_TYPE_STOP_USE */
+        ErtsNifSelectDataState *nif;      /* ERTS_EV_TYPE_NIF */
+        union {
+            erts_driver_t*  drv_ptr;    /* ERTS_EV_TYPE_STOP_USE */
+            ErtsResource* resource;   /* ERTS_EV_TYPE_STOP_NIF */
+        } stop;
     } driver;
-    ErtsPollEvents events;
-    unsigned short remove_cnt; /* number of removed_fd's referring to this fd */
+    ErtsPollEvents events;        /* The events that have been selected upon */
+    ErtsPollEvents active_events; /* The events currently active in the pollset */
     EventStateType type;
     EventStateFlags flags;
+    int count;                    /* Number of times this fd has triggered
+                                     without being deselected. */
 } ErtsDrvEventState;
 
-#ifdef ERTS_SMP
-struct removed_fd {
-    struct removed_fd *next;
+struct drv_ev_state_shared {
+
+    union {
+        erts_mtx_t lck;
+        byte _cache_line_alignment[ERTS_ALC_CACHE_LINE_ALIGN_SIZE(sizeof(erts_mtx_t))];
+    } locks[ERTS_CHECK_IO_DRV_EV_STATE_LOCK_CNT];
+
 #ifdef ERTS_SYS_CONTINOUS_FD_NUMBERS
-    ErtsSysFdType fd;
+    int max_fds;
+    erts_atomic_t len;
+    ErtsDrvEventState *v;
+    erts_mtx_t grow_lock; /* prevent lock-hogging of racing growers */
 #else
-    ErtsDrvEventState* state;
-    #ifdef DEBUG
-    ErtsSysFdType fd;
-    #endif
+    SafeHash tab;
+    int num_prealloc;
+    ErtsDrvEventState *prealloc_first;
+    erts_spinlock_t prealloc_lock;
 #endif
-
 };
-#endif
 
-#ifdef ERTS_SYS_CONTINOUS_FD_NUMBERS
-static int max_fds = -1;
-#endif
-#define DRV_EV_STATE_LOCK_CNT 16
-static union {
-    erts_smp_mtx_t lck;
-    byte _cache_line_alignment[64];
-}drv_ev_state_locks[DRV_EV_STATE_LOCK_CNT];
+int ERTS_WRITE_UNLIKELY(erts_no_pollsets) = 1;
+int ERTS_WRITE_UNLIKELY(erts_no_poll_threads) = 1;
+struct drv_ev_state_shared drv_ev_state;
 
-#ifdef ERTS_SMP
-static ERTS_INLINE erts_smp_mtx_t* fd_mtx(ErtsSysFdType fd)
-{
+static ERTS_INLINE int fd_hash(ErtsSysFdType fd) {
     int hash = (int)fd;
 # ifndef ERTS_SYS_CONTINOUS_FD_NUMBERS
     hash ^= (hash >> 9);
 # endif
-    return &drv_ev_state_locks[hash % DRV_EV_STATE_LOCK_CNT].lck;
+    return hash;
+}
+
+static ERTS_INLINE erts_mtx_t* fd_mtx(ErtsSysFdType fd)
+{
+    return &drv_ev_state.locks[fd_hash(fd) % ERTS_CHECK_IO_DRV_EV_STATE_LOCK_CNT].lck;
 }
-#else
-#  define fd_mtx(fd) NULL
-#endif
 
 #ifdef ERTS_SYS_CONTINOUS_FD_NUMBERS
 
-static erts_smp_atomic_t drv_ev_state_len;
-static ErtsDrvEventState *drv_ev_state;
-static erts_smp_mtx_t drv_ev_state_grow_lock; /* prevent lock-hogging of racing growers */
+static ERTS_INLINE ErtsDrvEventState *get_drv_ev_state(ErtsSysFdType fd)
+{
+    return &drv_ev_state.v[(int) fd];
+}
 
-#else
-static SafeHash drv_ev_state_tab;
-static int num_state_prealloc;
-static ErtsDrvEventState *state_prealloc_first;
-erts_smp_spinlock_t state_prealloc_lock;
+#define new_drv_ev_state(State, fd) (State)
+#define erase_drv_ev_state(State)
+
+static ERTS_INLINE int grow_drv_ev_state(ErtsSysFdType fd) {
+    int i;
+    int old_len;
+    int new_len;
+
+    if ((unsigned)fd >= (unsigned)erts_atomic_read_nob(&drv_ev_state.len)) {
+
+	if (fd < 0 || fd >= drv_ev_state.max_fds)
+            return 0;
+
+        erts_mtx_lock(&drv_ev_state.grow_lock);
+        old_len = erts_atomic_read_nob(&drv_ev_state.len);
+        if (fd >= old_len) {
+            new_len = erts_poll_new_table_len(old_len, fd + 1);
+            if (new_len > drv_ev_state.max_fds)
+                new_len = drv_ev_state.max_fds;
+
+            for (i=0; i<ERTS_CHECK_IO_DRV_EV_STATE_LOCK_CNT; i++) { /* lock all fd's */
+                erts_mtx_lock(&drv_ev_state.locks[i].lck);
+            }
+            drv_ev_state.v = (drv_ev_state.v
+                              ? erts_realloc(ERTS_ALC_T_DRV_EV_STATE,
+                                             drv_ev_state.v,
+                                             sizeof(ErtsDrvEventState)*new_len)
+                              : erts_alloc(ERTS_ALC_T_DRV_EV_STATE,
+                                           sizeof(ErtsDrvEventState)*new_len));
+            ERTS_CT_ASSERT(ERTS_EV_TYPE_NONE == 0);
+            sys_memzero(drv_ev_state.v+old_len,
+                        sizeof(ErtsDrvEventState) * (new_len - old_len));
+            for (i = old_len; i < new_len; i++) {
+                drv_ev_state.v[i].fd = (ErtsSysFdType) i;
+            }
+            erts_atomic_set_nob(&drv_ev_state.len, new_len);
+            for (i=0; i<ERTS_CHECK_IO_DRV_EV_STATE_LOCK_CNT; i++) {
+                erts_mtx_unlock(&drv_ev_state.locks[i].lck);
+            }
+        }
+        /*else already grown by racing thread */
+
+        erts_mtx_unlock(&drv_ev_state.grow_lock);
+    }
+    return 1;
+}
 
-static ERTS_INLINE ErtsDrvEventState *hash_get_drv_ev_state(ErtsSysFdType fd)
+static int drv_ev_state_len(void)
+{
+    return erts_atomic_read_nob(&drv_ev_state.len);
+}
+
+#else /* !ERTS_SYS_CONTINOUS_FD_NUMBERS */
+
+static ERTS_INLINE ErtsDrvEventState *get_drv_ev_state(ErtsSysFdType fd)
 {
     ErtsDrvEventState tmpl;
     tmpl.fd = fd;
-    return  (ErtsDrvEventState *) safe_hash_get(&drv_ev_state_tab, (void *) &tmpl);
+    return  (ErtsDrvEventState *) safe_hash_get(&drv_ev_state.tab, (void *) &tmpl);
 }
 
-static ERTS_INLINE ErtsDrvEventState* hash_new_drv_ev_state(ErtsSysFdType fd)
+static ERTS_INLINE ErtsDrvEventState* new_drv_ev_state(ErtsDrvEventState *state,
+                                                       ErtsSysFdType fd)
 {
     ErtsDrvEventState tmpl;
+
+    if (state)
+        return state;
+
     tmpl.fd = fd;
     tmpl.driver.select = NULL;
-#if ERTS_CIO_HAVE_DRV_EVENT
-    tmpl.driver.event = NULL;
-#endif
-    tmpl.driver.drv_ptr = NULL;
+    tmpl.driver.nif = NULL;
+    tmpl.driver.stop.drv_ptr = NULL;
     tmpl.events = 0;
-    tmpl.remove_cnt = 0;
+    tmpl.active_events = 0;
     tmpl.type = ERTS_EV_TYPE_NONE;
     tmpl.flags = 0;
-    return  (ErtsDrvEventState *) safe_hash_put(&drv_ev_state_tab, (void *) &tmpl);
+
+    return  (ErtsDrvEventState *) safe_hash_put(&drv_ev_state.tab, (void *) &tmpl);
+}
+
+static ERTS_INLINE void erase_drv_ev_state(ErtsDrvEventState *state)
+{
+    safe_hash_erase(&drv_ev_state.tab, (void *) state);
 }
 
-static ERTS_INLINE void hash_erase_drv_ev_state(ErtsDrvEventState *state)
+static int drv_ev_state_len(void)
 {
-    ASSERT(state->remove_cnt == 0);
-    safe_hash_erase(&drv_ev_state_tab, (void *) state);
+    return erts_atomic_read_nob(&drv_ev_state.tab.nitems);
 }
 
 #endif /* !ERTS_SYS_CONTINOUS_FD_NUMBERS */
 
 static void stale_drv_select(Eterm id, ErtsDrvEventState *state, int mode);
-static void select_steal(ErlDrvPort ix, ErtsDrvEventState *state, 
-			 int mode, int on);
-static void print_select_op(erts_dsprintf_buf_t *dsbufp,
-			    ErlDrvPort ix, ErtsSysFdType fd, int mode, int on);
-#ifdef ERTS_SYS_CONTINOUS_FD_NUMBERS
-static void select_large_fd_error(ErlDrvPort, ErtsSysFdType, int, int);
-#endif
-#if ERTS_CIO_HAVE_DRV_EVENT
-static void event_steal(ErlDrvPort ix, ErtsDrvEventState *state, 
-			ErlDrvEventData event_data);
-static void print_event_op(erts_dsprintf_buf_t *dsbufp,
-			   ErlDrvPort, ErtsSysFdType, ErlDrvEventData);    
+static void drv_select_steal(ErlDrvPort ix, ErtsDrvEventState *state,
+                             int mode, int on);
+static void nif_select_steal(ErtsDrvEventState *state, int mode,
+                             ErtsResource* resource, Eterm ref);
+
+static void print_drv_select_op(erts_dsprintf_buf_t *dsbufp,
+                                ErlDrvPort ix, ErtsSysFdType fd, int mode, int on);
+static void print_nif_select_op(erts_dsprintf_buf_t*, ErtsSysFdType,
+                                int mode, ErtsResource*, Eterm ref);
+
 #ifdef ERTS_SYS_CONTINOUS_FD_NUMBERS
-static void event_large_fd_error(ErlDrvPort, ErtsSysFdType, ErlDrvEventData);
-#endif
+static void drv_select_large_fd_error(ErlDrvPort, ErtsSysFdType, int, int);
+static void nif_select_large_fd_error(ErtsSysFdType, int, ErtsResource*,Eterm ref);
 #endif
-static void steal_pending_stop_select(erts_dsprintf_buf_t*, ErlDrvPort,
-				      ErtsDrvEventState*, int mode, int on);
-
-#ifdef ERTS_SMP
-ERTS_SCHED_PREF_QUICK_ALLOC_IMPL(removed_fd, struct removed_fd, 64, ERTS_ALC_T_FD_LIST)
+static void
+steal_pending_stop_use(erts_dsprintf_buf_t*, ErlDrvPort, ErtsDrvEventState*,
+                       int mode, int on);
+static void
+steal_pending_stop_nif(erts_dsprintf_buf_t *dsbufp, ErtsResource*,
+                       ErtsDrvEventState *state, int mode, int on);
+static ERTS_INLINE void
+check_fd_cleanup(ErtsDrvEventState *state,
+		 ErtsDrvSelectDataState **free_select,
+                 ErtsNifSelectDataState **free_nif);
+static ERTS_INLINE void iready(Eterm id, ErtsDrvEventState *state);
+static ERTS_INLINE void oready(Eterm id, ErtsDrvEventState *state);
+#ifdef DEBUG_PRINT_MODE
+static char *drvmode2str(int mode);
+static char *nifmode2str(enum ErlNifSelectFlags mode);
 #endif
 
 static ERTS_INLINE void
-init_iotask(ErtsIoTask *io_task)
+init_iotask(ErtsIoTask *io_task, ErtsSysFdType fd)
 {
     erts_port_task_handle_init(&io_task->task);
-    erts_smp_atomic_init_nob(&io_task->executed_time, ~((erts_aint_t) 0));
+    io_task->fd = fd;
 }
 
 static ERTS_INLINE int
-is_iotask_active(ErtsIoTask *io_task, erts_aint_t current_cio_time)
-{    
+is_iotask_active(ErtsIoTask *io_task)
+{
     if (erts_port_task_is_scheduled(&io_task->task))
 	return 1;
-    if (erts_smp_atomic_read_nob(&io_task->executed_time) == current_cio_time)
-	return 1;
     return 0;
 }
 
 static ERTS_INLINE ErtsDrvSelectDataState *
-alloc_drv_select_data(void)
+alloc_drv_select_data(ErtsSysFdType fd)
 {
     ErtsDrvSelectDataState *dsp = erts_alloc(ERTS_ALC_T_DRV_SEL_D_STATE,
 					     sizeof(ErtsDrvSelectDataState));
     dsp->inport = NIL;
     dsp->outport = NIL;
-    init_iotask(&dsp->iniotask);
-    init_iotask(&dsp->outiotask);
+    init_iotask(&dsp->iniotask, fd);
+    init_iotask(&dsp->outiotask, fd);
+    return dsp;
+}
+
+static ERTS_INLINE ErtsNifSelectDataState *
+alloc_nif_select_data(void)
+{
+    ErtsNifSelectDataState *dsp = erts_alloc(ERTS_ALC_T_NIF_SEL_D_STATE,
+					     sizeof(ErtsNifSelectDataState));
+    dsp->in.pid = NIL;
+    dsp->out.pid = NIL;
     return dsp;
 }
 
@@ -271,192 +374,181 @@ free_drv_select_data(ErtsDrvSelectDataState *dsp)
     erts_free(ERTS_ALC_T_DRV_SEL_D_STATE, dsp);   
 }
 
-#if ERTS_CIO_HAVE_DRV_EVENT
-
-static ERTS_INLINE ErtsDrvEventDataState *
-alloc_drv_event_data(void)
+static ERTS_INLINE void
+free_nif_select_data(ErtsNifSelectDataState *dsp)
 {
-    ErtsDrvEventDataState *dep = erts_alloc(ERTS_ALC_T_DRV_EV_D_STATE,
-					    sizeof(ErtsDrvEventDataState));
-    dep->port = NIL;
-    dep->data = NULL;
-    dep->removed_events = 0;
-#if ERTS_CIO_DEFER_ACTIVE_EVENTS
-    dep->deferred_events = 0;
-#endif
-    init_iotask(&dep->iotask);
-    return dep;
+    erts_free(ERTS_ALC_T_NIF_SEL_D_STATE, dsp);
 }
 
-static ERTS_INLINE void
-free_drv_event_data(ErtsDrvEventDataState *dep)
+static ERTS_INLINE int
+get_pollset_id(ErtsSysFdType fd)
 {
-    ASSERT(!erts_port_task_is_scheduled(&dep->iotask.task));
-    erts_free(ERTS_ALC_T_DRV_EV_D_STATE, dep);   
+    return fd_hash(fd) % erts_no_pollsets;
 }
 
-#endif /* ERTS_CIO_HAVE_DRV_EVENT */
-
-static ERTS_INLINE void
-remember_removed(ErtsDrvEventState *state, struct pollset_info* psi)
+static ERTS_INLINE ErtsPollSet *
+get_pollset(ErtsSysFdType fd)
 {
-#ifdef ERTS_SMP
-    struct removed_fd *fdlp;
-    ERTS_SMP_LC_ASSERT(erts_smp_lc_mtx_is_locked(fd_mtx(state->fd)));
-    if (erts_smp_atomic_read_nob(&psi->in_poll_wait)) {
-	state->remove_cnt++;
-	ASSERT(state->remove_cnt > 0);
-	fdlp = removed_fd_alloc();
-    #if defined(ERTS_SYS_CONTINOUS_FD_NUMBERS) || defined(DEBUG)
-    	fdlp->fd = state->fd;
-    #endif
-    #ifndef ERTS_SYS_CONTINOUS_FD_NUMBERS
-	fdlp->state = state;
-    #endif
-	erts_smp_spin_lock(&psi->removed_list_lock);
-	fdlp->next = psi->removed_list;
-	psi->removed_list = fdlp;
-	erts_smp_spin_unlock(&psi->removed_list_lock);
-    }
-#endif
+    return pollsetv[get_pollset_id(fd)];
 }
 
+#if ERTS_POLL_USE_FALLBACK
+static ERTS_INLINE ErtsPollSet *
+get_fallback_pollset(void)
+{
+    return flbk_pollset;
+}
+#endif
 
-static ERTS_INLINE int
-is_removed(ErtsDrvEventState *state)
+static ERTS_INLINE ErtsPollSet *
+get_scheduler_pollset(ErtsSysFdType fd)
 {
-#ifdef ERTS_SMP
-    /* Note that there is a possible race here, where an fd is removed
-       (increasing remove_cnt) and then added again just before erts_poll_wait
-       is called by erts_check_io. Any polled event on the re-added fd will then
-       be falsely ignored. But that does not matter, as the event will trigger
-       again next time erl_check_io is called. */
-    return state->remove_cnt > 0;
+#if ERTS_POLL_USE_SCHEDULER_POLLING
+    return sched_pollset;
 #else
-    return 0;
+    return get_pollset(fd);
 #endif
 }
 
-static void
-forget_removed(struct pollset_info* psi)
+/*
+ * Place a fd within a pollset. This will automatically use
+ * the fallback ps if needed.
+ */
+static ERTS_INLINE ErtsPollEvents
+erts_io_control_wakeup(ErtsDrvEventState *state, ErtsPollOp op,
+                       ErtsPollEvents pe, int *wake_poller)
 {
-#ifdef ERTS_SMP
-    struct removed_fd* fdlp;
-    struct removed_fd* tofree;
-
-    /* Fast track: if (atomic_ptr(removed_list)==NULL) return; */
-
-    erts_smp_spin_lock(&psi->removed_list_lock);
-    fdlp = psi->removed_list;
-    psi->removed_list = NULL;
-    erts_smp_spin_unlock(&psi->removed_list_lock);
-
-    while (fdlp) {
-	erts_driver_t* drv_ptr = NULL;
-	erts_smp_mtx_t* mtx;
-	ErtsSysFdType fd;
-	ErtsDrvEventState *state;
-
-#ifdef ERTS_SYS_CONTINOUS_FD_NUMBERS
-	fd = fdlp->fd;
-	mtx = fd_mtx(fd);
-	erts_smp_mtx_lock(mtx);
-	state = &drv_ev_state[(int) fd];
-#else
-	state = fdlp->state;
-	fd = state->fd;
-	ASSERT(fd == fdlp->fd);
-	mtx = fd_mtx(fd);
-	erts_smp_mtx_lock(mtx);
-#endif
-	ASSERT(state->remove_cnt > 0);
-	if (--state->remove_cnt == 0) {
-	    switch (state->type) {
-	    case ERTS_EV_TYPE_STOP_USE:
-		/* Now we can call stop_select */
-		drv_ptr = state->driver.drv_ptr;
-		ASSERT(drv_ptr);
-		state->type = ERTS_EV_TYPE_NONE;
-		state->flags &= ~ERTS_EV_FLAG_USED;
-		state->driver.drv_ptr = NULL;  
-		/* Fall through */
-	    case ERTS_EV_TYPE_NONE:
-#ifndef ERTS_SYS_CONTINOUS_FD_NUMBERS
-		hash_erase_drv_ev_state(state);
-#endif
-		break;
-	    case ERTS_EV_TYPE_DRV_SEL:
-	    case ERTS_EV_TYPE_DRV_EV:
-		break;
-	    default:
-		ASSERT(0);
-	    }
-	}
-	erts_smp_mtx_unlock(mtx);
-	if (drv_ptr) {
-	    int was_unmasked = erts_block_fpe();
-	    DTRACE1(driver_stop_select, drv_ptr->name);
-	    LTTNG1(driver_stop_select, drv_ptr->name);
-	    (*drv_ptr->stop_select) ((ErlDrvEvent) fd, NULL);
-	    erts_unblock_fpe(was_unmasked);
-	    if (drv_ptr->handle) {
-		erts_ddll_dereference_driver(drv_ptr->handle);
-	    }
-	}
-	tofree = fdlp;
-	fdlp = fdlp->next;
-	removed_fd_free(tofree);
+    ErtsSysFdType fd = state->fd;
+    ErtsPollEvents res = 0;
+    EventStateFlags flags = state->flags;
+
+    ERTS_LC_ASSERT(erts_lc_mtx_is_locked(fd_mtx(state->fd)));
+
+    if (!(flags & ERTS_EV_FLAG_FALLBACK)) {
+
+        if (op == ERTS_POLL_OP_DEL && (flags & ERTS_EV_FLAG_SCHEDULER)) {
+            erts_poll_control(get_scheduler_pollset(fd), fd, op, pe, wake_poller);
+            flags &= ~ERTS_EV_FLAG_IN_SCHEDULER;
+        }
+        if (!(flags & ERTS_EV_FLAG_IN_SCHEDULER) || (pe & ERTS_POLL_EV_OUT)) {
+            res = erts_poll_control(get_pollset(fd), fd, op, pe, wake_poller);
+        } else {
+            res = erts_poll_control(get_scheduler_pollset(fd), fd, op, pe, wake_poller);
+        }
+
+#if ERTS_POLL_USE_FALLBACK
+        if (op == ERTS_POLL_OP_ADD && res == ERTS_POLL_EV_NVAL) {
+            /* When an add fails with NVAL, the poll/kevent operation could not
+               put that fd in the pollset, so we instead put it into a fallback pollset */
+            state->flags |= ERTS_EV_FLAG_FALLBACK;
+            res = erts_poll_control_flbk(get_fallback_pollset(), fd, op, pe, wake_poller);
+        }
+    } else {
+        ASSERT(op != ERTS_POLL_OP_ADD);
+        res = erts_poll_control_flbk(get_fallback_pollset(), fd, op, pe, wake_poller);
+#endif
     }
-#endif /* ERTS_SMP */
+
+    return res;
 }
 
-#ifdef ERTS_SYS_CONTINOUS_FD_NUMBERS
-static void
-grow_drv_ev_state(int min_ix)
+static ERTS_INLINE ErtsPollEvents
+erts_io_control(ErtsDrvEventState *state, ErtsPollOp op, ErtsPollEvents pe)
 {
-    int i;
-    int old_len;
-    int new_len;
+    int wake_poller = 0;
+    return erts_io_control_wakeup(state, op, pe, &wake_poller);
+}
 
-    erts_smp_mtx_lock(&drv_ev_state_grow_lock);
-    old_len = erts_smp_atomic_read_nob(&drv_ev_state_len);
-    if (min_ix >= old_len) {
-        new_len = erts_poll_new_table_len(old_len, min_ix + 1);
-        if (new_len > max_fds)
-            new_len = max_fds;
+/* ToDo: Was inline in erl_check_io.h but now need struct erts_poll_thread */
+void
+erts_io_notify_port_task_executed(ErtsPortTaskType type,
+                                  ErtsPortTaskHandle *pthp,
+                                  void (*reset_handle)(ErtsPortTaskHandle *))
+{
+    ErtsIoTask *itp = ErtsContainerStruct(pthp, ErtsIoTask, task);
+    ErtsSysFdType fd = itp->fd;
+    erts_mtx_t *mtx = fd_mtx(fd);
+    ErtsPollOp op = ERTS_POLL_OP_MOD;
+    int active_events, new_events = 0;
+    ErtsDrvEventState *state;
+    ErtsDrvSelectDataState *free_select = NULL;
+    ErtsNifSelectDataState *free_nif = NULL;
+
+    ERTS_MSACC_PUSH_AND_SET_STATE_M_X(ERTS_MSACC_STATE_CHECK_IO);
+
+    erts_mtx_lock(mtx);
+    state = get_drv_ev_state(fd);
+
+    reset_handle(pthp);
+
+    active_events = state->active_events;
+
+    if (!(state->flags & ERTS_EV_FLAG_IN_SCHEDULER) || type == ERTS_PORT_TASK_OUTPUT) {
+        switch (type) {
+        case ERTS_PORT_TASK_INPUT:
+
+            DEBUG_PRINT_FD("executed ready_input", state);
+
+            ASSERT(!(state->active_events & ERTS_POLL_EV_IN));
+            if (state->events & ERTS_POLL_EV_IN) {
+                active_events |= ERTS_POLL_EV_IN;
+                if (state->count > 10 && ERTS_POLL_USE_SCHEDULER_POLLING) {
+                    if (!(state->flags & ERTS_EV_FLAG_SCHEDULER))
+                        op = ERTS_POLL_OP_ADD;
+                    state->flags |= ERTS_EV_FLAG_IN_SCHEDULER|ERTS_EV_FLAG_SCHEDULER;
+                    new_events = ERTS_POLL_EV_IN;
+                    DEBUG_PRINT_FD("moving to scheduler ps", state);
+                } else
+                    new_events = active_events;
+                if (!(state->flags & ERTS_EV_FLAG_FALLBACK) && ERTS_POLL_USE_SCHEDULER_POLLING)
+                    state->count++;
+            }
+            break;
+        case ERTS_PORT_TASK_OUTPUT:
+
+            DEBUG_PRINT_FD("executed ready_output", state);
+
+            ASSERT(!(state->active_events & ERTS_POLL_EV_OUT));
+            if (state->events & ERTS_POLL_EV_OUT) {
+                active_events |= ERTS_POLL_EV_OUT;
+                if (state->flags & ERTS_EV_FLAG_IN_SCHEDULER && active_events & ERTS_POLL_EV_IN)
+                    new_events = ERTS_POLL_EV_OUT;
+                else
+                    new_events = active_events;
+            }
+            break;
+        default:
+            erts_exit(ERTS_ABORT_EXIT, "Invalid IO port task type");
+            break;
+        }
+
+        if (state->active_events != active_events && new_events) {
+            state->active_events = active_events;
+            new_events = erts_io_control(state, op, new_events);
+        }
+
+        /* We were unable to re-insert the fd into the pollset, signal the callback. */
+        if (new_events & (ERTS_POLL_EV_ERR|ERTS_POLL_EV_NVAL)) {
+            if (state->active_events & ERTS_POLL_EV_IN)
+                iready(state->driver.select->inport, state);
+            if (state->active_events & ERTS_POLL_EV_OUT)
+                oready(state->driver.select->outport, state);
+            state->active_events = 0;
+        }
+    }
+
+    if (!active_events)
+        check_fd_cleanup(state, &free_select, &free_nif);
+
+    erts_mtx_unlock(mtx);
 
-	for (i=0; i<DRV_EV_STATE_LOCK_CNT; i++) { /* lock all fd's */
-	    erts_smp_mtx_lock(&drv_ev_state_locks[i].lck);
-	}
-	drv_ev_state = (drv_ev_state
-			? erts_realloc(ERTS_ALC_T_DRV_EV_STATE,
-				       drv_ev_state,
-				       sizeof(ErtsDrvEventState)*new_len)
-			: erts_alloc(ERTS_ALC_T_DRV_EV_STATE,
-				     sizeof(ErtsDrvEventState)*new_len));
-	for (i = old_len; i < new_len; i++) {
-	    drv_ev_state[i].fd = (ErtsSysFdType) i;
-	    drv_ev_state[i].driver.select = NULL;
-#if ERTS_CIO_HAVE_DRV_EVENT
-	    drv_ev_state[i].driver.event = NULL;
-#endif
-	    drv_ev_state[i].driver.drv_ptr = NULL;
-	    drv_ev_state[i].events = 0;
-	    drv_ev_state[i].remove_cnt = 0;
-	    drv_ev_state[i].type = ERTS_EV_TYPE_NONE;
-	    drv_ev_state[i].flags = 0;
-	}
-	erts_smp_atomic_set_nob(&drv_ev_state_len, new_len);
-	for (i=0; i<DRV_EV_STATE_LOCK_CNT; i++) {
-	    erts_smp_mtx_unlock(&drv_ev_state_locks[i].lck);
-	}
-    }
-    /*else already grown by racing thread */
+    if (free_select)
+        free_drv_select_data(free_select);
+    if (free_nif)
+        free_nif_select_data(free_nif);
 
-    erts_smp_mtx_unlock(&drv_ev_state_grow_lock);
+    ERTS_MSACC_POP_STATE_M_X();
 }
-#endif /* ERTS_SYS_CONTINOUS_FD_NUMBERS */
-
 
 static ERTS_INLINE void
 abort_task(Eterm id, ErtsPortTaskHandle *pthp, EventStateType type)
@@ -473,13 +565,7 @@ abort_tasks(ErtsDrvEventState *state, int mode)
     switch (mode) {
     case 0: check_type:
 	switch (state->type) {
-#if ERTS_CIO_HAVE_DRV_EVENT
-	case ERTS_EV_TYPE_DRV_EV:
-	    abort_task(state->driver.event->port,
-		       &state->driver.event->iotask.task,
-		       ERTS_EV_TYPE_DRV_EV);
-	    return;
-#endif
+        case ERTS_EV_TYPE_NIF:
 	case ERTS_EV_TYPE_NONE:
 	    return;
 	default:
@@ -508,16 +594,14 @@ abort_tasks(ErtsDrvEventState *state, int mode)
 static void
 deselect(ErtsDrvEventState *state, int mode)
 {
-    int do_wake = 0;
     ErtsPollEvents rm_events;
-    ERTS_SMP_LC_ASSERT(erts_smp_lc_mtx_is_locked(fd_mtx(state->fd)));
-    ASSERT(state->events);
+    ERTS_LC_ASSERT(erts_lc_mtx_is_locked(fd_mtx(state->fd)));
 
     abort_tasks(state, mode);
 
-    if (!mode)
+    if (!mode) {
 	rm_events = state->events;
-    else {
+    } else {
 	rm_events = 0;
 	ASSERT(state->type == ERTS_EV_TYPE_DRV_SEL);
 	if (mode & ERL_DRV_READ) {
@@ -530,516 +614,305 @@ deselect(ErtsDrvEventState *state, int mode)
 	}
     }
 
-    state->events = ERTS_CIO_POLL_CTL(pollset.ps, state->fd, rm_events, 0, &do_wake);
+    state->events &= ~rm_events;
+    state->active_events &= ~rm_events;
 
     if (!(state->events)) {
+        erts_io_control(state, ERTS_POLL_OP_DEL, 0);
 	switch (state->type) {
+        case ERTS_EV_TYPE_NIF:
+            state->driver.nif->in.pid = NIL;
+            state->driver.nif->out.pid = NIL;
+            enif_release_resource(state->driver.stop.resource->data);
+            state->driver.stop.resource = NULL;
+            break;
 	case ERTS_EV_TYPE_DRV_SEL:
 	    state->driver.select->inport = NIL;
 	    state->driver.select->outport = NIL;
 	    break;
-#if ERTS_CIO_HAVE_DRV_EVENT
-	case ERTS_EV_TYPE_DRV_EV:
-	    state->driver.event->port = NIL;
-	    state->driver.event->data = NULL;
-	    state->driver.event->removed_events = (ErtsPollEvents) 0;
-	    break;
-#endif
 	case ERTS_EV_TYPE_NONE:
 	    break;
 	default:
 	    ASSERT(0);
 	    break;
 	}
-	    
 	state->type = ERTS_EV_TYPE_NONE;
-	state->flags &= ~ERTS_EV_FLAG_USED;
-	remember_removed(state, &pollset);
+	state->flags = 0;
+    } else {
+        ErtsPollEvents new_events =
+            erts_io_control(state, ERTS_POLL_OP_MOD, state->active_events);
+
+        /* We were unable to re-insert the fd into the pollset, signal the callback. */
+        if (new_events & (ERTS_POLL_EV_ERR|ERTS_POLL_EV_NVAL)) {
+            if (state->active_events & ERTS_POLL_EV_IN)
+                iready(state->driver.select->inport, state);
+            if (state->active_events & ERTS_POLL_EV_OUT)
+                oready(state->driver.select->outport, state);
+            state->active_events = 0;
+        }
     }
 }
 
 #ifdef ERTS_SYS_CONTINOUS_FD_NUMBERS
-#  define IS_FD_UNKNOWN(state) ((state)->type == ERTS_EV_TYPE_NONE && (state)->remove_cnt == 0)
+#  define IS_FD_UNKNOWN(state) ((state)->type == ERTS_EV_TYPE_NONE)
 #else
 #  define IS_FD_UNKNOWN(state) ((state) == NULL)
 #endif
 
 static ERTS_INLINE void
 check_fd_cleanup(ErtsDrvEventState *state,
-#if ERTS_CIO_HAVE_DRV_EVENT
-		 ErtsDrvEventDataState **free_event,
-#endif
-		 ErtsDrvSelectDataState **free_select)
+		 ErtsDrvSelectDataState **free_select,
+                 ErtsNifSelectDataState **free_nif)
 {
-    erts_aint_t current_cio_time;
-
-    ERTS_SMP_LC_ASSERT(erts_smp_lc_mtx_is_locked(fd_mtx(state->fd)));
-
-    current_cio_time = erts_smp_atomic_read_acqb(&erts_check_io_time);
+    ERTS_LC_ASSERT(erts_lc_mtx_is_locked(fd_mtx(state->fd)));
     *free_select = NULL;
     if (state->driver.select
 	&& (state->type != ERTS_EV_TYPE_DRV_SEL)
-	&& !is_iotask_active(&state->driver.select->iniotask, current_cio_time)
-	&& !is_iotask_active(&state->driver.select->outiotask, current_cio_time)) {
-	
+	&& !is_iotask_active(&state->driver.select->iniotask)
+	&& !is_iotask_active(&state->driver.select->outiotask)) {
+
 	*free_select = state->driver.select;
 	state->driver.select = NULL;
     }
 
-#if ERTS_CIO_HAVE_DRV_EVENT
-    *free_event = NULL;
-    if (state->driver.event
-	&& (state->type != ERTS_EV_TYPE_DRV_EV)
-	&& !is_iotask_active(&state->driver.event->iotask,  current_cio_time)) {
-	
-	*free_event = state->driver.event;
-	state->driver.event = NULL;
+    *free_nif = NULL;
+    if (state->driver.nif && (state->type != ERTS_EV_TYPE_NIF)) {
+        *free_nif = state->driver.nif;
+        state->driver.nif = NULL;
     }
-#endif
 
-#ifndef ERTS_SYS_CONTINOUS_FD_NUMBERS
     if (((state->type != ERTS_EV_TYPE_NONE)
-	 | state->remove_cnt
-#if ERTS_CIO_HAVE_DRV_EVENT
-	 | (state->driver.event != NULL)
-#endif
+         | (state->driver.nif != NULL)
 	 | (state->driver.select != NULL)) == 0) {
 
-	hash_erase_drv_ev_state(state);
-
+	erase_drv_ev_state(state);
     }
-#endif
 }
 
-static ERTS_INLINE int
-check_cleanup_active_fd(ErtsSysFdType fd,
-#if ERTS_CIO_DEFER_ACTIVE_EVENTS
-			ErtsPollControlEntry *pce,
-			int *pce_ix,
-#endif
-			erts_aint_t current_cio_time)
-{
-    ErtsDrvEventState *state;
-    int active = 0;
-    erts_smp_mtx_t *mtx = fd_mtx(fd);
-    void *free_select = NULL;
-#if ERTS_CIO_HAVE_DRV_EVENT
-    void *free_event = NULL;
-#endif
-#if ERTS_CIO_DEFER_ACTIVE_EVENTS
-    ErtsPollEvents evon = 0, evoff = 0;
-#endif
-
-    erts_smp_mtx_lock(mtx);
-
-#ifdef ERTS_SYS_CONTINOUS_FD_NUMBERS
-    state = &drv_ev_state[(int) fd];
-#else
-    state = hash_get_drv_ev_state(fd); /* may be NULL! */
-    if (state)
-#endif
-    {
-	if (state->driver.select) {
-#if ERTS_CIO_DEFER_ACTIVE_EVENTS
-	    if (is_iotask_active(&state->driver.select->iniotask, current_cio_time)) {
-		active = 1;
-		if ((state->events & ERTS_POLL_EV_IN)
-		    && !(state->flags & ERTS_EV_FLAG_DEFER_IN_EV)) {
-		    evoff |= ERTS_POLL_EV_IN;
-		    state->flags |= ERTS_EV_FLAG_DEFER_IN_EV;
-		}
-	    }
-	    else if (state->flags & ERTS_EV_FLAG_DEFER_IN_EV) {
-		if (state->events & ERTS_POLL_EV_IN)
-		    evon |= ERTS_POLL_EV_IN;
-		state->flags &= ~ERTS_EV_FLAG_DEFER_IN_EV;
-	    }
-	    if (is_iotask_active(&state->driver.select->outiotask, current_cio_time)) {
-		active = 1;
-		if ((state->events & ERTS_POLL_EV_OUT)
-		    && !(state->flags & ERTS_EV_FLAG_DEFER_OUT_EV)) {
-		    evoff |= ERTS_POLL_EV_OUT;
-		    state->flags |= ERTS_EV_FLAG_DEFER_OUT_EV;
-		}
-	    }
-	    else if (state->flags & ERTS_EV_FLAG_DEFER_OUT_EV) {
-		if (state->events & ERTS_POLL_EV_OUT)
-		    evon |= ERTS_POLL_EV_OUT;
-		state->flags &= ~ERTS_EV_FLAG_DEFER_OUT_EV;
-	    }
-	    if (active)
-		(void) 0;
-	    else
+#ifdef __WIN32__
+# define MUST_DEFER(MAY_SLEEP) 1
 #else
-	    if (is_iotask_active(&state->driver.select->iniotask, current_cio_time)
-		|| is_iotask_active(&state->driver.select->outiotask, current_cio_time))
-		active = 1;
-	    else
-#endif
-		if (state->type != ERTS_EV_TYPE_DRV_SEL) {
-		free_select = state->driver.select;
-		state->driver.select = NULL;
-	    }
-	}
-
-#if ERTS_CIO_HAVE_DRV_EVENT
-	if (state->driver.event) {
-	    if (is_iotask_active(&state->driver.event->iotask, current_cio_time)) {
-#if ERTS_CIO_DEFER_ACTIVE_EVENTS
-		ErtsPollEvents evs = state->events & ~state->driver.event->deferred_events;
-		if (evs) {
-		    evoff |= evs;
-		    state->driver.event->deferred_events |= evs;
-		}
-#endif
-		active = 1;
-	    }
-	    else if (state->type != ERTS_EV_TYPE_DRV_EV) {
-		free_event = state->driver.event;
-		state->driver.event = NULL;
-	    }
-#if ERTS_CIO_DEFER_ACTIVE_EVENTS
-	    else {
-		ErtsPollEvents evs = state->events & state->driver.event->deferred_events;
-		if (evs) {
-		    evon |= evs;
-		    state->driver.event->deferred_events = 0;
-		}
-	    }
-#endif
-
-	}
-#endif
-
-#ifndef ERTS_SYS_CONTINOUS_FD_NUMBERS
-	if (((state->type != ERTS_EV_TYPE_NONE) | state->remove_cnt | active) == 0)
-	    hash_erase_drv_ev_state(state);
-#endif
-
-    }
-
-    erts_smp_mtx_unlock(mtx);
-
-    if (free_select)
-	free_drv_select_data(free_select);
-#if ERTS_CIO_HAVE_DRV_EVENT
-    if (free_event)
-	free_drv_event_data(free_event);
-#endif
-
-#if ERTS_CIO_DEFER_ACTIVE_EVENTS
-    if (evoff) {
-	ErtsPollControlEntry *pcep = &pce[(*pce_ix)++];
-	pcep->fd = fd;
-	pcep->events = evoff;
-	pcep->on = 0;
-    }
-    if (evon) {
-	ErtsPollControlEntry *pcep = &pce[(*pce_ix)++];
-	pcep->fd = fd;
-	pcep->events = evon;
-	pcep->on = 1;
-    }
-#endif
-
-    return active;
-}
-
-static void
-check_cleanup_active_fds(erts_aint_t current_cio_time)
-{
-    int six = pollset.active_fd.six;
-    int eix = pollset.active_fd.eix;
-    erts_aint32_t no = erts_smp_atomic32_read_dirty(&pollset.active_fd.no);
-    int size = pollset.active_fd.size;
-    int ix = six;
-#if ERTS_CIO_DEFER_ACTIVE_EVENTS
-    /* every fd might add two entries */
-    Uint pce_sz = 2*sizeof(ErtsPollControlEntry)*no;
-    ErtsPollControlEntry *pctrl_entries = (pce_sz
-					   ? erts_alloc(ERTS_ALC_T_TMP, pce_sz)
-					   : NULL);
-    int pctrl_ix = 0;
-#endif
-
-    while (ix != eix) {
-	ErtsSysFdType fd = pollset.active_fd.array[ix];
-	int nix = ix + 1;
-	if (nix >= size)
-	    nix = 0;
-	ASSERT(fd != ERTS_SYS_FD_INVALID);
-	if (!check_cleanup_active_fd(fd,
-#if ERTS_CIO_DEFER_ACTIVE_EVENTS
-				     pctrl_entries,
-				     &pctrl_ix,
-#endif
-				     current_cio_time)) {
-	    no--;
-	    if (ix == six) {
-#ifdef DEBUG
-		pollset.active_fd.array[ix] = ERTS_SYS_FD_INVALID;
-#endif
-		six = nix;
-	    }
-	    else {
-		pollset.active_fd.array[ix] = pollset.active_fd.array[six];
-#ifdef DEBUG
-		pollset.active_fd.array[six] = ERTS_SYS_FD_INVALID;
-#endif
-		six++;
-		if (six >= size)
-		    six = 0;
-	    }
-	}
-	ix = nix;
-    }
-
-#if ERTS_CIO_DEFER_ACTIVE_EVENTS
-    ASSERT(pctrl_ix <= pce_sz/sizeof(ErtsPollControlEntry));
-    if (pctrl_ix)
-	ERTS_CIO_POLL_CTLV(pollset.ps, pctrl_entries, pctrl_ix);
-    if (pctrl_entries)
-	erts_free(ERTS_ALC_T_TMP, pctrl_entries);
+# define MUST_DEFER(MAY_SLEEP) (MAY_SLEEP)
 #endif
 
-    pollset.active_fd.six = six;
-    pollset.active_fd.eix = eix;
-    erts_smp_atomic32_set_relb(&pollset.active_fd.no, no);
-}
-
-static ERTS_INLINE void
-add_active_fd(ErtsSysFdType fd)
-{
-    int eix = pollset.active_fd.eix;
-    int size = pollset.active_fd.size;
-    
-
-    pollset.active_fd.array[eix] = fd;
-
-    erts_smp_atomic32_set_relb(&pollset.active_fd.no,
-			       (erts_smp_atomic32_read_dirty(&pollset.active_fd.no)
-				+ 1));
-
-    eix++;
-    if (eix >= size)
-	eix = 0;
-    if (pollset.active_fd.six == eix) {
-	pollset.active_fd.six = 0;
-	eix = size;
-	size += ERTS_ACTIVE_FD_INC;
-	pollset.active_fd.array = erts_realloc(ERTS_ALC_T_ACTIVE_FD_ARR,
-					       pollset.active_fd.array,
-					       sizeof(ErtsSysFdType)*size);
-	pollset.active_fd.size = size;
-#ifdef DEBUG
-	{
-	    int i;
-	    for (i = eix + 1; i < size; i++)
-		pollset.active_fd.array[i] = ERTS_SYS_FD_INVALID;
-	}
-#endif
-
-    }
-
-    pollset.active_fd.eix = eix;
-}
-
 int
-ERTS_CIO_EXPORT(driver_select)(ErlDrvPort ix,
-			       ErlDrvEvent e,
-			       int mode,
-			       int on)
+driver_select(ErlDrvPort ix, ErlDrvEvent e, int mode, int on)
 {
     void (*stop_select_fn)(ErlDrvEvent, void*) = NULL;
     Port *prt = erts_drvport2port(ix);
     Eterm id = erts_drvport2id(ix);
     ErtsSysFdType fd = (ErtsSysFdType) e;
     ErtsPollEvents ctl_events = (ErtsPollEvents) 0;
-    ErtsPollEvents new_events, old_events;
+    ErtsPollEvents old_events;
+    ErtsPollEvents new_events;
+    ErtsPollOp ctl_op = ERTS_POLL_OP_MOD;
     ErtsDrvEventState *state;
-    int wake_poller;
+    int wake_poller = 0;
     int ret;
-#if ERTS_CIO_HAVE_DRV_EVENT
-    ErtsDrvEventDataState *free_event = NULL;
-#endif
     ErtsDrvSelectDataState *free_select = NULL;
+    ErtsNifSelectDataState *free_nif = NULL;
 #ifdef USE_VM_PROBES
     DTRACE_CHARBUF(name, 64);
 #endif
+    ERTS_MSACC_PUSH_AND_SET_STATE(ERTS_MSACC_STATE_CHECK_IO);
 
-    if (prt == ERTS_INVALID_ERL_DRV_PORT)
+    if (prt == ERTS_INVALID_ERL_DRV_PORT) {
+        ERTS_MSACC_POP_STATE();
 	return -1;
+    }
 
-    ERTS_SMP_LC_ASSERT(erts_lc_is_port_locked(prt));
+    ERTS_LC_ASSERT(erts_lc_is_port_locked(prt));
 
 #ifdef ERTS_SYS_CONTINOUS_FD_NUMBERS
-    if ((unsigned)fd >= (unsigned)erts_smp_atomic_read_nob(&drv_ev_state_len)) {
-	if (fd < 0) {
-	    return -1;    
-	}
-	if (fd >= max_fds) {
-	    select_large_fd_error(ix, fd, mode, on);
-	    return -1;
-	}
-	grow_drv_ev_state(fd);
+    if (!grow_drv_ev_state(fd)) {
+        if (fd > 0) drv_select_large_fd_error(ix, fd, mode, on);
+        ERTS_MSACC_POP_STATE();
+        return -1;
     }
 #endif
 
-    erts_smp_mtx_lock(fd_mtx(fd));
+    erts_mtx_lock(fd_mtx(fd));
 
-#ifdef ERTS_SYS_CONTINOUS_FD_NUMBERS
-    state = &drv_ev_state[(int) fd];
-#else
-    state = hash_get_drv_ev_state(fd); /* may be NULL! */
-#endif
+    state = get_drv_ev_state(fd); /* may be NULL! */
 
-    if (!on && (mode&ERL_DRV_USE_NO_CALLBACK) == ERL_DRV_USE) {
-	if (IS_FD_UNKNOWN(state)) {
-	    /* fast track to stop_select callback */
-	    stop_select_fn = prt->drv_ptr->stop_select;
-#ifdef USE_VM_PROBES
-	    strncpy(name, prt->drv_ptr->name,
-		    sizeof(DTRACE_CHARBUF_NAME(name))-1);
-	    name[sizeof(name)-1] = '\0';
-#endif
-	    ret = 0;
-	    goto done_unknown;
-	}
-	mode |= (ERL_DRV_READ | ERL_DRV_WRITE);
-	wake_poller = 1; /* to eject fd from pollset (if needed) */
+    DEBUG_PRINT_FD("driver_select(%T, %p, %s, %d)",
+                   state, id, fd, drvmode2str(mode), on);
+
+    if (!on) {
+        if (IS_FD_UNKNOWN(state)) {
+            if ((mode&ERL_DRV_USE_NO_CALLBACK) == ERL_DRV_USE) {
+                /* fast track to stop_select callback */
+                stop_select_fn = prt->drv_ptr->stop_select;
+        #ifdef USE_VM_PROBES
+                strncpy(name, prt->drv_ptr->name,
+                        sizeof(DTRACE_CHARBUF_NAME(name))-1);
+                name[sizeof(name)-1] = '\0';
+        #endif
+            }
+            ret = 0;
+            goto done_unknown;
+        }
+        else if ((mode&ERL_DRV_USE_NO_CALLBACK) == ERL_DRV_USE) {
+            mode |= (ERL_DRV_READ | ERL_DRV_WRITE);
+        }
     }
-    else wake_poller = 0;
 
-#ifndef ERTS_SYS_CONTINOUS_FD_NUMBERS
-    if (state == NULL) {
-	state = hash_new_drv_ev_state(fd);
+    state = new_drv_ev_state(state, fd);
+
+    switch (state->type) {
+    case ERTS_EV_TYPE_NIF:
+        drv_select_steal(ix, state, mode, on);
+        break;
+    case ERTS_EV_TYPE_STOP_USE: {
+        erts_dsprintf_buf_t *dsbufp = erts_create_logger_dsbuf();
+        print_drv_select_op(dsbufp, ix, state->fd, mode, on);
+        steal_pending_stop_use(dsbufp, ix, state, mode, on);
+        if (state->type == ERTS_EV_TYPE_STOP_USE) {
+            ret = 0;
+            goto done; /* stop_select still pending */
+        }
+        ASSERT(state->type == ERTS_EV_TYPE_NONE);
+        break;
     }
-#endif
+    case ERTS_EV_TYPE_STOP_NIF: {
+        erts_dsprintf_buf_t *dsbufp = erts_create_logger_dsbuf();
+        print_drv_select_op(dsbufp, ix, state->fd, mode, on);
+        steal_pending_stop_nif(dsbufp, NULL, state, mode, on);
+        ASSERT(state->type == ERTS_EV_TYPE_NONE);
+        break;
 
-#if ERTS_CIO_HAVE_DRV_EVENT
-    if (state->type == ERTS_EV_TYPE_DRV_EV)
-	select_steal(ix, state, mode, on);
-#endif
-    if (state->type == ERTS_EV_TYPE_STOP_USE) {
-	erts_dsprintf_buf_t *dsbufp = erts_create_logger_dsbuf();
-	print_select_op(dsbufp, ix, state->fd, mode, on);
-	steal_pending_stop_select(dsbufp, ix, state, mode, on);
-	if (state->type == ERTS_EV_TYPE_STOP_USE) {
-	    ret = 0;
-	    goto done; /* stop_select still pending */
-	}
-	ASSERT(state->type == ERTS_EV_TYPE_NONE);
+    }
+    default: break;
     }
 
     if (mode & ERL_DRV_READ) {
 	if (state->type == ERTS_EV_TYPE_DRV_SEL) {
 	    Eterm owner = state->driver.select->inport;
 	    if (owner != id && is_not_nil(owner))
-		select_steal(ix, state, mode, on);
+		drv_select_steal(ix, state, mode, on);
 	}
-	ctl_events |= ERTS_POLL_EV_IN;
+        ctl_events = ERTS_POLL_EV_IN;
     }
     if (mode & ERL_DRV_WRITE) {
 	if (state->type == ERTS_EV_TYPE_DRV_SEL) {
 	    Eterm owner = state->driver.select->outport;
 	    if (owner != id && is_not_nil(owner))
-		select_steal(ix, state, mode, on);
+		drv_select_steal(ix, state, mode, on);
 	}
 	ctl_events |= ERTS_POLL_EV_OUT;
-    }	
+    }
+
 
     ASSERT((state->type == ERTS_EV_TYPE_DRV_SEL) ||
 	   (state->type == ERTS_EV_TYPE_NONE && !state->events));
 
-    if (!on && !(state->flags & ERTS_EV_FLAG_USED) 
-	&& state->events && !(state->events & ~ctl_events)) {	
-	/* Old driver removing all events. At least wake poller.
-	   It will not make close() 100% safe but it will prevent
-	   actions delayed by poll timeout. */
-	wake_poller = 1;
+    old_events = state->events;
+
+    if (on) {
+        ctl_events &= ~old_events;
+        state->events |= ctl_events;
+        if (ctl_events & ERTS_POLL_EV_IN && (!state->driver.select || !is_iotask_active(&state->driver.select->iniotask)))
+            state->active_events |= ERTS_POLL_EV_IN;
+        if (ctl_events & ERTS_POLL_EV_OUT && (!state->driver.select || !is_iotask_active(&state->driver.select->outiotask)))
+            state->active_events |= ERTS_POLL_EV_OUT;
+        if (old_events == 0 && !(state->flags & ERTS_EV_FLAG_USED)) {
+            ctl_op = ERTS_POLL_OP_ADD;
+        }
+        new_events = state->active_events;
+        if (state->flags & ERTS_EV_FLAG_IN_SCHEDULER)
+            new_events &= ~ERTS_POLL_EV_IN;
     }
+    else {
+        ctl_events &= old_events;
+        state->events &= ~ctl_events;
+        state->active_events &= ~ctl_events;
+        new_events = state->active_events;
 
-    new_events = ERTS_CIO_POLL_CTL(pollset.ps, state->fd, ctl_events, on, &wake_poller);
+        if (ctl_events & ERTS_POLL_EV_IN) {
+            state->count = 0;
+            if (state->flags & ERTS_EV_FLAG_IN_SCHEDULER) {
+                new_events = 0;
+            }
+        }
 
-    if (new_events & (ERTS_POLL_EV_ERR|ERTS_POLL_EV_NVAL)) {
-	if (state->type == ERTS_EV_TYPE_DRV_SEL && !state->events) {
-	    state->type = ERTS_EV_TYPE_NONE;
-	    state->flags &= ~ERTS_EV_FLAG_USED;
-	    state->driver.select->inport = NIL;
-	    state->driver.select->outport = NIL;
-	}
-	ret = -1;
-	goto done;
+        if (!state->events) {
+            if (!(state->flags & ERTS_EV_FLAG_USED) || mode & ERL_DRV_USE)
+                ctl_op = ERTS_POLL_OP_DEL;
+        }
     }
 
-    old_events = state->events;
+    if (ctl_events || ctl_op == ERTS_POLL_OP_DEL) {
 
-    ASSERT(on
-	   ? (new_events == (state->events | ctl_events))
-	   : (new_events == (state->events & ~ctl_events)));
+        new_events = erts_io_control_wakeup(state, ctl_op,
+                                            new_events,
+                                            &wake_poller);
 
-    ASSERT(state->type == ERTS_EV_TYPE_DRV_SEL
-	   || state->type == ERTS_EV_TYPE_NONE);
+        ASSERT(state->type == ERTS_EV_TYPE_DRV_SEL || state->type == ERTS_EV_TYPE_NONE);
+    }
 
-    state->events = new_events;
-    if (ctl_events) {
-	if (on) {
+    if (on) {
+        if (ctl_events) {
 	    if (!state->driver.select)
-		state->driver.select = alloc_drv_select_data();
+		state->driver.select = alloc_drv_select_data(state->fd);
 	    if (state->type == ERTS_EV_TYPE_NONE)
 		state->type = ERTS_EV_TYPE_DRV_SEL;
 	    ASSERT(state->type == ERTS_EV_TYPE_DRV_SEL);
-	    if (ctl_events & ERTS_POLL_EV_IN)
+	    if (ctl_events & ERTS_POLL_EV_IN) {
 		state->driver.select->inport = id;
-	    if (ctl_events & ERTS_POLL_EV_OUT)
+                if (new_events & (ERTS_POLL_EV_ERR|ERTS_POLL_EV_NVAL))
+                    iready(id, state);
+            }
+	    if (ctl_events & ERTS_POLL_EV_OUT) {
 		state->driver.select->outport = id;
-	    if (mode & ERL_DRV_USE) {
+                if (new_events & (ERTS_POLL_EV_ERR|ERTS_POLL_EV_NVAL))
+                    oready(id, state);
+            }
+	    if (mode & ERL_DRV_USE)
 		state->flags |= ERTS_EV_FLAG_USED;
-	    }
-	}
-	else { /* off */
-	    if (state->type == ERTS_EV_TYPE_DRV_SEL) {
-		if (ctl_events & ERTS_POLL_EV_IN) {
-		    abort_tasks(state, ERL_DRV_READ);
-		    state->driver.select->inport = NIL;
-		}
-		if (ctl_events & ERTS_POLL_EV_OUT) {
-		    abort_tasks(state, ERL_DRV_WRITE);
-		    state->driver.select->outport = NIL;
-		}
-		if (new_events == 0) {
-		    if (old_events != 0) {
-			remember_removed(state, &pollset);
-		    }		    
-		    if ((mode & ERL_DRV_USE) || !(state->flags & ERTS_EV_FLAG_USED)) {
-			state->type = ERTS_EV_TYPE_NONE;
-			state->flags &= ~ERTS_EV_FLAG_USED;
-		    }
-		    /*else keep it, as fd will probably be selected upon again */
-		}
-	    }
-	    if ((mode & ERL_DRV_USE_NO_CALLBACK) == ERL_DRV_USE) {
-		erts_driver_t* drv_ptr = prt->drv_ptr;
-		ASSERT(new_events==0);
-		if (state->remove_cnt == 0 || !wake_poller) {
-		    /* Safe to close fd now as it is not in pollset
-		       or there was no need to eject fd (kernel poll) */
-		    stop_select_fn = drv_ptr->stop_select;
+        }
+    }
+    else { /* off */
+        if (state->type == ERTS_EV_TYPE_DRV_SEL) {
+            if (ctl_events & ERTS_POLL_EV_IN) {
+                abort_tasks(state, ERL_DRV_READ);
+                state->driver.select->inport = NIL;
+                state->flags &= ~ERTS_EV_FLAG_IN_SCHEDULER;
+            }
+            if (ctl_events & ERTS_POLL_EV_OUT) {
+                abort_tasks(state, ERL_DRV_WRITE);
+                state->driver.select->outport = NIL;
+            }
+            if (state->events == 0) {
+                if ((mode & ERL_DRV_USE) || !(state->flags & ERTS_EV_FLAG_USED)) {
+                    state->type = ERTS_EV_TYPE_NONE;
+                    if (state->flags & ERTS_EV_FLAG_SCHEDULER)
+                        erts_atomic32_read_bor_nob(&prt->state, ERTS_PORT_SFLG_CHECK_FD_CLEANUP);
+                    state->flags = 0;
+                }
+                /*else keep it, as fd will probably be selected upon again */
+            }
+        }
+        if ((mode & ERL_DRV_USE_NO_CALLBACK) == ERL_DRV_USE) {
+            erts_driver_t* drv_ptr = prt->drv_ptr;
+            ASSERT(state->events==0);
+            if (!wake_poller) {
+                /* Safe to close fd now as it is not in pollset
+                   or there was no need to eject fd (kernel poll) */
+                stop_select_fn = drv_ptr->stop_select;
 #ifdef USE_VM_PROBES
-		    strncpy(name, prt->drv_ptr->name, sizeof(name)-1);
-		    name[sizeof(name)-1] = '\0';
-#endif
-		}
-		else {
-		    /* Not safe to close fd, postpone stop_select callback. */
-		    state->type = ERTS_EV_TYPE_STOP_USE;
-		    state->driver.drv_ptr = drv_ptr;
-		    if (drv_ptr->handle) {
-			erts_ddll_reference_referenced_driver(drv_ptr->handle);
-		    }
-		}
-	    }
-	}
+                strncpy(name, prt->drv_ptr->name, sizeof(name)-1);
+                name[sizeof(name)-1] = '\0';
+#endif
+            }
+            else {
+                /* Not safe to close fd, postpone stop_select callback. */
+                state->type = ERTS_EV_TYPE_STOP_USE;
+                state->driver.stop.drv_ptr = drv_ptr;
+                if (drv_ptr->handle) {
+                    erts_ddll_reference_referenced_driver(drv_ptr->handle);
+                }
+            }
+        }
     }
    
     ret = 0;
@@ -1047,13 +920,11 @@ ERTS_CIO_EXPORT(driver_select)(ErlDrvPort ix,
 done:
 
     check_fd_cleanup(state,
-#if ERTS_CIO_HAVE_DRV_EVENT
-		     &free_event,
-#endif
-		     &free_select);
+		     &free_select,
+                     &free_nif);
 
 done_unknown:
-    erts_smp_mtx_unlock(fd_mtx(fd));
+    erts_mtx_unlock(fd_mtx(fd));
     if (stop_select_fn) {
 	int was_unmasked = erts_block_fpe();
 	DTRACE1(driver_stop_select, name);
@@ -1063,155 +934,245 @@ done_unknown:
     }
     if (free_select)
 	free_drv_select_data(free_select);
-#if ERTS_CIO_HAVE_DRV_EVENT
-    if (free_event)
-	free_drv_event_data(free_event);
-#endif
+    if (free_nif)
+        free_nif_select_data(free_nif);
+
+    ERTS_MSACC_POP_STATE();
+
     return ret;
 }
 
 int
-ERTS_CIO_EXPORT(driver_event)(ErlDrvPort ix,
-			      ErlDrvEvent e,
-			      ErlDrvEventData event_data)
+enif_select(ErlNifEnv* env,
+            ErlNifEvent e,
+            enum ErlNifSelectFlags mode,
+            void* obj,
+            const ErlNifPid* pid,
+            Eterm ref)
 {
-#if !ERTS_CIO_HAVE_DRV_EVENT
-    return -1;
-#else
+    int on;
+    ErtsResource* resource = DATA_TO_RESOURCE(obj);
     ErtsSysFdType fd = (ErtsSysFdType) e;
-    ErtsPollEvents events;
-    ErtsPollEvents add_events;
-    ErtsPollEvents remove_events;
-    Eterm id = erts_drvport2id(ix);
+    ErtsPollEvents ctl_events = (ErtsPollEvents) 0;
+    ErtsPollEvents old_events;
+    ErtsPollOp ctl_op = ERTS_POLL_OP_MOD;
     ErtsDrvEventState *state;
-    int do_wake = 0;
-    int ret;
-#if ERTS_CIO_HAVE_DRV_EVENT
-    ErtsDrvEventDataState *free_event;
-#endif
-    ErtsDrvSelectDataState *free_select;
-    Port *prt = erts_drvport2port(ix);
-
-    if (prt == ERTS_INVALID_ERL_DRV_PORT)
-	return -1;
+    int ret, wake_poller = 0;
+    enum { NO_STOP=0, CALL_STOP, CALL_STOP_AND_RELEASE } call_stop = NO_STOP;
+    ErtsDrvSelectDataState *free_select = NULL;
+    ErtsNifSelectDataState *free_nif = NULL;
 
-    ERTS_SMP_LC_ASSERT(erts_lc_is_port_locked(prt));
+    ASSERT(!resource->monitors);
 
 #ifdef ERTS_SYS_CONTINOUS_FD_NUMBERS
-    if ((unsigned)fd >= (unsigned)erts_smp_atomic_read_nob(&drv_ev_state_len)) {
-	if (fd < 0)
-	    return -1;    
-	if (fd >= max_fds) {
-	    event_large_fd_error(ix, fd, event_data);
-	    return -1;
-	}
-	grow_drv_ev_state(fd);
+    if (!grow_drv_ev_state(fd)) {
+        if (fd > 0) nif_select_large_fd_error(fd, mode, resource, ref);
+        return INT_MIN | ERL_NIF_SELECT_INVALID_EVENT;
     }
 #endif
 
-    erts_smp_mtx_lock(fd_mtx(fd));
+    erts_mtx_lock(fd_mtx(fd));
 
-#ifdef ERTS_SYS_CONTINOUS_FD_NUMBERS
-    state = &drv_ev_state[(int) fd];
-#else
-    /* Could use hash_new directly, but want to keep the normal case fast */
-    state = hash_get_drv_ev_state(fd);
-    if (state == NULL) {
-	state = hash_new_drv_ev_state(fd);
+    state = get_drv_ev_state(fd); /* may be NULL! */
+
+    DEBUG_PRINT_FD("enif_select(%T, %d, %s, %p, %T, %T)",
+                   state, env->proc->common.id, fd, nifmode2str(mode), resource,
+                   pid ? pid->pid : THE_NON_VALUE, ref);
+
+    if (mode & ERL_NIF_SELECT_STOP) {
+        ASSERT(resource->type->stop);
+        if (IS_FD_UNKNOWN(state)) {
+            /* fast track to stop callback */
+            call_stop = CALL_STOP;
+            ret = ERL_NIF_SELECT_STOP_CALLED;
+            goto done_unknown;
+        }
+        on = 0;
+        mode = ERL_DRV_READ | ERL_DRV_WRITE | ERL_DRV_USE;
+        ctl_events = ERTS_POLL_EV_IN | ERTS_POLL_EV_OUT;
+        ctl_op = ERTS_POLL_OP_DEL;
     }
-#endif
+    else {
+        on = 1;
+        ASSERT(mode);
+        if (mode & ERL_DRV_READ) {
+            ctl_events |= ERTS_POLL_EV_IN;
+        }
+        if (mode & ERL_DRV_WRITE) {
+            ctl_events |= ERTS_POLL_EV_OUT;
+        }
+    }
+
+    state = new_drv_ev_state(state,fd);
 
     switch (state->type) {
-    case ERTS_EV_TYPE_DRV_EV:
-	if (state->driver.event->port == id) break;
-	/*fall through*/
+    case ERTS_EV_TYPE_NIF:
+        /*
+         * Changing resource is considered stealing.
+         * Changing process and/or ref is ok (I think?).
+         */
+        if (state->driver.stop.resource != resource)
+            nif_select_steal(state, ERL_DRV_READ | ERL_DRV_WRITE, resource, ref);
+        break;
     case ERTS_EV_TYPE_DRV_SEL:
-	event_steal(ix, state, event_data);
-	break;
+        nif_select_steal(state, mode, resource, ref);
+        break;
     case ERTS_EV_TYPE_STOP_USE: {
-	erts_dsprintf_buf_t *dsbufp = erts_create_logger_dsbuf();
-	print_event_op(dsbufp, ix, fd, event_data);
-	steal_pending_stop_select(dsbufp, ix, state, 0, 1);
-	break;
-      }
-    }
-
-    ASSERT(state->type == ERTS_EV_TYPE_DRV_EV
-	   || state->type == ERTS_EV_TYPE_NONE);
+        erts_dsprintf_buf_t *dsbufp = erts_create_logger_dsbuf();
+        print_nif_select_op(dsbufp, fd, mode, resource, ref);
+        steal_pending_stop_use(dsbufp, ERTS_INVALID_ERL_DRV_PORT, state, mode, on);
+        ASSERT(state->type == ERTS_EV_TYPE_NONE);
+        break;
+    }
+    case ERTS_EV_TYPE_STOP_NIF: {
+        erts_dsprintf_buf_t *dsbufp = erts_create_logger_dsbuf();
+        print_nif_select_op(dsbufp, fd, mode, resource, ref);
+        steal_pending_stop_nif(dsbufp, resource, state, mode, on);
+        if (state->type == ERTS_EV_TYPE_STOP_NIF) {
+            ret = ERL_NIF_SELECT_STOP_SCHEDULED;  /* ?? */
+            goto done;
+        }
+        ASSERT(state->type == ERTS_EV_TYPE_NONE);
+        break;
+    }
+    default: break;
+    }
+
+    ASSERT((state->type == ERTS_EV_TYPE_NIF) ||
+	   (state->type == ERTS_EV_TYPE_NONE && !state->events));
 
-    events = state->events;
+    old_events = state->events;
 
-    if (!event_data) {
-	remove_events = events;
-	add_events = 0;
+    if (on) {
+        ctl_events &= ~old_events;
+        state->events |= ctl_events;
+        state->active_events |= ctl_events;
+        if (state->type == ERTS_EV_TYPE_NONE)
+            ctl_op = ERTS_POLL_OP_ADD;
     }
     else {
-	remove_events = ~event_data->events & events;
-	add_events = ~events & event_data->events;
+        ctl_events &= old_events;
+        state->events &= ~ctl_events;
+        state->active_events &= ~ctl_events;
     }
 
-    if (add_events) {
-	events = ERTS_CIO_POLL_CTL(pollset.ps, state->fd, add_events, 1, &do_wake);
-	if (events & (ERTS_POLL_EV_ERR|ERTS_POLL_EV_NVAL)) {
-	    ret = -1;
-	    goto done;
-	}
-    }
-    if (remove_events) {
-	events = ERTS_CIO_POLL_CTL(pollset.ps, state->fd, remove_events, 0, &do_wake);
-	if (events & (ERTS_POLL_EV_ERR|ERTS_POLL_EV_NVAL)) {
-	    ret = -1;
-	    goto done;
-	}
-    }
-    if (event_data && event_data->events != 0) {
-	if (state->type == ERTS_EV_TYPE_DRV_EV) {
-	    state->driver.event->removed_events &= ~add_events;
-	    state->driver.event->removed_events |= remove_events;
-	}
-	else {
-	    if (!state->driver.event)
-		state->driver.event = alloc_drv_event_data();
-	    state->driver.event->port = id;
-	    state->driver.event->removed_events = (ErtsPollEvents) 0;
-	    state->type = ERTS_EV_TYPE_DRV_EV;
-	}
-	state->driver.event->data = event_data;
-    }
-    else {
-	if (state->type == ERTS_EV_TYPE_DRV_EV) {
-	    abort_tasks(state, 0);
-	    state->driver.event->port = NIL;
-	    state->driver.event->data = NULL;
-	    state->driver.event->removed_events = (ErtsPollEvents) 0;
-	}
-	state->type = ERTS_EV_TYPE_NONE;
-	remember_removed(state, &pollset);
+    if (ctl_events || ctl_op == ERTS_POLL_OP_DEL) {
+        ErtsPollEvents new_events;
+
+        new_events = erts_io_control_wakeup(state, ctl_op,
+                                            state->active_events,
+                                            &wake_poller);
+
+        if (new_events & (ERTS_POLL_EV_ERR|ERTS_POLL_EV_NVAL)) {
+            if (state->type == ERTS_EV_TYPE_NIF && !old_events) {
+                state->type = ERTS_EV_TYPE_NONE;
+                state->flags = 0;
+                state->driver.nif->in.pid = NIL;
+                state->driver.nif->out.pid = NIL;
+                state->driver.stop.resource = NULL;
+            }
+            ret = INT_MIN | ERL_NIF_SELECT_FAILED;
+            goto done;
+        }
+        ASSERT(new_events == state->events);
     }
-    state->events = events;
-    ASSERT(event_data ? events == event_data->events : events == 0); 
 
-    ret = 0;
+    ASSERT(state->type == ERTS_EV_TYPE_NIF
+	   || state->type == ERTS_EV_TYPE_NONE);
+
+    if (on) {
+        const Eterm recipient = pid ? pid->pid : env->proc->common.id;
+        Uint32* refn;
+        if (!state->driver.nif)
+            state->driver.nif = alloc_nif_select_data();
+        if (state->type == ERTS_EV_TYPE_NONE) {
+            state->type = ERTS_EV_TYPE_NIF;
+            state->driver.stop.resource = resource;
+            enif_keep_resource(resource->data);
+        }
+        ASSERT(state->type == ERTS_EV_TYPE_NIF);
+        ASSERT(state->driver.stop.resource == resource);
+        if (mode & ERL_DRV_READ) {
+            state->driver.nif->in.pid = recipient;
+            if (is_immed(ref)) {
+                state->driver.nif->in.immed = ref;
+            } else {
+                ASSERT(is_internal_ref(ref));
+                refn = internal_ref_numbers(ref);
+                state->driver.nif->in.immed = THE_NON_VALUE;
+                sys_memcpy(state->driver.nif->in.refn, refn,
+                           sizeof(state->driver.nif->in.refn));
+            }
+        }
+        if (mode & ERL_DRV_WRITE) {
+            state->driver.nif->out.pid = recipient;
+            if (is_immed(ref)) {
+                state->driver.nif->out.immed = ref;
+            } else {
+                ASSERT(is_internal_ref(ref));
+                refn = internal_ref_numbers(ref);
+                state->driver.nif->out.immed = THE_NON_VALUE;
+                sys_memcpy(state->driver.nif->out.refn, refn,
+                           sizeof(state->driver.nif->out.refn));
+            }
+        }
+        ret = 0;
+    }
+    else { /* off */
+        if (state->type == ERTS_EV_TYPE_NIF) {
+            state->driver.nif->in.pid = NIL;
+            state->driver.nif->out.pid = NIL;
+        }
+        ASSERT(state->events==0);
+        if (!wake_poller) {
+            /*
+             * Safe to close fd now as it is not in pollset
+             * or there was no need to eject fd (kernel poll)
+             */
+            if (state->type == ERTS_EV_TYPE_NIF) {
+                ASSERT(state->driver.stop.resource == resource);
+                call_stop = CALL_STOP_AND_RELEASE;
+                state->driver.stop.resource = NULL;
+            }
+            else {
+                ASSERT(!state->driver.stop.resource);
+                call_stop = CALL_STOP;
+            }
+            state->type = ERTS_EV_TYPE_NONE;
+            ret = ERL_NIF_SELECT_STOP_CALLED;
+        }
+        else {
+            /* Not safe to close fd, postpone stop_select callback. */
+            if (state->type == ERTS_EV_TYPE_NONE) {
+                ASSERT(!state->driver.stop.resource);
+                state->driver.stop.resource = resource;
+                enif_keep_resource(resource);
+            }
+            state->type = ERTS_EV_TYPE_STOP_NIF;
+            ret = ERL_NIF_SELECT_STOP_SCHEDULED;
+        }
+    }
 
 done:
 
     check_fd_cleanup(state,
-#if ERTS_CIO_HAVE_DRV_EVENT
-		     &free_event,
-#endif
-		     &free_select);
-
-    erts_smp_mtx_unlock(fd_mtx(fd));
+		     &free_select,
+                     &free_nif);
 
+done_unknown:
+    erts_mtx_unlock(fd_mtx(fd));
+    if (call_stop) {
+        erts_resource_stop(resource, (ErlNifEvent)fd, 1);
+        if (call_stop == CALL_STOP_AND_RELEASE) {
+            enif_release_resource(resource->data);
+        }
+    }
     if (free_select)
 	free_drv_select_data(free_select);
-#if ERTS_CIO_HAVE_DRV_EVENT
-    if (free_event)
-	free_drv_event_data(free_event);
-#endif
+    if (free_nif)
+        free_nif_select_data(free_nif);
 
     return ret;
-#endif
 }
 
 static ERTS_INLINE int
@@ -1240,13 +1201,14 @@ need2steal(ErtsDrvEventState *state, int mode)
 				  state,
 				  ERL_DRV_WRITE);
 	break;
-#if ERTS_CIO_HAVE_DRV_EVENT
-    case ERTS_EV_TYPE_DRV_EV:
-	do_steal |= chk_stale(state->driver.event->port, state, 0);
-	break;
-#endif
+    case ERTS_EV_TYPE_NIF:
+        ASSERT(state->driver.stop.resource);
+        do_steal = 1;
+        break;
+
     case ERTS_EV_TYPE_STOP_USE:
-	ASSERT(0);
+    case ERTS_EV_TYPE_STOP_NIF:
+        ASSERT(0);
 	break;
     default:
 	break;
@@ -1277,7 +1239,7 @@ print_driver_name(erts_dsprintf_buf_t *dsbufp, Eterm id)
 static void
 steal(erts_dsprintf_buf_t *dsbufp, ErtsDrvEventState *state, int mode)
 {
-    erts_dsprintf(dsbufp, "stealing control of fd=%d from ", (int) GET_FD(state->fd));
+    erts_dsprintf(dsbufp, "stealing control of fd=%d from ", (int) state->fd);
     switch (state->type) {
     case ERTS_EV_TYPE_DRV_SEL: {
 	int deselect_mode = 0;
@@ -1301,49 +1263,52 @@ steal(erts_dsprintf_buf_t *dsbufp, ErtsDrvEventState *state, int mode)
 	if (deselect_mode)
 	    deselect(state, deselect_mode);
 	else {
-	    erts_dsprintf(dsbufp, "no one", (int) GET_FD(state->fd));
-	    ASSERT(0);
-	}
-	erts_dsprintf(dsbufp, "\n");
-	break;
-    }
-#if ERTS_CIO_HAVE_DRV_EVENT
-    case ERTS_EV_TYPE_DRV_EV: {
-	Eterm eid = state->driver.event->port;
-	if (is_nil(eid)) {
 	    erts_dsprintf(dsbufp, "no one", (int) state->fd);
 	    ASSERT(0);
 	}
-	else {
-	    erts_dsprintf(dsbufp, "event driver ");
-	    print_driver_name(dsbufp, eid);
-	    erts_dsprintf(dsbufp, "%T ", eid);
-	}
 	erts_dsprintf(dsbufp, "\n");
-	deselect(state, 0);
 	break;
     }
-#endif
-    case ERTS_EV_TYPE_STOP_USE: {
+    case ERTS_EV_TYPE_NIF: {
+        Eterm iid = state->driver.nif->in.pid;
+        Eterm oid = state->driver.nif->out.pid;
+        const char* with = "with";
+        ErlNifResourceType* rt = state->driver.stop.resource->type;
+
+        erts_dsprintf(dsbufp, "resource %T:%T", rt->module, rt->name);
+
+        if (is_not_nil(iid)) {
+            erts_dsprintf(dsbufp, " %s in-pid %T", with, iid);
+            with = "and";
+        }
+        if (is_not_nil(oid)) {
+            erts_dsprintf(dsbufp, " %s out-pid %T", with, oid);
+        }
+        deselect(state, 0);
+        erts_dsprintf(dsbufp, "\n");
+        break;
+    }
+    case ERTS_EV_TYPE_STOP_USE:
+    case ERTS_EV_TYPE_STOP_NIF: {
 	ASSERT(0);
 	break;
     }
     default:
-	erts_dsprintf(dsbufp, "no one\n", (int) GET_FD(state->fd));
+	erts_dsprintf(dsbufp, "no one\n", (int) state->fd);
 	ASSERT(0);
     }
 }
 
 static void
-print_select_op(erts_dsprintf_buf_t *dsbufp,
-		ErlDrvPort ix, ErtsSysFdType fd, int mode, int on)
+print_drv_select_op(erts_dsprintf_buf_t *dsbufp,
+                    ErlDrvPort ix, ErtsSysFdType fd, int mode, int on)
 {
     Port *pp = erts_drvport2port(ix);
     erts_dsprintf(dsbufp,
 		  "driver_select(%p, %d,%s%s%s%s, %d) "
 		  "by ",
 		  ix,
-		  (int) GET_FD(fd),
+		  (int) fd,
 		  mode & ERL_DRV_READ ? " ERL_DRV_READ" : "",
 		  mode & ERL_DRV_WRITE ? " ERL_DRV_WRITE" : "",
 		  mode & ERL_DRV_USE ? " ERL_DRV_USE" : "",
@@ -1354,11 +1319,40 @@ print_select_op(erts_dsprintf_buf_t *dsbufp,
 }
 
 static void
-select_steal(ErlDrvPort ix, ErtsDrvEventState *state, int mode, int on)
+print_nif_select_op(erts_dsprintf_buf_t *dsbufp,
+                    ErtsSysFdType fd, int mode,
+                    ErtsResource* resource, Eterm ref)
+{
+    erts_dsprintf(dsbufp,
+		  "enif_select(_, %d,%s%s%s, %T:%T, %T) ",
+		  (int) fd,
+		  mode & ERL_NIF_SELECT_READ ? " READ" : "",
+		  mode & ERL_NIF_SELECT_WRITE ? " WRITE" : "",
+		  mode & ERL_NIF_SELECT_STOP ? " STOP" : "",
+		  resource->type->module,
+                  resource->type->name,
+                  ref);
+}
+
+
+static void
+drv_select_steal(ErlDrvPort ix, ErtsDrvEventState *state, int mode, int on)
 {
     if (need2steal(state, mode)) {
 	erts_dsprintf_buf_t *dsbufp = erts_create_logger_dsbuf();
-	print_select_op(dsbufp, ix, state->fd, mode, on);
+	print_drv_select_op(dsbufp, ix, state->fd, mode, on);
+	steal(dsbufp, state, mode);
+	erts_send_error_to_logger_nogl(dsbufp);
+    }
+}
+
+static void
+nif_select_steal(ErtsDrvEventState *state, int mode,
+                 ErtsResource* resource, Eterm ref)
+{
+    if (need2steal(state, mode)) {
+	erts_dsprintf_buf_t *dsbufp = erts_create_logger_dsbuf();
+	print_nif_select_op(dsbufp, state->fd, mode, resource, ref);
 	steal(dsbufp, state, mode);
 	erts_send_error_to_logger_nogl(dsbufp);
     }
@@ -1370,14 +1364,24 @@ large_fd_error_common(erts_dsprintf_buf_t *dsbufp, ErtsSysFdType fd)
 {
     erts_dsprintf(dsbufp,
 		  "fd=%d is larger than the largest allowed fd=%d\n",
-		  (int) fd, max_fds - 1);
+		  (int) fd, drv_ev_state.max_fds - 1);
 }
 
 static void
-select_large_fd_error(ErlDrvPort ix, ErtsSysFdType fd, int mode, int on)
+drv_select_large_fd_error(ErlDrvPort ix, ErtsSysFdType fd, int mode, int on)
 {
     erts_dsprintf_buf_t *dsbufp = erts_create_logger_dsbuf();
-    print_select_op(dsbufp, ix, fd, mode, on);
+    print_drv_select_op(dsbufp, ix, fd, mode, on);
+    erts_dsprintf(dsbufp, "failed: ");
+    large_fd_error_common(dsbufp, fd);
+    erts_send_error_to_logger_nogl(dsbufp);
+}
+static void
+nif_select_large_fd_error(ErtsSysFdType fd, int mode,
+                          ErtsResource* resource, Eterm ref)
+{
+    erts_dsprintf_buf_t *dsbufp = erts_create_logger_dsbuf();
+    print_nif_select_op(dsbufp, fd, mode, resource, ref);
     erts_dsprintf(dsbufp, "failed: ");
     large_fd_error_common(dsbufp, fd);
     erts_send_error_to_logger_nogl(dsbufp);
@@ -1387,97 +1391,87 @@ select_large_fd_error(ErlDrvPort ix, ErtsSysFdType fd, int mode, int on)
 
 
 static void
-steal_pending_stop_select(erts_dsprintf_buf_t *dsbufp, ErlDrvPort ix,
-			  ErtsDrvEventState *state, int mode, int on)
+steal_pending_stop_use(erts_dsprintf_buf_t *dsbufp, ErlDrvPort ix,
+                       ErtsDrvEventState *state, int mode, int on)
 {
+    int cancel = 0;
     ASSERT(state->type == ERTS_EV_TYPE_STOP_USE);
-    erts_dsprintf(dsbufp, "failed: fd=%d (re)selected before stop_select "
-		          "was called for driver %s\n",
-		  (int) GET_FD(state->fd), state->driver.drv_ptr->name);
-    erts_send_error_to_logger_nogl(dsbufp);
 
     if (on) {
 	/* Either fd-owner changed its mind about closing
 	 * or closed fd before stop_select callback and fd is now reused.
 	 * In either case stop_select should not be called.
-	 */	    
-	state->type = ERTS_EV_TYPE_NONE;
-	state->flags &= ~ERTS_EV_FLAG_USED;
-	if (state->driver.drv_ptr->handle) {
-	    erts_ddll_dereference_driver(state->driver.drv_ptr->handle);
-	}
-	state->driver.drv_ptr = NULL;
+	 */
+        cancel = 1;
     }
     else if ((mode & ERL_DRV_USE_NO_CALLBACK) == ERL_DRV_USE) {
 	Port *prt = erts_drvport2port(ix);
-	erts_driver_t* drv_ptr = prt != ERTS_INVALID_ERL_DRV_PORT ? prt->drv_ptr : NULL;
-	if (drv_ptr && drv_ptr != state->driver.drv_ptr) {
-	    /* Some other driver wants the stop_select callback */
-	    if (state->driver.drv_ptr->handle) {
-		erts_ddll_dereference_driver(state->driver.drv_ptr->handle);
-	    }
-	    if (drv_ptr->handle) {
-		erts_ddll_reference_referenced_driver(drv_ptr->handle);
-	    }
-	    state->driver.drv_ptr = drv_ptr;
-	}    
+	if (prt == ERTS_INVALID_ERL_DRV_PORT
+            || prt->drv_ptr != state->driver.stop.drv_ptr) {
+	    /* Some other driver or nif wants the stop_select callback */
+            cancel = 1;
+        }
+    }
+
+    if (cancel) {
+        erts_dsprintf(dsbufp, "called before stop_select was called for driver '%s'\n",
+                      state->driver.stop.drv_ptr->name);
+        if (state->driver.stop.drv_ptr->handle) {
+            erts_ddll_dereference_driver(state->driver.stop.drv_ptr->handle);
+        }
+        state->type = ERTS_EV_TYPE_NONE;
+        state->flags = 0;
+        state->driver.stop.drv_ptr = NULL;
     }
-
+    else {
+        erts_dsprintf(dsbufp, "ignored repeated call\n");
+    }
+    erts_send_error_to_logger_nogl(dsbufp);
 }
 
-
-#if ERTS_CIO_HAVE_DRV_EVENT
-
 static void
-print_event_op(erts_dsprintf_buf_t *dsbufp,
-	       ErlDrvPort ix, ErtsSysFdType fd, ErlDrvEventData event_data)
+steal_pending_stop_nif(erts_dsprintf_buf_t *dsbufp, ErtsResource* resource,
+                       ErtsDrvEventState *state, int mode, int on)
 {
-    Port *pp = erts_drvport2port(ix);
-    erts_dsprintf(dsbufp, "driver_event(%p, %d, ", ix, (int) fd);
-    if (!event_data)
-	erts_dsprintf(dsbufp, "NULL");
-    else
-	erts_dsprintf(dsbufp, "{0x%x, 0x%x}",
-		      (unsigned int) event_data->events,
-		      (unsigned int) event_data->revents);
-    erts_dsprintf(dsbufp, ") by ");
-    if (pp != ERTS_INVALID_ERL_DRV_PORT)
-	print_driver_name(dsbufp, pp->common.id);
-    erts_dsprintf(dsbufp, "driver %T ", pp != ERTS_INVALID_ERL_DRV_PORT ? pp->common.id : NIL);
-}
+    int cancel = 0;
 
-static void
-event_steal(ErlDrvPort ix, ErtsDrvEventState *state, ErlDrvEventData event_data)
-{
-    if (need2steal(state, ERL_DRV_READ|ERL_DRV_WRITE)) {
-	erts_dsprintf_buf_t *dsbufp = erts_create_logger_dsbuf();
-	print_event_op(dsbufp, ix, state->fd, event_data);
-	steal(dsbufp, state, ERL_DRV_READ|ERL_DRV_WRITE);
-	erts_send_error_to_logger_nogl(dsbufp);
+    ASSERT(state->type == ERTS_EV_TYPE_STOP_NIF);
+    ASSERT(state->driver.stop.resource);
+
+    if (on) {
+        ASSERT(mode & (ERL_NIF_SELECT_READ | ERL_NIF_SELECT_WRITE));
+        /* Either fd-owner changed its mind about closing
+         * or closed fd before stop callback and fd is now reused.
+         * In either case, stop should not be called.
+         */
+        cancel = 1;
     }
-    else if (state->type == ERTS_EV_TYPE_DRV_SEL) {
-	ASSERT(state->flags & ERTS_EV_FLAG_USED);
-	deselect(state, 0);
+    else if ((mode & ERL_DRV_USE_NO_CALLBACK) == ERL_DRV_USE
+             && resource != state->driver.stop.resource) {
+        /* Some driver or other resource wants the stop callback */
+        cancel = 1;
     }
-}
 
-#ifdef ERTS_SYS_CONTINOUS_FD_NUMBERS
-static void
-event_large_fd_error(ErlDrvPort ix, ErtsSysFdType fd, ErlDrvEventData event_data)
-{
-    erts_dsprintf_buf_t *dsbufp = erts_create_logger_dsbuf();
-    print_event_op(dsbufp, ix, fd, event_data);
-    erts_dsprintf(dsbufp, "failed: ");
-    large_fd_error_common(dsbufp, fd);
+    if (cancel) {
+        ErlNifResourceType* rt = state->driver.stop.resource->type;
+        erts_dsprintf(dsbufp, "called before stop was called for NIF resource %T:%T\n",
+                      rt->module, rt->name);
+
+        enif_release_resource(state->driver.stop.resource->data);
+        state->type = ERTS_EV_TYPE_NONE;
+        state->flags = 0;
+        state->driver.stop.resource = NULL;
+    }
+    else {
+        erts_dsprintf(dsbufp, "ignored repeated call\n");
+    }
     erts_send_error_to_logger_nogl(dsbufp);
+
 }
-#endif
-#endif
 
 static ERTS_INLINE int
 io_task_schedule_allowed(ErtsDrvEventState *state,
-			 ErtsPortTaskType type,
-			 erts_aint_t current_cio_time)
+			 ErtsPortTaskType type)
 {
     ErtsIoTask *io_task;
 
@@ -1485,179 +1479,159 @@ io_task_schedule_allowed(ErtsDrvEventState *state,
     case ERTS_PORT_TASK_INPUT:
 	if (!state->driver.select)
 	    return 0;
-#if ERTS_CIO_HAVE_DRV_EVENT
-	if (state->driver.event)
-	    return 0;
-#endif
 	io_task = &state->driver.select->iniotask;
 	break;
     case ERTS_PORT_TASK_OUTPUT:
 	if (!state->driver.select)
 	    return 0;
-#if ERTS_CIO_HAVE_DRV_EVENT
-	if (state->driver.event)
-	    return 0;
-#endif
 	io_task = &state->driver.select->outiotask;
 	break;
-#if ERTS_CIO_HAVE_DRV_EVENT
-    case ERTS_PORT_TASK_EVENT:
-	if (!state->driver.event)
-	    return 0;
-	if (state->driver.select)
-	    return 0;
-	io_task = &state->driver.event->iotask;
-	break;
-#endif
     default:
 	ERTS_INTERNAL_ERROR("Invalid I/O-task type");
 	return 0;
     }
 
-    return !is_iotask_active(io_task, current_cio_time);
+    return !is_iotask_active(io_task);
 }
 
 static ERTS_INLINE void
-iready(Eterm id, ErtsDrvEventState *state, erts_aint_t current_cio_time)
+iready(Eterm id, ErtsDrvEventState *state)
 {
     if (io_task_schedule_allowed(state,
-				 ERTS_PORT_TASK_INPUT,
-				 current_cio_time)) {
+				 ERTS_PORT_TASK_INPUT)) {
 	ErtsIoTask *iotask = &state->driver.select->iniotask;
-	erts_smp_atomic_set_nob(&iotask->executed_time, current_cio_time);
 	if (erts_port_task_schedule(id,
 				    &iotask->task,
 				    ERTS_PORT_TASK_INPUT,
-				    (ErlDrvEvent) state->fd) != 0) {
+				    (ErlDrvEvent) state->fd,
+                                    state->flags & ERTS_EV_FLAG_IN_SCHEDULER) != 0) {
 	    stale_drv_select(id, state, ERL_DRV_READ);
-	}
-	add_active_fd(state->fd);
+	} else {
+            DEBUG_PRINT_FD("schedule ready_input(%T, %d)",
+                           state, id, state->fd);
+        }
     }
 }
 
 static ERTS_INLINE void
-oready(Eterm id, ErtsDrvEventState *state, erts_aint_t current_cio_time)
+oready(Eterm id, ErtsDrvEventState *state)
 {
     if (io_task_schedule_allowed(state,
-				 ERTS_PORT_TASK_OUTPUT,
-				 current_cio_time)) {
+				 ERTS_PORT_TASK_OUTPUT)) {
 	ErtsIoTask *iotask = &state->driver.select->outiotask;
-	erts_smp_atomic_set_nob(&iotask->executed_time, current_cio_time);
 	if (erts_port_task_schedule(id,
 				    &iotask->task,
 				    ERTS_PORT_TASK_OUTPUT,
-				    (ErlDrvEvent) state->fd) != 0) {
+				    (ErlDrvEvent) state->fd,
+                                    0) != 0) {
 	    stale_drv_select(id, state, ERL_DRV_WRITE);
-	}
-	add_active_fd(state->fd);
+	} else {
+            DEBUG_PRINT_FD("schedule ready_output(%T, %d)", state, id, state->fd);
+        }
     }
 }
 
-#if ERTS_CIO_HAVE_DRV_EVENT
 static ERTS_INLINE void
-eready(Eterm id, ErtsDrvEventState *state, ErlDrvEventData event_data,
-       erts_aint_t current_cio_time)
+send_event_tuple(struct erts_nif_select_event* e, ErtsResource* resource,
+                 Eterm event_atom)
 {
-    if (io_task_schedule_allowed(state,
-				 ERTS_PORT_TASK_EVENT,
-				 current_cio_time)) {
-	ErtsIoTask *iotask = &state->driver.event->iotask;
-	erts_smp_atomic_set_nob(&iotask->executed_time, current_cio_time);
-	if (erts_port_task_schedule(id,
-				    &iotask->task,
-				    ERTS_PORT_TASK_EVENT,
-				    (ErlDrvEvent) state->fd,
-				    event_data) != 0) {
-	    stale_drv_select(id, state, 0);
-	}
-	add_active_fd(state->fd);
+    Process* rp = erts_proc_lookup(e->pid);
+    ErtsProcLocks rp_locks = 0;
+    ErtsMessage* mp;
+    ErlOffHeap* ohp;
+    ErtsBinary* bin;
+    Eterm* hp;
+    Uint hsz;
+    Eterm resource_term, ref_term, tuple;
+
+    if (!rp) {
+        return;
     }
-}
-#endif
 
-static void bad_fd_in_pollset( ErtsDrvEventState *, Eterm, Eterm, ErtsPollEvents);
+    bin = ERTS_MAGIC_BIN_FROM_UNALIGNED_DATA(resource);
 
-#ifdef ERTS_POLL_NEED_ASYNC_INTERRUPT_SUPPORT
-void
-ERTS_CIO_EXPORT(erts_check_io_async_sig_interrupt)(void)
-{
-    ERTS_CIO_POLL_AS_INTR(pollset.ps);
+     /* {select, Resource, Ref, EventAtom} */
+    if (is_value(e->immed)) {
+        hsz = 5 + ERTS_MAGIC_REF_THING_SIZE;
+    }
+    else {
+        hsz = 5 + ERTS_MAGIC_REF_THING_SIZE + ERTS_REF_THING_SIZE;
+    }
+
+    mp = erts_alloc_message_heap(rp, &rp_locks, hsz, &hp, &ohp);
+
+    resource_term = erts_mk_magic_ref(&hp, ohp, &bin->binary);
+    if (is_value(e->immed)) {
+        ASSERT(is_immed(e->immed));
+        ref_term = e->immed;
+    }
+    else {
+        write_ref_thing(hp, e->refn[0], e->refn[1], e->refn[2]);
+        ref_term = make_internal_ref(hp);
+        hp += ERTS_REF_THING_SIZE;
+    }
+    tuple = TUPLE4(hp, am_select, resource_term, ref_term, event_atom);
+
+    erts_queue_message(rp, rp_locks, mp, tuple, am_system);
+
+    if (rp_locks)
+        erts_proc_unlock(rp, rp_locks);
 }
-#endif
+
+static void bad_fd_in_pollset(ErtsDrvEventState *, Eterm inport, Eterm outport);
 
 void
-ERTS_CIO_EXPORT(erts_check_io_interrupt)(int set)
+erts_check_io_interrupt(ErtsPollThread *psi, int set)
 {
-    ERTS_CIO_POLL_INTR(pollset.ps, set);
+    if (psi) {
+#if ERTS_POLL_USE_FALLBACK
+        if (psi->ps == get_fallback_pollset()) {
+            erts_poll_interrupt_flbk(psi->ps, set);
+            return;
+        }
+#endif
+        erts_poll_interrupt(psi->ps, set);
+    }
 }
 
-void
-ERTS_CIO_EXPORT(erts_check_io_interrupt_timed)(int set,
-					       ErtsMonotonicTime timeout_time)
-{
-    ERTS_CIO_POLL_INTR_TMD(pollset.ps, set, timeout_time);
+ErtsPollThread *
+erts_create_pollset_thread(int id, ErtsThrPrgrData *tpd) {
+    psiv[id].tpd = tpd;
+    return psiv+id;
 }
 
 void
-ERTS_CIO_EXPORT(erts_check_io)(int do_wait)
+erts_check_io(ErtsPollThread *psi, ErtsMonotonicTime timeout_time)
 {
-    ErtsPollResFd *pollres;
     int pollres_len;
-    ErtsMonotonicTime timeout_time;
     int poll_ret, i;
-    erts_aint_t current_cio_time;
-    ErtsSchedulerData *esdp = erts_get_scheduler_data();
-
-    ASSERT(esdp);
+    ERTS_MSACC_PUSH_AND_SET_STATE(ERTS_MSACC_STATE_CHECK_IO);
 
  restart:
 
-#ifdef ERTS_BREAK_REQUESTED
-    if (ERTS_BREAK_REQUESTED)
-	erts_do_break_handling();
-#endif
-
-    /* Figure out timeout value */
-    timeout_time = (do_wait
-		    ? erts_check_next_timeout_time(esdp)
-		    : ERTS_POLL_NO_TIMEOUT /* poll only */);
-
-    /*
-     * No need for an atomic inc op when incrementing
-     * erts_check_io_time, since only one thread can
-     * check io at a time.
-     */
-    current_cio_time = erts_smp_atomic_read_dirty(&erts_check_io_time);
-    current_cio_time++;
-    erts_smp_atomic_set_relb(&erts_check_io_time, current_cio_time);
-
-    check_cleanup_active_fds(current_cio_time);
-
 #ifdef ERTS_ENABLE_LOCK_CHECK
     erts_lc_check_exact(NULL, 0); /* No locks should be locked */
 #endif
 
-    pollres_len = erts_smp_atomic32_read_dirty(&pollset.active_fd.no) + ERTS_CHECK_IO_POLL_RES_LEN;
+    pollres_len = psi->pollres_len;
 
-    pollres = erts_alloc(ERTS_ALC_T_TMP, sizeof(ErtsPollResFd)*pollres_len);
+#if ERTS_POLL_USE_FALLBACK
+    if (psi->ps == get_fallback_pollset()) {
 
-    erts_smp_atomic_set_nob(&pollset.in_poll_wait, 1);
+        poll_ret = erts_poll_wait_flbk(psi->ps, psi->pollres, &pollres_len, psi->tpd, timeout_time);
 
-    poll_ret = ERTS_CIO_POLL_WAIT(pollset.ps, pollres, &pollres_len, timeout_time);
+    } else
+#endif
+    {
+        poll_ret = erts_poll_wait(psi->ps, psi->pollres, &pollres_len, psi->tpd, timeout_time);
+    }
 
 #ifdef ERTS_ENABLE_LOCK_CHECK
     erts_lc_check_exact(NULL, 0); /* No locks should be locked */
 #endif
 
-#ifdef ERTS_BREAK_REQUESTED
-    if (ERTS_BREAK_REQUESTED)
-	erts_do_break_handling();
-#endif
-
     if (poll_ret != 0) {
-	erts_smp_atomic_set_nob(&pollset.in_poll_wait, 0);
-	forget_removed(&pollset);
-	erts_free(ERTS_ALC_T_TMP, pollres);
+
 	if (poll_ret == EAGAIN) {
 	    goto restart;
 	}
@@ -1673,130 +1647,227 @@ ERTS_CIO_EXPORT(erts_check_io)(int do_wait)
 			  erl_errno_id(poll_ret), poll_ret);
 	    erts_send_error_to_logger_nogl(dsbufp);
 	}
+        ERTS_MSACC_POP_STATE();
 	return;
     }
 
     for (i = 0; i < pollres_len; i++) {
 
-	ErtsSysFdType fd = (ErtsSysFdType) pollres[i].fd;
+        erts_driver_t* drv_ptr = NULL;
+        ErtsResource* resource = NULL;
+        ErtsDrvSelectDataState *free_select = NULL;
+        ErtsNifSelectDataState *free_nif = NULL;
+	ErtsSysFdType fd = (ErtsSysFdType) ERTS_POLL_RES_GET_FD(&psi->pollres[i]);
 	ErtsDrvEventState *state;
+        ErtsPollEvents revents = ERTS_POLL_RES_GET_EVTS(&psi->pollres[i]);
 
-	erts_smp_mtx_lock(fd_mtx(fd));
+        /* The fd will be set to -1 if a pollset internal fd was triggered
+           that was determined to be too expensive to remove from the result.
+        */
+        if (fd == -1) continue;
+
+	erts_mtx_lock(fd_mtx(fd));
+
+	state = get_drv_ev_state(fd);
 
-#ifdef ERTS_SYS_CONTINOUS_FD_NUMBERS
-	state = &drv_ev_state[ (int) fd];
-#else
-	state = hash_get_drv_ev_state(fd);
 	if (!state) {
-	    goto next_pollres;
+            erts_mtx_unlock(fd_mtx(fd));
+            continue;
 	}
-#endif
 
-	/* Skip this fd if it was removed from pollset */
-	if (is_removed(state)) {
-	    goto next_pollres;
-	}
+        DEBUG_PRINT_FD("triggered %s", state, ev2str(revents));
+
+        if (revents & ERTS_POLL_EV_ERR) {
+            /*
+             * Handle error events by triggering all in/out events
+             * that has been selected on.
+             * We *do not* want to call a callback that corresponds
+             * to an event not selected.
+             */
+            revents = state->active_events;
+            state->active_events = 0;
+
+            if (state->flags & ERTS_EV_FLAG_IN_SCHEDULER) {
+                erts_io_control(state, ERTS_POLL_OP_MOD, 0);
+                state->flags &= ~ERTS_EV_FLAG_IN_SCHEDULER;
+            }
+        } else {
+
+            /* Disregard any events that are not active at the moment,
+               for instance this could happen if the driver/nif does
+               select/deselect in rapid succession. */
+            revents &= state->active_events | ERTS_POLL_EV_NVAL;
+
+            if (psi->ps != get_scheduler_pollset(fd) || !ERTS_POLL_USE_SCHEDULER_POLLING) {
+                ErtsPollEvents reactive_events;
+                state->active_events &= ~revents;
+
+                reactive_events = state->active_events;
+
+                if (state->flags & ERTS_EV_FLAG_IN_SCHEDULER)
+                    reactive_events &= ~ERTS_POLL_EV_IN;
+
+                /* Reactivate the poll op if there are still active events */
+                if (reactive_events) {
+                    ErtsPollEvents new_events;
+                    DEBUG_PRINT_FD("re-enable %s", state, ev2str(reactive_events));
+
+                    new_events = erts_io_control(state, ERTS_POLL_OP_MOD, reactive_events);
+
+                    /* Unable to re-enable the fd, signal all callbacks */
+                    if (new_events & (ERTS_POLL_EV_ERR|ERTS_POLL_EV_NVAL)) {
+                        revents |= reactive_events;
+                        state->active_events &= ~reactive_events;
+                    }
+                }
+            }
+        }
 
 	switch (state->type) {
 	case ERTS_EV_TYPE_DRV_SEL: { /* Requested via driver_select()... */
-	    ErtsPollEvents revents;
-	    ErtsPollEvents revent_mask;
-
-	    revent_mask = ~(ERTS_POLL_EV_IN|ERTS_POLL_EV_OUT);
-	    revent_mask |= state->events;
-	    revents = pollres[i].events & revent_mask;
-
-	    if (revents & ERTS_POLL_EV_ERR) {
-		/*
-		 * Let the driver handle the error condition. Only input,
-		 * only output, or nothing might have been selected.
-		 * We *do not* want to call a callback that corresponds
-		 * to an event not selected. revents might give us a clue
-		 * on which one to call.
-		 */ 
-		if ((revents & ERTS_POLL_EV_IN)
-		    || (!(revents & ERTS_POLL_EV_OUT)
-			&& state->events & ERTS_POLL_EV_IN)) {
-		    iready(state->driver.select->inport, state, current_cio_time);
-		}
-		else if (state->events & ERTS_POLL_EV_OUT) {
-		    oready(state->driver.select->outport, state, current_cio_time);
-		}
-	    }
-	    else if (revents & (ERTS_POLL_EV_IN|ERTS_POLL_EV_OUT)) {
+
+            if (revents & (ERTS_POLL_EV_IN|ERTS_POLL_EV_OUT)) {
 		if (revents & ERTS_POLL_EV_OUT) {
-		    oready(state->driver.select->outport, state, current_cio_time);
+		    oready(state->driver.select->outport, state);
 		}
 		/* Someone might have deselected input since revents
 		   was read (true also on the non-smp emulator since
 		   oready() may have been called); therefore, update
 		   revents... */
-		revents &= ~(~state->events & ERTS_POLL_EV_IN);
+                revents &= state->events;
 		if (revents & ERTS_POLL_EV_IN) {
-		    iready(state->driver.select->inport, state, current_cio_time);
+		    iready(state->driver.select->inport, state);
 		}
 	    }
 	    else if (revents & ERTS_POLL_EV_NVAL) {
 		bad_fd_in_pollset(state,
-				  state->driver.select->inport,
-				  state->driver.select->outport,
-				  state->events);
-		add_active_fd(state->fd);
-	    }
-	    break;
-	}
-
-#if ERTS_CIO_HAVE_DRV_EVENT
-	case ERTS_EV_TYPE_DRV_EV: { /* Requested via driver_event()... */
-	    ErlDrvEventData event_data;
-	    ErtsPollEvents revents;
-	    ASSERT(state->driver.event);
-	    ASSERT(state->driver.event->data);
-	    event_data = state->driver.event->data;
-	    revents = pollres[i].events;
-	    revents &= ~state->driver.event->removed_events;
-
-	    if (revents) {
-		event_data->events = state->events;
-		event_data->revents = revents;
-		eready(state->driver.event->port, state, event_data, current_cio_time);
+                                  state->driver.select->inport,
+                                  state->driver.select->outport);
+                check_fd_cleanup(state, &free_select, &free_nif);
 	    }
 	    break;
 	}
-#endif
 
+        case ERTS_EV_TYPE_NIF: { /* Requested via enif_select()... */
+            struct erts_nif_select_event in = {NIL};
+            struct erts_nif_select_event out = {NIL};
+            ErtsResource* resource = NULL;
+
+            if (revents & (ERTS_POLL_EV_IN|ERTS_POLL_EV_OUT)) {
+                if (revents & ERTS_POLL_EV_OUT) {
+                    if (is_not_nil(state->driver.nif->out.pid)) {
+                        out = state->driver.nif->out;
+                        resource = state->driver.stop.resource;
+                        state->driver.nif->out.pid = NIL;
+                    }
+                }
+                if (revents & ERTS_POLL_EV_IN) {
+                    if (is_not_nil(state->driver.nif->in.pid)) {
+                        in = state->driver.nif->in;
+                        resource = state->driver.stop.resource;
+                        state->driver.nif->in.pid = NIL;
+                    }
+                }
+                state->events &= ~revents;
+            }
+            else if (revents & ERTS_POLL_EV_NVAL) {
+                bad_fd_in_pollset(state, NIL, NIL);
+                check_fd_cleanup(state, &free_select, &free_nif);
+            }
+
+            erts_mtx_unlock(fd_mtx(fd));
+
+            if (is_not_nil(in.pid)) {
+                send_event_tuple(&in, resource, am_ready_input);
+            }
+            if (is_not_nil(out.pid)) {
+                send_event_tuple(&out, resource, am_ready_output);
+            }
+            continue;
+        }
+
+        case ERTS_EV_TYPE_STOP_NIF: {
+            resource = state->driver.stop.resource;
+            state->type = ERTS_EV_TYPE_NONE;
+            goto case_ERTS_EV_TYPE_NONE;
+        }
+
+        case ERTS_EV_TYPE_STOP_USE: {
+#if ERTS_POLL_USE_FALLBACK
+            ASSERT(psi->ps == get_fallback_pollset());
+#endif
+            drv_ptr = state->driver.stop.drv_ptr;
+            state->type = ERTS_EV_TYPE_NONE;
+            /* fallthrough */
 	case ERTS_EV_TYPE_NONE: /* Deselected ... */
+        case_ERTS_EV_TYPE_NONE:
+            ASSERT(!state->events && !state->active_events && !state->flags);
+            check_fd_cleanup(state, &free_select, &free_nif);
 	    break;
+        }
 
 	default: { /* Error */
 	    erts_dsprintf_buf_t *dsbufp;
 	    dsbufp = erts_create_logger_dsbuf();
 	    erts_dsprintf(dsbufp,
 			  "Invalid event request type for fd in erts_poll()! "
-			  "fd=%d, event request type=%sd\n", (int) state->fd,
+			  "fd=%d, event request type=%d\n", (int) state->fd,
 			  (int) state->type);
 	    ASSERT(0);
 	    deselect(state, 0);
-	    add_active_fd(state->fd);
 	    break;
 	}
 	}
 
-	next_pollres:;
-#ifdef ERTS_SMP
-	erts_smp_mtx_unlock(fd_mtx(fd));
-#endif
-    }
+	erts_mtx_unlock(fd_mtx(fd));
 
-    erts_smp_atomic_set_nob(&pollset.in_poll_wait, 0);
-    erts_free(ERTS_ALC_T_TMP, pollres);
-    forget_removed(&pollset);
+        if (drv_ptr) {
+            int was_unmasked = erts_block_fpe();
+            DTRACE1(driver_stop_select, drv_ptr->name);
+            LTTNG1(driver_stop_select, drv_ptr->name);
+            (*drv_ptr->stop_select)((ErlDrvEvent) fd, NULL);
+            erts_unblock_fpe(was_unmasked);
+            if (drv_ptr->handle) {
+		erts_ddll_dereference_driver(drv_ptr->handle);
+	    }
+        }
+        if (resource) {
+            erts_resource_stop(resource, (ErlNifEvent)fd, 0);
+            enif_release_resource(resource->data);
+        }
+        if (free_select)
+            free_drv_select_data(free_select);
+        if (free_nif)
+            free_nif_select_data(free_nif);
+    }
+
+    /* The entire pollres array was filled with events,
+     * grow it for the next call. We do this for two reasons:
+     * 1. Pulling out more events in on go will increase throughput
+     * 2. If the polling implementation is not fair, this will make
+     *    sure that we get all fds that we can. i.e. if 12 fds are
+     *    constantly active, but we only have a pollres_len of 10,
+     *    two of the fds may never be triggered depending on what the
+     *    kernel decides to do.
+     **/
+    if (pollres_len == psi->pollres_len) {
+        int ev_state_len = drv_ev_state_len();
+        erts_free(ERTS_ALC_T_POLLSET, psi->pollres);
+        psi->pollres_len *= 2;
+        /* Never grow it larger than the current drv_ev_state.len size */
+        if (psi->pollres_len > ev_state_len)
+            psi->pollres_len = ev_state_len;
+        psi->pollres = erts_alloc(ERTS_ALC_T_POLLSET,
+                                  sizeof(ErtsPollResFd) * psi->pollres_len);
+    }
+
+    ERTS_MSACC_POP_STATE();
 }
 
 static void
-bad_fd_in_pollset(ErtsDrvEventState *state, Eterm inport, 
-		  Eterm outport, ErtsPollEvents events)
+bad_fd_in_pollset(ErtsDrvEventState *state, Eterm inport, Eterm outport)
 {
+    ErtsPollEvents events = state->events;
     erts_dsprintf_buf_t *dsbufp = erts_create_logger_dsbuf();
 
     if (events & (ERTS_POLL_EV_IN|ERTS_POLL_EV_OUT)) {
@@ -1820,27 +1891,36 @@ bad_fd_in_pollset(ErtsDrvEventState *state, Eterm inport,
 	erts_dsprintf(dsbufp,
 		      "Bad %s fd in erts_poll()! fd=%d, ",
 		      io_str, (int) state->fd);
-	if (is_nil(port)) {
-	    ErtsPortNames *ipnp = erts_get_port_names(inport, ERTS_INVALID_ERL_DRV_PORT);
-	    ErtsPortNames *opnp = erts_get_port_names(outport, ERTS_INVALID_ERL_DRV_PORT);
-	    erts_dsprintf(dsbufp, "ports=%T/%T, drivers=%s/%s, names=%s/%s\n",
-			  is_nil(inport) ? am_undefined : inport,
-			  is_nil(outport) ? am_undefined : outport,
-			  ipnp->driver_name ? ipnp->driver_name : "<unknown>",
-			  opnp->driver_name ? opnp->driver_name : "<unknown>",
-			  ipnp->name ? ipnp->name : "<unknown>",
-			  opnp->name ? opnp->name : "<unknown>");
-	    erts_free_port_names(ipnp);
-	    erts_free_port_names(opnp);
-	}
-	else {
-	    ErtsPortNames *pnp = erts_get_port_names(port, ERTS_INVALID_ERL_DRV_PORT);
-	    erts_dsprintf(dsbufp, "port=%T, driver=%s, name=%s\n",
-			  is_nil(port) ? am_undefined : port,
-			  pnp->driver_name ? pnp->driver_name : "<unknown>",
-			  pnp->name ? pnp->name : "<unknown>");
-	    erts_free_port_names(pnp);
-	}
+        if (state->type == ERTS_EV_TYPE_DRV_SEL) {
+            if (is_nil(port)) {
+                ErtsPortNames *ipnp = erts_get_port_names(inport, ERTS_INVALID_ERL_DRV_PORT);
+                ErtsPortNames *opnp = erts_get_port_names(outport, ERTS_INVALID_ERL_DRV_PORT);
+                erts_dsprintf(dsbufp, "ports=%T/%T, drivers=%s/%s, names=%s/%s\n",
+                              is_nil(inport) ? am_undefined : inport,
+                              is_nil(outport) ? am_undefined : outport,
+                              ipnp->driver_name ? ipnp->driver_name : "<unknown>",
+                              opnp->driver_name ? opnp->driver_name : "<unknown>",
+                              ipnp->name ? ipnp->name : "<unknown>",
+                              opnp->name ? opnp->name : "<unknown>");
+                erts_free_port_names(ipnp);
+                erts_free_port_names(opnp);
+            }
+            else {
+                ErtsPortNames *pnp = erts_get_port_names(port, ERTS_INVALID_ERL_DRV_PORT);
+                erts_dsprintf(dsbufp, "port=%T, driver=%s, name=%s\n",
+                              is_nil(port) ? am_undefined : port,
+                              pnp->driver_name ? pnp->driver_name : "<unknown>",
+                              pnp->name ? pnp->name : "<unknown>");
+                erts_free_port_names(pnp);
+            }
+        }
+        else {
+            ErlNifResourceType* rt;
+            ASSERT(state->type == ERTS_EV_TYPE_NIF);
+            ASSERT(state->driver.stop.resource);
+            rt = state->driver.stop.resource->type;
+            erts_dsprintf(dsbufp, "resource={%T,%T}\n", rt->module, rt->name);
+        }
     }
     else {
 	erts_dsprintf(dsbufp, "Bad fd in erts_poll()! fd=%d\n", (int) state->fd);
@@ -1875,16 +1955,16 @@ static int drv_ev_state_cmp(void *des1, void *des2)
 static void *drv_ev_state_alloc(void *des_tmpl)
 {
     ErtsDrvEventState *evstate;
-    erts_smp_spin_lock(&state_prealloc_lock);
-    if (state_prealloc_first == NULL) {
-	erts_smp_spin_unlock(&state_prealloc_lock);
+    erts_spin_lock(&drv_ev_state.prealloc_lock);
+    if (drv_ev_state.prealloc_first == NULL) {
+	erts_spin_unlock(&drv_ev_state.prealloc_lock);
 	evstate = (ErtsDrvEventState *) 
 	    erts_alloc(ERTS_ALC_T_DRV_EV_STATE, sizeof(ErtsDrvEventState));
     } else {
-	evstate = state_prealloc_first;
-	state_prealloc_first = (ErtsDrvEventState *) evstate->hb.next;
-	--num_state_prealloc;
-	erts_smp_spin_unlock(&state_prealloc_lock);
+	evstate = drv_ev_state.prealloc_first;
+	drv_ev_state.prealloc_first = (ErtsDrvEventState *) evstate->hb.next;
+	--drv_ev_state.num_prealloc;
+	erts_spin_unlock(&drv_ev_state.prealloc_lock);
     }
     /* XXX: Already valid data if prealloced, could ignore template! */
     *evstate = *((ErtsDrvEventState *) des_tmpl);
@@ -1894,59 +1974,214 @@ static void *drv_ev_state_alloc(void *des_tmpl)
 
 static void drv_ev_state_free(void *des)
 {
-    erts_smp_spin_lock(&state_prealloc_lock);
-    ((ErtsDrvEventState *) des)->hb.next = &state_prealloc_first->hb;
-    state_prealloc_first = (ErtsDrvEventState *) des;
-    ++num_state_prealloc;
-    erts_smp_spin_unlock(&state_prealloc_lock);
+    erts_spin_lock(&drv_ev_state.prealloc_lock);
+    ((ErtsDrvEventState *) des)->hb.next = &drv_ev_state.prealloc_first->hb;
+    drv_ev_state.prealloc_first = (ErtsDrvEventState *) des;
+    ++drv_ev_state.num_prealloc;
+    erts_spin_unlock(&drv_ev_state.prealloc_lock);
 }
 #endif
 
-void
-ERTS_CIO_EXPORT(erts_init_check_io)(void)
+#define ERTS_MAX_NO_OF_POLL_THREADS ERTS_MAX_NO_OF_SCHEDULERS
+
+static char *
+get_arg(char* rest, char** argv, int* ip)
 {
-    erts_smp_atomic_init_nob(&erts_check_io_time, 0);
-    erts_smp_atomic_init_nob(&pollset.in_poll_wait, 0);
-
-    ERTS_CIO_POLL_INIT();
-    pollset.ps = ERTS_CIO_NEW_POLLSET();
-
-    pollset.active_fd.six = 0;
-    pollset.active_fd.eix = 0;
-    erts_smp_atomic32_init_nob(&pollset.active_fd.no, 0);
-    pollset.active_fd.size = ERTS_ACTIVE_FD_INC;
-    pollset.active_fd.array = erts_alloc(ERTS_ALC_T_ACTIVE_FD_ARR,
-					 sizeof(ErtsSysFdType)*ERTS_ACTIVE_FD_INC);
-#ifdef DEBUG
-    {
-	int i;
-	for (i = 0; i < ERTS_ACTIVE_FD_INC; i++)
-	    pollset.active_fd.array[i] = ERTS_SYS_FD_INVALID;
+    int i = *ip;
+    if (*rest == '\0') {
+	if (argv[i+1] == NULL) {
+	    erts_fprintf(stderr, "too few arguments\n");
+	    erts_usage();
+	}
+        argv[i++] = NULL;
+        rest = argv[i];
     }
+    argv[i] = NULL;
+    *ip = i;
+    return rest;
+}
+
+static void
+parse_args(int *argc, char **argv, int concurrent_waiters)
+{
+    int i = 0, j;
+    int no_pollsets = 0, no_poll_threads = 0,
+        no_pollsets_percentage = 0,
+        no_poll_threads_percentage = 0;
+    ASSERT(argc && argv);
+    while (i < *argc) {
+	if(argv[i][0] == '-') {
+	    switch (argv[i][1]) {
+            case 'I': {
+                if (strncmp(argv[i]+2, "Ot", 2) == 0) {
+                    char *arg = get_arg(argv[i]+4, argv, &i);
+                    if (sscanf(arg, "%d", &no_poll_threads) != 1 ||
+                        no_poll_threads < 1 ||
+                        ERTS_MAX_NO_OF_POLL_THREADS < no_poll_threads) {
+                        erts_fprintf(stderr,"bad I/O poll threads number: %s\n", arg);
+                        erts_usage();
+                    }
+                } else if (strncmp(argv[i]+2, "Op", 3) == 0) {
+                    char *arg = get_arg(argv[i]+4, argv, &i);
+                    if (sscanf(arg, "%d", &no_pollsets) != 1 ||
+                        no_pollsets < 1) {
+                        erts_fprintf(stderr,"bad I/O pollset number: %s\n", arg);
+                        erts_usage();
+                    }
+                } else if (strncmp(argv[i]+2, "OPt", 4) == 0) {
+                    char *arg = get_arg(argv[i]+5, argv, &i);
+                    if (sscanf(arg, "%d", &no_poll_threads_percentage) != 1 ||
+                        no_poll_threads_percentage < 0 ||
+                        no_poll_threads_percentage > 100) {
+                        erts_fprintf(stderr,"bad I/O poll thread percentage number: %s\n", arg);
+                        erts_usage();
+                    }
+                } else if (strncmp(argv[i]+2, "OPp", 4) == 0) {
+                    char *arg = get_arg(argv[i]+5, argv, &i);
+                    if (sscanf(arg, "%d", &no_pollsets_percentage) != 1 ||
+                        no_pollsets_percentage < 0 ||
+                        no_pollsets_percentage > 100) {
+                        erts_fprintf(stderr,"bad I/O pollset percentage number: %s\n", arg);
+                        erts_usage();
+                    }
+                } else {
+                    break;
+                }
+                break;
+            }
+            case 'K':
+                (void)get_arg(argv[i]+2, argv, &i);
+                break;
+            case '-':
+                goto args_parsed;
+            default:
+                break;
+            }
+        }
+        i++;
+    }
+
+args_parsed:
+
+    if (!concurrent_waiters) {
+        no_pollsets = no_poll_threads;
+        no_pollsets_percentage = 100;
+    }
+
+    if (no_poll_threads == 0) {
+        if (no_poll_threads_percentage == 0)
+            no_poll_threads = 1; /* This is the default */
+        else {
+            no_poll_threads = erts_no_schedulers * no_poll_threads_percentage / 100;
+            if (no_poll_threads < 1)
+                no_poll_threads = 1;
+        }
+    }
+
+    if (no_pollsets == 0) {
+        if (no_pollsets_percentage == 0)
+            no_pollsets = 1; /* This is the default */
+        else {
+            no_pollsets = no_poll_threads * no_pollsets_percentage / 100;
+            if (no_pollsets < 1)
+                no_pollsets = 1;
+        }
+    }
+
+    if (no_poll_threads < no_pollsets) {
+        erts_fprintf(stderr,
+                     "number of IO poll threads has to be greater or equal to "
+                     "the number of \nIO pollsets. Current values are set to: \n"
+                     "  -IOt %d -IOp %d\n",
+                     no_poll_threads, no_pollsets);
+        erts_usage();
+    }
+
+    /* Handled arguments have been marked with NULL. Slide arguments
+       not handled towards the beginning of argv. */
+    for (i = 0, j = 0; i < *argc; i++) {
+	if (argv[i])
+	    argv[j++] = argv[i];
+    }
+    *argc = j;
+
+    erts_no_pollsets = no_pollsets;
+    erts_no_poll_threads = no_poll_threads;
+}
+
+void
+erts_init_check_io(int *argc, char **argv)
+{
+    int j, concurrent_waiters, no_poll_threads;
+    ERTS_CT_ASSERT((INT_MIN & (ERL_NIF_SELECT_STOP_CALLED |
+                               ERL_NIF_SELECT_STOP_SCHEDULED |
+                               ERL_NIF_SELECT_INVALID_EVENT |
+                               ERL_NIF_SELECT_FAILED)) == 0);
+
+
+    erts_poll_init(&concurrent_waiters);
+#if ERTS_POLL_USE_FALLBACK
+    erts_poll_init_flbk(NULL);
 #endif
 
+    parse_args(argc, argv, concurrent_waiters);
 
-#ifdef ERTS_SMP
-    init_removed_fd_alloc();
-    pollset.removed_list = NULL;
-    erts_smp_spinlock_init(&pollset.removed_list_lock,
-			   "pollset_rm_list");
-    {
-	int i;
-	for (i=0; i<DRV_EV_STATE_LOCK_CNT; i++) {
-#ifdef ERTS_ENABLE_LOCK_COUNT
-	    erts_smp_mtx_init_x(&drv_ev_state_locks[i].lck, "drv_ev_state", make_small(i));
-#else
-	    erts_smp_mtx_init(&drv_ev_state_locks[i].lck, "drv_ev_state");
+    /* Create the actual pollsets */
+    pollsetv = erts_alloc(ERTS_ALC_T_POLLSET,sizeof(ErtsPollSet *) * erts_no_pollsets);
+
+    for (j=0; j < erts_no_pollsets; j++)
+        pollsetv[j] = erts_poll_create_pollset(j);
+
+    no_poll_threads = erts_no_poll_threads;
+
+    j = -1;
+
+#if ERTS_POLL_USE_SCHEDULER_POLLING
+    sched_pollset = erts_poll_create_pollset(j--);
+    no_poll_threads++;
 #endif
-	}
-    }
+
+#if ERTS_POLL_USE_FALLBACK
+    flbk_pollset = erts_poll_create_pollset_flbk(j--);
+    no_poll_threads++;
+#endif
+
+    psiv = erts_alloc(ERTS_ALC_T_POLLSET, sizeof(ErtsPollThread) * no_poll_threads);
+
+#if ERTS_POLL_USE_FALLBACK
+    psiv[0].pollres_len = ERTS_CHECK_IO_POLL_RES_LEN;
+    psiv[0].pollres = erts_alloc(ERTS_ALC_T_POLLSET,
+        sizeof(ErtsPollResFd) * ERTS_CHECK_IO_POLL_RES_LEN);
+    psiv[0].ps = get_fallback_pollset();
+    psiv++;
+#endif
+
+#if ERTS_POLL_USE_SCHEDULER_POLLING
+    psiv[0].pollres_len = ERTS_CHECK_IO_POLL_RES_LEN;
+    psiv[0].pollres = erts_alloc(ERTS_ALC_T_POLLSET,
+        sizeof(ErtsPollResFd) * ERTS_CHECK_IO_POLL_RES_LEN);
+    psiv[0].ps = get_scheduler_pollset(0);
+    psiv++;
 #endif
+
+    for (j = 0; j < erts_no_poll_threads; j++) {
+        psiv[j].pollres_len = ERTS_CHECK_IO_POLL_RES_LEN;
+        psiv[j].pollres = erts_alloc(ERTS_ALC_T_POLLSET,
+                                      sizeof(ErtsPollResFd) * ERTS_CHECK_IO_POLL_RES_LEN);
+        psiv[j].ps = pollsetv[j % erts_no_pollsets];
+    }
+
+    for (j=0; j < ERTS_CHECK_IO_DRV_EV_STATE_LOCK_CNT; j++) {
+        erts_mtx_init(&drv_ev_state.locks[j].lck, "drv_ev_state", make_small(j),
+                          ERTS_LOCK_FLAGS_PROPERTY_STATIC | ERTS_LOCK_FLAGS_CATEGORY_IO);
+    }
+
 #ifdef ERTS_SYS_CONTINOUS_FD_NUMBERS
-    max_fds = ERTS_CIO_POLL_MAX_FDS();
-    erts_smp_atomic_init_nob(&drv_ev_state_len, 0);
-    drv_ev_state = NULL;
-    erts_smp_mtx_init(&drv_ev_state_grow_lock, "drv_ev_state_grow");
+    drv_ev_state.max_fds = erts_poll_max_fds();
+    erts_atomic_init_nob(&drv_ev_state.len, 0);
+    drv_ev_state.v = NULL;
+    erts_mtx_init(&drv_ev_state.grow_lock, "drv_ev_state_grow", NIL,
+        ERTS_LOCK_FLAGS_PROPERTY_STATIC | ERTS_LOCK_FLAGS_CATEGORY_IO);
 #else
     {
 	SafeHashFunctions hf;
@@ -1954,152 +2189,196 @@ ERTS_CIO_EXPORT(erts_init_check_io)(void)
 	hf.cmp = &drv_ev_state_cmp;
 	hf.alloc = &drv_ev_state_alloc;
 	hf.free = &drv_ev_state_free;
-	num_state_prealloc = 0;
-	state_prealloc_first = NULL;
-	erts_smp_spinlock_init(&state_prealloc_lock,"state_prealloc");
-
-	safe_hash_init(ERTS_ALC_T_DRV_EV_STATE, &drv_ev_state_tab, "drv_ev_state_tab", 
-		       DRV_EV_STATE_HTAB_SIZE, hf);
+	drv_ev_state.num_prealloc = 0;
+	drv_ev_state.prealloc_first = NULL;
+	erts_spinlock_init(&drv_ev_state.prealloc_lock, "state_prealloc", NIL,
+                               ERTS_LOCK_FLAGS_PROPERTY_STATIC | ERTS_LOCK_FLAGS_CATEGORY_IO);
+	safe_hash_init(ERTS_ALC_T_DRV_EV_STATE, &drv_ev_state.tab, "drv_ev_state_tab",
+            ERTS_LOCK_FLAGS_CATEGORY_IO, DRV_EV_STATE_HTAB_SIZE, hf);
     }
 #endif
 }
 
 int
-ERTS_CIO_EXPORT(erts_check_io_max_files)(void)
+erts_check_io_max_files(void)
 {
 #ifdef  ERTS_SYS_CONTINOUS_FD_NUMBERS
-    return max_fds;
+    return drv_ev_state.max_fds;
 #else
-    return ERTS_POLL_EXPORT(erts_poll_max_fds)();
+    return erts_poll_max_fds();
 #endif
 }
 
 Uint
-ERTS_CIO_EXPORT(erts_check_io_size)(void)
+erts_check_io_size(void)
 {
-    Uint res;
+    Uint res = 0;
     ErtsPollInfo pi;
-    ERTS_CIO_POLL_INFO(pollset.ps, &pi);
-    res = pi.memory_size;
+    int i;
+
+#if ERTS_POLL_USE_FALLBACK
+    erts_poll_info(get_fallback_pollset(), &pi);
+    res += pi.memory_size;
+#endif
+
+#if ERTS_POLL_USE_SCHEDULER_POLLING
+    erts_poll_info(get_scheduler_pollset(0), &pi);
+    res += pi.memory_size;
+#endif
+
+    for (i = 0; i < erts_no_pollsets; i++) {
+        erts_poll_info(pollsetv[i], &pi);
+        res += pi.memory_size;
+    }
 #ifdef ERTS_SYS_CONTINOUS_FD_NUMBERS
-    res += sizeof(ErtsDrvEventState) * erts_smp_atomic_read_nob(&drv_ev_state_len);
+    res += sizeof(ErtsDrvEventState) * erts_atomic_read_nob(&drv_ev_state.len);
 #else
-    res += safe_hash_table_sz(&drv_ev_state_tab);
+    res += safe_hash_table_sz(&drv_ev_state.tab);
     {
 	SafeHashInfo hi;
-	safe_hash_get_info(&hi, &drv_ev_state_tab);
+	safe_hash_get_info(&hi, &drv_ev_state.tab);
 	res += hi.objs * sizeof(ErtsDrvEventState);
     }
-    erts_smp_spin_lock(&state_prealloc_lock);
-    res += num_state_prealloc * sizeof(ErtsDrvEventState);
-    erts_smp_spin_unlock(&state_prealloc_lock);
+    erts_spin_lock(&drv_ev_state.prealloc_lock);
+    res += drv_ev_state.num_prealloc * sizeof(ErtsDrvEventState);
+    erts_spin_unlock(&drv_ev_state.prealloc_lock);
 #endif
     return res;
 }
 
 Eterm
-ERTS_CIO_EXPORT(erts_check_io_info)(void *proc)
+erts_check_io_info(void *proc)
 {
     Process *p = (Process *) proc;
-    Eterm tags[16], values[16], res;
-    Uint sz, *szp, *hp, **hpp, memory_size;
-    Sint i;
-    ErtsPollInfo pi;
-    erts_aint_t cio_time = erts_smp_atomic_read_acqb(&erts_check_io_time);
-    int active_fds = (int) erts_smp_atomic32_read_acqb(&pollset.active_fd.no);
+    Eterm tags[16], values[16], res, list = NIL;
+    Uint sz, *szp, *hp, **hpp;
+    ErtsPollInfo *piv;
+    Sint i, j = 0, len;
+    int no_pollsets = erts_no_pollsets + ERTS_POLL_USE_FALLBACK + ERTS_POLL_USE_SCHEDULER_POLLING;
+    ERTS_CT_ASSERT(ERTS_POLL_USE_FALLBACK == 0 || ERTS_POLL_USE_FALLBACK == 1);
+    ERTS_CT_ASSERT(ERTS_POLL_USE_SCHEDULER_POLLING == 0 || ERTS_POLL_USE_SCHEDULER_POLLING == 1);
 
-    while (1) {
-	erts_aint_t post_cio_time;
-	int post_active_fds;
+    piv = erts_alloc(ERTS_ALC_T_TMP, sizeof(ErtsPollInfo) * no_pollsets);
 
-	ERTS_CIO_POLL_INFO(pollset.ps, &pi);
+#if ERTS_POLL_USE_FALLBACK
+    erts_poll_info_flbk(get_fallback_pollset(), &piv[0]);
+    piv[0].poll_threads = 1;
+    piv[0].active_fds = 0;
+    piv++;
+#endif
 
-	post_cio_time = erts_smp_atomic_read_mb(&erts_check_io_time);
-	post_active_fds = (int) erts_smp_atomic32_read_acqb(&pollset.active_fd.no);
-	if (cio_time == post_cio_time && active_fds == post_active_fds)
-	    break;
-	cio_time = post_cio_time;
-	active_fds = post_active_fds;
+#if ERTS_POLL_USE_SCHEDULER_POLLING
+    erts_poll_info(get_scheduler_pollset(0), &piv[0]);
+    piv[0].poll_threads = 1;
+    piv[0].active_fds = 0;
+    piv++;
+#endif
+
+    for (j = 0; j < erts_no_pollsets; j++) {
+        erts_poll_info(pollsetv[j], &piv[j]);
+        piv[j].active_fds = 0;
+        piv[j].poll_threads = erts_no_poll_threads / erts_no_pollsets;
+        if (erts_no_poll_threads % erts_no_pollsets > j)
+            piv[j].poll_threads++;
     }
 
-    memory_size = pi.memory_size;
 #ifdef ERTS_SYS_CONTINOUS_FD_NUMBERS
-    memory_size += sizeof(ErtsDrvEventState) * erts_smp_atomic_read_nob(&drv_ev_state_len);
+    i = 0;
+    erts_mtx_lock(&drv_ev_state.grow_lock);
+    len = erts_atomic_read_nob(&drv_ev_state.len);
+    for (i = 0; i < ERTS_CHECK_IO_DRV_EV_STATE_LOCK_CNT; i++) {
+        erts_mtx_lock(&drv_ev_state.locks[i].lck);
+        for (j = i; j < len; j+=ERTS_CHECK_IO_DRV_EV_STATE_LOCK_CNT) {
+            ErtsDrvEventState *state = get_drv_ev_state(j);
+            int pollsetid = get_pollset_id(j);
+            ASSERT(fd_mtx(j) == &drv_ev_state.locks[i].lck);
+            if (state->flags & ERTS_EV_FLAG_FALLBACK)
+                pollsetid = -1;
+            if (state->driver.select
+                && (state->type == ERTS_EV_TYPE_DRV_SEL)
+                && (is_iotask_active(&state->driver.select->iniotask)
+                    || is_iotask_active(&state->driver.select->outiotask)))
+                piv[pollsetid].active_fds++;
+        }
+        erts_mtx_unlock(&drv_ev_state.locks[i].lck);
+    }
+    erts_mtx_unlock(&drv_ev_state.grow_lock);
+
+    piv[0].memory_size += sizeof(ErtsDrvEventState) * erts_atomic_read_nob(&drv_ev_state.len);
 #else
-    memory_size += safe_hash_table_sz(&drv_ev_state_tab);
+    piv[0].memory_size += safe_hash_table_sz(&drv_ev_state.tab);
     {
-	SafeHashInfo hi;
-	safe_hash_get_info(&hi, &drv_ev_state_tab);
-	memory_size += hi.objs * sizeof(ErtsDrvEventState);
+        SafeHashInfo hi;
+        safe_hash_get_info(&hi, &drv_ev_state.tab);
+        piv[0].memory_size += hi.objs * sizeof(ErtsDrvEventState);
     }
-    erts_smp_spin_lock(&state_prealloc_lock);
-    memory_size += num_state_prealloc * sizeof(ErtsDrvEventState);
-    erts_smp_spin_unlock(&state_prealloc_lock);
+    erts_spin_lock(&drv_ev_state.prealloc_lock);
+    piv[0].memory_size += drv_ev_state.num_prealloc * sizeof(ErtsDrvEventState);
+    erts_spin_unlock(&drv_ev_state.prealloc_lock);
 #endif
 
     hpp = NULL;
     szp = &sz;
     sz = 0;
 
+    piv -= ERTS_POLL_USE_FALLBACK;
+    piv -= ERTS_POLL_USE_SCHEDULER_POLLING;
+
  bld_it:
-    i = 0;
 
-    tags[i] = erts_bld_atom(hpp, szp, "name");
-    values[i++] = erts_bld_atom(hpp, szp, "erts_poll");
+    for (j = no_pollsets-1; j >= 0; j--) {
+        i = 0;
 
-    tags[i] = erts_bld_atom(hpp, szp, "primary");
-    values[i++] = erts_bld_atom(hpp, szp, pi.primary);
+        tags[i] = erts_bld_atom(hpp, szp, "name");
+        values[i++] = erts_bld_atom(hpp, szp, "erts_poll");
 
-    tags[i] = erts_bld_atom(hpp, szp, "fallback");
-    values[i++] = erts_bld_atom(hpp, szp, pi.fallback ? pi.fallback : "false");
+        tags[i] = erts_bld_atom(hpp, szp, "primary");
+        values[i++] = erts_bld_atom(hpp, szp, piv[j].primary);
 
-    tags[i] = erts_bld_atom(hpp, szp, "kernel_poll");
-    values[i++] = erts_bld_atom(hpp, szp,
-				pi.kernel_poll ? pi.kernel_poll : "false");
+        tags[i] = erts_bld_atom(hpp, szp, "kernel_poll");
+        values[i++] = erts_bld_atom(hpp, szp,
+                                    piv[j].kernel_poll ? piv[j].kernel_poll : "false");
 
-    tags[i] = erts_bld_atom(hpp, szp, "memory_size");
-    values[i++] = erts_bld_uint(hpp, szp, memory_size);
+        tags[i] = erts_bld_atom(hpp, szp, "memory_size");
+        values[i++] = erts_bld_uint(hpp, szp, piv[j].memory_size);
 
-    tags[i] = erts_bld_atom(hpp, szp, "total_poll_set_size");
-    values[i++] = erts_bld_uint(hpp, szp, (Uint) pi.poll_set_size);
+        tags[i] = erts_bld_atom(hpp, szp, "total_poll_set_size");
+        values[i++] = erts_bld_uint(hpp, szp, piv[j].poll_set_size);
 
-    if (pi.fallback) {
-	tags[i] = erts_bld_atom(hpp, szp, "fallback_poll_set_size");
-	values[i++] = erts_bld_uint(hpp, szp, (Uint) pi.fallback_poll_set_size);
-    }
+        tags[i] = erts_bld_atom(hpp, szp, "lazy_updates");
+        values[i++] = piv[j].lazy_updates ? am_true : am_false;
 
-    tags[i] = erts_bld_atom(hpp, szp, "lazy_updates");
-    values[i++] = pi.lazy_updates ? am_true : am_false;
+        tags[i] = erts_bld_atom(hpp, szp, "pending_updates");
+        values[i++] = erts_bld_uint(hpp, szp, piv[j].pending_updates);
 
-    if (pi.lazy_updates) {
-	tags[i] = erts_bld_atom(hpp, szp, "pending_updates");
-	values[i++] = erts_bld_uint(hpp, szp, (Uint) pi.pending_updates);
-    }
+        tags[i] = erts_bld_atom(hpp, szp, "batch_updates");
+        values[i++] = piv[j].batch_updates ? am_true : am_false;
 
-    tags[i] = erts_bld_atom(hpp, szp, "batch_updates");
-    values[i++] = pi.batch_updates ? am_true : am_false;
+        tags[i] = erts_bld_atom(hpp, szp, "concurrent_updates");
+        values[i++] = piv[j].concurrent_updates ? am_true : am_false;
 
-    tags[i] = erts_bld_atom(hpp, szp, "concurrent_updates");
-    values[i++] = pi.concurrent_updates ? am_true : am_false;
+        tags[i] = erts_bld_atom(hpp, szp, "fallback");
+        values[i++] = piv[j].is_fallback ? am_true : am_false;
 
-    tags[i] = erts_bld_atom(hpp, szp, "max_fds");
-    values[i++] = erts_bld_uint(hpp, szp, (Uint) pi.max_fds);
+        tags[i] = erts_bld_atom(hpp, szp, "max_fds");
+        values[i++] = erts_bld_uint(hpp, szp, piv[j].max_fds);
 
-    tags[i] = erts_bld_atom(hpp, szp, "active_fds");
-    values[i++] = erts_bld_uint(hpp, szp, (Uint) active_fds);
+        tags[i] = erts_bld_atom(hpp, szp, "active_fds");
+        values[i++] = erts_bld_uint(hpp, szp, piv[j].active_fds);
 
-#ifdef ERTS_POLL_COUNT_AVOIDED_WAKEUPS
-    tags[i] = erts_bld_atom(hpp, szp, "no_avoided_wakeups");
-    values[i++] = erts_bld_uint(hpp, szp, (Uint) pi.no_avoided_wakeups);
+        tags[i] = erts_bld_atom(hpp, szp, "poll_threads");
+        values[i++] = erts_bld_uint(hpp, szp, piv[j].poll_threads);
 
-    tags[i] = erts_bld_atom(hpp, szp, "no_avoided_interrupts");
-    values[i++] = erts_bld_uint(hpp, szp, (Uint) pi.no_avoided_interrupts);
+        res = erts_bld_2tup_list(hpp, szp, i, tags, values);
 
-    tags[i] = erts_bld_atom(hpp, szp, "no_interrupt_timed");
-    values[i++] = erts_bld_uint(hpp, szp, (Uint) pi.no_interrupt_timed);
-#endif
-
-    res = erts_bld_2tup_list(hpp, szp, i, tags, values);
+        if (!hpp) {
+            *szp += 2;
+        }
+        else {
+            list = CONS(*hpp, res, list);
+            *hpp += 2;
+        }
+    }
 
     if (!hpp) {
 	hp = HAlloc(p, sz);
@@ -2108,352 +2387,454 @@ ERTS_CIO_EXPORT(erts_check_io_info)(void *proc)
 	goto bld_it;
     }
 
-    return res;
+    erts_free(ERTS_ALC_T_TMP, piv);
+
+    return list;
 }
 
 static ERTS_INLINE ErtsPollEvents
-print_events(ErtsPollEvents ev)
+print_events(erts_dsprintf_buf_t *dsbufp, ErtsPollEvents ev)
 {
     int first = 1;
+    if(ev == ERTS_POLL_EV_NONE) {
+        erts_dsprintf(dsbufp, "N/A");
+        return 0;
+    }
     if(ev & ERTS_POLL_EV_IN) {
 	ev &= ~ERTS_POLL_EV_IN;
-	erts_printf("%s%s", first ? "" : "|", "IN");
+	erts_dsprintf(dsbufp, "%s%s", first ? "" : "|", "IN");
 	first = 0;
     }
     if(ev & ERTS_POLL_EV_OUT) {
 	ev &= ~ERTS_POLL_EV_OUT;
-	erts_printf("%s%s", first ? "" : "|", "OUT");
+	erts_dsprintf(dsbufp, "%s%s", first ? "" : "|", "OUT");
 	first = 0;
     }
     /* The following should not appear... */
     if(ev & ERTS_POLL_EV_NVAL) {
-	erts_printf("%s%s", first ? "" : "|", "NVAL");
+	erts_dsprintf(dsbufp, "%s%s", first ? "" : "|", "NVAL");
 	first = 0;
     }
     if(ev & ERTS_POLL_EV_ERR) {
-	erts_printf("%s%s", first ? "" : "|", "ERR");
+	erts_dsprintf(dsbufp, "%s%s", first ? "" : "|", "ERR");
 	first = 0;
     }
     if (ev)
-	erts_printf("%s0x%b32x", first ? "" : "|", (Uint32) ev);
+	erts_dsprintf(dsbufp, "%s0x%b32x", first ? "" : "|", (Uint32) ev);
     return ev;
 }
 
+static ERTS_INLINE void
+print_flags(erts_dsprintf_buf_t *dsbufp, EventStateFlags f)
+{
+    erts_dsprintf(dsbufp, "%s", flag2str(f));
+}
+
+#ifdef DEBUG_PRINT_MODE
+
+static ERTS_INLINE char *
+drvmode2str(int mode) {
+    switch (mode) {
+    case ERL_DRV_READ|ERL_DRV_USE: return "READ|USE";
+    case ERL_DRV_WRITE|ERL_DRV_USE: return "WRITE|USE";
+    case ERL_DRV_READ|ERL_DRV_WRITE|ERL_DRV_USE: return "READ|WRITE|USE";
+    case ERL_DRV_USE: return "USE";
+    case ERL_DRV_READ: return "READ";
+    case ERL_DRV_WRITE: return "WRITE";
+    case ERL_DRV_READ|ERL_DRV_WRITE: return "READ|WRITE";
+    default: return "UNKNOWN";
+    }
+}
+
+static ERTS_INLINE char *
+nifmode2str(enum ErlNifSelectFlags mode) {
+    switch (mode) {
+    case ERL_NIF_SELECT_READ: return "READ";
+    case ERL_NIF_SELECT_WRITE: return "WRITE";
+    case ERL_NIF_SELECT_STOP: return "STOP";
+    default: return "UNKNOWN";
+    }
+}
+
+#endif
+
 typedef struct {
     int used_fds;
     int num_errors;
     int no_driver_select_structs;
-    int no_driver_event_structs;
+    int no_enif_select_structs;
 #ifdef ERTS_SYS_CONTINOUS_FD_NUMBERS
     int internal_fds;
     ErtsPollEvents *epep;
 #endif
 } IterDebugCounters;
 
-static void doit_erts_check_io_debug(void *vstate, void *vcounters)
+static int erts_debug_print_checkio_state(erts_dsprintf_buf_t *dsbufp,
+                                          ErtsDrvEventState *state,
+                                          ErtsPollEvents ep_events,
+                                          int internal)
 {
-    ErtsDrvEventState *state = (ErtsDrvEventState *) vstate;
-    IterDebugCounters *counters = (IterDebugCounters *) vcounters;
-    ErtsPollEvents cio_events = state->events;
-    ErtsSysFdType fd = state->fd;
-#ifdef ERTS_SYS_CONTINOUS_FD_NUMBERS
-    int internal = 0;
-    ErtsPollEvents ep_events = counters->epep[(int) fd];
-#endif
-    int err = 0;
-
 #if defined(HAVE_FSTAT) && !defined(NO_FSTAT_ON_SYS_FD_TYPE)
     struct stat stat_buf;
 #endif
-
-    if (state->driver.select)
-	counters->no_driver_select_structs++;
-#if ERTS_CIO_HAVE_DRV_EVENT
-    if (state->driver.event)
-	counters->no_driver_event_structs++;
-#endif
-
+    ErtsSysFdType fd = state->fd;
+    ErtsPollEvents cio_events = state->events;
+    int err = 0;
 #ifdef ERTS_SYS_CONTINOUS_FD_NUMBERS
-    if (state->events || ep_events) {
-	if (ep_events & ERTS_POLL_EV_NVAL) {
-	    ep_events &= ~ERTS_POLL_EV_NVAL;
-	    internal = 1;
-	    counters->internal_fds++;
-	}
-	else
-	    counters->used_fds++;
-#else
-    if (state->events) {
-	counters->used_fds++;
+    ErtsPollEvents aio_events = state->active_events;
 #endif
-	
-	erts_printf("fd=%d ", (int) fd);
-	
+    erts_dsprintf(dsbufp, "pollset=%d fd=%d ",
+                state->flags & ERTS_EV_FLAG_FALLBACK ? -1 : get_pollset_id(fd), (int) fd);
+
 #if defined(HAVE_FSTAT) && !defined(NO_FSTAT_ON_SYS_FD_TYPE)
-	if (fstat((int) fd, &stat_buf) < 0)
-	    erts_printf("type=unknown ");
-	else {
-	    erts_printf("type=");
+    if (fstat((int) fd, &stat_buf) < 0)
+        erts_dsprintf(dsbufp, "type=unknown ");
+    else {
+        erts_dsprintf(dsbufp, "type=");
 #ifdef S_ISSOCK
-	    if (S_ISSOCK(stat_buf.st_mode))
-		erts_printf("sock ");
-	    else
+        if (S_ISSOCK(stat_buf.st_mode))
+            erts_dsprintf(dsbufp, "sock ");
+        else
 #endif
 #ifdef S_ISFIFO
 	    if (S_ISFIFO(stat_buf.st_mode))
-		erts_printf("fifo ");
+		erts_dsprintf(dsbufp, "fifo ");
 	    else
 #endif
 #ifdef S_ISCHR
-	    if (S_ISCHR(stat_buf.st_mode))
-		erts_printf("chr ");
-	    else
+                if (S_ISCHR(stat_buf.st_mode))
+                    erts_dsprintf(dsbufp, "chr ");
+                else
 #endif
 #ifdef S_ISDIR
-	    if (S_ISDIR(stat_buf.st_mode))
-		erts_printf("dir ");
-	    else
+                    if (S_ISDIR(stat_buf.st_mode))
+                        erts_dsprintf(dsbufp, "dir ");
+                    else
 #endif
 #ifdef S_ISBLK
-	    if (S_ISBLK(stat_buf.st_mode))
-		erts_printf("blk ");
-	    else
+                        if (S_ISBLK(stat_buf.st_mode))
+                            erts_dsprintf(dsbufp, "blk ");
+                        else
 #endif
 #ifdef S_ISREG
-	    if (S_ISREG(stat_buf.st_mode))
-		erts_printf("reg ");
-	    else
+                            if (S_ISREG(stat_buf.st_mode))
+                                erts_dsprintf(dsbufp, "reg ");
+                            else
 #endif
 #ifdef S_ISLNK
-	    if (S_ISLNK(stat_buf.st_mode))
-		erts_printf("lnk ");
-	    else
+                                if (S_ISLNK(stat_buf.st_mode))
+                                    erts_dsprintf(dsbufp, "lnk ");
+                                else
 #endif
 #ifdef S_ISDOOR
-	    if (S_ISDOOR(stat_buf.st_mode))
-		erts_printf("door ");
-	    else
+                                    if (S_ISDOOR(stat_buf.st_mode))
+                                        erts_dsprintf(dsbufp, "door ");
+                                    else
 #endif
 #ifdef S_ISWHT
-	    if (S_ISWHT(stat_buf.st_mode))
-		erts_printf("wht ");
-	    else
+                                        if (S_ISWHT(stat_buf.st_mode))
+                                            erts_dsprintf(dsbufp, "wht ");
+                                        else
 #endif
 #ifdef S_ISXATTR
-	    if (S_ISXATTR(stat_buf.st_mode))
-		erts_printf("xattr ");
-	    else
+                                            if (S_ISXATTR(stat_buf.st_mode))
+                                                erts_dsprintf(dsbufp, "xattr ");
+                                            else
 #endif
-		erts_printf("unknown ");
-	}
+                                                erts_dsprintf(dsbufp, "unknown ");
+    }
 #else
-	erts_printf("type=unknown ");
+    erts_dsprintf(dsbufp, "type=unknown ");
 #endif
 
-	if (state->type == ERTS_EV_TYPE_DRV_SEL) {
-	    erts_printf("driver_select ");
-	    
+    if (state->type == ERTS_EV_TYPE_DRV_SEL) {
+        erts_dsprintf(dsbufp, "driver_select ");
+
 #ifdef ERTS_SYS_CONTINOUS_FD_NUMBERS
-	    if (internal) {
-		erts_printf("internal ");
-		err = 1;		    
-	    }
-	    
-	    if (cio_events == ep_events) {
-		erts_printf("ev=");
-		if (print_events(cio_events) != 0)
-		    err = 1;
-	    }
-	    else {
-		err = 1;
-		erts_printf("cio_ev=");
-		print_events(cio_events);
-		erts_printf(" ep_ev=");
-		print_events(ep_events);
-	    }
+        if (internal) {
+            erts_dsprintf(dsbufp, "internal ");
+            err = 1;
+        }
+        if (aio_events == cio_events) {
+            if (cio_events == ep_events) {
+                erts_dsprintf(dsbufp, "ev=");
+                if (print_events(dsbufp, cio_events) != 0)
+                    err = 1;
+            }
+            else {
+                ErtsPollEvents ev = cio_events;
+                if (ev != ep_events && ep_events != ERTS_POLL_EV_NONE)
+                    err = 1;
+                erts_dsprintf(dsbufp, "cio_ev=");
+                print_events(dsbufp, cio_events);
+                erts_dsprintf(dsbufp, " ep_ev=");
+                print_events(dsbufp, ep_events);
+            }
+        } else {
+            erts_dsprintf(dsbufp, "cio_ev=");
+            print_events(dsbufp, cio_events);
+            erts_dsprintf(dsbufp, " aio_ev=");
+            print_events(dsbufp, aio_events);
+            if ((aio_events != ep_events && ep_events != ERTS_POLL_EV_NONE) ||
+                (aio_events != 0 && ep_events == ERTS_POLL_EV_NONE)) {
+                erts_dsprintf(dsbufp, " ep_ev=");
+                print_events(dsbufp, ep_events);
+                err = 1;
+            }
+        }
 #else
-	    if (print_events(cio_events) != 0)
-		err = 1;
-#endif
-	    erts_printf(" ");
-	    if (cio_events & ERTS_POLL_EV_IN) {
-		Eterm id = state->driver.select->inport;
-		if (is_nil(id)) {
-		    erts_printf("inport=none inname=none indrv=none ");
-		    err = 1;
-		}
-		else {
-		    ErtsPortNames *pnp = erts_get_port_names(id, ERTS_INVALID_ERL_DRV_PORT);
-		    erts_printf(" inport=%T inname=%s indrv=%s ",
-				id,
-				pnp->name ? pnp->name : "unknown",
-				(pnp->driver_name
-				 ? pnp->driver_name
-				 : "unknown"));
-		    erts_free_port_names(pnp);
-		}
-	    }
-	    if (cio_events & ERTS_POLL_EV_OUT) {
-		Eterm id = state->driver.select->outport;
-		if (is_nil(id)) {
-		    erts_printf("outport=none outname=none outdrv=none ");
-		    err = 1;
-		}
-		else {
-		    ErtsPortNames *pnp = erts_get_port_names(id, ERTS_INVALID_ERL_DRV_PORT);
-		    erts_printf(" outport=%T outname=%s outdrv=%s ",
-				id,
-				pnp->name ? pnp->name : "unknown",
-				(pnp->driver_name
-				 ? pnp->driver_name
-				 : "unknown"));
-		    erts_free_port_names(pnp);
-		}
-	    }
-	}
-#if ERTS_CIO_HAVE_DRV_EVENT
-	else if (state->type == ERTS_EV_TYPE_DRV_EV) {
-	    Eterm id;
-	    erts_printf("driver_event ");
+        if (print_events(dsbufp, cio_events) != 0)
+            err = 1;
+#endif
+        erts_dsprintf(dsbufp, " ");
+        if (cio_events & ERTS_POLL_EV_IN) {
+            Eterm id = state->driver.select->inport;
+            if (is_nil(id)) {
+                erts_dsprintf(dsbufp, "inport=none inname=none indrv=none ");
+                err = 1;
+            }
+            else {
+                ErtsPortNames *pnp = erts_get_port_names(id, ERTS_INVALID_ERL_DRV_PORT);
+                erts_dsprintf(dsbufp, " inport=%T inname=%s indrv=%s ",
+                            id,
+                            pnp->name ? pnp->name : "unknown",
+                            (pnp->driver_name
+                             ? pnp->driver_name
+                             : "unknown"));
+                erts_free_port_names(pnp);
+            }
+        }
+        if (cio_events & ERTS_POLL_EV_OUT) {
+            Eterm id = state->driver.select->outport;
+            if (is_nil(id)) {
+                erts_dsprintf(dsbufp, "outport=none outname=none outdrv=none ");
+                err = 1;
+            }
+            else {
+                ErtsPortNames *pnp = erts_get_port_names(id, ERTS_INVALID_ERL_DRV_PORT);
+                erts_dsprintf(dsbufp, " outport=%T outname=%s outdrv=%s ",
+                            id,
+                            pnp->name ? pnp->name : "unknown",
+                            (pnp->driver_name
+                             ? pnp->driver_name
+                             : "unknown"));
+                erts_free_port_names(pnp);
+            }
+        }
+    }
+    else if (state->type == ERTS_EV_TYPE_NIF) {
+        ErtsResource* r;
+        erts_dsprintf(dsbufp, "enif_select ");
+
 #ifdef ERTS_SYS_CONTINOUS_FD_NUMBERS
-	    if (internal) {
-		erts_printf("internal ");
-		err = 1;		    
-	    }
-	    if (cio_events == ep_events) {
-		erts_printf("ev=0x%b32x", (Uint32) cio_events);
-	    }
-	    else {
-		err = 1;
-		erts_printf("cio_ev=0x%b32x", (Uint32) cio_events);
-		erts_printf(" ep_ev=0x%b32x", (Uint32) ep_events);
-	    }
+        if (internal) {
+            erts_dsprintf(dsbufp, "internal ");
+            err = 1;
+        }
+
+        if (cio_events == ep_events) {
+            erts_dsprintf(dsbufp, "ev=");
+            if (print_events(dsbufp, cio_events) != 0)
+                err = 1;
+        }
+        else {
+            err = 1;
+            erts_dsprintf(dsbufp, "cio_ev=");
+            print_events(dsbufp, cio_events);
+            erts_dsprintf(dsbufp, " ep_ev=");
+            print_events(dsbufp, ep_events);
+        }
 #else
-	    erts_printf("ev=0x%b32x", (Uint32) cio_events);
+        if (print_events(dsbufp, cio_events) != 0)
+            err = 1;
 #endif
-	    id = state->driver.event->port;
-	    if (is_nil(id)) {
-		erts_printf(" port=none name=none drv=none ");
-		err = 1;
-	    }
-	    else {
-		ErtsPortNames *pnp = erts_get_port_names(id, ERTS_INVALID_ERL_DRV_PORT);
-		erts_printf(" port=%T name=%s drv=%s ",
-			    id,
-			    pnp->name ? pnp->name : "unknown",
-			    (pnp->driver_name
-			     ? pnp->driver_name
-			     : "unknown"));
-		erts_free_port_names(pnp);
-	    }
-	}
+        erts_dsprintf(dsbufp, " inpid=%T", state->driver.nif->in.pid);
+        erts_dsprintf(dsbufp, " outpid=%T", state->driver.nif->out.pid);
+        r = state->driver.stop.resource;
+        erts_dsprintf(dsbufp, " resource=%p(%T:%T)", r, r->type->module, r->type->name);
+    }
+#ifdef ERTS_SYS_CONTINOUS_FD_NUMBERS
+    else if (internal) {
+        erts_dsprintf(dsbufp, "internal ");
+        if (cio_events) {
+            err = 1;
+            erts_dsprintf(dsbufp, "cio_ev=");
+            print_events(dsbufp, cio_events);
+        }
+        if (ep_events) {
+            erts_dsprintf(dsbufp, "ep_ev=");
+            print_events(dsbufp, ep_events);
+        }
+    }
 #endif
+    else {
+        err = 1;
+        erts_dsprintf(dsbufp, "control_type=%d ", (int)state->type);
 #ifdef ERTS_SYS_CONTINOUS_FD_NUMBERS
-	else if (internal) {
-	    erts_printf("internal ");
-	    if (cio_events) {
-		err = 1;
-		erts_printf("cio_ev=");
-		print_events(cio_events);
-	    }
-	    if (ep_events) {
-		erts_printf("ep_ev=");
-		print_events(ep_events);
-	    }
-	}
+        if (cio_events == ep_events) {
+            erts_dsprintf(dsbufp, "ev=");
+            print_events(dsbufp, cio_events);
+        }
+        else {
+            erts_dsprintf(dsbufp, "cio_ev="); print_events(dsbufp, cio_events);
+            erts_dsprintf(dsbufp, " ep_ev="); print_events(dsbufp, ep_events);
+        }
+#else
+        erts_dsprintf(dsbufp, "ev=0x%b32x", (Uint32) cio_events);
 #endif
-	else {
-	    err = 1;
-	    erts_printf("control_type=%d ", (int)state->type);
+    }
+
+    erts_dsprintf(dsbufp, " flags="); print_flags(dsbufp, state->flags);
+    if (err) {
+        erts_dsprintf(dsbufp, " ERROR");
+    }
+    erts_dsprintf(dsbufp, "\r\n");
+    return err;
+}
+
+static void doit_erts_check_io_debug(void *vstate, void *vcounters,
+                                     erts_dsprintf_buf_t *dsbufp)
+{
+    ErtsDrvEventState *state = (ErtsDrvEventState *) vstate;
+    IterDebugCounters *counters = (IterDebugCounters *) vcounters;
+    int internal = 0;
 #ifdef ERTS_SYS_CONTINOUS_FD_NUMBERS
-	    if (cio_events == ep_events) {
-		erts_printf("ev=0x%b32x", (Uint32) cio_events);
-	    }
-	    else {
-		erts_printf("cio_ev=0x%b32x", (Uint32) cio_events);
-		erts_printf(" ep_ev=0x%b32x", (Uint32) ep_events);
-	    }
+    ErtsSysFdType fd = state->fd;
+    ErtsPollEvents ep_events = counters->epep[(int) fd];
 #else
-	    erts_printf("ev=0x%b32x", (Uint32) cio_events);
+    ErtsPollEvents ep_events = ERTS_POLL_EV_NONE;
 #endif
+
+    if (state->driver.select) {
+	counters->no_driver_select_structs++;
+        ASSERT(state->events || (ep_events != 0 && ep_events != ERTS_POLL_EV_NONE));
+    }
+    if (state->driver.nif) {
+        counters->no_enif_select_structs++;
+        ASSERT(state->events || (ep_events != 0 && ep_events != ERTS_POLL_EV_NONE));
+    }
+
+#ifdef ERTS_SYS_CONTINOUS_FD_NUMBERS
+    if (state->events || (ep_events != 0 && ep_events != ERTS_POLL_EV_NONE)) {
+	if (ep_events & ERTS_POLL_EV_NVAL) {
+	    ep_events &= ~ERTS_POLL_EV_NVAL;
+	    internal = 1;
+	    counters->internal_fds++;
 	}
-	
-	if (err) {
+	else
+	    counters->used_fds++;
+#else
+    if (state->events) {
+	counters->used_fds++;
+#endif
+	if (erts_debug_print_checkio_state(dsbufp, state, ep_events, internal)) {
 	    counters->num_errors++;
-	    erts_printf(" ERROR");
 	}
-	erts_printf("\n");
     }
 }
-    
+
+/* ciodpi can be NULL when called from etp-commands */
 int
-ERTS_CIO_EXPORT(erts_check_io_debug)(ErtsCheckIoDebugInfo *ciodip)
+erts_check_io_debug(ErtsCheckIoDebugInfo *ciodip)
 {
+    erts_dsprintf_buf_t *dsbufp = erts_create_logger_dsbuf();
 #ifdef ERTS_SYS_CONTINOUS_FD_NUMBERS
-    int fd, len;
+    int fd, len, i;
 #endif
-    IterDebugCounters counters;
+    IterDebugCounters counters = {0};
 #ifdef ERTS_SYS_CONTINOUS_FD_NUMBERS
     ErtsDrvEventState null_des;
 
     null_des.driver.select = NULL;
-#if ERTS_CIO_HAVE_DRV_EVENT
-    null_des.driver.event = NULL;
-#endif
-    null_des.driver.drv_ptr = NULL;
+    null_des.driver.nif = NULL;
+    null_des.driver.stop.drv_ptr = NULL;
     null_des.events = 0;
-    null_des.remove_cnt = 0;
     null_des.type = ERTS_EV_TYPE_NONE;
+    null_des.flags = 0;
+
+    counters.epep = erts_alloc(ERTS_ALC_T_TMP,
+                               sizeof(ErtsPollEvents)*drv_ev_state.max_fds);
 #endif
 
-    erts_printf("--- fds in pollset --------------------------------------\n");
 
-#if defined(ERTS_SMP) && defined(ERTS_ENABLE_LOCK_CHECK)
+#if defined(ERTS_ENABLE_LOCK_CHECK)
     erts_lc_check_exact(NULL, 0); /* No locks should be locked */
 #endif
 
-    erts_smp_thr_progress_block(); /* stop the world to avoid messy locking */
+    if (ciodip)
+        erts_thr_progress_block(); /* stop the world to avoid messy locking */
 
 #ifdef ERTS_SYS_CONTINOUS_FD_NUMBERS
-    counters.epep = erts_alloc(ERTS_ALC_T_TMP, sizeof(ErtsPollEvents)*max_fds);
-    ERTS_POLL_EXPORT(erts_poll_get_selected_events)(pollset.ps, counters.epep, max_fds);
-    counters.internal_fds = 0;
-#endif
-    counters.used_fds = 0;
-    counters.num_errors = 0;
-    counters.no_driver_select_structs = 0;
-    counters.no_driver_event_structs = 0;
+    len = erts_atomic_read_nob(&drv_ev_state.len);
 
-#ifdef ERTS_SYS_CONTINOUS_FD_NUMBERS
-    len = erts_smp_atomic_read_nob(&drv_ev_state_len);
+#if ERTS_POLL_USE_FALLBACK
+    erts_dsprintf(dsbufp, "--- fds in flbk pollset ---------------------------------\n");
+    erts_poll_get_selected_events_flbk(get_fallback_pollset(), counters.epep,
+                                       drv_ev_state.max_fds);
     for (fd = 0; fd < len; fd++) {
-	doit_erts_check_io_debug((void *) &drv_ev_state[fd], (void *) &counters);
+        if (drv_ev_state.v[fd].flags & ERTS_EV_FLAG_FALLBACK)
+            doit_erts_check_io_debug(&drv_ev_state.v[fd], &counters, dsbufp);
     }
-    for ( ; fd < max_fds; fd++) {
-	null_des.fd = fd;
-	doit_erts_check_io_debug((void *) &null_des, (void *) &counters);
+#endif
+#if ERTS_POLL_USE_SCHEDULER_POLLING
+    erts_dsprintf(dsbufp, "--- fds in scheduler pollset ----------------------------\n");
+    erts_poll_get_selected_events(get_scheduler_pollset(0), counters.epep,
+                                  drv_ev_state.max_fds);
+    for (fd = 0; fd < len; fd++) {
+        if (drv_ev_state.v[fd].flags & ERTS_EV_FLAG_SCHEDULER) {
+            if (drv_ev_state.v[fd].events && drv_ev_state.v[fd].events != ERTS_POLL_EV_NONE)
+                counters.epep[fd] &= ~ERTS_POLL_EV_OUT;
+            doit_erts_check_io_debug(&drv_ev_state.v[fd], &counters, dsbufp);
+        }
+    }
+#endif
+
+    erts_dsprintf(dsbufp, "--- fds in pollset --------------------------------------\n");
+
+    for (i = 0; i < erts_no_pollsets; i++) {
+        erts_poll_get_selected_events(pollsetv[i],
+                                      counters.epep,
+                                      drv_ev_state.max_fds);
+        for (fd = 0; fd < len; fd++) {
+            if (!(drv_ev_state.v[fd].flags & ERTS_EV_FLAG_FALLBACK)
+                && get_pollset_id(fd) == i) {
+                if (counters.epep[fd] != ERTS_POLL_EV_NONE &&
+                    drv_ev_state.v[fd].flags & ERTS_EV_FLAG_IN_SCHEDULER) {
+                    /* We add the in flag if it is enabled in the scheduler pollset
+                       and get_selected_events works on the platform */
+                    counters.epep[fd] |= ERTS_POLL_EV_IN;
+                }
+                doit_erts_check_io_debug(&drv_ev_state.v[fd], &counters, dsbufp);
+            }
+        }
+    }
+    for (fd = len ; fd < drv_ev_state.max_fds; fd++) {
+        null_des.fd = fd;
+        doit_erts_check_io_debug(&null_des, &counters, dsbufp);
     }
 #else
-    safe_hash_for_each(&drv_ev_state_tab, &doit_erts_check_io_debug, (void *) &counters);
+    safe_hash_for_each(&drv_ev_state.tab, &doit_erts_check_io_debug,
+                       &counters, dsbufp);
 #endif
 
-    erts_smp_thr_progress_unblock();
+    if (ciodip)
+        erts_thr_progress_unblock();
 
-    ciodip->no_used_fds = counters.used_fds;
-    ciodip->no_driver_select_structs = counters.no_driver_select_structs;
-    ciodip->no_driver_event_structs = counters.no_driver_event_structs;
+    if (ciodip) {
+        ciodip->no_used_fds = counters.used_fds;
+        ciodip->no_driver_select_structs = counters.no_driver_select_structs;
+        ciodip->no_enif_select_structs = counters.no_enif_select_structs;
+    }
 
-    erts_printf("\n");
-    erts_printf("used fds=%d\n", counters.used_fds);
-    erts_printf("Number of driver_select() structures=%d\n", counters.no_driver_select_structs);
-#if ERTS_CIO_HAVE_DRV_EVENT
-    erts_printf("Number of driver_event() structures=%d\n", counters.no_driver_event_structs);
-#endif
+    erts_dsprintf(dsbufp, "\n");
+    erts_dsprintf(dsbufp, "used fds=%d\n", counters.used_fds);
+    erts_dsprintf(dsbufp, "Number of driver_select() structures=%d\n", counters.no_driver_select_structs);
+    erts_dsprintf(dsbufp, "Number of enif_select() structures=%d\n", counters.no_enif_select_structs);
 #ifdef ERTS_SYS_CONTINOUS_FD_NUMBERS
-    erts_printf("internal fds=%d\n", counters.internal_fds);
+    erts_dsprintf(dsbufp, "internal fds=%d\n", counters.internal_fds);
 #endif
-    erts_printf("---------------------------------------------------------\n");
-    fflush(stdout);
+    erts_dsprintf(dsbufp, "---------------------------------------------------------\n");
+    erts_send_error_to_logger_nogl(dsbufp);
 #ifdef ERTS_SYS_CONTINOUS_FD_NUMBERS
     erts_free(ERTS_ALC_T_TMP, (void *) counters.epep);
 #endif
@@ -2461,3 +2842,20 @@ ERTS_CIO_EXPORT(erts_check_io_debug)(ErtsCheckIoDebugInfo *ciodip)
     return counters.num_errors;
 }
 
+#ifdef ERTS_ENABLE_LOCK_COUNT
+void erts_lcnt_update_cio_locks(int enable) {
+    int i;
+#ifndef ERTS_SYS_CONTINOUS_FD_NUMBERS
+    erts_lcnt_enable_hash_lock_count(&drv_ev_state.tab, ERTS_LOCK_FLAGS_CATEGORY_IO, enable);
+#else
+    (void)enable;
+#endif
+
+#if ERTS_POLL_USE_FALLBACK
+    erts_lcnt_enable_pollset_lock_count_flbk(get_fallback_pollset(), enable);
+#endif
+
+    for (i = 0; i < erts_no_pollsets; i++)
+        erts_lcnt_enable_pollset_lock_count(pollsetv[i], enable);
+}
+#endif /* ERTS_ENABLE_LOCK_COUNT */
diff --git a/erts/emulator/sys/common/erl_check_io.h b/erts/emulator/sys/common/erl_check_io.h
index 14f1ea3f43..31182be5ec 100644
--- a/erts/emulator/sys/common/erl_check_io.h
+++ b/erts/emulator/sys/common/erl_check_io.h
@@ -1,7 +1,7 @@
 /*
  * %CopyrightBegin%
  * 
- * Copyright Ericsson AB 2006-2016. All Rights Reserved.
+ * Copyright Ericsson AB 2006-2017. All Rights Reserved.
  * 
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -18,10 +18,11 @@
  * %CopyrightEnd%
  */
 
-/*
- * Description:	Check I/O
+/**
+ * @description Check I/O, a cross platform IO polling framework for ERTS
  *
- * Author: 	Rickard Green
+ * @author Rickard Green
+ * @author Lukas Larsson
  */
 
 #ifndef ERL_CHECK_IO_H__
@@ -30,68 +31,82 @@
 #include "sys.h"
 #include "erl_sys_driver.h"
 
-#ifdef ERTS_ENABLE_KERNEL_POLL
-
-int driver_select_kp(ErlDrvPort, ErlDrvEvent, int, int);
-int driver_select_nkp(ErlDrvPort, ErlDrvEvent, int, int);
-int driver_event_kp(ErlDrvPort, ErlDrvEvent, ErlDrvEventData);
-int driver_event_nkp(ErlDrvPort, ErlDrvEvent, ErlDrvEventData);
-Uint erts_check_io_size_kp(void);
-Uint erts_check_io_size_nkp(void);
-Eterm erts_check_io_info_kp(void *);
-Eterm erts_check_io_info_nkp(void *);
-int erts_check_io_max_files_kp(void);
-int erts_check_io_max_files_nkp(void);
-#ifdef ERTS_POLL_NEED_ASYNC_INTERRUPT_SUPPORT
-void erts_check_io_async_sig_interrupt_kp(void);
-void erts_check_io_async_sig_interrupt_nkp(void);
-#endif
-void erts_check_io_interrupt_kp(int);
-void erts_check_io_interrupt_nkp(int);
-void erts_check_io_interrupt_timed_kp(int, ErtsMonotonicTime);
-void erts_check_io_interrupt_timed_nkp(int, ErtsMonotonicTime);
-void erts_check_io_kp(int);
-void erts_check_io_nkp(int);
-void erts_init_check_io_kp(void);
-void erts_init_check_io_nkp(void);
-int erts_check_io_debug_kp(ErtsCheckIoDebugInfo *);
-int erts_check_io_debug_nkp(ErtsCheckIoDebugInfo *);
-
-#else /* !ERTS_ENABLE_KERNEL_POLL */
+/** @brief a structure that is used by each polling thread */
+struct erts_poll_thread;
 
+/**
+ * Get the memory size of the check io framework
+ */
 Uint erts_check_io_size(void);
-Eterm erts_check_io_info(void *);
+/**
+ * Returns an Eterm with information about all the pollsets active at the
+ * moment.
+ *
+ * @param proc the Process* to allocate the result on. It is passed as
+ *  void * because of header include problems.
+ */
+Eterm erts_check_io_info(void *proc);
+/**
+ * Should be called when a port IO task has been executed in order to re-enable
+ * or clear the information about the fd.
+ *
+ * @param type The type of event that has been completed.
+ * @param handle The port task handle of the event.
+ * @param reset A function pointer to be called when the port task handle
+ *  should be reset.
+ */
+void erts_io_notify_port_task_executed(ErtsPortTaskType type,
+                                       ErtsPortTaskHandle *handle,
+                                       void (*reset)(ErtsPortTaskHandle *));
+/**
+ * Returns the maximum number of fds that the check io framework can handle.
+ */
 int erts_check_io_max_files(void);
-#ifdef ERTS_POLL_NEED_ASYNC_INTERRUPT_SUPPORT
-void erts_check_io_async_sig_interrupt(void);
-#endif
-void erts_check_io_interrupt(int);
-void erts_check_io_interrupt_timed(int, ErtsMonotonicTime);
-void erts_check_io(int);
-void erts_init_check_io(void);
-
+/**
+ * Called by any thread that should check for new IO events. This function will
+ * not return unless erts_check_io_interrupt(pt, 1) is called by another thread.
+ *
+ * @param pt the poll thread structure to use.
+ */
+void erts_check_io(struct erts_poll_thread *pt, ErtsMonotonicTime timeout_time);
+/**
+ * Initialize the check io framework. This function will parse the arguments
+ * and delete any entries that it is interested in.
+ *
+ * @param argc the number of arguments
+ * @param argv an array with the arguments
+ */
+void erts_init_check_io(int *argc, char **argv);
+/**
+ * Interrupt the poll thread so that it can execute other code.
+ *
+ * Should be called with set = 0 by the waiting thread before calling
+ * erts_check_io.
+ *
+ * @param pt the poll thread to wake
+ * @param set whether to set or clear the interrupt flag
+ */
+void erts_check_io_interrupt(struct erts_poll_thread *pt, int set);
+/**
+ * Create a new poll thread structure that is associated with the number no.
+ * It is the callers responsibility that no is unique.
+ *
+ * @param no the id of the pollset thread, -2 = aux thread, -1 = scheduler
+ * @param tpd the thread progress data of the pollset thread
+ */
+struct erts_poll_thread* erts_create_pollset_thread(int no, ErtsThrPrgrData *tpd);
+#ifdef ERTS_ENABLE_LOCK_COUNT
+/**
+ * Toggle lock counting on all check io locks
+ */
+void erts_lcnt_update_cio_locks(int enable);
 #endif
 
-extern erts_smp_atomic_t erts_check_io_time;
-
 typedef struct {
     ErtsPortTaskHandle task;
-    erts_smp_atomic_t executed_time;
+    ErtsSysFdType fd;
 } ErtsIoTask;
 
-ERTS_GLB_INLINE void erts_io_notify_port_task_executed(ErtsPortTaskHandle *pthp);
-
-#if ERTS_GLB_INLINE_INCL_FUNC_DEF
-
-ERTS_GLB_INLINE void
-erts_io_notify_port_task_executed(ErtsPortTaskHandle *pthp)
-{
-    ErtsIoTask *itp = (ErtsIoTask *) (((char *) pthp) - offsetof(ErtsIoTask, task));
-    erts_aint_t ci_time = erts_smp_atomic_read_acqb(&erts_check_io_time);
-    erts_smp_atomic_set_relb(&itp->executed_time, ci_time);
-}
-
-#endif
 
 #endif /*  ERL_CHECK_IO_H__ */
 
@@ -99,41 +114,37 @@ erts_io_notify_port_task_executed(ErtsPortTaskHandle *pthp)
 #define ERL_CHECK_IO_INTERNAL__
 #endif
 
+#define ERTS_CHECK_IO_DRV_EV_STATE_LOCK_CNT 128
+
+/* Controls how many pollsets to allocate. Fd's are hashed into
+   each pollset based on the FD. When doing non-concurrent updates
+   there will be one pollset per thread.
+*/
+extern int erts_no_pollsets;
+extern int erts_no_poll_threads;
+
+
 #ifndef ERL_CHECK_IO_INTERNAL__
 #define ERL_CHECK_IO_INTERNAL__
 #include "erl_poll.h"
 #include "erl_port_task.h"
 
-#ifdef __WIN32__
-/*
- * Current erts_poll implementation for Windows cannot handle
- * active events in the set of events polled.
- */
-#  define ERTS_CIO_DEFER_ACTIVE_EVENTS 1
-#else
-#  define ERTS_CIO_DEFER_ACTIVE_EVENTS 0
-#endif
-
-/*
- * ErtsDrvEventDataState is used by driver_event() which is almost never
- * used. We allocate ErtsDrvEventDataState separate since we dont wan't
- * the size of ErtsDrvEventState to increase due to driver_event()
- * information.
- */
-typedef struct {
-    Eterm port;
-    ErlDrvEventData data;
-    ErtsPollEvents removed_events;
-#if ERTS_CIO_DEFER_ACTIVE_EVENTS
-    ErtsPollEvents deferred_events;
-#endif
-    ErtsIoTask iotask;
-} ErtsDrvEventDataState;
-
 typedef struct {
     Eterm inport;
     Eterm outport;
     ErtsIoTask iniotask;
     ErtsIoTask outiotask;
 } ErtsDrvSelectDataState;
+
+struct erts_nif_select_event {
+    Eterm pid;
+    Eterm immed;
+    Uint32 refn[ERTS_REF_NUMBERS];
+};
+
+typedef struct {
+    struct erts_nif_select_event in;
+    struct erts_nif_select_event out;
+} ErtsNifSelectDataState;
+
 #endif /* #ifndef ERL_CHECK_IO_INTERNAL__ */
diff --git a/erts/emulator/sys/common/erl_mmap.c b/erts/emulator/sys/common/erl_mmap.c
index 7bbb406f29..b0d9fc0776 100644
--- a/erts/emulator/sys/common/erl_mmap.c
+++ b/erts/emulator/sys/common/erl_mmap.c
@@ -1,7 +1,7 @@
 /*
  * %CopyrightBegin%
  *
- * Copyright Ericsson AB 2002-2016. All Rights Reserved.
+ * Copyright Ericsson AB 2002-2018. All Rights Reserved.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -21,9 +21,9 @@
 #  include "config.h"
 #endif
 
+#define ERTS_WANT_MEM_MAPPERS
 #include "sys.h"
 #include "erl_process.h"
-#include "erl_smp.h"
 #include "atom.h"
 #include "erl_mmap.h"
 #include <stddef.h>
@@ -61,11 +61,11 @@
     (((UWord) (PTR)) - ((UWord) mm->sa.bot)			\
      < ((UWord) mm->sua.top) - ((UWord) mm->sa.bot))
 #define ERTS_MMAP_IN_SUPERALIGNED_AREA(PTR)				\
-    (ERTS_SMP_LC_ASSERT(erts_lc_mtx_is_locked(&mm->mtx)),	\
+    (ERTS_LC_ASSERT(erts_lc_mtx_is_locked(&mm->mtx)),	\
      (((UWord) (PTR)) - ((UWord) mm->sa.bot)			\
       < ((UWord) mm->sa.top) - ((UWord) mm->sa.bot)))
 #define ERTS_MMAP_IN_SUPERUNALIGNED_AREA(PTR)				\
-    (ERTS_SMP_LC_ASSERT(erts_lc_mtx_is_locked(&mm->mtx)),	\
+    (ERTS_LC_ASSERT(erts_lc_mtx_is_locked(&mm->mtx)),	\
      (((UWord) (PTR)) - ((UWord) mm->sua.bot)			\
       < ((UWord) mm->sua.top) - ((UWord) mm->sua.bot)))
 
@@ -198,10 +198,10 @@ static ErtsMMapOp mmap_ops[ERTS_MMAP_OP_RINGBUF_SZ];
 
 #define ERTS_MMAP_OP_LCK(RES, IN_SZ, OUT_SZ)			\
     do {							\
-	erts_smp_mtx_lock(&mm->mtx);			\
+	erts_mtx_lock(&mm->mtx);			\
 	ERTS_MMAP_OP_START((IN_SZ));				\
 	ERTS_MMAP_OP_END((RES), (OUT_SZ));			\
-	erts_smp_mtx_unlock(&mm->mtx);			\
+	erts_mtx_unlock(&mm->mtx);			\
     } while (0)
 
 #define ERTS_MUNMAP_OP(PTR, SZ)					\
@@ -220,9 +220,9 @@ static ErtsMMapOp mmap_ops[ERTS_MMAP_OP_RINGBUF_SZ];
 
 #define ERTS_MUNMAP_OP_LCK(PTR, SZ)				\
     do {							\
-	erts_smp_mtx_lock(&mm->mtx);			\
+	erts_mtx_lock(&mm->mtx);			\
 	ERTS_MUNMAP_OP((PTR), (SZ));				\
-	erts_smp_mtx_unlock(&mm->mtx);			\
+	erts_mtx_unlock(&mm->mtx);			\
     } while (0)
 
 #define ERTS_MREMAP_OP_START(OLD_PTR, OLD_SZ, IN_SZ)		\
@@ -248,10 +248,10 @@ static ErtsMMapOp mmap_ops[ERTS_MMAP_OP_RINGBUF_SZ];
 
 #define ERTS_MREMAP_OP_LCK(RES, OLD_PTR, OLD_SZ, IN_SZ, OUT_SZ)	\
     do {							\
-	erts_smp_mtx_lock(&mm->mtx);			\
+	erts_mtx_lock(&mm->mtx);			\
 	ERTS_MREMAP_OP_START((OLD_PTR), (OLD_SZ), (IN_SZ));	\
 	ERTS_MREMAP_OP_END((RES), (OUT_SZ));			\
-	erts_smp_mtx_unlock(&mm->mtx);			\
+	erts_mtx_unlock(&mm->mtx);			\
     } while (0)
 
 #define ERTS_MMAP_OP_ABORT()					\
@@ -296,11 +296,10 @@ typedef struct {
 }ErtsFreeSegMap;
 
 struct ErtsMemMapper_ {
-    int (*reserve_physical)(char *, UWord, int exec);
+    int (*reserve_physical)(char *, UWord);
     void (*unreserve_physical)(char *, UWord);
     int supercarrier;
     int no_os_mmap;
-    int executable;   /* is client a native code allocator? */
     /*
      * Super unaligned area is located above super aligned
      * area. That is, `sa.bot` is beginning of the super
@@ -320,7 +319,7 @@ struct ErtsMemMapper_ {
 #if HAVE_MMAP && (!defined(MAP_ANON) && !defined(MAP_ANONYMOUS))
     int mmap_fd;
 #endif
-    erts_smp_mtx_t mtx;
+    erts_mtx_t mtx;
     struct {
 	char *free_list;
 	char *unused_start;
@@ -358,11 +357,6 @@ char* erts_literals_start;
 UWord erts_literals_size;
 #endif
 
-#ifdef ERTS_ALC_A_EXEC
-ErtsMemMapper erts_exec_mmapper;
-#endif
-
-
 
 #define ERTS_MMAP_SIZE_SC_SA_INC(SZ) 						\
     do {									\
@@ -1241,7 +1235,6 @@ Eterm build_free_seg_list(Process* p, ErtsFreeSegMap* map)
 
 #if HAVE_MMAP
 #  define ERTS_MMAP_PROT		(PROT_READ|PROT_WRITE)
-#  define ERTS_MMAP_PROT_EXEC		(PROT_READ|PROT_WRITE|PROT_EXEC)
 #  if defined(MAP_ANONYMOUS)
 #    define ERTS_MMAP_FLAGS		(MAP_ANON|MAP_PRIVATE)
 #    define ERTS_MMAP_FD		(-1)
@@ -1255,26 +1248,24 @@ Eterm build_free_seg_list(Process* p, ErtsFreeSegMap* map)
 #endif
 
 static ERTS_INLINE void *
-os_mmap(void *hint_ptr, UWord size, int try_superalign, int executable)
+os_mmap(void *hint_ptr, UWord size, int try_superalign)
 {
 #if HAVE_MMAP
-    const int prot = executable ? ERTS_MMAP_PROT_EXEC : ERTS_MMAP_PROT;
     void *res;
 #ifdef MAP_ALIGN
     if (try_superalign)
-	res = mmap((void *) ERTS_SUPERALIGNED_SIZE, size, prot,
+	res = mmap((void *) ERTS_SUPERALIGNED_SIZE, size, ERTS_MMAP_PROT,
 		   ERTS_MMAP_FLAGS|MAP_ALIGN, ERTS_MMAP_FD, 0);
     else
 #endif
-	res = mmap((void *) hint_ptr, size, prot,
+	res = mmap((void *) hint_ptr, size, ERTS_MMAP_PROT,
 		   ERTS_MMAP_FLAGS, ERTS_MMAP_FD, 0);
     if (res == MAP_FAILED)
 	return NULL;
     return res;
 #elif HAVE_VIRTUALALLOC
-    const DWORD prot = executable ? PAGE_EXECUTE_READWRITE : PAGE_READWRITE;
     return (void *) VirtualAlloc(NULL, (SIZE_T) size,
-				 MEM_COMMIT|MEM_RESERVE, prot);
+				 MEM_COMMIT|MEM_RESERVE, PAGE_READWRITE);
 #else
 #  error "missing mmap() or similar"
 #endif
@@ -1331,7 +1322,6 @@ os_mremap(void *ptr, UWord old_size, UWord new_size, int try_superalign)
 #if HAVE_MMAP
 
 #define ERTS_MMAP_RESERVE_PROT		(ERTS_MMAP_PROT)
-#define ERTS_MMAP_RESERVE_PROT_EXEC	(ERTS_MMAP_PROT_EXEC)
 #define ERTS_MMAP_RESERVE_FLAGS		(ERTS_MMAP_FLAGS|MAP_FIXED)
 #define ERTS_MMAP_UNRESERVE_PROT	(PROT_NONE)
 #if defined(__FreeBSD__)
@@ -1347,10 +1337,9 @@ os_mremap(void *ptr, UWord old_size, UWord new_size, int try_superalign)
 #endif /* __FreeBSD__ */
 
 static int
-os_reserve_physical(char *ptr, UWord size, int exec)
+os_reserve_physical(char *ptr, UWord size)
 {
-    const int prot = exec ? ERTS_MMAP_RESERVE_PROT_EXEC : ERTS_MMAP_RESERVE_PROT;
-    void *res = mmap((void *) ptr, (size_t) size, prot,
+    void *res = mmap((void *) ptr, (size_t) size, ERTS_MMAP_RESERVE_PROT,
 		     ERTS_MMAP_RESERVE_FLAGS, ERTS_MMAP_FD, 0);
     if (res == (void *) MAP_FAILED)
 	return 0;
@@ -1367,37 +1356,11 @@ os_unreserve_physical(char *ptr, UWord size)
 }
 
 static void *
-os_mmap_virtual(char *ptr, UWord size, int exec)
+os_mmap_virtual(char *ptr, UWord size)
 {
     int flags = ERTS_MMAP_VIRTUAL_FLAGS;
     void* res;
 
-#ifdef ERTS_ALC_A_EXEC
-    if (exec) {
-        ASSERT(!ptr);
-        /* OTP-19.0: Nice hack below cut-and-pasted from hipe_amd64.c */
-
-#  ifdef MAP_32BIT
-        /* If we got MAP_32BIT (Linux), then use that to ask for low memory */
-        flags |= MAP_32BIT;
-#  else
-        /* FreeBSD doesn't have MAP_32BIT, and it doesn't respect
-           a plain map_hint (returns high mappings even though the
-           hint refers to a free area), so we have to use both map_hint
-           and MAP_FIXED to get addresses below the 2GB boundary.
-           This is even worse than the Linux/ppc64 case.
-           Similarly, Solaris 10 doesn't have MAP_32BIT,
-           and it doesn't respect a plain map_hint. */
-        ptr = (char*)(512*1024*1024); /* 0.5GB */
-
-#    if defined(__FreeBSD__) || defined(__sun__)
-        flags |= MAP_FIXED;
-#    endif
-#  endif /* !MAP_32BIT */
-    }
-#else /* !ERTS_ALC_A_EXEC */
-    ASSERT(!exec);
-#endif
     res = mmap((void *) ptr, (size_t) size, ERTS_MMAP_VIRTUAL_PROT,
                flags, ERTS_MMAP_FD, 0);
     if (res == (void *) MAP_FAILED)
@@ -1412,7 +1375,7 @@ os_mmap_virtual(char *ptr, UWord size, int exec)
 
 #endif /* ERTS_HAVE_OS_MMAP */
 
-static int reserve_noop(char *ptr, UWord size, int exec)
+static int reserve_noop(char *ptr, UWord size)
 {
 #ifdef ERTS_MMAP_DEBUG_FILL_AREAS
     Uint32 *uip, *end = (Uint32 *) (ptr + size);
@@ -1455,7 +1418,7 @@ alloc_desc_insert_free_seg(ErtsMemMapper* mm,
 
 #if ERTS_HAVE_OS_MMAP
     if (!mm->no_os_mmap) {
-        ptr = os_mmap(mm->desc.new_area_hint, ERTS_PAGEALIGNED_SIZE, 0, 0);
+        ptr = os_mmap(mm->desc.new_area_hint, ERTS_PAGEALIGNED_SIZE, 0);
         if (ptr) {
             mm->desc.new_area_hint = ptr+ERTS_PAGEALIGNED_SIZE;
             ERTS_MMAP_SIZE_OS_INC(ERTS_PAGEALIGNED_SIZE);
@@ -1474,7 +1437,7 @@ alloc_desc_insert_free_seg(ErtsMemMapper* mm,
     da_map = &mm->sua.map;
     desc = lookup_free_seg(da_map, ERTS_PAGEALIGNED_SIZE);
     if (desc) {
-	if (mm->reserve_physical(desc->start, ERTS_PAGEALIGNED_SIZE, 0))
+	if (mm->reserve_physical(desc->start, ERTS_PAGEALIGNED_SIZE))
 	    ERTS_MMAP_SIZE_SC_SUA_INC(ERTS_PAGEALIGNED_SIZE);
 	else
 	    desc = NULL;
@@ -1484,7 +1447,7 @@ alloc_desc_insert_free_seg(ErtsMemMapper* mm,
 	da_map = &mm->sa.map;
 	desc = lookup_free_seg(da_map, ERTS_PAGEALIGNED_SIZE);
 	if (desc) {
-	    if (mm->reserve_physical(desc->start, ERTS_PAGEALIGNED_SIZE, 0))
+	    if (mm->reserve_physical(desc->start, ERTS_PAGEALIGNED_SIZE))
 		ERTS_MMAP_SIZE_SC_SA_INC(ERTS_PAGEALIGNED_SIZE);
 	    else
 		desc = NULL;
@@ -1536,7 +1499,7 @@ erts_mmap(ErtsMemMapper* mm, Uint32 flags, UWord *sizep)
 	ErtsFreeSegDesc *desc;
 	Uint32 superaligned = (ERTS_MMAPFLG_SUPERALIGNED & flags);
 
-	erts_smp_mtx_lock(&mm->mtx);
+	erts_mtx_lock(&mm->mtx);
 
 	ERTS_MMAP_OP_START(*sizep);
 
@@ -1545,7 +1508,7 @@ erts_mmap(ErtsMemMapper* mm, Uint32 flags, UWord *sizep)
 	    if (desc) {
 		seg = desc->start;
 		end = seg+asize;
-		if (!mm->reserve_physical(seg, asize, mm->executable))
+		if (!mm->reserve_physical(seg, asize))
 		    goto supercarrier_reserve_failure;
 		if (desc->end == end) {
 		    delete_free_seg(&mm->sua.map, desc);
@@ -1560,8 +1523,7 @@ erts_mmap(ErtsMemMapper* mm, Uint32 flags, UWord *sizep)
 	    }
 
 	    if (asize <= mm->sua.bot - mm->sa.top) {
-		if (!mm->reserve_physical(mm->sua.bot - asize, asize,
-                                          mm->executable))
+		if (!mm->reserve_physical(mm->sua.bot - asize, asize))
 		    goto supercarrier_reserve_failure;
 		mm->sua.bot -= asize;
 		seg = mm->sua.bot;
@@ -1577,8 +1539,7 @@ erts_mmap(ErtsMemMapper* mm, Uint32 flags, UWord *sizep)
 	    char *start = seg = desc->start;
 	    seg = (char *) ERTS_SUPERALIGNED_CEILING(seg);
 	    end = seg+asize;
-	    if (!mm->reserve_physical(start, (UWord) (end - start),
-                                      mm->executable))
+	    if (!mm->reserve_physical(start, (UWord) (end - start)))
 		goto supercarrier_reserve_failure;
 	    ERTS_MMAP_SIZE_SC_SA_INC(asize);
 	    if (desc->end == end) {
@@ -1610,8 +1571,7 @@ erts_mmap(ErtsMemMapper* mm, Uint32 flags, UWord *sizep)
 
 	    if (asize + (seg - start) <= mm->sua.bot - start) {
 		end = seg + asize;
-		if (!mm->reserve_physical(start, (UWord) (end - start),
-                                          mm->executable))
+		if (!mm->reserve_physical(start, (UWord) (end - start)))
 		    goto supercarrier_reserve_failure;
 		mm->sa.top = end;
 		ERTS_MMAP_SIZE_SC_SA_INC(asize);
@@ -1633,8 +1593,7 @@ erts_mmap(ErtsMemMapper* mm, Uint32 flags, UWord *sizep)
 
 		seg = (char *) ERTS_SUPERALIGNED_CEILING(org_start);
 		end = seg + asize;
-		if (!mm->reserve_physical(seg, (UWord) (org_end - seg),
-                                          mm->executable))
+		if (!mm->reserve_physical(seg, (UWord) (org_end - seg)))
 		    goto supercarrier_reserve_failure;
 		ERTS_MMAP_SIZE_SC_SUA_INC(asize);
 		if (org_start != seg) {
@@ -1660,20 +1619,20 @@ erts_mmap(ErtsMemMapper* mm, Uint32 flags, UWord *sizep)
 	}
 
 	ERTS_MMAP_OP_ABORT();
-	erts_smp_mtx_unlock(&mm->mtx);
+	erts_mtx_unlock(&mm->mtx);
     }
 
 #if ERTS_HAVE_OS_MMAP
     /* Map using OS primitives */
     if (!(ERTS_MMAPFLG_SUPERCARRIER_ONLY & flags) && !mm->no_os_mmap) {
 	if (!(ERTS_MMAPFLG_SUPERALIGNED & flags)) {
-	    seg = os_mmap(NULL, asize, 0, mm->executable);
+	    seg = os_mmap(NULL, asize, 0);
 	    if (!seg)
 		goto failure;
 	}
 	else {
 	    asize = ERTS_SUPERALIGNED_CEILING(*sizep);
-	    seg = os_mmap(NULL, asize, 1, mm->executable);
+	    seg = os_mmap(NULL, asize, 1);
 	    if (!seg)
 		goto failure;
 
@@ -1683,8 +1642,7 @@ erts_mmap(ErtsMemMapper* mm, Uint32 flags, UWord *sizep)
 
 		os_munmap(seg, asize);
 
-		ptr = os_mmap(NULL, asize + ERTS_SUPERALIGNED_SIZE, 1,
-                              mm->executable);
+		ptr = os_mmap(NULL, asize + ERTS_SUPERALIGNED_SIZE, 1);
 		if (!ptr)
 		    goto failure;
 
@@ -1724,13 +1682,13 @@ supercarrier_success:
 #endif
 
     ERTS_MMAP_OP_END(seg, asize);
-    erts_smp_mtx_unlock(&mm->mtx);
+    erts_mtx_unlock(&mm->mtx);
 
     *sizep = asize;
     return (void *) seg;
 
 supercarrier_reserve_failure:
-    erts_smp_mtx_unlock(&mm->mtx);
+    erts_mtx_unlock(&mm->mtx);
     *sizep = 0;
     return NULL;
 }
@@ -1760,7 +1718,7 @@ erts_munmap(ErtsMemMapper* mm, Uint32 flags, void *ptr, UWord size)
 	start = (char *) ptr;
 	end = start + size;
 
-	erts_smp_mtx_lock(&mm->mtx);
+	erts_mtx_lock(&mm->mtx);
 
 	ERTS_MUNMAP_OP(ptr, size);
 
@@ -1829,7 +1787,7 @@ erts_munmap(ErtsMemMapper* mm, Uint32 flags, void *ptr, UWord size)
 	    if (unres_sz)
 		mm->unreserve_physical(((char *) ptr) + ad_sz, unres_sz);
 
-            erts_smp_mtx_unlock(&mm->mtx);
+            erts_mtx_unlock(&mm->mtx);
 	}
     }
 }
@@ -1878,7 +1836,7 @@ erts_mremap(ErtsMemMapper* mm,
 	    return NULL;
 	}
 
-#if ERTS_HAVE_OS_MREMAP || ERTS_HAVE_GENUINE_OS_MMAP
+#if defined(ERTS_HAVE_OS_MREMAP) || defined(ERTS_HAVE_GENUINE_OS_MMAP)
 	superaligned = (ERTS_MMAPFLG_SUPERALIGNED & flags);
 
 	if (superaligned) {
@@ -1898,7 +1856,7 @@ erts_mremap(ErtsMemMapper* mm,
 	    }
 	}
 
-#if ERTS_HAVE_GENUINE_OS_MMAP
+#ifdef ERTS_HAVE_GENUINE_OS_MMAP
 	if (asize < old_size
 	    && (!superaligned
 		|| ERTS_IS_SUPERALIGNED(ptr))) {
@@ -1913,7 +1871,7 @@ erts_mremap(ErtsMemMapper* mm,
 	    return ptr;
 	}
 #endif
-#if ERTS_HAVE_OS_MREMAP
+#ifdef ERTS_HAVE_OS_MREMAP
 	if (superaligned)
 	    return remap_move(mm, flags, new_ptr, old_size, sizep);
 	else {
@@ -1948,12 +1906,12 @@ erts_mremap(ErtsMemMapper* mm,
 		 ? ERTS_SUPERALIGNED_CEILING(*sizep)
 		 : ERTS_PAGEALIGNED_CEILING(*sizep));
 
-	erts_smp_mtx_lock(&mm->mtx);
+	erts_mtx_lock(&mm->mtx);
 
 	if (ERTS_MMAP_IN_SUPERALIGNED_AREA(ptr)
 	    ? (!superaligned && lookup_free_seg(&mm->sua.map, asize))
 	    : (superaligned && lookup_free_seg(&mm->sa.map, asize))) {
-	    erts_smp_mtx_unlock(&mm->mtx);
+	    erts_mtx_unlock(&mm->mtx);
 	    /*
 	     * Segment currently in wrong area (due to a previous memory
 	     * shortage), move it to the right area.
@@ -2019,8 +1977,7 @@ erts_mremap(ErtsMemMapper* mm,
 
 	    if (next && new_end <= next->end) {
 		if (!mm->reserve_physical(((char *) ptr) + old_size,
-                                          asize - old_size,
-                                          mm->executable))
+                                          asize - old_size))
 		    goto supercarrier_reserve_failure;
 		if (new_end < next->end)
 		    resize_free_seg(&mm->sua.map, next, new_end, next->end);
@@ -2038,8 +1995,7 @@ erts_mremap(ErtsMemMapper* mm,
 	    if (end == mm->sa.top) {
 		if (new_end <= mm->sua.bot) {
 		    if (!mm->reserve_physical(((char *) ptr) + old_size,
-                                              asize - old_size,
-                                              mm->executable))
+                                              asize - old_size))
 			goto supercarrier_reserve_failure;
 		    mm->sa.top = new_end;
 		    new_ptr = ptr;
@@ -2051,8 +2007,7 @@ erts_mremap(ErtsMemMapper* mm,
 		adjacent_free_seg(&mm->sa.map, start, end, &prev, &next);
 		if (next && new_end <= next->end) {
 		    if (!mm->reserve_physical(((char *) ptr) + old_size,
-                                              asize - old_size,
-                                              mm->executable))
+                                              asize - old_size))
 			goto supercarrier_reserve_failure;
 		    if (new_end < next->end)
 			resize_free_seg(&mm->sa.map, next, new_end, next->end);
@@ -2068,7 +2023,7 @@ erts_mremap(ErtsMemMapper* mm,
 	}
 
 	ERTS_MMAP_OP_ABORT();
-	erts_smp_mtx_unlock(&mm->mtx);
+	erts_mtx_unlock(&mm->mtx);
 
 	/* Failed to resize... */
     }
@@ -2090,14 +2045,14 @@ supercarrier_resize_success:
 #endif
 
     ERTS_MREMAP_OP_END(new_ptr, asize);
-    erts_smp_mtx_unlock(&mm->mtx);
+    erts_mtx_unlock(&mm->mtx);
 
     *sizep = asize;
     return new_ptr;
 
 supercarrier_reserve_failure:
     ERTS_MREMAP_OP_END(NULL, old_size);
-    erts_smp_mtx_unlock(&mm->mtx);
+    erts_mtx_unlock(&mm->mtx);
     *sizep = old_size;
     return NULL;
     
@@ -2172,7 +2127,7 @@ static void hard_dbg_mseg_init(void);
 #endif
 
 void
-erts_mmap_init(ErtsMemMapper* mm, ErtsMMapInit *init, int executable)
+erts_mmap_init(ErtsMemMapper* mm, ErtsMMapInit *init)
 {
     static int is_first_call = 1;
     int virtual_map = 0;
@@ -2204,7 +2159,6 @@ erts_mmap_init(ErtsMemMapper* mm, ErtsMMapInit *init, int executable)
     mm->supercarrier = 0;
     mm->reserve_physical = reserve_noop;
     mm->unreserve_physical = unreserve_noop;
-    mm->executable = executable;
 
 #if HAVE_MMAP && !defined(MAP_ANON)
     mm->mmap_fd = open("/dev/zero", O_RDWR);
@@ -2212,9 +2166,11 @@ erts_mmap_init(ErtsMemMapper* mm, ErtsMMapInit *init, int executable)
 	erts_exit(1, "erts_mmap: Failed to open /dev/zero\n");
 #endif
 
-    erts_smp_mtx_init(&mm->mtx, "erts_mmap");
+    erts_mtx_init(&mm->mtx, "erts_mmap", NIL,
+        ERTS_LOCK_FLAGS_PROPERTY_STATIC | ERTS_LOCK_FLAGS_CATEGORY_GENERIC);
     if (is_first_call) {
-        erts_mtx_init(&am.init_mutex, "mmap_init_atoms");
+        erts_mtx_init(&am.init_mutex, "mmap_init_atoms", NIL,
+            ERTS_LOCK_FLAGS_PROPERTY_STATIC | ERTS_LOCK_FLAGS_CATEGORY_GENERIC);
     }
 
 #ifdef ERTS_HAVE_OS_PHYSICAL_MEMORY_RESERVATION
@@ -2224,7 +2180,7 @@ erts_mmap_init(ErtsMemMapper* mm, ErtsMMapInit *init, int executable)
 	ptr = (char *) ERTS_PAGEALIGNED_CEILING(init->virtual_range.start);
 	end = (char *) ERTS_PAGEALIGNED_FLOOR(init->virtual_range.end);
 	sz = end - ptr;
-	start = os_mmap_virtual(ptr, sz, executable);
+	start = os_mmap_virtual(ptr, sz);
 	if (!start || start > ptr || start >= end)
 	    erts_exit(1,
 		     "erts_mmap: Failed to create virtual range for super carrier\n");
@@ -2249,7 +2205,7 @@ erts_mmap_init(ErtsMemMapper* mm, ErtsMMapInit *init, int executable)
 	sz = ERTS_PAGEALIGNED_CEILING(init->scs);
 #ifdef ERTS_HAVE_OS_PHYSICAL_MEMORY_RESERVATION
 	if (!init->scrpm) {
-	    start = os_mmap_virtual(NULL, sz, executable);
+	    start = os_mmap_virtual(NULL, sz);
 	    mm->reserve_physical = os_reserve_physical;
 	    mm->unreserve_physical = os_unreserve_physical;
 	    virtual_map = 1;
@@ -2261,7 +2217,7 @@ erts_mmap_init(ErtsMemMapper* mm, ErtsMMapInit *init, int executable)
 	     * The whole supercarrier will by physically
 	     * reserved all the time.
 	     */
-	    start = os_mmap(NULL, sz, 1, executable);
+	    start = os_mmap(NULL, sz, 1);
 	}
 	if (!start)
 	    erts_exit(1,
@@ -2335,7 +2291,7 @@ erts_mmap_init(ErtsMemMapper* mm, ErtsMMapInit *init, int executable)
 	    mm->sua.top -= ERTS_PAGEALIGNED_SIZE;
 	    mm->size.supercarrier.used.total += ERTS_PAGEALIGNED_SIZE;
 #ifdef ERTS_HAVE_OS_PHYSICAL_MEMORY_RESERVATION
-	    if (!virtual_map || os_reserve_physical(mm->sua.top, ERTS_PAGEALIGNED_SIZE, 0))
+	    if (!virtual_map || os_reserve_physical(mm->sua.top, ERTS_PAGEALIGNED_SIZE))
 #endif
 		add_free_desc_area(mm, mm->sua.top, end);
             mm->desc.reserved += (end - mm->sua.top) / sizeof(ErtsFreeSegDesc);
@@ -2348,7 +2304,7 @@ erts_mmap_init(ErtsMemMapper* mm, ErtsMMapInit *init, int executable)
 	 * will be used for free segment descritors.
 	 */
 #ifdef ERTS_HAVE_OS_PHYSICAL_MEMORY_RESERVATION
-	if (virtual_map && !os_reserve_physical(start, mm->sa.bot - start, 0))
+	if (virtual_map && !os_reserve_physical(start, mm->sa.bot - start))
 	    erts_exit(1, "erts_mmap: Failed to reserve physical memory for descriptors\n");
 #endif
 	mm->desc.unused_start = start;
@@ -2390,7 +2346,7 @@ add_2tup(Uint **hpp, Uint *szp, Eterm *lp, Eterm el1, Eterm el2)
 }
 
 Eterm erts_mmap_info(ErtsMemMapper* mm,
-                     int *print_to_p,
+                     fmtfn_t *print_to_p,
                      void *print_to_arg,
                      Eterm** hpp, Uint* szp,
                      struct erts_mmap_info_struct* emis)
@@ -2405,7 +2361,7 @@ Eterm erts_mmap_info(ErtsMemMapper* mm,
     Eterm res = THE_NON_VALUE;
 
     if (!hpp) {
-        erts_smp_mtx_lock(&mm->mtx);
+        erts_mtx_lock(&mm->mtx);
         emis->sizes[0] = mm->size.supercarrier.total;
         emis->sizes[1] = mm->sa.top  - mm->sa.bot;
         emis->sizes[2] = mm->sua.top - mm->sua.bot;
@@ -2421,7 +2377,7 @@ Eterm erts_mmap_info(ErtsMemMapper* mm,
         emis->segs[5] = mm->sua.map.nseg;
 
         emis->os_used = mm->size.os.used;
-        erts_smp_mtx_unlock(&mm->mtx);
+        erts_mtx_unlock(&mm->mtx);
     }
 
     list[lix] = erts_mmap_info_options(mm, "option ", print_to_p, print_to_arg,
@@ -2431,7 +2387,7 @@ Eterm erts_mmap_info(ErtsMemMapper* mm,
 
 
     if (print_to_p) {
-        int to = *print_to_p;
+        fmtfn_t to = *print_to_p;
 	void *arg = print_to_arg;
         if (mm->supercarrier) {
             const char* prefix = "supercarrier ";
@@ -2485,7 +2441,7 @@ Eterm erts_mmap_info(ErtsMemMapper* mm,
 
 Eterm erts_mmap_info_options(ErtsMemMapper* mm,
                              char *prefix,
-                             int *print_to_p,
+                             fmtfn_t *print_to_p,
                              void *print_to_arg,
                              Uint **hpp,
                              Uint *szp)
@@ -2496,7 +2452,7 @@ Eterm erts_mmap_info_options(ErtsMemMapper* mm,
     Eterm res = THE_NON_VALUE;
 
     if (print_to_p) {
-        int to = *print_to_p;
+        fmtfn_t to = *print_to_p;
 	void *arg = print_to_arg;
         erts_print(to, arg, "%sscs: %bpu\n", prefix, scs);
         if (mm->supercarrier) {
@@ -2541,14 +2497,14 @@ Eterm erts_mmap_debug_info(Process* p)
         Eterm *hp, *hp_end;
         Uint may_need;
 
-        erts_smp_mtx_lock(&mm->mtx);
+        erts_mtx_lock(&mm->mtx);
         values[0] = (UWord)mm->sa.bot;
         values[1] = (UWord)mm->sa.top;
         values[2] = (UWord)mm->sua.bot;
         values[3] = (UWord)mm->sua.top;
         sa_list = build_free_seg_list(p, &mm->sa.map);
         sua_list = build_free_seg_list(p, &mm->sua.map);
-        erts_smp_mtx_unlock(&mm->mtx);
+        erts_mtx_unlock(&mm->mtx);
 
         may_need = 4*(2+3+2) + 2*(2+3);
         hp = HAlloc(p, may_need);
@@ -2558,8 +2514,8 @@ Eterm erts_mmap_debug_info(Process* p)
                                             sizeof(values)/sizeof(*values),
                                             tags, values);
 
-        sa_list = TUPLE2(hp, am_atom_put("sa_free_segs",12), sa_list); hp+=3;
-        sua_list = TUPLE2(hp, am_atom_put("sua_free_segs",13), sua_list); hp+=3;
+        sa_list = TUPLE2(hp, ERTS_MAKE_AM("sa_free_segs"), sa_list); hp+=3;
+        sua_list = TUPLE2(hp, ERTS_MAKE_AM("sua_free_segs"), sua_list); hp+=3;
         list = CONS(hp, sua_list, list); hp+=2;
         list = CONS(hp, sa_list, list); hp+=2;
 
@@ -2816,7 +2772,8 @@ static void hard_dbg_mseg_init(void)
 {
     ErtsFreeSegDesc_fake* p;
 
-    erts_mtx_init(&hard_dbg_mseg_mtx, "hard_dbg_mseg");
+    erts_mtx_init(&hard_dbg_mseg_mtx, "hard_dbg_mseg", NIL,
+        ERTS_LOCK_FLAGS_PROPERTY_STATIC | ERTS_LOCK_FLAGS_CATEGORY_DEBUG);
     hard_dbg_mseg_tree.root = NULL;
     hard_dbg_mseg_tree.order = ADDR_ORDER;
 
diff --git a/erts/emulator/sys/common/erl_mmap.h b/erts/emulator/sys/common/erl_mmap.h
index fa51b663fa..539daea419 100644
--- a/erts/emulator/sys/common/erl_mmap.h
+++ b/erts/emulator/sys/common/erl_mmap.h
@@ -1,7 +1,7 @@
 /*
  * %CopyrightBegin%
  *
- * Copyright Ericsson AB 2013-2016. All Rights Reserved.
+ * Copyright Ericsson AB 2013-2018. All Rights Reserved.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -22,6 +22,7 @@
 #define ERL_MMAP_H__
 
 #include "sys.h"
+#include "erl_printf.h"
 
 #define ERTS_MMAP_SUPERALIGNED_BITS (18)
 /* Affects hard limits for sbct and lmbcs documented in erts_alloc.xml */
@@ -92,11 +93,6 @@ typedef struct {
 #define ERTS_MMAP_INIT_LITERAL_INITER \
     {{NULL, NULL}, {NULL, NULL}, ERTS_LITERAL_VIRTUAL_AREA_SIZE, 1, (1 << 10), 0}
 
-#define ERTS_HIPE_EXEC_VIRTUAL_AREA_SIZE (UWORD_CONSTANT(512)*1024*1024)
-
-#define ERTS_MMAP_INIT_HIPE_EXEC_INITER \
-    {{NULL, NULL}, {NULL, NULL}, ERTS_HIPE_EXEC_VIRTUAL_AREA_SIZE, 1, (1 << 10), 0}
-
 
 #define ERTS_SUPERALIGNED_SIZE \
     (1 << ERTS_MMAP_SUPERALIGNED_BITS)
@@ -139,17 +135,17 @@ void *erts_mmap(ErtsMemMapper*, Uint32 flags, UWord *sizep);
 void erts_munmap(ErtsMemMapper*, Uint32 flags, void *ptr, UWord size);
 void *erts_mremap(ErtsMemMapper*, Uint32 flags, void *ptr, UWord old_size, UWord *sizep);
 int erts_mmap_in_supercarrier(ErtsMemMapper*, void *ptr);
-void erts_mmap_init(ErtsMemMapper*, ErtsMMapInit*, int executable);
+void erts_mmap_init(ErtsMemMapper*, ErtsMMapInit*);
 struct erts_mmap_info_struct
 {
     UWord sizes[6];
     UWord segs[6];
     UWord os_used;
 };
-Eterm erts_mmap_info(ErtsMemMapper*, int *print_to_p, void *print_to_arg,
+Eterm erts_mmap_info(ErtsMemMapper*, fmtfn_t *print_to_p, void *print_to_arg,
                      Eterm** hpp, Uint* szp, struct erts_mmap_info_struct*);
 Eterm erts_mmap_info_options(ErtsMemMapper*,
-                             char *prefix, int *print_to_p, void *print_to_arg,
+                             char *prefix, fmtfn_t *print_to_p, void *print_to_arg,
                              Uint **hpp, Uint *szp);
 
 
@@ -157,12 +153,14 @@ Eterm erts_mmap_info_options(ErtsMemMapper*,
 #  include "erl_alloc_types.h"
 
 extern ErtsMemMapper erts_dflt_mmapper;
-#  if defined(ARCH_64) && defined(ERTS_HAVE_OS_PHYSICAL_MEMORY_RESERVATION)
+
+# if defined(ERTS_HAVE_OS_PHYSICAL_MEMORY_RESERVATION)
+
+#  if defined(ARCH_64)
 extern ErtsMemMapper erts_literal_mmapper;
 #  endif
-#  ifdef ERTS_ALC_A_EXEC
-extern ErtsMemMapper erts_exec_mmapper;
-#  endif
+
+# endif /* ERTS_HAVE_OS_PHYSICAL_MEMORY_RESERVATION */
 #endif /* ERTS_WANT_MEM_MAPPERS */
 
 /*#define HARD_DEBUG_MSEG*/
diff --git a/erts/emulator/sys/common/erl_mseg.c b/erts/emulator/sys/common/erl_mseg.c
index f3306a888c..030e5b00a7 100644
--- a/erts/emulator/sys/common/erl_mseg.c
+++ b/erts/emulator/sys/common/erl_mseg.c
@@ -1,7 +1,7 @@
 /*
  * %CopyrightBegin%
  *
- * Copyright Ericsson AB 2002-2016. All Rights Reserved.
+ * Copyright Ericsson AB 2002-2018. All Rights Reserved.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -83,11 +83,13 @@ static const int debruijn[32] = {
     31, 27, 13, 23, 21, 19, 16,  7, 26, 12, 18,  6, 11,  5, 10,  9
 };
 
-#define LOG2(X) (debruijn[((Uint32)(((X) & -(X)) * 0x077CB531U)) >> 27])
+#define LSB(X) (debruijn[((Uint32)(((X) & -(X)) * 0x077CB531U)) >> 27])
 
 #define CACHE_AREAS      (32 - MSEG_ALIGN_BITS)
 
-#define SIZE_TO_CACHE_AREA_IDX(S)   (LOG2((S)) - MSEG_ALIGN_BITS)
+/* FIXME: segment sizes > 2 GB result in bogus negative indices */
+/* NOTE: using LSB instead of proper log2 only works if S is a power of 2 */
+#define SIZE_TO_CACHE_AREA_IDX(S)   (LSB((S)) - MSEG_ALIGN_BITS)
 #define MAX_CACHE_SIZE   (30)
 
 #define MSEG_FLG_IS_2POW(X)    ((X) & ERTS_MSEG_FLG_2POW)
@@ -186,7 +188,6 @@ typedef union {
 static int no_mseg_allocators;
 static ErtsAlgndMsegAllctr_t *aligned_mseg_allctr;
 
-#ifdef ERTS_SMP
 
 #define ERTS_MSEG_ALLCTR_IX(IX) \
   (&aligned_mseg_allctr[(IX)].mseg_alloc)
@@ -197,18 +198,6 @@ static ErtsAlgndMsegAllctr_t *aligned_mseg_allctr;
 #define ERTS_MSEG_ALLCTR_OPT(OPT) \
   ((OPT)->sched_spec ? ERTS_MSEG_ALLCTR_SS() : ERTS_MSEG_ALLCTR_IX(0))
 
-#else
-
-#define ERTS_MSEG_ALLCTR_IX(IX) \
-  (&aligned_mseg_allctr[0].mseg_alloc)
-
-#define ERTS_MSEG_ALLCTR_SS() \
-  (&aligned_mseg_allctr[0].mseg_alloc)
-
-#define ERTS_MSEG_ALLCTR_OPT(OPT) \
-  (&aligned_mseg_allctr[0].mseg_alloc)
-
-#endif
 
 #define ERTS_MSEG_LOCK(MA)		\
 do {					\
@@ -350,11 +339,11 @@ mseg_recreate(ErtsMsegAllctr_t *ma, Uint flags, void *old_seg, UWord old_size, U
 do {									\
     if ((MA)->is_thread_safe)						\
 	ERTS_LC_ASSERT(erts_lc_mtx_is_locked(&(MA)->mtx)		\
-		       || erts_smp_thr_progress_is_blocking()		\
+		       || erts_thr_progress_is_blocking()		\
 		       || ERTS_IS_CRASH_DUMPING);			\
     else								\
 	ERTS_LC_ASSERT((MA)->ix == (int) erts_get_scheduler_id()	\
-		       || erts_smp_thr_progress_is_blocking()		\
+		       || erts_thr_progress_is_blocking()		\
 		       || ERTS_IS_CRASH_DUMPING);			\
 } while (0)
 #else
@@ -378,7 +367,7 @@ static ERTS_INLINE int cache_bless_segment(ErtsMsegAllctr_t *ma, void *seg, UWor
 
     ASSERT(!MSEG_FLG_IS_2POW(flags) || (MSEG_FLG_IS_2POW(flags) && MAP_IS_ALIGNED(seg) && IS_2POW(size)));
 
-    /* The idea is that sbc caching is prefered over mbc caching.
+    /* The idea is that sbc caching is preferred over mbc caching.
      * Blocks are normally allocated in mb carriers and thus cached there.
      * Large blocks has no such cache and it is up to mseg to cache them to speed things up.
      */
@@ -396,6 +385,9 @@ static ERTS_INLINE int cache_bless_segment(ErtsMsegAllctr_t *ma, void *seg, UWor
 	if (MSEG_FLG_IS_2POW(flags)) {
 	    int ix = SIZE_TO_CACHE_AREA_IDX(size);
 
+            if (ix < 0)
+                return 0;
+
 	    ASSERT(ix < CACHE_AREAS);
 	    ASSERT((1 << (ix + MSEG_ALIGN_BITS)) == size);
 
@@ -471,6 +463,9 @@ static ERTS_INLINE void *cache_get_segment(ErtsMsegAllctr_t *ma, UWord *size_p,
 
 	ASSERT(IS_2POW(size));
 
+        if (ix < 0)
+            return NULL;
+
 	for( i = ix; i < CACHE_AREAS; i++) {
 
 	    if (erts_circleq_is_empty(&(ma->cache_powered_node[i])))
@@ -991,7 +986,7 @@ add_4tup(Uint **hpp, Uint *szp, Eterm *lp,
 static Eterm
 info_options(ErtsMsegAllctr_t *ma,
 	     char *prefix,
-	     int *print_to_p,
+	     fmtfn_t *print_to_p,
 	     void *print_to_arg,
 	     Uint **hpp,
 	     Uint *szp)
@@ -999,7 +994,7 @@ info_options(ErtsMsegAllctr_t *ma,
     Eterm res = NIL;
 
     if (print_to_p) {
-	int to = *print_to_p;
+	fmtfn_t to = *print_to_p;
 	void *arg = print_to_arg;
 	erts_print(to, arg, "%samcbf: %beu\n", prefix, ma->abs_max_cache_bad_fit);
 	erts_print(to, arg, "%srmcbf: %beu\n", prefix, ma->rel_max_cache_bad_fit);
@@ -1027,7 +1022,7 @@ info_options(ErtsMsegAllctr_t *ma,
 }
 
 static Eterm
-info_calls(ErtsMsegAllctr_t *ma, int *print_to_p, void *print_to_arg, Uint **hpp, Uint *szp)
+info_calls(ErtsMsegAllctr_t *ma, fmtfn_t *print_to_p, void *print_to_arg, Uint **hpp, Uint *szp)
 {
     Eterm res = THE_NON_VALUE;
 
@@ -1040,7 +1035,7 @@ info_calls(ErtsMsegAllctr_t *ma, int *print_to_p, void *print_to_arg, Uint **hpp
 	erts_print(TO, TOA, "mseg_%s calls: %b32u%09b32u\n", #CC,		\
 		   ma->calls.CC.giga_no, ma->calls.CC.no)
 
-	int to = *print_to_p;
+	fmtfn_t to = *print_to_p;
 	void *arg = print_to_arg;
 
 	PRINT_CC(to, arg, alloc);
@@ -1106,7 +1101,7 @@ info_calls(ErtsMsegAllctr_t *ma, int *print_to_p, void *print_to_arg, Uint **hpp
 }
 
 static Eterm
-info_status(ErtsMsegAllctr_t *ma, int *print_to_p, void *print_to_arg,
+info_status(ErtsMsegAllctr_t *ma, fmtfn_t *print_to_p, void *print_to_arg,
 	    int begin_new_max_period, int only_sz, Uint **hpp, Uint *szp)
 {
     Eterm res = THE_NON_VALUE;
@@ -1117,7 +1112,7 @@ info_status(ErtsMsegAllctr_t *ma, int *print_to_p, void *print_to_arg,
 	ma->segments.max_ever.sz = ma->segments.max.sz;
 
     if (print_to_p) {
-	int to = *print_to_p;
+	fmtfn_t to = *print_to_p;
 	void *arg = print_to_arg;
 
         if (!only_sz) {
@@ -1165,7 +1160,7 @@ info_status(ErtsMsegAllctr_t *ma, int *print_to_p, void *print_to_arg,
     return res;
 }
 
-static Eterm info_memkind(ErtsMsegAllctr_t *ma, int *print_to_p, void *print_to_arg,
+static Eterm info_memkind(ErtsMsegAllctr_t *ma, fmtfn_t *print_to_p, void *print_to_arg,
 			  int begin_max_per, int only_sz, Uint **hpp, Uint *szp)
 {
     Eterm res = THE_NON_VALUE;
@@ -1196,7 +1191,7 @@ static Eterm info_memkind(ErtsMsegAllctr_t *ma, int *print_to_p, void *print_to_
 }
 
 static Eterm
-info_version(ErtsMsegAllctr_t *ma, int *print_to_p, void *print_to_arg, Uint **hpp, Uint *szp)
+info_version(ErtsMsegAllctr_t *ma, fmtfn_t *print_to_p, void *print_to_arg, Uint **hpp, Uint *szp)
 {
     Eterm res = THE_NON_VALUE;
 
@@ -1218,7 +1213,7 @@ info_version(ErtsMsegAllctr_t *ma, int *print_to_p, void *print_to_arg, Uint **h
 
 Eterm
 erts_mseg_info_options(int ix,
-		       int *print_to_p, void *print_to_arg,
+		       fmtfn_t *print_to_p, void *print_to_arg,
 		       Uint **hpp, Uint *szp)
 {
     ErtsMsegAllctr_t *ma = ERTS_MSEG_ALLCTR_IX(ix);
@@ -1231,7 +1226,7 @@ erts_mseg_info_options(int ix,
 
 Eterm
 erts_mseg_info(int ix,
-	       int *print_to_p,
+	       fmtfn_t *print_to_p,
 	       void *print_to_arg,
 	       int begin_max_per,
                int only_sz,
@@ -1396,11 +1391,7 @@ erts_mseg_init(ErtsMsegInit_t *init)
     int i;
     UWord x;
 
-#ifdef ERTS_SMP
     no_mseg_allocators = init->nos + 1;
-#else
-    no_mseg_allocators = 1;
-#endif
 
     x = (UWord) malloc(sizeof(ErtsAlgndMsegAllctr_t)
 		       *no_mseg_allocators
@@ -1412,17 +1403,12 @@ erts_mseg_init(ErtsMsegInit_t *init)
 
     atoms_initialized = 0;
 
-    erts_mtx_init(&init_atoms_mutex, "mseg_init_atoms");
+    erts_mtx_init(&init_atoms_mutex, "mseg_init_atoms", NIL,
+        ERTS_LOCK_FLAGS_PROPERTY_STATIC | ERTS_LOCK_FLAGS_CATEGORY_GENERIC);
 
-#ifdef ERTS_ALC_A_EXEC
-    /* Initialize erts_exec_mapper *FIRST*, to increase probability
-     * of getting low memory for HiPE AMD64's small code model.
-     */
-    erts_mmap_init(&erts_exec_mmapper, &init->exec_mmap, 1);
-#endif
-    erts_mmap_init(&erts_dflt_mmapper, &init->dflt_mmap, 0);
+    erts_mmap_init(&erts_dflt_mmapper, &init->dflt_mmap);
 #if defined(ARCH_64) && defined(ERTS_HAVE_OS_PHYSICAL_MEMORY_RESERVATION)
-    erts_mmap_init(&erts_literal_mmapper, &init->literal_mmap, 0);
+    erts_mmap_init(&erts_literal_mmapper, &init->literal_mmap);
 #endif
 
     if (!IS_2POW(GET_PAGE_SIZE))
@@ -1441,7 +1427,8 @@ erts_mseg_init(ErtsMsegInit_t *init)
 	    ma->is_thread_safe = 0;
 	else {
 	    ma->is_thread_safe = 1;
-	    erts_mtx_init(&ma->mtx, "mseg");
+            erts_mtx_init(&ma->mtx, "mseg", make_small(i),
+                ERTS_LOCK_FLAGS_PROPERTY_STATIC | ERTS_LOCK_FLAGS_CATEGORY_ALLOCATOR);
 	}
 
 	ma->is_cache_check_scheduled = 0;
diff --git a/erts/emulator/sys/common/erl_mseg.h b/erts/emulator/sys/common/erl_mseg.h
index a43b409e94..ea9060ddac 100644
--- a/erts/emulator/sys/common/erl_mseg.h
+++ b/erts/emulator/sys/common/erl_mseg.h
@@ -1,7 +1,7 @@
 /*
  * %CopyrightBegin%
  *
- * Copyright Ericsson AB 2002-2016. All Rights Reserved.
+ * Copyright Ericsson AB 2002-2018. All Rights Reserved.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -61,7 +61,6 @@ typedef struct {
     Uint nos;
     ErtsMMapInit dflt_mmap;
     ErtsMMapInit literal_mmap;
-    ErtsMMapInit exec_mmap;
 } ErtsMsegInit_t;
 
 #define ERTS_MSEG_INIT_DEFAULT_INITIALIZER				\
@@ -72,7 +71,6 @@ typedef struct {
     1000,		/* cci:   Cache check interval		*/	\
     ERTS_MMAP_INIT_DEFAULT_INITER,					\
     ERTS_MMAP_INIT_LITERAL_INITER,                                      \
-    ERTS_MMAP_INIT_HIPE_EXEC_INITER                                     \
 }
 
 typedef struct {
@@ -98,8 +96,8 @@ Uint  erts_mseg_unit_size(void);
 void  erts_mseg_init(ErtsMsegInit_t *init);
 void  erts_mseg_late_init(void); /* Have to be called after all allocators,
 				   threads and timers have been initialized. */
-Eterm erts_mseg_info_options(int, int *, void*, Uint **, Uint *);
-Eterm erts_mseg_info(int, int *, void*, int, int, Uint **, Uint *);
+Eterm erts_mseg_info_options(int, fmtfn_t*, void*, Uint **, Uint *);
+Eterm erts_mseg_info(int, fmtfn_t *, void*, int, int, Uint **, Uint *);
 
 #endif /* #if HAVE_ERTS_MSEG */
 
diff --git a/erts/emulator/sys/common/erl_os_monotonic_time_extender.c b/erts/emulator/sys/common/erl_os_monotonic_time_extender.c
index d53190fdd5..5844e7eeb7 100644
--- a/erts/emulator/sys/common/erl_os_monotonic_time_extender.c
+++ b/erts/emulator/sys/common/erl_os_monotonic_time_extender.c
@@ -1,7 +1,7 @@
 /*
  * %CopyrightBegin%
  * 
- * Copyright Ericsson AB 2015-2016. All Rights Reserved.
+ * Copyright Ericsson AB 2015-2018. All Rights Reserved.
  * 
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -23,7 +23,6 @@
 #endif
 #include "erl_os_monotonic_time_extender.h"
 
-#ifdef USE_THREADS
 
 static void *os_monotonic_time_extender(void *vstatep)
 {
@@ -49,30 +48,22 @@ static void *os_monotonic_time_extender(void *vstatep)
 }
 
 static erts_tid_t os_monotonic_extender_tid;
-#endif
 
 void
 erts_init_os_monotonic_time_extender(ErtsOsMonotonicTimeExtendState *statep,
 				     Uint32 (*raw_os_monotonic_time)(void),
 				     int check_seconds)
 {
-#ifdef USE_THREADS
     statep->raw_os_monotonic_time = raw_os_monotonic_time;
     erts_atomic32_init_nob(&statep->extend[0], (erts_aint32_t) 0);
     erts_atomic32_init_nob(&statep->extend[1], (erts_aint32_t) 0);
     statep->check_interval = check_seconds;
 
-#else
-    statep->extend[0] = (Uint32) 0;
-    statep->extend[1] = (Uint32) 0;
-    statep->last_msb = (ErtsMonotonicTime) 0;
-#endif
 }
 
 void
 erts_late_init_os_monotonic_time_extender(ErtsOsMonotonicTimeExtendState *statep)
 {
-#ifdef USE_THREADS
     erts_thr_opts_t thr_opts = ERTS_THR_OPTS_DEFAULT_INITER;
     thr_opts.detached = 1;
     thr_opts.suggested_stack_size = 4;
@@ -85,5 +76,4 @@ erts_late_init_os_monotonic_time_extender(ErtsOsMonotonicTimeExtendState *statep
 		    os_monotonic_time_extender,
 		    (void*) statep,
 		    &thr_opts);
-#endif
 }
diff --git a/erts/emulator/sys/common/erl_os_monotonic_time_extender.h b/erts/emulator/sys/common/erl_os_monotonic_time_extender.h
index 8089c9aed9..f6659fe973 100644
--- a/erts/emulator/sys/common/erl_os_monotonic_time_extender.h
+++ b/erts/emulator/sys/common/erl_os_monotonic_time_extender.h
@@ -1,7 +1,7 @@
 /*
  * %CopyrightBegin%
  * 
- * Copyright Ericsson AB 2015. All Rights Reserved.
+ * Copyright Ericsson AB 2015-2018. All Rights Reserved.
  * 
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -25,36 +25,16 @@
 #include "erl_threads.h"
 
 typedef struct {
-#ifdef USE_THREADS
     Uint32 (*raw_os_monotonic_time)(void);
     erts_atomic32_t extend[2];
     int check_interval;
-#else
-    Uint32 extend[2];
-    ErtsMonotonicTime last_msb;
-#endif
 } ErtsOsMonotonicTimeExtendState;
 
-#ifdef USE_THREADS
-#  define ERTS_CHK_EXTEND_OS_MONOTONIC_TIME(S, RT) ((void) 1)
 #  define ERTS_EXTEND_OS_MONOTONIC_TIME(S, RT)				\
     ((((ErtsMonotonicTime)						\
        erts_atomic32_read_nob(&((S)->extend[((int) ((RT) >> 31)) & 1]))) \
       << 32)								\
      + (RT))
-#else
-#  define ERTS_CHK_EXTEND_OS_MONOTONIC_TIME(S, RT)			\
-    do {								\
-	Uint32 msb__ = (RT) & (((Uint32) 1) << 31);			\
-	if (msb__ != (S)->last_msb) {					\
-	    int ix__ = ((int) ((S)->last_msb >> 31)) & 1;		\
-	    (S)->extend[ix__]++;					\
-	    (S)->last_msb = msb;					\
-	}								\
-    } while (0)
-#  define ERTS_EXTEND_OS_MONOTONIC_TIME(S, RT)				\
-    ((((ErtsMonotonicTime) (S)->extend[((int) ((RT) >> 31)) & 1]) << 32) + (RT))
-#endif
 
 void
 erts_init_os_monotonic_time_extender(ErtsOsMonotonicTimeExtendState *statep,
diff --git a/erts/emulator/sys/common/erl_osenv.c b/erts/emulator/sys/common/erl_osenv.c
new file mode 100644
index 0000000000..6a16377736
--- /dev/null
+++ b/erts/emulator/sys/common/erl_osenv.c
@@ -0,0 +1,404 @@
+/*
+ * %CopyrightBegin%
+ *
+ * Copyright Ericsson AB 2017-2018. All Rights Reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ * %CopyrightEnd%
+ */
+
+#include "erl_osenv.h"
+
+#include "global.h"
+#include "erl_alloc.h"
+#include "erl_process.h"
+
+#define STACKBUF_SIZE (512)
+
+typedef struct __env_rbtnode_t {
+    struct __env_rbtnode_t *parent;
+    struct __env_rbtnode_t *left;
+    struct __env_rbtnode_t *right;
+
+    int is_red;
+
+    erts_osenv_data_t key;
+    erts_osenv_data_t value;
+} env_rbtnode_t;
+
+#define ERTS_RBT_PREFIX env
+#define ERTS_RBT_T env_rbtnode_t
+#define ERTS_RBT_KEY_T erts_osenv_data_t
+#define ERTS_RBT_FLAGS_T int
+#define ERTS_RBT_INIT_EMPTY_TNODE(T) \
+    do { \
+        (T)->parent = NULL; \
+        (T)->left = NULL; \
+        (T)->right = NULL; \
+        (T)->is_red = 0; \
+    } while(0)
+#define ERTS_RBT_IS_RED(T) ((T)->is_red)
+#define ERTS_RBT_SET_RED(T) ((T)->is_red = 1)
+#define ERTS_RBT_IS_BLACK(T) (!ERTS_RBT_IS_RED(T))
+#define ERTS_RBT_SET_BLACK(T) ((T)->is_red = 0)
+#define ERTS_RBT_GET_FLAGS(T) ((T)->is_red)
+#define ERTS_RBT_SET_FLAGS(T, F) ((T)->is_red = F)
+#define ERTS_RBT_GET_PARENT(T) ((T)->parent)
+#define ERTS_RBT_SET_PARENT(T, P) ((T)->parent = P)
+#define ERTS_RBT_GET_RIGHT(T) ((T)->right)
+#define ERTS_RBT_SET_RIGHT(T, R) ((T)->right = (R))
+#define ERTS_RBT_GET_LEFT(T) ((T)->left)
+#define ERTS_RBT_SET_LEFT(T, L) ((T)->left = (L))
+#define ERTS_RBT_GET_KEY(T) ((T)->key)
+#define ERTS_RBT_IS_LT(KX, KY) (compare_env_keys(KX, KY) < 0)
+#define ERTS_RBT_IS_EQ(KX, KY) (compare_env_keys(KX, KY) == 0)
+#define ERTS_RBT_WANT_FOREACH_DESTROY
+#define ERTS_RBT_WANT_FOREACH
+#define ERTS_RBT_WANT_REPLACE
+#define ERTS_RBT_WANT_DELETE
+#define ERTS_RBT_WANT_INSERT
+#define ERTS_RBT_WANT_LOOKUP
+
+static int compare_env_keys(const erts_osenv_data_t a, const erts_osenv_data_t b);
+
+#include "erl_rbtree.h"
+
+static int compare_env_keys(const erts_osenv_data_t a, const erts_osenv_data_t b) {
+    int relation;
+
+#ifdef __WIN32__
+    /* Environment variables are case-insensitive on Windows. */
+    relation = _wcsnicmp((const WCHAR*)a.data, (const WCHAR*)b.data,
+                         MIN(a.length, b.length) / sizeof(WCHAR));
+#else
+    relation = sys_memcmp(a.data, b.data, MIN(a.length, b.length));
+#endif
+
+    if(relation != 0) {
+        return relation;
+    }
+
+    if(a.length < b.length) {
+        return -1;
+    } else if(a.length == b.length) {
+        return 0;
+    } else {
+        return 1;
+    }
+}
+
+static void *convert_value_to_native(Eterm term, char *stackbuf,
+        int stackbuf_size, Sint *length) {
+    int encoding;
+    void *result;
+
+    if(is_atom(term)) {
+        return NULL;
+    }
+
+    encoding = erts_get_native_filename_encoding();
+    *length = erts_native_filename_need(term, encoding);
+
+    if(*length < 0) {
+        return NULL;
+    } else if(*length >= stackbuf_size) {
+        result = erts_alloc(ERTS_ALC_T_TMP, *length);
+    } else {
+        result = stackbuf;
+    }
+
+    erts_native_filename_put(term, encoding, (byte*)result);
+
+    return result;
+}
+
+static void *convert_key_to_native(Eterm term, char *stackbuf,
+        int stackbuf_size, Sint *length) {
+    byte *name_iterator, *name_end;
+    void *result;
+    int encoding;
+
+    result = convert_value_to_native(term, stackbuf, stackbuf_size, length);
+
+    if(result == NULL || length == 0) {
+        return NULL;
+    }
+
+    encoding = erts_get_native_filename_encoding();
+
+    name_iterator = (byte*)result;
+    name_end = &name_iterator[*length];
+
+#ifdef __WIN32__
+    /* Windows stores per-drive working directories as variables starting with
+     * '=', so we skip the first character to tolerate that. */
+    name_iterator = erts_raw_env_next_char(name_iterator, encoding);
+#endif
+
+    while(name_iterator < name_end) {
+        if(erts_raw_env_char_is_7bit_ascii_char('=', name_iterator, encoding)) {
+            if(result != stackbuf) {
+                erts_free(ERTS_ALC_T_TMP, result);
+            }
+
+            return NULL;
+        }
+
+        name_iterator = erts_raw_env_next_char(name_iterator, encoding);
+    }
+
+    return result;
+}
+
+void erts_osenv_init(erts_osenv_t *env) {
+    env->variable_count = 0;
+    env->content_size = 0;
+    env->tree = NULL;
+}
+
+static void destroy_foreach(env_rbtnode_t *node, void *_state) {
+    erts_free(ERTS_ALC_T_ENVIRONMENT, node);
+    (void)_state;
+}
+
+void erts_osenv_clear(erts_osenv_t *env) {
+    env_rbt_foreach_destroy(&env->tree, &destroy_foreach, NULL);
+    erts_osenv_init(env);
+}
+
+struct __env_merge {
+    int overwrite_existing;
+    erts_osenv_t *env;
+};
+
+static void merge_foreach(env_rbtnode_t *node, void *_state) {
+    struct __env_merge *state = (struct __env_merge*)(_state);
+    env_rbtnode_t *existing_node;
+
+    existing_node = env_rbt_lookup(state->env->tree, node->key);
+
+    if(existing_node == NULL || state->overwrite_existing) {
+        erts_osenv_put_native(state->env, &node->key, &node->value);
+    }
+}
+
+void erts_osenv_merge(erts_osenv_t *env, const erts_osenv_t *with, int overwrite) {
+    struct __env_merge merge_state;
+
+    merge_state.overwrite_existing = overwrite;
+    merge_state.env = env;
+
+    env_rbt_foreach(with->tree, merge_foreach, &merge_state);
+}
+
+struct __env_foreach_term {
+    erts_osenv_foreach_term_cb_t user_callback;
+    struct process *process;
+    void *user_state;
+};
+
+static void foreach_term_wrapper(env_rbtnode_t *node, void *_state) {
+    struct __env_foreach_term *state = (struct __env_foreach_term*)_state;
+    Eterm key, value;
+
+    key = erts_convert_native_to_filename(state->process,
+        node->key.length, (byte*)node->key.data);
+    value = erts_convert_native_to_filename(state->process,
+        node->value.length, (byte*)node->value.data);
+
+    state->user_callback(state->process, state->user_state, key, value);
+}
+
+void erts_osenv_foreach_term(const erts_osenv_t *env, struct process *process,
+        void *state, erts_osenv_foreach_term_cb_t callback) {
+    struct __env_foreach_term wrapper_state;
+
+    wrapper_state.user_callback = callback;
+    wrapper_state.user_state = state;
+    wrapper_state.process = process;
+
+    env_rbt_foreach(env->tree, foreach_term_wrapper, &wrapper_state);
+}
+
+int erts_osenv_get_term(const erts_osenv_t *env, Process *process,
+        Eterm key_term, Eterm *out_term) {
+    char key_stackbuf[STACKBUF_SIZE];
+    erts_osenv_data_t key;
+    int result;
+
+    key.data = convert_key_to_native(key_term, key_stackbuf,
+        STACKBUF_SIZE, &key.length);
+    result = -1;
+
+    if(key.data != NULL) {
+        env_rbtnode_t *node;
+
+        node = env_rbt_lookup(env->tree, key);
+        result = 0;
+
+        if(node != NULL) {
+            (*out_term) = erts_convert_native_to_filename(process,
+                node->value.length, (byte*)node->value.data);
+            result = 1;
+        }
+
+        if(key.data != key_stackbuf) {
+            erts_free(ERTS_ALC_T_TMP, key.data);
+        }
+    }
+
+    return result;
+}
+
+int erts_osenv_put_term(erts_osenv_t *env, Eterm key_term, Eterm value_term) {
+    char key_stackbuf[STACKBUF_SIZE], value_stackbuf[STACKBUF_SIZE];
+    erts_osenv_data_t key, value;
+    int result;
+
+    key.data = convert_key_to_native(key_term, key_stackbuf,
+        STACKBUF_SIZE, &key.length);
+    value.data = convert_value_to_native(value_term, value_stackbuf,
+        STACKBUF_SIZE, &value.length);
+    result = -1;
+
+    if(value.data != NULL && key.data != NULL) {
+        result = erts_osenv_put_native(env, &key, &value);
+    }
+
+    if(value.data != NULL && value.data != value_stackbuf) {
+        erts_free(ERTS_ALC_T_TMP, value.data);
+    }
+
+    if(key.data != NULL && key.data != key_stackbuf) {
+        erts_free(ERTS_ALC_T_TMP, key.data);
+    }
+
+    return result;
+}
+
+int erts_osenv_unset_term(erts_osenv_t *env, Eterm key_term) {
+    char key_stackbuf[STACKBUF_SIZE];
+    erts_osenv_data_t key;
+    int result;
+
+    key.data = convert_key_to_native(key_term, key_stackbuf,
+        STACKBUF_SIZE, &key.length);
+    result = -1;
+
+    if(key.data != NULL) {
+        result = erts_osenv_unset_native(env, &key);
+
+        if(key.data != key_stackbuf) {
+            erts_free(ERTS_ALC_T_TMP, key.data);
+        }
+    }
+
+    return result;
+}
+
+/* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
+
+struct __env_foreach_native {
+    erts_osenv_foreach_native_cb_t user_callback;
+    void *user_state;
+};
+
+static void foreach_native_wrapper(env_rbtnode_t *node, void *_state) {
+    struct __env_foreach_native *state = (struct __env_foreach_native*)_state;
+
+    state->user_callback(state->user_state, &node->key, &node->value);
+}
+
+void erts_osenv_foreach_native(const erts_osenv_t *env, void *state,
+        erts_osenv_foreach_native_cb_t callback) {
+    struct __env_foreach_native wrapper_state;
+
+    wrapper_state.user_callback = callback;
+    wrapper_state.user_state = state;
+
+    env_rbt_foreach(env->tree, foreach_native_wrapper, &wrapper_state);
+}
+
+int erts_osenv_get_native(const erts_osenv_t *env,
+        const erts_osenv_data_t *key,
+        erts_osenv_data_t *value) {
+    env_rbtnode_t *node = env_rbt_lookup(env->tree, *key);
+
+    if(node != NULL) {
+        if(value != NULL) {
+            if(node->value.length > value->length) {
+                return -1;
+            }
+
+            sys_memcpy(value->data, node->value.data, node->value.length);
+            value->length = node->value.length;
+        }
+
+        return 1;
+    }
+
+    return 0;
+}
+
+int erts_osenv_put_native(erts_osenv_t *env, const erts_osenv_data_t *key,
+        const erts_osenv_data_t *value) {
+    env_rbtnode_t *old_node, *new_node;
+
+    new_node = erts_alloc(ERTS_ALC_T_ENVIRONMENT, sizeof(env_rbtnode_t) +
+        key->length + value->length);
+
+    new_node->key.data = (char*)(&new_node[1]);
+    new_node->key.length = key->length;
+    new_node->value.data = &((char*)new_node->key.data)[key->length];
+    new_node->value.length = value->length;
+
+    sys_memcpy(new_node->key.data, key->data, key->length);
+    sys_memcpy(new_node->value.data, value->data, value->length);
+
+    old_node = env_rbt_lookup(env->tree, *key);
+
+    if(old_node != NULL) {
+        env->content_size -= old_node->value.length;
+        env->content_size -= old_node->key.length;
+        env_rbt_replace(&env->tree, old_node, new_node);
+    } else {
+        env_rbt_insert(&env->tree, new_node);
+        env->variable_count++;
+    }
+
+    env->content_size += new_node->value.length;
+    env->content_size += new_node->key.length;
+
+    if(old_node != NULL) {
+        erts_free(ERTS_ALC_T_ENVIRONMENT, old_node);
+    }
+
+    return 1;
+}
+
+int erts_osenv_unset_native(erts_osenv_t *env, const erts_osenv_data_t *key) {
+    env_rbtnode_t *old_node = env_rbt_lookup(env->tree, *key);
+
+    if(old_node != NULL) {
+        env->content_size -= old_node->value.length;
+        env->content_size -= old_node->key.length;
+        env->variable_count -= 1;
+
+        env_rbt_delete(&env->tree, old_node);
+        erts_free(ERTS_ALC_T_ENVIRONMENT, old_node);
+        return 1;
+    }
+
+    return 0;
+}
diff --git a/erts/emulator/sys/common/erl_osenv.h b/erts/emulator/sys/common/erl_osenv.h
new file mode 100644
index 0000000000..4777f2148a
--- /dev/null
+++ b/erts/emulator/sys/common/erl_osenv.h
@@ -0,0 +1,121 @@
+/*
+ * %CopyrightBegin%
+ *
+ * Copyright Ericsson AB 2017. All Rights Reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ * %CopyrightEnd%
+ */
+
+/* This is a replacement for getenv(3) and friends, operating on instances so
+ * we can keep a common implementation for both the global and local (per-port)
+ * environments.
+ *
+ * The instances are not thread-safe on their own but unlike getenv(3) we're
+ * guaranteed to be the only user, so placing locks around all our accesses
+ * will suffice.
+ *
+ * Use erts_sys_rwlock_global_osenv to access the global environment. */
+
+#ifndef __ERL_OSENV_H__
+#define __ERL_OSENV_H__
+
+#ifdef HAVE_CONFIG_H
+#  include "config.h"
+#endif
+
+typedef struct __erts_osenv_data_t erts_osenv_data_t;
+
+typedef struct __erts_osenv_t {
+    struct __env_rbtnode_t *tree;
+    int variable_count;
+    int content_size;
+} erts_osenv_t;
+
+#include "sys.h"
+
+struct __erts_osenv_data_t {
+    Sint length;
+    void *data;
+};
+
+void erts_osenv_init(erts_osenv_t *env);
+void erts_osenv_clear(erts_osenv_t *env);
+
+/* @brief Merges \c with into \c env
+ *
+ * @param overwrite Whether to overwrite existing entries or keep them as they
+ * are. */
+void erts_osenv_merge(erts_osenv_t *env, const erts_osenv_t *with, int overwrite);
+
+/* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
+
+/* @brief Copies env[key] into \c value
+ *
+ * @return 1 on success, 0 if the key couldn't be found, and -1 if the input
+ * was invalid. */
+int erts_osenv_get_term(const erts_osenv_t *env, struct process *process,
+    Eterm key, Eterm *value);
+
+/* @brief Copies \c value into \c env[key]
+ *
+ * @return 1 on success, -1 if the input was invalid. */
+int erts_osenv_put_term(erts_osenv_t *env, Eterm key, Eterm value);
+
+/* @brief Removes \c env[key]
+ *
+ * @return 1 on success, 0 if the key couldn't be found, and -1 if the input
+ * was invalid. */
+int erts_osenv_unset_term(erts_osenv_t *env, Eterm key);
+
+/* @brief Copies env[key] into \c value
+ *
+ * @param value [in,out] The buffer to copy the value into, may be NULL if you
+ * only wish to query presence.
+ *
+ * @return 1 on success, 0 if the key couldn't be found, and -1 if if the value
+ * didn't fit into the buffer. */
+int erts_osenv_get_native(const erts_osenv_t *env, const erts_osenv_data_t *key,
+    erts_osenv_data_t *value);
+
+/* @brief Copies \c value into \c env[key]
+ *
+ * @return 1 on success, -1 on failure. */
+int erts_osenv_put_native(erts_osenv_t *env, const erts_osenv_data_t *key,
+    const erts_osenv_data_t *value);
+
+/* @brief Removes \c key from the env.
+ *
+ * @return 1 on success, 0 if the key couldn't be found. */
+int erts_osenv_unset_native(erts_osenv_t *env, const erts_osenv_data_t *key);
+
+/* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
+
+typedef void (*erts_osenv_foreach_term_cb_t)(struct process *process,
+    void *state, Eterm key, Eterm value);
+
+typedef void (*erts_osenv_foreach_native_cb_t)(void *state,
+    const erts_osenv_data_t *key,
+    const erts_osenv_data_t *value);
+
+/* @brief Walks through all environment variables, calling \c callback for each
+ * one. It's unsafe to modify \c env within the callback. */
+void erts_osenv_foreach_term(const erts_osenv_t *env, struct process *process,
+    void *state, erts_osenv_foreach_term_cb_t callback);
+
+/* @copydoc erts_osenv_foreach_term */
+void erts_osenv_foreach_native(const erts_osenv_t *env, void *state,
+    erts_osenv_foreach_native_cb_t callback);
+
+#endif
diff --git a/erts/emulator/sys/common/erl_poll.c b/erts/emulator/sys/common/erl_poll.c
index b8a28bcc18..51d50933ff 100644
--- a/erts/emulator/sys/common/erl_poll.c
+++ b/erts/emulator/sys/common/erl_poll.c
@@ -1,7 +1,7 @@
 /*
  * %CopyrightBegin%
  *
- * Copyright Ericsson AB 2006-2016. All Rights Reserved.
+ * Copyright Ericsson AB 2006-2018. All Rights Reserved.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -18,9 +18,8 @@
  * %CopyrightEnd%
  */
 
-/*
- * Description:	Poll interface suitable for ERTS with or without
- *              SMP support.
+/**
+ * @description Poll interface suitable for ERTS
  *
  *		The interface is currently implemented using:
  *		- select
@@ -29,12 +28,36 @@
  *              - epoll with poll or select as fallback
  *              - kqueue with poll or select as fallback
  *
- *		Some time in the future it will also be
- *		implemented using Solaris ports.
  *
+ * @author Rickard Green
+ * @author Lukas Larsson
+ *
+ * There are two major different implementations off IO polling in this
+ * file. The concurrent and non-concurrent implementations.
+ * When available epoll/kqueue are used to implement the concurrent
+ * versions. poll, select and dev/poll use non-concurrent updates.
+ *
+ * Concurrent version:
+ *   In the concurrent version erts_poll_control directly modifies
+ *   the kernel pollset without waking the thread that is waiting
+ *   on events. Also the ErtsPollResFd type is directly mapped to
+ *   the native event type, so no extra copying is needed. Note that
+ *   as no locking at all is done, fds can be triggered that have been
+ *   removed from the pollset. The check_io layer has to deal with this.
+ *
+ * Non-concurrent version:
+ *   In the non-concurrent version, the pollset has an internal representation
+ *   of the pollset that is updated by erts_poll_control. When an fd is updated,
+ *   its number is placed in the update request queue and then the waiting thread
+ *   is woken in order to see the change. The internal data in the pollset is
+ *   protected by a mutex that has to be taken by both the modifying and waiting
+ *   thread at different times.
  *
+ *   The non-concurrent pollset cannot have fd's closed in it while a thread is
+ *   waiting on that fd. In order to fix this, when an ERTS_POLL_OP_DEL command
+ *   is issued, the fd is marked as closing and the waiting thread is woken. The
+ *   fd is then returned in the waiting threads results as ERTS_POLL_EV_NONE.
  *
- * Author: 	Rickard Green
  */
 
 #ifdef HAVE_CONFIG_H
@@ -51,8 +74,8 @@
 #ifndef WANT_NONBLOCKING
 #  define WANT_NONBLOCKING
 #endif
-#define ERTS_WANT_GOT_SIGUSR1
 
+#include "erl_thr_progress.h"
 #include "erl_poll.h"
 #if ERTS_POLL_USE_KQUEUE
 #  include <sys/types.h>
@@ -63,6 +86,8 @@
 #  ifdef SYS_SELECT_H
 #    include <sys/select.h>
 #  endif
+#elif defined(_DARWIN_UNLIMITED_SELECT)
+#  undef _DARWIN_UNLIMITED_SELECT
 #endif
 #ifdef NO_SYSCONF
 #  if ERTS_POLL_USE_SELECT
@@ -71,7 +96,6 @@
 #    include <limits.h>
 #  endif
 #endif
-#include "erl_thr_progress.h"
 #include "erl_driver.h"
 #include "erl_alloc.h"
 #include "erl_msacc.h"
@@ -84,33 +108,60 @@
 #error "Missing implementation of erts_poll()"
 #endif
 
-#if defined(ERTS_KERNEL_POLL_VERSION) && !ERTS_POLL_USE_KERNEL_POLL
-#error "Missing kernel poll implementation of erts_poll()"
-#endif
+#if 0
+#define ERTS_POLL_DEBUG_PRINT 1
 
-#if defined(ERTS_NO_KERNEL_POLL_VERSION) && ERTS_POLL_USE_KERNEL_POLL
-#error "Kernel poll used when it shouldn't be used"
-#endif
+#define DEBUG_PRINT(FMT, PS, ...)                                       \
+    do {                                                                \
+        int myerrno = errno;                                            \
+        erts_printf("%d: " FMT "\r\n", (PS)->id, ##__VA_ARGS__);        \
+        errno = myerrno;                                                \
+    } while(0)
 
-#if 0
-#define ERTS_POLL_DEBUG_PRINT
+/* Define to print info about modifications done to each fd */
+#define DEBUG_PRINT_FD(FMT, PS, FD, ...) DEBUG_PRINT("%d: " FMT, PS, FD, ##__VA_ARGS__)
+/* Define to print entry and exit from erts_poll_wait (can be very spammy) */
+// #define DEBUG_PRINT_WAIT(FMT, PS, ...) DEBUG_PRINT(FMT, PS, ##__VA_ARGS__)
+// #define DEBUG_PRINT_WAIT(FMT, PS, ...) do { if ((PS)->id != -1) DEBUG_PRINT(FMT, PS, ##__VA_ARGS__); } while(0)
+
+#else
+#define ERTS_POLL_DEBUG_PRINT 0
+#define DEBUG_PRINT(...)
 #endif
 
-#if defined(DEBUG) && 0
-#define HARD_DEBUG
+#ifndef DEBUG_PRINT_FD
+#define DEBUG_PRINT_FD(...)
+#endif
+#ifndef DEBUG_PRINT_WAIT
+#define DEBUG_PRINT_WAIT(...)
 #endif
 
-#ifdef _DARWIN_UNLIMITED_SELECT
+
+#if defined(_DARWIN_UNLIMITED_SELECT) && ERTS_POLL_USE_SELECT
 typedef struct {
     size_t sz;
     fd_set* ptr;
 }ERTS_fd_set;
-#  define ERTS_FD_CLR(fd, fds)	FD_CLR((fd), (fds)->ptr)
-#  define ERTS_FD_SET(fd, fds)	FD_SET((fd), (fds)->ptr)
-#  define ERTS_FD_ISSET(fd,fds) FD_ISSET((fd), (fds)->ptr)
+
 #  define ERTS_FD_ZERO(fds)	memset((fds)->ptr, 0, (fds)->sz)
 #  define ERTS_FD_SIZE(n)	((((n)+NFDBITS-1)/NFDBITS)*sizeof(fd_mask))
 
+static ERTS_INLINE void ERTS_FD_CLR(int fd, ERTS_fd_set *fds)
+{
+    ASSERT(ERTS_FD_SIZE(fd+1) <= fds->sz);
+    FD_CLR(fd, fds->ptr);
+}
+static ERTS_INLINE void ERTS_FD_SET(int fd, ERTS_fd_set *fds)
+{
+    ASSERT(ERTS_FD_SIZE(fd+1) <= fds->sz);
+    FD_SET(fd, fds->ptr);
+}
+static ERTS_INLINE int ERTS_FD_ISSET(int fd, ERTS_fd_set *fds)
+{
+    ASSERT(ERTS_FD_SIZE(fd+1) <= fds->sz);
+    return FD_ISSET(fd, fds->ptr);
+}
+
 static void ERTS_FD_COPY(ERTS_fd_set *src, ERTS_fd_set *dst)
 {
     if (dst->sz != src->sz) {
@@ -146,74 +197,43 @@ int ERTS_SELECT(int nfds, ERTS_fd_set *readfds, ERTS_fd_set *writefds,
 #  define ERTS_SELECT	select
 #endif
 
-#define ERTS_POLL_USE_BATCH_UPDATE_POLLSET (ERTS_POLL_USE_DEVPOLL \
-					    || ERTS_POLL_USE_KQUEUE)
-#define ERTS_POLL_USE_UPDATE_REQUESTS_QUEUE \
-   (defined(ERTS_SMP) || ERTS_POLL_USE_KERNEL_POLL || ERTS_POLL_USE_POLL)
-
-#define ERTS_POLL_USE_CONCURRENT_UPDATE \
-   (defined(ERTS_SMP) && ERTS_POLL_USE_EPOLL)
+#define ERTS_POLL_IS_FALLBACK (ERTS_POLL_USE_POLL || ERTS_POLL_USE_SELECT) && ERTS_ENABLE_KERNEL_POLL
 
-#define ERTS_POLL_COALESCE_KP_RES (ERTS_POLL_USE_KQUEUE || ERTS_POLL_USE_EPOLL)
+#define ERTS_POLL_USE_CONCURRENT_UPDATE (ERTS_POLL_USE_EPOLL || ERTS_POLL_USE_KQUEUE)
 
-#ifdef ERTS_POLL_NEED_ASYNC_INTERRUPT_SUPPORT
-#  define ERTS_POLL_ASYNC_INTERRUPT_SUPPORT 1
-#else
-#  define ERTS_POLL_ASYNC_INTERRUPT_SUPPORT 0
-#endif
+#define ERTS_POLL_USE_WAKEUP(ps) (!ERTS_POLL_USE_CONCURRENT_UPDATE || (ps)->id < 0)
 
-#define ERTS_POLL_USE_WAKEUP_PIPE \
-   (ERTS_POLL_ASYNC_INTERRUPT_SUPPORT || defined(USE_THREADS))
+#if !ERTS_POLL_USE_CONCURRENT_UPDATE
 
-#ifdef ERTS_SMP
+#define ERTS_POLLSET_SET_HAVE_UPDATE_REQUESTS(PS) \
+  erts_atomic32_set_nob(&(PS)->have_update_requests, (erts_aint32_t) 1)
+#define ERTS_POLLSET_UNSET_HAVE_UPDATE_REQUESTS(PS) \
+  erts_atomic32_set_nob(&(PS)->have_update_requests, (erts_aint32_t) 0)
+#define ERTS_POLLSET_HAVE_UPDATE_REQUESTS(PS) \
+  ((int) erts_atomic32_read_nob(&(PS)->have_update_requests))
 
 #define ERTS_POLLSET_LOCK(PS) \
-  erts_smp_mtx_lock(&(PS)->mtx)
+  erts_mtx_lock(&(PS)->mtx)
 #define ERTS_POLLSET_UNLOCK(PS) \
-  erts_smp_mtx_unlock(&(PS)->mtx)
-
-#define ERTS_POLLSET_SET_POLLED_CHK(PS) \
-  ((int) erts_atomic32_xchg_nob(&(PS)->polled, (erts_aint32_t) 1))
-#define ERTS_POLLSET_UNSET_POLLED(PS) \
-  erts_atomic32_set_nob(&(PS)->polled, (erts_aint32_t) 0)
-#define ERTS_POLLSET_IS_POLLED(PS) \
-  ((int) erts_atomic32_read_nob(&(PS)->polled))
+  erts_mtx_unlock(&(PS)->mtx)
 
 #else
 
-#define ERTS_POLLSET_LOCK(PS)
-#define ERTS_POLLSET_UNLOCK(PS)
-#define ERTS_POLLSET_SET_POLLED_CHK(PS) 0
-#define ERTS_POLLSET_UNSET_POLLED(PS)
-#define ERTS_POLLSET_IS_POLLED(PS) 0
-
-#endif
-
-#if ERTS_POLL_USE_UPDATE_REQUESTS_QUEUE
-#define ERTS_POLLSET_SET_HAVE_UPDATE_REQUESTS(PS) \
-  erts_smp_atomic32_set_nob(&(PS)->have_update_requests, (erts_aint32_t) 1)
-#define ERTS_POLLSET_UNSET_HAVE_UPDATE_REQUESTS(PS) \
-  erts_smp_atomic32_set_nob(&(PS)->have_update_requests, (erts_aint32_t) 0)
-#define ERTS_POLLSET_HAVE_UPDATE_REQUESTS(PS) \
-  ((int) erts_smp_atomic32_read_nob(&(PS)->have_update_requests))
-#else
 #define ERTS_POLLSET_SET_HAVE_UPDATE_REQUESTS(PS)
 #define ERTS_POLLSET_UNSET_HAVE_UPDATE_REQUESTS(PS)
 #define ERTS_POLLSET_HAVE_UPDATE_REQUESTS(PS) 0
-#endif
 
-#if ERTS_POLL_USE_FALLBACK
-#  if ERTS_POLL_USE_POLL
-#    define ERTS_POLL_NEED_FALLBACK(PS) ((PS)->no_poll_fds > 1)
-#  elif ERTS_POLL_USE_SELECT
-#    define ERTS_POLL_NEED_FALLBACK(PS) ((PS)->no_select_fds > 1)
-#  endif
+#define ERTS_POLLSET_LOCK(PS)
+#define ERTS_POLLSET_UNLOCK(PS)
+
 #endif
+
 /*
  * --- Data types ------------------------------------------------------------
  */
 
-#if ERTS_POLL_USE_UPDATE_REQUESTS_QUEUE
+#if !ERTS_POLL_USE_CONCURRENT_UPDATE
+
 #define ERTS_POLLSET_UPDATE_REQ_BLOCK_SIZE 128
 
 typedef struct ErtsPollSetUpdateRequestsBlock_ ErtsPollSetUpdateRequestsBlock;
@@ -223,266 +243,190 @@ struct ErtsPollSetUpdateRequestsBlock_ {
     int fds[ERTS_POLLSET_UPDATE_REQ_BLOCK_SIZE];
 };
 
-#endif
-
-
-#if ERTS_POLL_USE_UPDATE_REQUESTS_QUEUE
 #  define ERTS_POLL_FD_FLG_INURQ	(((unsigned short) 1) << 0)
-#endif
-#if ERTS_POLL_USE_FALLBACK
-#  define ERTS_POLL_FD_FLG_INFLBCK	(((unsigned short) 1) << 1)
-#  define ERTS_POLL_FD_FLG_USEFLBCK	(((unsigned short) 1) << 2)
-#endif
-#if ERTS_POLL_USE_KERNEL_POLL || defined(ERTS_SMP)
-#  define ERTS_POLL_FD_FLG_RST		(((unsigned short) 1) << 3)
-#endif
+#  define ERTS_POLL_FD_FLG_RST		(((unsigned short) 1) << 1)
+
 typedef struct {
 #if ERTS_POLL_USE_POLL
     int pix;
 #endif
+
     ErtsPollEvents used_events;
     ErtsPollEvents events;
-#if ERTS_POLL_COALESCE_KP_RES
-    unsigned short res_ev_ix;
-#endif
-#if ERTS_POLL_USE_UPDATE_REQUESTS_QUEUE || ERTS_POLL_USE_FALLBACK
     unsigned short flags;
-#endif
 
 } ErtsFdStatus;
 
-
-#if ERTS_POLL_COALESCE_KP_RES
-/* res_ev_ix max value */
-#define ERTS_POLL_MAX_RES ((1 << sizeof(unsigned short)*8) - 1)
-#endif
-
-#if ERTS_POLL_USE_KQUEUE
-
-#define ERTS_POLL_KQ_OP_HANDLED			1
-#define ERTS_POLL_KQ_OP_DEL_R			2
-#define ERTS_POLL_KQ_OP_DEL_W			3
-#define ERTS_POLL_KQ_OP_ADD_R			4
-#define ERTS_POLL_KQ_OP_ADD_W			5
-#define ERTS_POLL_KQ_OP_ADD2_R			6
-#define ERTS_POLL_KQ_OP_ADD2_W			7
-
 #endif
 
-struct ErtsPollSet_ {
-    ErtsPollSet next;
+/*
+ * This struct is not really exported, but it's nice to
+ * get unique names in debugger for kp/nkp
+ */
+struct ERTS_POLL_EXPORT(erts_pollset) {
+    int id;
     int internal_fd_limit;
-    ErtsFdStatus *fds_status;
-    erts_smp_atomic_t no_of_user_fds;
-    int fds_status_len;
+    erts_atomic_t no_of_user_fds;
+
 #if ERTS_POLL_USE_KERNEL_POLL
     int kp_fd;
-    int res_events_len;
-#if ERTS_POLL_USE_EPOLL
-    struct epoll_event *res_events;
-#elif ERTS_POLL_USE_KQUEUE
-    struct kevent *res_events;
-#elif ERTS_POLL_USE_DEVPOLL
-    struct pollfd *res_events;
-#endif
+    int oneshot;
 #endif /* ERTS_POLL_USE_KERNEL_POLL */
+
 #if ERTS_POLL_USE_POLL
     int next_poll_fds_ix;
     int no_poll_fds;
     int poll_fds_len;
-    struct pollfd*poll_fds;
+    struct pollfd *poll_fds;
 #elif ERTS_POLL_USE_SELECT
     int next_sel_fd;
     int max_fd;
-#if ERTS_POLL_USE_FALLBACK
-    int no_select_fds;
-#endif
     ERTS_fd_set input_fds;
     ERTS_fd_set res_input_fds;
     ERTS_fd_set output_fds;
     ERTS_fd_set res_output_fds;
+#elif ERTS_POLL_USE_DEVPOLL
+    struct pollfd *poll_fds;
+    int poll_fds_ix;
 #endif
-#if ERTS_POLL_USE_UPDATE_REQUESTS_QUEUE
+
+#if !ERTS_POLL_USE_CONCURRENT_UPDATE
+    ErtsFdStatus *fds_status;
+    int fds_status_len;
     ErtsPollSetUpdateRequestsBlock update_requests;
     ErtsPollSetUpdateRequestsBlock *curr_upd_req_block;
-    erts_smp_atomic32_t have_update_requests;
-#endif
-#ifdef ERTS_SMP
-    erts_atomic32_t polled;
-    erts_smp_mtx_t mtx;
-#endif
-#if ERTS_POLL_USE_WAKEUP_PIPE
-    int wake_fds[2];
+    erts_atomic32_t have_update_requests;
+    erts_mtx_t mtx;
+#else
+    int do_wakeup;
 #endif
+
 #if ERTS_POLL_USE_TIMERFD
     int timer_fd;
 #endif
-#if ERTS_POLL_USE_FALLBACK
-    int fallback_used;
-#endif
-#if defined(USE_THREADS) || ERTS_POLL_ASYNC_INTERRUPT_SUPPORT
+    ErtsMonotonicTime timeout_time;
     erts_atomic32_t wakeup_state;
-#endif
-    erts_atomic64_t timeout_time;
-#ifdef ERTS_POLL_COUNT_AVOIDED_WAKEUPS
-    erts_smp_atomic_t no_avoided_wakeups;
-    erts_smp_atomic_t no_avoided_interrupts;
-    erts_smp_atomic_t no_interrupt_timed;
-#endif
+    int wake_fds[2];
 };
 
 void erts_silence_warn_unused_result(long unused);
 static void fatal_error(char *format, ...);
-static void fatal_error_async_signal_safe(char *error_str);
 
 static int max_fds = -1;
-static ErtsPollSet pollsets;
-static erts_smp_spinlock_t pollsets_lock;
 
 #if ERTS_POLL_USE_POLL
 
+#if !ERTS_POLL_IS_FALLBACK
+static ERTS_INLINE short ev2pollev(ErtsPollEvents ev)
+{
+    return ERTS_POLL_EV_E2N(ev);
+}
+
+static ERTS_INLINE ErtsPollEvents pollev2ev(short ev)
+{
+    return ERTS_POLL_EV_N2E(ev);
+}
+
+#else /* ERTS_POLL_IS_FALLBACK */
+
 static ERTS_INLINE short
 ev2pollev(ErtsPollEvents ev)
 {
-#if !ERTS_POLL_USE_FALLBACK || ERTS_POLL_USE_KQUEUE
-    return ERTS_POLL_EV_E2N(ev);
-#else /* Note, we only map events we are interested in */
     short res_ev = (short) 0;
     if (ev & ERTS_POLL_EV_IN)
-	res_ev |= ERTS_POLL_EV_NKP_IN;
+       res_ev |= ERTS_POLL_EV_NKP_IN;
     if (ev & ERTS_POLL_EV_OUT)
-	res_ev |= ERTS_POLL_EV_NKP_OUT;
+       res_ev |= ERTS_POLL_EV_NKP_OUT;
     return res_ev;
-#endif
 }
 
 static ERTS_INLINE ErtsPollEvents
 pollev2ev(short ev)
 {
-#if !ERTS_POLL_USE_FALLBACK || ERTS_POLL_USE_KQUEUE
-    return ERTS_POLL_EV_N2E(ev);
-#else /* Note, we only map events we are interested in */
     ErtsPollEvents res_ev = (ErtsPollEvents) 0;
     if (ev & ERTS_POLL_EV_NKP_IN)
-	res_ev |= ERTS_POLL_EV_IN;
+       res_ev |= ERTS_POLL_EV_IN;
     if (ev & ERTS_POLL_EV_NKP_OUT)
-	res_ev |= ERTS_POLL_EV_OUT;
+       res_ev |= ERTS_POLL_EV_OUT;
     if (ev & ERTS_POLL_EV_NKP_ERR)
-	res_ev |= ERTS_POLL_EV_ERR;
+       res_ev |= ERTS_POLL_EV_ERR;
     if (ev & ERTS_POLL_EV_NKP_NVAL)
-	res_ev |= ERTS_POLL_EV_NVAL;
-    return res_ev;
-#endif
+       res_ev |= ERTS_POLL_EV_NVAL;
+   return res_ev;
 }
 
-#endif
+#endif /* !ERTS_POLL_IS_FALLBACK */
+
+#endif /* ERTS_POLL_USE_POLL */
+
 
 #ifdef HARD_DEBUG
 static void check_poll_result(ErtsPollResFd pr[], int len);
-#if ERTS_POLL_USE_DEVPOLL
-static void check_poll_status(ErtsPollSet ps);
-#endif /* ERTS_POLL_USE_DEVPOLL */
 #endif /* HARD_DEBUG */
-#ifdef ERTS_POLL_DEBUG_PRINT
+#if ERTS_POLL_USE_DEVPOLL && defined(DEBUG)
+static void check_poll_status(ErtsPollSet *ps);
+#endif /* ERTS_POLL_USE_DEVPOLL && DEBUG */
 static void print_misc_debug_info(void);
+#if ERTS_POLL_USE_EPOLL
+uint32_t epoll_events(int kp_fd, int fd);
 #endif
 
-static ERTS_INLINE void
-init_timeout_time(ErtsPollSet ps)
-{
-    erts_atomic64_init_nob(&ps->timeout_time,
-			   (erts_aint64_t) ERTS_MONOTONIC_TIME_MAX);
-}
-
-static ERTS_INLINE void
-set_timeout_time(ErtsPollSet ps, ErtsMonotonicTime time)
-{
-    erts_atomic64_set_relb(&ps->timeout_time,
-			   (erts_aint64_t) time);
-}
-
-static ERTS_INLINE ErtsMonotonicTime
-get_timeout_time(ErtsPollSet ps)
-{
-    return (ErtsMonotonicTime) erts_atomic64_read_acqb(&ps->timeout_time);
-}
-
 #define ERTS_POLL_NOT_WOKEN	0
 #define ERTS_POLL_WOKEN		-1
 #define ERTS_POLL_WOKEN_INTR	1
 
 static ERTS_INLINE void
-reset_wakeup_state(ErtsPollSet ps)
+reset_wakeup_state(ErtsPollSet *ps)
 {
-#if defined(USE_THREADS) || ERTS_POLL_ASYNC_INTERRUPT_SUPPORT
     erts_atomic32_set_mb(&ps->wakeup_state, ERTS_POLL_NOT_WOKEN);
-#endif
 }
 
 static ERTS_INLINE int
-is_woken(ErtsPollSet ps)
+is_woken(ErtsPollSet *ps)
 {
-#if defined(USE_THREADS) || ERTS_POLL_ASYNC_INTERRUPT_SUPPORT
     return erts_atomic32_read_acqb(&ps->wakeup_state) != ERTS_POLL_NOT_WOKEN;
-#else
-    return 0;
-#endif
 }
 
 static ERTS_INLINE int
-is_interrupted_reset(ErtsPollSet ps)
+is_interrupted_reset(ErtsPollSet *ps)
 {
-#if defined(USE_THREADS) || ERTS_POLL_ASYNC_INTERRUPT_SUPPORT
     return (erts_atomic32_xchg_acqb(&ps->wakeup_state, ERTS_POLL_NOT_WOKEN)
 	    == ERTS_POLL_WOKEN_INTR);
-#else
-    return 0;
-#endif
 }
 
 static ERTS_INLINE void
-woke_up(ErtsPollSet ps)
+woke_up(ErtsPollSet *ps)
 {
-#if defined(USE_THREADS) || ERTS_POLL_ASYNC_INTERRUPT_SUPPORT
     erts_aint32_t wakeup_state = erts_atomic32_read_acqb(&ps->wakeup_state);
     if (wakeup_state == ERTS_POLL_NOT_WOKEN)
 	(void) erts_atomic32_cmpxchg_nob(&ps->wakeup_state,
 					 ERTS_POLL_WOKEN,
 					 ERTS_POLL_NOT_WOKEN);
     ASSERT(erts_atomic32_read_nob(&ps->wakeup_state) != ERTS_POLL_NOT_WOKEN);
-#endif
 }
 
 /*
  * --- Wakeup pipe -----------------------------------------------------------
  */
 
-#if ERTS_POLL_USE_WAKEUP_PIPE
-
 static ERTS_INLINE void
-wake_poller(ErtsPollSet ps, int interrupted, int async_signal_safe)
+wake_poller(ErtsPollSet *ps, int interrupted)
 {
     int wake;
-    if (async_signal_safe)
-	wake = 1;
-    else {
-	erts_aint32_t wakeup_state;
-	if (!interrupted)
-	    wakeup_state = erts_atomic32_cmpxchg_relb(&ps->wakeup_state,
-						      ERTS_POLL_WOKEN,
-						      ERTS_POLL_NOT_WOKEN);
-	else
-            wakeup_state = erts_atomic32_xchg_relb(&ps->wakeup_state,
-                                                   ERTS_POLL_WOKEN_INTR);
-	wake = wakeup_state == ERTS_POLL_NOT_WOKEN;
-    }
-    /*
-     * NOTE: This function might be called from signal handlers in the
-     *       non-smp case; therefore, it has to be async-signal safe in
-     *       the non-smp case.
-     */
-    if (wake) {
+    erts_aint32_t wakeup_state;
+    if (!interrupted)
+        wakeup_state = erts_atomic32_cmpxchg_relb(&ps->wakeup_state,
+                                                  ERTS_POLL_WOKEN,
+                                                  ERTS_POLL_NOT_WOKEN);
+    else
+        wakeup_state = erts_atomic32_xchg_relb(&ps->wakeup_state,
+                                               ERTS_POLL_WOKEN_INTR);
+    wake = wakeup_state == ERTS_POLL_NOT_WOKEN;
+
+    if (wake)
+    {
 	ssize_t res;
+        DEBUG_PRINT_WAIT("wake_poller(%d)", ps, interrupted);
 	if (ps->wake_fds[1] < 0)
 	    return; /* Not initialized yet */
 	do {
@@ -490,36 +434,27 @@ wake_poller(ErtsPollSet ps, int interrupted, int async_signal_safe)
 	    res = write(ps->wake_fds[1], "!", 1);
 	} while (res < 0 && errno == EINTR);
 	if (res <= 0 && errno != ERRNO_BLOCK) {
-	    if (async_signal_safe)
-		fatal_error_async_signal_safe(__FILE__
-					      ":XXX:wake_poller(): "
-					      "Failed to write on wakeup pipe\n");
-	    else
-		fatal_error("%s:%d:wake_poller(): "
-			    "Failed to write to wakeup pipe fd=%d: "
-			    "%s (%d)\n",
-			    __FILE__, __LINE__,
-			    ps->wake_fds[1],
-			    erl_errno_id(errno), errno);
+            fatal_error("%s:%d:wake_poller(): "
+                        "Failed to write to wakeup pipe fd=%d: "
+                        "%s (%d)\n",
+                        __FILE__, __LINE__,
+                        ps->wake_fds[1],
+                        erl_errno_id(errno), errno);
 	}
     }
 }
 
 static ERTS_INLINE void
-cleanup_wakeup_pipe(ErtsPollSet ps)
+cleanup_wakeup_pipe(ErtsPollSet *ps)
 {
-#if ERTS_POLL_ASYNC_INTERRUPT_SUPPORT
     int intr = 0;
-#endif
     int fd = ps->wake_fds[0];
     int res;
     do {
 	char buf[32];
 	res = read(fd, buf, sizeof(buf));
-#if ERTS_POLL_ASYNC_INTERRUPT_SUPPORT
 	if (res > 0)
 	    intr = 1;
-#endif
     } while (res > 0 || (res < 0 && errno == EINTR));
     if (res < 0 && errno != ERRNO_BLOCK) {
 	fatal_error("%s:%d:cleanup_wakeup_pipe(): "
@@ -529,14 +464,12 @@ cleanup_wakeup_pipe(ErtsPollSet ps)
 		    fd,
 		    erl_errno_id(errno), errno);
     }
-#if ERTS_POLL_ASYNC_INTERRUPT_SUPPORT
     if (intr)
 	erts_atomic32_set_nob(&ps->wakeup_state, ERTS_POLL_WOKEN_INTR);
-#endif
 }
 
 static void
-create_wakeup_pipe(ErtsPollSet ps)
+create_wakeup_pipe(ErtsPollSet *ps)
 {
     int do_wake = 0;
     int wake_fds[2];
@@ -553,20 +486,13 @@ create_wakeup_pipe(ErtsPollSet ps)
     SET_NONBLOCKING(wake_fds[0]);
     SET_NONBLOCKING(wake_fds[1]);
 
-#ifdef ERTS_POLL_DEBUG_PRINT
-    erts_printf("wakeup fds = {%d, %d}\n", wake_fds[0], wake_fds[1]);
-#endif
+    DEBUG_PRINT("wakeup fds = {%d, %d}", ps, wake_fds[0], wake_fds[1]);
 
     ERTS_POLL_EXPORT(erts_poll_control)(ps,
 					wake_fds[0],
+                                        ERTS_POLL_OP_ADD,
 					ERTS_POLL_EV_IN,
-					1, &do_wake);
-#if ERTS_POLL_USE_FALLBACK
-    /* We depend on the wakeup pipe being handled by kernel poll */
-    if (ps->fds_status[wake_fds[0]].flags & ERTS_POLL_FD_FLG_INFLBCK)
-	fatal_error("%s:%d:create_wakeup_pipe(): Internal error\n",
-		    __FILE__, __LINE__);
-#endif
+                                        &do_wake);
     if (ps->internal_fd_limit <= wake_fds[1])
 	ps->internal_fd_limit = wake_fds[1] + 1;
     if (ps->internal_fd_limit <= wake_fds[0])
@@ -575,8 +501,6 @@ create_wakeup_pipe(ErtsPollSet ps)
     ps->wake_fds[1] = wake_fds[1];
 }
 
-#endif /* ERTS_POLL_USE_WAKEUP_PIPE */
-
 /*
  * --- timer fd -----------------------------------------------------------
  */
@@ -587,28 +511,22 @@ create_wakeup_pipe(ErtsPollSet ps)
    timeouts, i.e. we want to sleep with < ms accuracy. */
 
 static void
-create_timerfd(ErtsPollSet ps)
+create_timerfd(ErtsPollSet *ps)
 {
     int do_wake = 0;
-    int timer_fd;
-    timer_fd = timerfd_create(CLOCK_MONOTONIC,0);
+    int timer_fd = timerfd_create(CLOCK_MONOTONIC,0);
     ERTS_POLL_EXPORT(erts_poll_control)(ps,
 					timer_fd,
+                                        ERTS_POLL_OP_ADD,
 					ERTS_POLL_EV_IN,
-					1, &do_wake);
-#if ERTS_POLL_USE_FALLBACK
-    /* We depend on the wakeup pipe being handled by kernel poll */
-    if (ps->fds_status[timer_fd].flags & ERTS_POLL_FD_FLG_INFLBCK)
-	fatal_error("%s:%d:create_wakeup_pipe(): Internal error\n",
-		    __FILE__, __LINE__);
-#endif
+                                        &do_wake);
     if (ps->internal_fd_limit <= timer_fd)
 	ps->internal_fd_limit = timer_fd + 1;
     ps->timer_fd = timer_fd;
 }
 
 static ERTS_INLINE void
-timerfd_set(ErtsPollSet ps, struct itimerspec *its)
+timerfd_set(ErtsPollSet *ps, struct itimerspec *its)
 {
 #ifdef DEBUG
     struct itimerspec old_its;
@@ -626,7 +544,7 @@ timerfd_set(ErtsPollSet ps, struct itimerspec *its)
 }
 
 static ERTS_INLINE int
-timerfd_clear(ErtsPollSet ps, int res, int max_res) {
+timerfd_clear(ErtsPollSet *ps, ErtsPollResFd pr[], int res, int max_res) {
 
     struct itimerspec its;
     /* we always have to clear the timer */
@@ -637,7 +555,7 @@ timerfd_clear(ErtsPollSet ps, int res, int max_res) {
     timerfd_settime(ps->timer_fd, 0, &its, NULL);
 
     /* only timeout fd triggered */
-    if (res == 1 && ps->res_events[0].data.fd == ps->timer_fd)
+    if (res == 1 && pr[0].data.fd == ps->timer_fd)
         return 0;
 
     return res;
@@ -645,14 +563,14 @@ timerfd_clear(ErtsPollSet ps, int res, int max_res) {
 
 #endif /* ERTS_POLL_USE_TIMERFD */
 
-
 /*
  * --- Poll set update requests ----------------------------------------------
  */
-#if ERTS_POLL_USE_UPDATE_REQUESTS_QUEUE
+
+#if !ERTS_POLL_USE_CONCURRENT_UPDATE
 
 static ERTS_INLINE void
-enqueue_update_request(ErtsPollSet ps, int fd)
+enqueue_update_request(ErtsPollSet *ps, int fd)
 {
     ErtsPollSetUpdateRequestsBlock *urqbp;
 
@@ -667,13 +585,11 @@ enqueue_update_request(ErtsPollSet ps, int fd)
     urqbp = ps->curr_upd_req_block;
 
     if (urqbp->len == ERTS_POLLSET_UPDATE_REQ_BLOCK_SIZE) {
-	ASSERT(!urqbp->next);
 	urqbp = erts_alloc(ERTS_ALC_T_POLLSET_UPDREQ,
 			   sizeof(ErtsPollSetUpdateRequestsBlock));
-	ps->curr_upd_req_block->next = urqbp;
-	ps->curr_upd_req_block = urqbp;
-	urqbp->next = NULL;
+	urqbp->next = ps->curr_upd_req_block;
 	urqbp->len = 0;
+	ps->curr_upd_req_block = urqbp;
     }
 
     ps->fds_status[fd].flags |= ERTS_POLL_FD_FLG_INURQ;
@@ -681,29 +597,29 @@ enqueue_update_request(ErtsPollSet ps, int fd)
 }
 
 static ERTS_INLINE void
-free_update_requests_block(ErtsPollSet ps,
+free_update_requests_block(ErtsPollSet *ps,
 			   ErtsPollSetUpdateRequestsBlock *urqbp)
 {
     if (urqbp != &ps->update_requests)
 	erts_free(ERTS_ALC_T_POLLSET_UPDREQ, (void *) urqbp);
     else {
-	urqbp->next = NULL;
 	urqbp->len = 0;
     }
 }
 
-#endif /* ERTS_POLL_USE_UPDATE_REQUESTS_QUEUE */
+#endif /* !ERTS_POLL_USE_CONCURRENT_UPDATE */
 
 /*
  * --- Growing poll set structures -------------------------------------------
  */
 
-#ifndef ERTS_KERNEL_POLL_VERSION   /* only one shared implementation */
+#if !ERTS_NO_KERNEL_POLL_VERSION || !ERTS_ENABLE_KERNEL_POLL
+/* only one shared implementation */
 
 #define ERTS_FD_TABLE_MIN_LENGTH	1024
 #define ERTS_FD_TABLE_EXP_THRESHOLD	(2048*1024)
 
-int erts_poll_new_table_len (int old_len, int need_len)
+int erts_poll_new_table_len(int old_len, int need_len)
 {
     int new_len;
 
@@ -713,7 +629,7 @@ int erts_poll_new_table_len (int old_len, int need_len)
     }
     else {
         new_len = old_len;
-        do {            
+        do {
             if (new_len < ERTS_FD_TABLE_EXP_THRESHOLD)
                 new_len *= 2;
             else
@@ -726,30 +642,9 @@ int erts_poll_new_table_len (int old_len, int need_len)
 }
 #endif
 
-#if ERTS_POLL_USE_KERNEL_POLL
-static void
-grow_res_events(ErtsPollSet ps, int new_len)
-{
-    size_t new_size = sizeof(
-#if ERTS_POLL_USE_EPOLL
-	struct epoll_event
-#elif ERTS_POLL_USE_DEVPOLL
-	struct pollfd
-#elif ERTS_POLL_USE_KQUEUE
-	struct kevent
-#endif
-	) * erts_poll_new_table_len(ps->res_events_len, new_len);
-    /* We do not need to save previously stored data */
-    if (ps->res_events)
-	erts_free(ERTS_ALC_T_POLL_RES_EVS, ps->res_events);
-    ps->res_events = erts_alloc(ERTS_ALC_T_POLL_RES_EVS, new_size);
-    ps->res_events_len = new_len;
-}
-#endif /* ERTS_POLL_USE_KERNEL_POLL */
-
 #if ERTS_POLL_USE_POLL
 static void
-grow_poll_fds(ErtsPollSet ps, int min_ix)
+grow_poll_fds(ErtsPollSet *ps, int min_ix)
 {
     int i;
     int new_len = erts_poll_new_table_len(ps->poll_fds_len, min_ix + 1);
@@ -793,12 +688,20 @@ ensure_select_fds(int fd, ERTS_fd_set* in, ERTS_fd_set* out)
 	grow_select_fds(fd, out);
     }
 }
+static ERTS_INLINE int
+check_select_fds(int fd, ERTS_fd_set* in, ERTS_fd_set* out)
+{
+    ASSERT(in->sz == out->sz);
+    return (ERTS_FD_SIZE(fd+1) <= in->sz);
+}
 #else
 #  define ensure_select_fds(fd, in, out) do {} while(0)
+#  define check_select_fds(fd, in, out) (1)
 #endif /* _DARWIN_UNLIMITED_SELECT */
 
+#if !ERTS_POLL_USE_CONCURRENT_UPDATE
 static void
-grow_fds_status(ErtsPollSet ps, int min_fd)
+grow_fds_status(ErtsPollSet *ps, int min_fd)
 {
     int i;
     int new_len = erts_poll_new_table_len(ps->fds_status_len, min_fd + 1);
@@ -817,461 +720,54 @@ grow_fds_status(ErtsPollSet ps, int min_fd)
 #endif
 	ps->fds_status[i].used_events = (ErtsPollEvents) 0;
 	ps->fds_status[i].events = (ErtsPollEvents) 0;
-#if ERTS_POLL_COALESCE_KP_RES
-	ps->fds_status[i].res_ev_ix = (unsigned short) ERTS_POLL_MAX_RES;
-#endif
-#if ERTS_POLL_USE_UPDATE_REQUESTS_QUEUE || ERTS_POLL_USE_FALLBACK
 	ps->fds_status[i].flags = (unsigned short) 0;
-#endif
     }
     ps->fds_status_len = new_len;
 }
+#endif
 
 /*
  * --- Selecting fd to poll on -----------------------------------------------
  */
 
-#if ERTS_POLL_USE_FALLBACK
-static int update_fallback_pollset(ErtsPollSet ps, int fd);
-#endif
-
-static ERTS_INLINE int
-need_update(ErtsPollSet ps, int fd)
-{
-#if ERTS_POLL_USE_KERNEL_POLL
-    int reset;
-#endif
-
-    ASSERT(fd < ps->fds_status_len);
-
-#if ERTS_POLL_USE_KERNEL_POLL
-    reset = (int) (ps->fds_status[fd].flags & ERTS_POLL_FD_FLG_RST);
-    if (reset && !ps->fds_status[fd].used_events) {
-	ps->fds_status[fd].flags &= ~ERTS_POLL_FD_FLG_RST;
-	reset = 0;
-    }
-#elif defined(ERTS_SMP)
-    ps->fds_status[fd].flags &= ~ERTS_POLL_FD_FLG_RST;
-#endif
-
-    if (ps->fds_status[fd].used_events != ps->fds_status[fd].events)
-	return 1;
-
-#if ERTS_POLL_USE_KERNEL_POLL
-    return reset;
-#else
-    return 0;
-#endif
-}
-
-#if ERTS_POLL_USE_BATCH_UPDATE_POLLSET
-
-#if ERTS_POLL_USE_KQUEUE
-#define ERTS_POLL_MIN_BATCH_BUF_SIZE 128
-#else
-#define ERTS_POLL_MIN_BATCH_BUF_SIZE 64
-#endif
-
-typedef struct {
-    int len;
-    int size;
-#if ERTS_POLL_USE_DEVPOLL
-    struct pollfd *buf;
-#elif ERTS_POLL_USE_KQUEUE
-    struct kevent *buf;
-    struct kevent *ebuf;
-#endif
-} ErtsPollBatchBuf;
-
-
-static ERTS_INLINE void
-setup_batch_buf(ErtsPollSet ps, ErtsPollBatchBuf *bbp)
-{
-    bbp->len = 0;
-#if ERTS_POLL_USE_DEVPOLL
-    bbp->size = ps->res_events_len;
-    bbp->buf = ps->res_events;
-#elif ERTS_POLL_USE_KQUEUE
-    bbp->size = ps->res_events_len/2;
-    bbp->buf = ps->res_events;
-    bbp->ebuf = bbp->buf + bbp->size;
-#endif
-}
-
-
-#if ERTS_POLL_USE_DEVPOLL
-
-static void
-write_batch_buf(ErtsPollSet ps, ErtsPollBatchBuf *bbp)
-{
-    ssize_t wres;
-    char *buf = (char *) bbp->buf;
-    size_t buf_size = sizeof(struct pollfd)*bbp->len;
-    
-    while (1) {
-	wres = write(ps->kp_fd, (void *) buf, buf_size);
-	if (wres < 0) {
-	    if (errno == EINTR)
-		continue;
-	    fatal_error("%s:%d:write_batch_buf(): "
-			"Failed to write to /dev/poll: "
-			"%s (%d)\n",
-			__FILE__, __LINE__,
-			erl_errno_id(errno), errno);
-	}
-	buf_size -= wres;
-	if (buf_size <= 0)
-	    break;
-	buf += wres;
-    }
-
-    if (buf_size < 0) {
-	fatal_error("%s:%d:write_devpoll_buf(): Internal error\n",
-		    __FILE__, __LINE__);
-    }
-    bbp->len = 0;
-}
-
-#elif ERTS_POLL_USE_KQUEUE
-
-static void
-write_batch_buf(ErtsPollSet ps, ErtsPollBatchBuf *bbp)
-{
-    int res;
-    int len = bbp->len;
-    struct kevent *buf = bbp->buf;
-    struct timespec ts = {0, 0};
-
-    do {
-	res = kevent(ps->kp_fd, buf, len, NULL, 0, &ts);
-    } while (res < 0 && errno == EINTR);
-    if (res < 0) {
-	int i;
-	struct kevent *ebuf = bbp->ebuf;
-	do {
-	    res = kevent(ps->kp_fd, buf, len, ebuf, len, &ts);
-	} while (res < 0 && errno == EINTR);
-	if (res < 0) {
-	    fatal_error("%s:%d: kevent() failed: %s (%d)\n",
-			__FILE__, __LINE__, erl_errno_id(errno), errno);
-	}
-	for (i = 0; i < res; i++) {
-	    if (ebuf[i].flags & EV_ERROR) {
-		short filter;
-		int fd = (int) ebuf[i].ident;
-
-		switch ((int) (long) ebuf[i].udata) {
-
-		    /*
-		     * Since we use a lazy update approach EV_DELETE will
-		     * frequently fail. This since kqueue automatically
-		     * removes a file descriptor that is closed from the
-		     * poll set.
-		     */
-		case ERTS_POLL_KQ_OP_DEL_R:
-		case ERTS_POLL_KQ_OP_DEL_W:
-		case ERTS_POLL_KQ_OP_HANDLED:
-		    break;
-
-		    /*
-		     * According to the kqueue man page EVFILT_READ support
-		     * does not imply EVFILT_WRITE support; therefore,
-		     * if an EV_ADD fail, we may have to remove other
-		     * events on this fd in the kqueue pollset before
-		     * adding fd to the fallback pollset.
-		     */
-		case ERTS_POLL_KQ_OP_ADD_W:
-		    if (ps->fds_status[fd].used_events & ERTS_POLL_EV_IN) {
-			filter = EVFILT_READ;
-			goto rm_add_fb;
-		    }
-		    goto add_fb;
-		case ERTS_POLL_KQ_OP_ADD_R:
-		    if (ps->fds_status[fd].used_events & ERTS_POLL_EV_OUT) {
-			filter = EVFILT_WRITE;
-			goto rm_add_fb;
-		    }
-		    goto add_fb;
-		case ERTS_POLL_KQ_OP_ADD2_W:
-		case ERTS_POLL_KQ_OP_ADD2_R: {
-		    int j;
-		    for (j = i+1; j < res; j++) {
-			if (fd == (int) ebuf[j].ident) {
-			    ebuf[j].udata = (void *) ERTS_POLL_KQ_OP_HANDLED;
-			    if (!(ebuf[j].flags & EV_ERROR)) {
-				switch ((int) (long) ebuf[j].udata) {
-				case ERTS_POLL_KQ_OP_ADD2_W:
-				    filter = EVFILT_WRITE;
-				    goto rm_add_fb;
-				case ERTS_POLL_KQ_OP_ADD2_R:
-				    filter = EVFILT_READ;
-				    goto rm_add_fb;
-				default:
-				    fatal_error("%s:%d:write_batch_buf(): "
-						"Internal error",
-						__FILE__, __LINE__);
-				    break;
-				}
-			    }
-			    goto add_fb;
-			}
-		    }
-		    /* The other add succeded... */
-		    filter = ((((int) (long) ebuf[i].udata)
-			       == ERTS_POLL_KQ_OP_ADD2_W)
-			      ? EVFILT_READ
-			      : EVFILT_WRITE);
-		rm_add_fb:
-		    { 
-			struct kevent kev;
-			struct timespec ts = {0, 0};
-			EV_SET(&kev, fd, filter, EV_DELETE, 0, 0, 0);
-			(void) kevent(ps->kp_fd, &kev, 1, NULL, 0, &ts);
-		    }
-
-		add_fb:
-		    ps->fds_status[fd].flags |= ERTS_POLL_FD_FLG_USEFLBCK;
-		    ASSERT(ps->fds_status[fd].used_events);
-		    ps->fds_status[fd].used_events = 0;
-		    erts_smp_atomic_dec_nob(&ps->no_of_user_fds);
-		    update_fallback_pollset(ps, fd);
-		    ASSERT(ps->fds_status[fd].flags & ERTS_POLL_FD_FLG_INFLBCK);
-		    break;
-		}
-		default:
-		    fatal_error("%s:%d:write_batch_buf(): Internal error",
-				__FILE__, __LINE__);
-		    break;
-		}
-	    }
-	}
-    }
-    bbp->len = 0;
-}
-
-#endif /* ERTS_POLL_USE_KQUEUE */
-
-static ERTS_INLINE void
-batch_update_pollset(ErtsPollSet ps, int fd, ErtsPollBatchBuf *bbp)
-{
-    int buf_len;
-#if ERTS_POLL_USE_DEVPOLL
-    short events;
-    struct pollfd *buf;
-#elif ERTS_POLL_USE_KQUEUE
-    struct kevent *buf;
-#endif
-
-#ifdef ERTS_POLL_DEBUG_PRINT
-    erts_printf("Doing lazy update on fd=%d\n", fd);
-#endif
-
-    if (!need_update(ps, fd))
-	return;
-
-    /* Make sure we have room for at least maximum no of entries
-       per fd */
-    if (bbp->size - bbp->len < 2)
-	write_batch_buf(ps, bbp);
-
-    buf_len = bbp->len;
-    buf = bbp->buf;
-
-    ASSERT(fd < ps->fds_status_len);
-
-#if ERTS_POLL_USE_DEVPOLL
-    events = ERTS_POLL_EV_E2N(ps->fds_status[fd].events);
-    if (!events) {
-	buf[buf_len].events = POLLREMOVE;
-	erts_smp_atomic_dec_nob(&ps->no_of_user_fds);
-    }
-    else if (!ps->fds_status[fd].used_events) {
-	buf[buf_len].events = events;
-	erts_smp_atomic_inc_nob(&ps->no_of_user_fds);
-    }
-    else {
-	if ((ps->fds_status[fd].flags & ERTS_POLL_FD_FLG_RST)
-	    || (ps->fds_status[fd].used_events & ~events)) {
-	    /* Reset or removed events... */
-	    buf[buf_len].fd = fd;
-	    buf[buf_len].events = POLLREMOVE;
-	    buf[buf_len++].revents = 0;
-	}
-	buf[buf_len].events = events;
-    }
-    buf[buf_len].fd = fd;
-    buf[buf_len++].revents = 0;
-
-#elif ERTS_POLL_USE_KQUEUE
-
-    if (ps->fds_status[fd].flags & ERTS_POLL_FD_FLG_INFLBCK) {
-	if (ps->fds_status[fd].flags & ERTS_POLL_FD_FLG_USEFLBCK)
-	    update_fallback_pollset(ps, fd);
-	else { /* Remove from fallback and try kqueue */
-	    ErtsPollEvents events = ps->fds_status[fd].events;
-	    ps->fds_status[fd].events = (ErtsPollEvents) 0;
-	    update_fallback_pollset(ps, fd);
-	    ASSERT(!(ps->fds_status[fd].flags & ERTS_POLL_FD_FLG_INFLBCK));
-	    if (events) {
-		ps->fds_status[fd].events = events;
-		goto try_kqueue;
-	    }
-	}
-    }
-    else {
-	ErtsPollEvents events, used_events;
-	int mod_w, mod_r;
-    try_kqueue:
-	events = ERTS_POLL_EV_E2N(ps->fds_status[fd].events);
-	used_events = ERTS_POLL_EV_E2N(ps->fds_status[fd].used_events);
-	if (!(ps->fds_status[fd].flags & ERTS_POLL_FD_FLG_RST)) {
-	    if (!used_events &&
-		(events & ERTS_POLL_EV_IN) && (events & ERTS_POLL_EV_OUT))
-		goto do_add_rw;
-	    mod_r = ((events & ERTS_POLL_EV_IN)
-		     != (used_events & ERTS_POLL_EV_IN));
-	    mod_w = ((events & ERTS_POLL_EV_OUT)
-		     != (used_events & ERTS_POLL_EV_OUT));
-	    goto do_mod;
-	}
-	else { /* Reset */
-	    if ((events & ERTS_POLL_EV_IN) && (events & ERTS_POLL_EV_OUT)) {
-	    do_add_rw:
-		EV_SET(&buf[buf_len], fd, EVFILT_READ, EV_ADD,
-		       0, 0, (void *) ERTS_POLL_KQ_OP_ADD2_R);
-		buf_len++;
-		EV_SET(&buf[buf_len], fd, EVFILT_WRITE, EV_ADD,
-		       0, 0, (void *) ERTS_POLL_KQ_OP_ADD2_W);
-		buf_len++;
-
-	    }
-	    else {
-		mod_r = 1;
-		mod_w = 1;
-	    do_mod:
-		if (mod_r) {
-		    if (events & ERTS_POLL_EV_IN) {
-			EV_SET(&buf[buf_len], fd, EVFILT_READ, EV_ADD,
-			       0, 0, (void *) ERTS_POLL_KQ_OP_ADD_R);
-			buf_len++;
-		    }
-		    else if (used_events & ERTS_POLL_EV_IN) {
-			EV_SET(&buf[buf_len], fd, EVFILT_READ, EV_DELETE,
-			       0, 0, (void *) ERTS_POLL_KQ_OP_DEL_R);
-			buf_len++;
-		    }
-		}
-		if (mod_w) {
-		    if (events & ERTS_POLL_EV_OUT) {
-			EV_SET(&buf[buf_len], fd, EVFILT_WRITE, EV_ADD,
-			       0, 0, (void *) ERTS_POLL_KQ_OP_ADD_W);
-			buf_len++;
-		    }
-		    else if (used_events & ERTS_POLL_EV_OUT) {
-			EV_SET(&buf[buf_len], fd, EVFILT_WRITE, EV_DELETE,
-			       0, 0, (void *) ERTS_POLL_KQ_OP_DEL_W);
-			buf_len++;
-		    }
-		}
-	    }
-	}
-	if (used_events) {
-	    if (!events) {
-		erts_smp_atomic_dec_nob(&ps->no_of_user_fds);
-	    }
-	}
-	else {
-	    if (events)
-		erts_smp_atomic_inc_nob(&ps->no_of_user_fds);
-	}
-	ASSERT((events & ~(ERTS_POLL_EV_IN|ERTS_POLL_EV_OUT)) == 0);
-	ASSERT((used_events & ~(ERTS_POLL_EV_IN|ERTS_POLL_EV_OUT)) == 0);
-    }	    
-
-#endif
-
-    ps->fds_status[fd].flags &= ~ERTS_POLL_FD_FLG_RST;
-    ps->fds_status[fd].used_events = ps->fds_status[fd].events;
-
-    bbp->len = buf_len;
-}
-
-#else /* !ERTS_POLL_USE_BATCH_UPDATE_POLLSET */
-
 #if ERTS_POLL_USE_EPOLL
 static int
-#if ERTS_POLL_USE_CONCURRENT_UPDATE
-conc_update_pollset(ErtsPollSet ps, int fd, int *update_fallback)
-#else
-update_pollset(ErtsPollSet ps, int fd)
-#endif
+update_pollset(ErtsPollSet *ps, int fd, ErtsPollOp op, ErtsPollEvents events)
 {
     int res;
-    int op;
+    int epoll_op = EPOLL_CTL_MOD;
     struct epoll_event epe_templ;
     struct epoll_event epe;
 
-    ASSERT(fd < ps->fds_status_len);
-
-    if (!need_update(ps, fd))
-	return 0;
-
-#ifdef ERTS_POLL_DEBUG_PRINT
-    erts_printf("Doing update on fd=%d\n", fd);
-#endif
-    if (ps->fds_status[fd].flags & ERTS_POLL_FD_FLG_INFLBCK) {
-#if ERTS_POLL_USE_CONCURRENT_UPDATE
-	if (!*update_fallback) {
-	    *update_fallback = 1;
-	    return 0;
-	}
-#endif
-	if (ps->fds_status[fd].flags & ERTS_POLL_FD_FLG_USEFLBCK) {
-	    return update_fallback_pollset(ps, fd);
-	}
-	else { /* Remove from fallback and try epoll */
-	    ErtsPollEvents events = ps->fds_status[fd].events;
-	    ps->fds_status[fd].events = (ErtsPollEvents) 0;
-	    res = update_fallback_pollset(ps, fd);
-	    ASSERT(!(ps->fds_status[fd].flags & ERTS_POLL_FD_FLG_INFLBCK));
-	    if (!events)
-		return res;
-	    ps->fds_status[fd].events = events;
-	}
-    }
-
-    epe_templ.events = ERTS_POLL_EV_E2N(ps->fds_status[fd].events);
+    epe_templ.events = ERTS_POLL_EV_E2N(events);
     epe_templ.data.fd = fd;
 
+    if (ps->oneshot)
+        epe_templ.events |= EPOLLONESHOT;
+
 #ifdef VALGRIND
     /* Silence invalid valgrind warning ... */
     memset((void *) &epe.data, 0, sizeof(epoll_data_t));
 #endif
 
-    if (epe_templ.events && ps->fds_status[fd].flags & ERTS_POLL_FD_FLG_RST) {
-	do {
-	    /* We init 'epe' every time since epoll_ctl() may modify it
-	       (not declared const and not documented as const). */
-	    epe.events = epe_templ.events;
-	    epe.data.fd = epe_templ.data.fd;
-	    res = epoll_ctl(ps->kp_fd, EPOLL_CTL_DEL, fd, &epe);
-	} while (res != 0 && errno == EINTR);
-	erts_smp_atomic_dec_nob(&ps->no_of_user_fds);
-	ps->fds_status[fd].used_events = 0;
-    }
-
-    if (!epe_templ.events) {
+    switch (op) {
+    case ERTS_POLL_OP_DEL:
 	/* A note on EPOLL_CTL_DEL: linux kernel versions before 2.6.9
 	   need a non-NULL event pointer even though it is ignored... */
-	op = EPOLL_CTL_DEL;
-	erts_smp_atomic_dec_nob(&ps->no_of_user_fds);
-    }
-    else if (!ps->fds_status[fd].used_events) {
-	op = EPOLL_CTL_ADD;
-	erts_smp_atomic_inc_nob(&ps->no_of_user_fds);
-    }
-    else {
-	op = EPOLL_CTL_MOD;
+        epoll_op = EPOLL_CTL_DEL;
+        epe_templ.events = 0;
+	erts_atomic_dec_nob(&ps->no_of_user_fds);
+        break;
+    case ERTS_POLL_OP_ADD:
+        epoll_op = EPOLL_CTL_ADD;
+	erts_atomic_inc_nob(&ps->no_of_user_fds);
+        break;
+    case ERTS_POLL_OP_MOD:
+        epoll_op = EPOLL_CTL_MOD;
+        break;
+    default:
+        ASSERT(0);
+        break;
     }
 
     do {
@@ -1279,33 +775,32 @@ update_pollset(ErtsPollSet ps, int fd)
 	   (not declared const and not documented as const). */
 	epe.events = epe_templ.events;
 	epe.data.fd = epe_templ.data.fd;
-	res = epoll_ctl(ps->kp_fd, op, fd, &epe);
+	res = epoll_ctl(ps->kp_fd, epoll_op, fd, &epe);
     } while (res != 0 && errno == EINTR);
 
-#if defined(ERTS_POLL_DEBUG_PRINT) && 1
+#if ERTS_POLL_DEBUG_PRINT
     {
 	int saved_errno = errno;
-	erts_printf("%s = epoll_ctl(%d, %s, %d, {Ox%x, %d})\n",
-		     res == 0 ? "0" : erl_errno_id(errno),
-		     ps->kp_fd,
-		     (op == EPOLL_CTL_ADD
-		      ? "EPOLL_CTL_ADD"
-		      : (op == EPOLL_CTL_MOD
-			 ? "EPOLL_CTL_MOD"
-			 : (op == EPOLL_CTL_DEL
-			    ? "EPOLL_CTL_DEL"
-			    : "UNKNOWN"))),
-		     fd,
-		     epe_templ.events,
-		     fd);
+	DEBUG_PRINT_FD("%s = epoll_ctl(%d, %s, %d, {0x%x, %d})",
+                       ps, fd,
+                       res == 0 ? "0" : erl_errno_id(errno),
+                       ps->kp_fd,
+                       (epoll_op == EPOLL_CTL_ADD
+                        ? "EPOLL_CTL_ADD"
+                        : (epoll_op == EPOLL_CTL_MOD
+                           ? "EPOLL_CTL_MOD"
+                           : (epoll_op == EPOLL_CTL_DEL
+                              ? "EPOLL_CTL_DEL"
+                              : "UNKNOWN"))),
+                       fd,
+                       epe_templ.events,
+                       fd);
 	errno = saved_errno;
     }
 #endif
-    if (res == 0)
-	ps->fds_status[fd].used_events = ps->fds_status[fd].events;
-    else {
+    if (res != 0) {
 	switch (op) {
-	case EPOLL_CTL_MOD:
+	case ERTS_POLL_OP_MOD:
 	    epe.events = 0;
 	    do {
 		/* We init 'epe' every time since epoll_ctl() may modify it
@@ -1314,29 +809,18 @@ update_pollset(ErtsPollSet ps, int fd)
 		epe.data.fd = fd;
 		res = epoll_ctl(ps->kp_fd, EPOLL_CTL_DEL, fd, &epe);
 	    } while (res != 0 && errno == EINTR);
-	    ps->fds_status[fd].used_events = 0;
 	/* Fall through ... */
-	case EPOLL_CTL_ADD: {
-	    ps->fds_status[fd].flags |= ERTS_POLL_FD_FLG_USEFLBCK;
-	    erts_smp_atomic_dec_nob(&ps->no_of_user_fds);
-#if ERTS_POLL_USE_CONCURRENT_UPDATE
-	    if (!*update_fallback) {
-		*update_fallback = 1;
-		return 0;
-	    }
-#endif
-	    ASSERT(!(ps->fds_status[fd].flags & ERTS_POLL_FD_FLG_INFLBCK));
-	    res = update_fallback_pollset(ps, fd);
-	    ASSERT(ps->fds_status[fd].flags & ERTS_POLL_FD_FLG_INFLBCK);
+	case ERTS_POLL_OP_ADD: {
+	    erts_atomic_dec_nob(&ps->no_of_user_fds);
+            res = ERTS_POLL_EV_NVAL;
 	    break;
 	}
-	case EPOLL_CTL_DEL: {
+	case ERTS_POLL_OP_DEL: {
 	    /*
 	     * Since we use a lazy update approach EPOLL_CTL_DEL will
 	     * frequently fail. This since epoll automatically removes
 	     * a filedescriptor that is closed from the poll set.
 	     */
-	    ps->fds_status[fd].used_events = 0;
 	    res = 0;
 	    break;
 	}
@@ -1345,68 +829,308 @@ update_pollset(ErtsPollSet ps, int fd)
 			__FILE__, __LINE__);
 	    break;
 	}
+    } else {
+        res = events;
     }
-    ps->fds_status[fd].flags &= ~ERTS_POLL_FD_FLG_RST;
     return res;
 }
 
-#if ERTS_POLL_USE_CONCURRENT_UPDATE
+#endif /* ERTS_POLL_USE_EPOLL */
+
+#if ERTS_POLL_USE_KQUEUE
+
+/* Some versions of the EV_SET macro used kevp multiple times,
+   so we define out own version that make sure that it is safe
+   to do kevp++ in the argument list. */
+#define ERTS_EV_SET(kevp, a, b, c, f) do {              \
+        struct kevent *kevp_ = kevp;                    \
+        EV_SET(kevp_, a, b, c, 0, 0, f);                \
+    } while(0)
+
 static int
-update_pollset(ErtsPollSet ps, int fd)
+update_pollset(ErtsPollSet *ps, int fd, ErtsPollOp op, ErtsPollEvents events)
 {
-    int update_fallback = 1;
-    return conc_update_pollset(ps, fd, &update_fallback);
-}
-#endif
+    int res = 0, len = 0;
+    struct kevent evts[2];
+    struct timespec ts = {0, 0};
+    uint32_t oneshot = 0;
+
+    if (op == ERTS_POLL_OP_ADD) {
+        /* This is a hack to make the "noshell" option work; kqueue can poll
+         * these fds but will not report EV_EOF, so we return NVAL to use the
+         * fallback instead.
+         *
+         * This may be common to all pipes but we have no way to tell whether
+         * an fd is a pipe or not. */
+        switch (fd) {
+        case STDIN_FILENO:
+        case STDOUT_FILENO:
+        case STDERR_FILENO:
+            return ERTS_POLL_EV_NVAL;
+        default:
+            break;
+        }
+    }
+
+#if defined(EV_DISPATCH) && !defined(__OpenBSD__)
+    /* If we have EV_DISPATCH we use it, unless we are on OpenBSD as the
+       behavior of EV_EOF seems to be edge triggered there and we need it
+       to be level triggered.
+
+       The kevent descriptions for both read and write are added on OP_ADD
+       and removed on OP_DEL. And then after than only EV_ENABLE|EV_DISPATCH
+       are used.
+
+       It could be possible to not modify the pollset when disabling and/or
+       deleting events, but that may cause the poll threads to be awoken
+       a lot more than they should so we take the cost here instead of
+       in the poll thread.
+
+       Note: We need to have EV_DISPATCH both when the event is enabled and
+       disabled, as otherwise the event may be triggered twice on each re-arm.
+       Not sure if this is intended or not (can't find anything about it in the
+       man page), but it seems to be the way it works...
+    */
+
+    if (ps->oneshot)
+        oneshot = EV_DISPATCH;
+
+    if (op == ERTS_POLL_OP_DEL) {
+        erts_atomic_dec_nob(&ps->no_of_user_fds);
+        /* We could probably skip this delete, do we want to? */
+        ERTS_EV_SET(&evts[len++], fd, EVFILT_READ, EV_DELETE, (void *) 0);
+        ERTS_EV_SET(&evts[len++], fd, EVFILT_WRITE, EV_DELETE, (void *) 0);
+    } else if (op == ERTS_POLL_OP_ADD) {
+        uint32_t flags;
+        erts_atomic_inc_nob(&ps->no_of_user_fds);
+
+        flags = EV_ADD|oneshot;
+        flags |= ((events & ERTS_POLL_EV_IN) ? 0 : EV_DISABLE);
+        ERTS_EV_SET(&evts[len++], fd, EVFILT_READ, flags, (void *) ERTS_POLL_EV_IN);
+
+        flags = EV_ADD|oneshot;
+        flags |= ((events & ERTS_POLL_EV_OUT) ? 0 : EV_DISABLE);
+        ERTS_EV_SET(&evts[len++], fd, EVFILT_WRITE, flags, (void *) ERTS_POLL_EV_OUT);
+    } else {
+        uint32_t flags;
+        ASSERT(op == ERTS_POLL_OP_MOD);
+
+        flags = oneshot;
+        flags |= (events & ERTS_POLL_EV_IN) ? EV_ENABLE : EV_DISABLE;
+        ERTS_EV_SET(&evts[len++], fd, EVFILT_READ, flags, (void *) ERTS_POLL_EV_IN);
+
+        flags = oneshot;
+        flags |= (events & ERTS_POLL_EV_OUT) ? EV_ENABLE : EV_DISABLE;
+        ERTS_EV_SET(&evts[len++], fd, EVFILT_WRITE, flags, (void *) ERTS_POLL_EV_OUT);
+    }
+#else
+    uint32_t flags = EV_ADD;
 
-#endif /* ERTS_POLL_USE_EPOLL */
+    if (ps->oneshot) flags |= EV_ONESHOT;
 
-#endif /* ERTS_POLL_USE_BATCH_UPDATE_POLLSET */
+    if (op == ERTS_POLL_OP_DEL) {
+        erts_atomic_dec_nob(&ps->no_of_user_fds);
+        /* We don't do anything when a delete is issued. The fds will be removed
+           when they are triggered, or when they are closed. */
+        events = 0;
+    } else if (op == ERTS_POLL_OP_ADD) {
+        erts_atomic_inc_nob(&ps->no_of_user_fds);
+    }
 
-#if ERTS_POLL_USE_POLL || ERTS_POLL_USE_SELECT || ERTS_POLL_USE_FALLBACK
+    if (events & ERTS_POLL_EV_IN) {
+        ERTS_EV_SET(&evts[len++], fd, EVFILT_READ, flags, (void *) ERTS_POLL_EV_IN);
+    }
+    if (events & ERTS_POLL_EV_OUT) {
+        ERTS_EV_SET(&evts[len++], fd, EVFILT_WRITE, flags, (void *) ERTS_POLL_EV_OUT);
+    }
 
-#if ERTS_POLL_USE_FALLBACK
-static int update_fallback_pollset(ErtsPollSet ps, int fd)
-#else
-static int update_pollset(ErtsPollSet ps, int fd)
 #endif
-{
-#ifdef ERTS_POLL_DEBUG_PRINT
-#if ERTS_POLL_USE_FALLBACK
-    erts_printf("Doing fallback update on fd=%d\n", fd);
+    if (len)
+        do {
+            res = kevent(ps->kp_fd, evts, len, NULL, 0, &ts);
+        } while (res < 0 && errno == EINTR);
+#if ERTS_POLL_DEBUG_PRINT
+    {
+        int saved_errno = errno, i;
+        char keventb[255], *keventbp = keventb;
+        if (res < 0)
+            keventbp += sprintf(keventbp,"%s = ",erl_errno_id(saved_errno));
+        else
+            keventbp += sprintf(keventbp,"%d = ",res);
+        keventbp += sprintf(keventbp, "kevent(%d, {",ps->kp_fd);
+        for (i = 0; i < len; i++) {
+            const char *flags = "UNKNOWN";
+            if (evts[i].flags == (EV_DELETE)) flags = "EV_DELETE";
+            if (evts[i].flags == (EV_ADD|EV_ONESHOT)) flags = "EV_ADD|EV_ONESHOT";
+            if (evts[i].flags == (EV_ADD)) flags = "EV_ADD";
+#ifdef EV_DISPATCH
+            if (evts[i].flags == (EV_ADD|EV_DISPATCH)) flags = "EV_ADD|EV_DISPATCH";
+            if (evts[i].flags == (EV_ADD|EV_DISABLE)) flags = "EV_ADD|EV_DISABLE";
+            if (evts[i].flags == (EV_ENABLE|EV_DISPATCH)) flags = "EV_ENABLE|EV_DISPATCH";
+            if (evts[i].flags == (EV_ENABLE)) flags = "EV_ENABLE";
+            if (evts[i].flags == (EV_DISABLE)) flags = "EV_DISABLE";
+            if (evts[i].flags == (EV_DISABLE|EV_DISPATCH)) flags = "EV_DISABLE|EV_DISABLE";
+            if (evts[i].flags == (EV_DISABLE)) flags = "EV_DISABLE";
+#endif
+
+            keventbp += sprintf(keventbp, "%s{%lu, %s, %s}",i > 0 ? ", " : "",
+                                evts[i].ident,
+                                (evts[i].filter == EVFILT_READ
+                                 ? "EVFILT_READ"
+                                 : (evts[i].filter == EVFILT_WRITE
+                                    ? "EVFILT_WRITE"
+                                    : "UNKNOWN")), flags);
+        }
+        keventbp += sprintf(keventbp, "}, %d)", len);
+        DEBUG_PRINT_FD("%s", ps, fd, keventb);
+        errno = saved_errno;
+    }
+#endif
+    if (res < 0) {
+        if (op != ERTS_POLL_OP_DEL) {
+#ifdef EV_RECEIPT
+            struct kevent receipt_evts[2];
+            len = 0;
+            ERTS_EV_SET(&evts[len++], fd, EVFILT_WRITE, EV_DELETE|EV_RECEIPT, (void *) 0);
+            ERTS_EV_SET(&evts[len++], fd, EVFILT_READ, EV_DELETE|EV_RECEIPT, (void *) 0);
+            do {
+                res = kevent(ps->kp_fd, evts, len, receipt_evts, 2, &ts);
+            } while (res < 0 && errno == EINTR);
 #else
-    erts_printf("Doing update on fd=%d\n", fd);
+            ERTS_EV_SET(&evts[0], fd, EVFILT_WRITE, EV_DELETE, (void *) 0);
+            do {
+                res = kevent(ps->kp_fd, evts, 1, NULL, 0, &ts);
+            } while (res < 0 && errno == EINTR);
+            ERTS_EV_SET(&evts[0], fd, EVFILT_READ, EV_DELETE, (void *) 0);
+            do {
+                res = kevent(ps->kp_fd, evts, 1, NULL, 0, &ts);
+            } while (res < 0 && errno == EINTR);
+#endif
+            if (op == ERTS_POLL_OP_ADD)
+                erts_atomic_dec_nob(&ps->no_of_user_fds);
+            events = ERTS_POLL_EV_NVAL;
+        } else
+            events = 0;
+    }
+    return events;
+}
+
+#endif /* ERTS_POLL_USE_KQUEUE */
+
+#if !ERTS_POLL_USE_CONCURRENT_UPDATE
+
+static ERTS_INLINE void
+init_batch_update(ErtsPollSet *ps, int len)
+{
+#if ERTS_POLL_USE_DEVPOLL
+    ASSERT(ps->poll_fds == NULL);
+    ps->poll_fds = erts_alloc(ERTS_ALC_T_TMP, sizeof(struct pollfd) * len);
+    ps->poll_fds_ix = 0;
 #endif
+}
+
+static ERTS_INLINE void
+write_batch_update(ErtsPollSet *ps)
+{
+#if ERTS_POLL_USE_DEVPOLL
+    ssize_t wres;
+    char *buf = (char *) ps->poll_fds;
+    size_t buf_size = sizeof(struct pollfd)*ps->poll_fds_ix;
+
+    while (1) {
+	wres = write(ps->kp_fd, (void *) buf, buf_size);
+	if (wres < 0) {
+	    if (errno == EINTR)
+		continue;
+	    fatal_error("%s:%d:write_batch_buf(): "
+			"Failed to write to /dev/poll: "
+			"%s (%d)\n",
+			__FILE__, __LINE__,
+			erl_errno_id(errno), errno);
+	}
+#if ERTS_POLL_DEBUG_PRINT
+        {
+            int saved_errno = errno, i;
+            char devpollb[2048], *devpollbp = devpollb;
+            devpollbp += sprintf(devpollbp, "%d = devpoll(%d, {", wres, ps->kp_fd);
+            for (i = 0; i < wres / sizeof(struct pollfd); i++) {
+                if (devpollbp == devpollb)
+                    devpollbp += sprintf(devpollbp, "%d = devpoll(%d, {", wres, ps->kp_fd);
+                devpollbp += sprintf(devpollbp, "%s{fd = %d, events = %s}",
+                                     i > 0 ? ", " : "",
+                                     ps->poll_fds[i].fd,
+                                     ev2str(ps->poll_fds[i].events));
+                if (devpollbp - devpollb > 512) {
+                    devpollbp += sprintf(devpollbp, "}, %d)", ps->poll_fds_ix);
+                    DEBUG_PRINT("%s", ps, devpollb);
+                    devpollbp = devpollb;
+                }
+            }
+            devpollbp += sprintf(devpollbp, "}, %d)", ps->poll_fds_ix);
+            DEBUG_PRINT("%s", ps, devpollb);
+            errno = saved_errno;
+        }
 #endif
 
-    ASSERT(fd < ps->fds_status_len);
-#if ERTS_POLL_USE_FALLBACK
-    ASSERT(ps->fds_status[fd].used_events
-	   ? (ps->fds_status[fd].flags & ERTS_POLL_FD_FLG_INFLBCK)
-	   : (ps->fds_status[fd].flags & ERTS_POLL_FD_FLG_USEFLBCK));
+	buf_size -= wres;
+	if (buf_size <= 0)
+	    break;
+	buf += wres;
+    }
+
+    if (buf_size < 0) {
+	fatal_error("%s:%d:write_devpoll_buf(): Internal error\n",
+		    __FILE__, __LINE__);
+    }
+    erts_free(ERTS_ALC_T_TMP, ps->poll_fds);
+    ps->poll_fds = NULL;
 #endif
+}
 
-    if (!need_update(ps, fd))
-	return 0;
+static ERTS_INLINE int
+need_update(ErtsPollSet *ps, int fd, int *resetp)
+{
+    int reset;
+    ASSERT(fd < ps->fds_status_len);
 
-#if ERTS_POLL_USE_FALLBACK
+    reset = (int) (ps->fds_status[fd].flags & ERTS_POLL_FD_FLG_RST);
     ps->fds_status[fd].flags &= ~ERTS_POLL_FD_FLG_RST;
-#endif
+
+    *resetp = reset;
+
+    if (reset || ps->fds_status[fd].used_events != ps->fds_status[fd].events)
+	return 1;
+
+    return 0;
+}
+
+static int update_pollset(ErtsPollSet *ps, ErtsPollResFd pr[], int fd)
+{
+    int res = 0, reset = 0;
+    ErtsPollEvents events = ps->fds_status[fd].events;
+    ASSERT(fd < ps->fds_status_len);
+
+    if (!need_update(ps, fd, &reset))
+	return res;
 
 #if ERTS_POLL_USE_POLL	/* --- poll -------------------------------- */
-    if (!ps->fds_status[fd].events) {
+    if (!events) {
 	int pix = ps->fds_status[fd].pix;
 	int last_pix;
+
+        if (reset) {
+            /* When a fd has been reset, we tell the caller of erts_poll_wait
+               this by setting the fd as ERTS_POLL_EV_NONE */
+            ERTS_POLL_RES_SET_FD(&pr[res], fd);
+            ERTS_POLL_RES_SET_EVTS(&pr[res], ERTS_POLL_EV_NONE);
+            DEBUG_PRINT_FD("trig %s (poll)", ps, fd, ev2str(ERTS_POLL_EV_NONE));
+            res++;
+        }
+
 	if (pix < 0) {
-#if ERTS_POLL_USE_FALLBACK
-	    ASSERT(!(ps->fds_status[fd].flags & ERTS_POLL_FD_FLG_INFLBCK));
-#endif
-	    return -1;
+	    return res;
 	}
-#if ERTS_POLL_USE_FALLBACK
-	ASSERT(ps->fds_status[fd].flags & ERTS_POLL_FD_FLG_INFLBCK);
-#endif
-	erts_smp_atomic_dec_nob(&ps->no_of_user_fds);
+	erts_atomic_dec_nob(&ps->no_of_user_fds);
 	last_pix = --ps->no_poll_fds;
 	if (pix != last_pix) {
 	/* Move last pix to this pix */
@@ -1422,127 +1146,153 @@ static int update_pollset(ErtsPollSet ps, int fd)
 	/* Clear this fd status */
 	ps->fds_status[fd].pix = -1;
 	ps->fds_status[fd].used_events = (ErtsPollEvents) 0;
-#if ERTS_POLL_USE_FALLBACK
-	ps->fds_status[fd].flags &= ~ERTS_POLL_FD_FLG_INFLBCK;
-#endif
+
     }
     else {
 	int pix = ps->fds_status[fd].pix;
 	if (pix < 0) {
-#if ERTS_POLL_USE_FALLBACK
-	    ASSERT(!(ps->fds_status[fd].flags & ERTS_POLL_FD_FLG_INFLBCK)
-		    || fd == ps->kp_fd);
-#endif
-	    erts_smp_atomic_inc_nob(&ps->no_of_user_fds);
+	    erts_atomic_inc_nob(&ps->no_of_user_fds);
 	    ps->fds_status[fd].pix = pix = ps->no_poll_fds++;
 	    if (pix >= ps->poll_fds_len)
 		grow_poll_fds(ps, pix);
 	    ps->poll_fds[pix].fd = fd;
 	    ps->fds_status[fd].pix = pix;
-#if ERTS_POLL_USE_FALLBACK
-	    ps->fds_status[fd].flags |= ERTS_POLL_FD_FLG_INFLBCK;
-#endif
 	}
 
-#if ERTS_POLL_USE_FALLBACK
-	ASSERT(ps->fds_status[fd].flags & ERTS_POLL_FD_FLG_INFLBCK);
-#endif
-
 	/* Events to be used in next poll */
-	ps->poll_fds[pix].events = ev2pollev(ps->fds_status[fd].events);
+	ps->poll_fds[pix].events = ev2pollev(events);
 	if (ps->poll_fds[pix].revents) {
 	    /* Remove result events that we should not poll for anymore */
 	    ps->poll_fds[pix].revents
 		&= ev2pollev(~(~ps->fds_status[fd].used_events
-			       & ps->fds_status[fd].events));
+			       & events));
 	}
 	/* Save events to be used in next poll */
-	ps->fds_status[fd].used_events = ps->fds_status[fd].events;
+	ps->fds_status[fd].used_events = events;
     }
-    return 0;
+    return res;
 #elif ERTS_POLL_USE_SELECT	/* --- select ------------------------------ */
-    {
-	ErtsPollEvents events = ps->fds_status[fd].events;
+    if (!events) {
+
+        if (reset) {
+            /* When a fd has been reset, we tell the caller of erts_poll_wait
+               this by setting the fd as ERTS_POLL_EV_NONE */
+            ERTS_POLL_RES_SET_FD(&pr[res], fd);
+            ERTS_POLL_RES_SET_EVTS(&pr[res], ERTS_POLL_EV_NONE);
+            DEBUG_PRINT_FD("trig %s (select)", ps, fd, ev2str(ERTS_POLL_EV_NONE));
+            res++;
+        }
+
+        if (check_select_fds(fd, &ps->input_fds, &ps->output_fds)) {
+            ERTS_FD_CLR(fd, &ps->input_fds);
+            ERTS_FD_CLR(fd, &ps->output_fds);
+        }
+
+        if (ps->fds_status[fd].used_events) {
+            erts_atomic_dec_nob(&ps->no_of_user_fds);
+            ps->fds_status[fd].used_events = (ErtsPollEvents) 0;
+        }
+
+        if (fd == ps->max_fd) {
+            int max = ps->max_fd;
+            for (max = ps->max_fd; max >= 0; max--)
+                if (ps->fds_status[max].used_events)
+                    break;
+            ps->max_fd = max;
+        }
+
+    } else {
+
 	ensure_select_fds(fd, &ps->input_fds, &ps->output_fds);
-	if ((ERTS_POLL_EV_IN & events)
-	    != (ERTS_POLL_EV_IN & ps->fds_status[fd].used_events)) {
-	    if (ERTS_POLL_EV_IN & events) {
-		ERTS_FD_SET(fd, &ps->input_fds);
-	    }
-	    else {
-		ERTS_FD_CLR(fd, &ps->input_fds);
-	    }
-	}
-	if ((ERTS_POLL_EV_OUT & events)
-	    != (ERTS_POLL_EV_OUT & ps->fds_status[fd].used_events)) {
-	    if (ERTS_POLL_EV_OUT & events) {
-		ERTS_FD_SET(fd, &ps->output_fds);
-	    }
-	    else {
-		ERTS_FD_CLR(fd, &ps->output_fds);
-	    }
-	}
 
-	if (!ps->fds_status[fd].used_events) {
-	    ASSERT(events);
-	    erts_smp_atomic_inc_nob(&ps->no_of_user_fds);
-#if ERTS_POLL_USE_FALLBACK
-	    ps->no_select_fds++;
-	    ps->fds_status[fd].flags |= ERTS_POLL_FD_FLG_INFLBCK;
-#endif
-	}
-	else if (!events) {
-	    ASSERT(ps->fds_status[fd].used_events);
-	    erts_smp_atomic_dec_nob(&ps->no_of_user_fds);
-	    ps->fds_status[fd].events = events;
-#if ERTS_POLL_USE_FALLBACK
-	    ps->no_select_fds--;
-	    ps->fds_status[fd].flags &= ~ERTS_POLL_FD_FLG_INFLBCK;
-#endif
-	}
+        if (!ps->fds_status[fd].used_events)
+            erts_atomic_inc_nob(&ps->no_of_user_fds);
+
+        if (events & ERTS_POLL_EV_IN)
+            ERTS_FD_SET(fd, &ps->input_fds);
+        else
+            ERTS_FD_CLR(fd, &ps->input_fds);
+
+        if (events & ERTS_POLL_EV_OUT)
+            ERTS_FD_SET(fd, &ps->output_fds);
+        else
+            ERTS_FD_CLR(fd, &ps->output_fds);
 
 	ps->fds_status[fd].used_events = events;
 
-	if (events && fd > ps->max_fd)
-	    ps->max_fd = fd;
-	else if (!events && fd == ps->max_fd) {
-	    int max = ps->max_fd;
-	    for (max = ps->max_fd; max >= 0; max--)
-		if (ps->fds_status[max].used_events)
-		    break;
-	    ps->max_fd = max;
-	}
+        if (fd > ps->max_fd)
+            ps->max_fd = fd;
     }
-    return 0;
-#endif
-}
 
-#endif /* ERTS_POLL_USE_POLL || ERTS_POLL_USE_SELECT || ERTS_POLL_USE_FALLBACK */
+    return res;
+#elif ERTS_POLL_USE_DEVPOLL
 
-#if ERTS_POLL_USE_UPDATE_REQUESTS_QUEUE
+    if (!events) {
 
-static void
-handle_update_requests(ErtsPollSet ps)
-{
-    ErtsPollSetUpdateRequestsBlock *urqbp = &ps->update_requests;
-#if ERTS_POLL_USE_BATCH_UPDATE_POLLSET
-    ErtsPollBatchBuf bb;
-    setup_batch_buf(ps, &bb);
+        if (reset) {
+            /* When a fd has been reset, we tell the caller of erts_poll_wait
+               this by setting the fd as ERTS_POLL_EV_NONE */
+            ERTS_POLL_RES_SET_FD(&pr[res], fd);
+            ERTS_POLL_RES_SET_EVTS(&pr[res], ERTS_POLL_EV_NONE);
+            DEBUG_PRINT_FD("trig %s (devpoll)", ps, fd, ev2str(ERTS_POLL_EV_NONE));
+            res++;
+        }
+
+        ps->poll_fds[ps->poll_fds_ix].fd = fd;
+        ps->poll_fds[ps->poll_fds_ix].revents = 0;
+        ps->poll_fds[ps->poll_fds_ix++].events = POLLREMOVE;
+
+        if (ps->fds_status[fd].used_events) {
+            erts_atomic_dec_nob(&ps->no_of_user_fds);
+            ps->fds_status[fd].used_events = 0;
+        }
+
+    } else {
+        if (!ps->fds_status[fd].used_events) {
+            erts_atomic_inc_nob(&ps->no_of_user_fds);
+        }
+        ps->poll_fds[ps->poll_fds_ix].fd = fd;
+        ps->poll_fds[ps->poll_fds_ix].revents = 0;
+        ps->poll_fds[ps->poll_fds_ix++].events = ERTS_POLL_EV_E2N(events);
+        ps->fds_status[fd].used_events = ps->fds_status[fd].events;
+    }
+
+    return res;
 #endif
+}
+
+static int
+handle_update_requests(ErtsPollSet *ps, ErtsPollResFd pr[], int no_fds)
+{
+    int res = 0;
+    ErtsPollSetUpdateRequestsBlock *urqbp = ps->curr_upd_req_block;
 
     while (urqbp) {
 	ErtsPollSetUpdateRequestsBlock *free_urqbp = urqbp;
 	int i;
 	int len = urqbp->len;
+
+        init_batch_update(ps, len);
+
 	for (i = 0; i < len; i++) {
 	    int fd = urqbp->fds[i];
 	    ASSERT(fd < ps->fds_status_len);
-	    ps->fds_status[fd].flags &= ~ERTS_POLL_FD_FLG_INURQ;
-#if ERTS_POLL_USE_BATCH_UPDATE_POLLSET
-	    batch_update_pollset(ps, fd, &bb);
-#else
-	    update_pollset(ps, fd);
-#endif
+            ASSERT(ps->fds_status[fd].flags & ERTS_POLL_FD_FLG_INURQ);
+
+            /* We have run out of PollResFd slots to put results in,
+               so we yield here and return later for more. */
+            if (res == no_fds && pr != NULL) {
+                memmove(urqbp->fds, urqbp->fds+i, sizeof(int) * (len - i));
+                urqbp->len -= i;
+                ps->curr_upd_req_block = urqbp;
+                write_batch_update(ps);
+                return res;
+            }
+
+            if (ps->fds_status[fd].flags & ERTS_POLL_FD_FLG_INURQ) {
+                ps->fds_status[fd].flags &= ~ERTS_POLL_FD_FLG_INURQ;
+                res += update_pollset(ps, pr + res, fd);
+            }
 	}
 
 	free_urqbp = urqbp;
@@ -1550,12 +1300,9 @@ handle_update_requests(ErtsPollSet ps)
 
 	free_update_requests_block(ps, free_urqbp);
 
-    }
+        write_batch_update(ps);
 
-#if ERTS_POLL_USE_BATCH_UPDATE_POLLSET
-    if (bb.len)
-	write_batch_buf(ps, &bb);
-#endif
+    }
 
     ps->curr_upd_req_block = &ps->update_requests;
 
@@ -1564,17 +1311,19 @@ handle_update_requests(ErtsPollSet ps)
 #endif
 
     ERTS_POLLSET_UNSET_HAVE_UPDATE_REQUESTS(ps);
+    return res;
 }
 
-#endif /* ERTS_POLL_USE_UPDATE_REQUESTS_QUEUE */
+#endif /* !ERTS_POLL_USE_CONCURRENT_UPDATE */
 
 static ERTS_INLINE ErtsPollEvents
-poll_control(ErtsPollSet ps, int fd, ErtsPollEvents events, int on, int *do_wake)
+poll_control(ErtsPollSet *ps, int fd, ErtsPollOp op,
+             ErtsPollEvents events, int *do_wake)
 {
     ErtsPollEvents new_events;
 
     if (fd < ps->internal_fd_limit || fd >= max_fds) {
-	if (fd < 0) {
+	if (fd < 0 || fd >= max_fds) {
 	    new_events = ERTS_POLL_EV_ERR;
 	    goto done;
 	}
@@ -1584,130 +1333,59 @@ poll_control(ErtsPollSet ps, int fd, ErtsPollEvents events, int on, int *do_wake
 	    goto done;
 	}
 #endif
-#if ERTS_POLL_USE_WAKEUP_PIPE
 	if (fd == ps->wake_fds[0] || fd == ps->wake_fds[1]) {
 	    new_events = ERTS_POLL_EV_NVAL;
 	    goto done;
 	}
-#endif
 #if ERTS_POLL_USE_TIMERFD
-	if (fd == ps->timer_fd) {
+        if (fd == ps->timer_fd) {
 	    new_events = ERTS_POLL_EV_NVAL;
-	    goto done;
-	}
+            goto done;
+        }
 #endif
     }
 
+#if ERTS_POLL_USE_CONCURRENT_UPDATE
+
+    new_events = update_pollset(ps, fd, op, events);
+
+#else /* !ERTS_POLL_USE_CONCURRENT_UPDATE */
     if (fd >= ps->fds_status_len)
 	grow_fds_status(ps, fd);
 
     ASSERT(fd < ps->fds_status_len);
 
-    new_events = ps->fds_status[fd].events;
-
-    if (events == 0) {
-	*do_wake = 0;
-	goto done;
-    }
-
-    if (on)
-	new_events |= events;
-    else
-	new_events &= ~events;
-
-    if (new_events == (ErtsPollEvents) 0) {
-#if ERTS_POLL_USE_KERNEL_POLL || defined(ERTS_SMP)
-	ps->fds_status[fd].flags |= ERTS_POLL_FD_FLG_RST;
-#endif
-#if ERTS_POLL_USE_FALLBACK
-	ps->fds_status[fd].flags &= ~ERTS_POLL_FD_FLG_USEFLBCK;
-#endif
-    }
-
-    ps->fds_status[fd].events = new_events;
-
-    if (new_events == ps->fds_status[fd].used_events
-#if ERTS_POLL_USE_KERNEL_POLL || defined(ERTS_SMP)
-	&& !(ps->fds_status[fd].flags & ERTS_POLL_FD_FLG_RST)
-#endif
-	) {
-	*do_wake = 0;
-	goto done;
-    }
-
-#if !ERTS_POLL_USE_UPDATE_REQUESTS_QUEUE
-    if (update_pollset(ps, fd) != 0)
-	new_events = ERTS_POLL_EV_ERR;
-#else /* ERTS_POLL_USE_UPDATE_REQUESTS_QUEUE */
-
-#if ERTS_POLL_USE_CONCURRENT_UPDATE
-    if (ERTS_POLLSET_IS_POLLED(ps)) {
-	int update_fallback = 0;
-	conc_update_pollset(ps, fd, &update_fallback);
-	if (!update_fallback) {
-	    *do_wake = 0; /* no need to wake kernel poller */
-	    goto done;
-	}
+    if (op == ERTS_POLL_OP_DEL) {
+        ps->fds_status[fd].flags |= ERTS_POLL_FD_FLG_RST;
+        ps->fds_status[fd].events = 0;
+        *do_wake = 1;
+    } else if (op == ERTS_POLL_OP_ADD) {
+        ASSERT(ps->fds_status[fd].events == 0);
+        ps->fds_status[fd].events = events;
+        *do_wake = 1;
+    } else {
+        ASSERT(op == ERTS_POLL_OP_MOD);
+        ps->fds_status[fd].events = events;
+        *do_wake = 1;
     }
-#endif
+    new_events = ps->fds_status[fd].events;
 
     enqueue_update_request(ps, fd);
-	
-#ifdef ERTS_SMP
-    /*
-     * If new events have been added, we need to wake up the
-     * polling thread, but if events have been removed we don't.
-     */
-    if ((new_events && (ps->fds_status[fd].flags & ERTS_POLL_FD_FLG_RST))
-	|| (~ps->fds_status[fd].used_events & new_events))
-	*do_wake = 1;
-#endif /* ERTS_SMP */
-
-#endif /* ERTS_POLL_USE_UPDATE_REQUESTS_QUEUE */
+
+#endif /* !ERTS_POLL_USE_CONCURRENT_UPDATE */
 
  done:
-#ifdef ERTS_POLL_DEBUG_PRINT
-     erts_printf("0x%x = poll_control(ps, %d, 0x%x, %s) do_wake=%d\n",
-		 (int) new_events, fd, (int) events, (on ? "on" : "off"), *do_wake);
-#endif
+    DEBUG_PRINT_FD("%s = %s(%p, %d, %s, %s) do_wake=%d",
+                   ps, fd, ev2str(new_events), __FUNCTION__, ps,
+                   fd, op2str(op), ev2str(events), *do_wake);
     return new_events;
 }
 
-void
-ERTS_POLL_EXPORT(erts_poll_controlv)(ErtsPollSet ps,
-				     ErtsPollControlEntry pcev[],
-				     int len)
-{
-    int i;
-    int do_wake;
-    int final_do_wake = 0;
-
-    ERTS_POLLSET_LOCK(ps);
-
-    for (i = 0; i < len; i++) {
-	do_wake = 0;
-	pcev[i].events = poll_control(ps,
-				      pcev[i].fd,
-				      pcev[i].events,
-				      pcev[i].on,
-				      &do_wake);
-	final_do_wake |= do_wake;
-    }
-
-    ERTS_POLLSET_UNLOCK(ps);
-
-#ifdef ERTS_SMP
-    if (final_do_wake)
-	wake_poller(ps, 0, 0);
-#endif /* ERTS_SMP */
-
-}
-
 ErtsPollEvents
-ERTS_POLL_EXPORT(erts_poll_control)(ErtsPollSet ps,
+ERTS_POLL_EXPORT(erts_poll_control)(ErtsPollSet *ps,
 				    ErtsSysFdType fd,
+                                    ErtsPollOp op,
 				    ErtsPollEvents events,
-				    int on,
 				    int* do_wake) /* In: Wake up polling thread */
 				                  /* Out: Poller is woken */
 {
@@ -1715,15 +1393,12 @@ ERTS_POLL_EXPORT(erts_poll_control)(ErtsPollSet ps,
 
     ERTS_POLLSET_LOCK(ps);
 
-    res = poll_control(ps, fd, events, on, do_wake);
+    res = poll_control(ps, fd, op, events, do_wake);
 
     ERTS_POLLSET_UNLOCK(ps);
 
-#ifdef ERTS_SMP
-    if (*do_wake) {
-	wake_poller(ps, 0, 0);
-    }
-#endif /* ERTS_SMP */
+    if (*do_wake)
+	wake_poller(ps, 0);
 
     return res;
 }
@@ -1735,188 +1410,73 @@ ERTS_POLL_EXPORT(erts_poll_control)(ErtsPollSet ps,
 #if ERTS_POLL_USE_KERNEL_POLL
 
 static ERTS_INLINE int
-save_kp_result(ErtsPollSet ps, ErtsPollResFd pr[], int max_res, int chk_fds_res)
+ERTS_POLL_EXPORT(save_result)(ErtsPollSet *ps, ErtsPollResFd pr[], int max_res, int chk_fds_res, int ebadf)
 {
-    int res = 0;
-    int i;
-    int n = chk_fds_res < max_res ? chk_fds_res : max_res;
-#if ERTS_POLL_USE_WAKEUP_PIPE
+    int n = chk_fds_res < max_res ? chk_fds_res : max_res, i;
+    int res = n;
     int wake_fd = ps->wake_fds[0];
-#endif
-#if ERTS_POLL_USE_TIMERFD
-    int timer_fd = ps->timer_fd;
-#endif
 
-    for (i = 0; i < n; i++) {
+    if (ERTS_POLL_USE_WAKEUP(ps) || ERTS_POLL_DEBUG_PRINT || ERTS_POLL_USE_TIMERFD) {
 
-#if ERTS_POLL_USE_EPOLL		/* --- epoll ------------------------------- */
+        for (i = 0; i < n; i++) {
+            int fd = ERTS_POLL_RES_GET_FD(&pr[i]);
+#if ERTS_POLL_DEBUG_PRINT
+            ErtsPollEvents evts = ERTS_POLL_RES_GET_EVTS(pr+i);
 
-	if (ps->res_events[i].events) {
-	    int fd = ps->res_events[i].data.fd;
-	    int ix;
-	    ErtsPollEvents revents;
-#if ERTS_POLL_USE_WAKEUP_PIPE
-	    if (fd == wake_fd) {
-		cleanup_wakeup_pipe(ps);
-		continue;
-	    }
-#endif
-#if ERTS_POLL_USE_TIMERFD
-            if (fd == timer_fd) {
-                continue;
-            }
-#endif
-	    ASSERT(!(ps->fds_status[fd].flags & ERTS_POLL_FD_FLG_INFLBCK));
-	    /* epoll_wait() can repeat the same fd in result array... */
-	    ix = (int) ps->fds_status[fd].res_ev_ix;
-	    ASSERT(ix >= 0);
-	    if (ix >= res || pr[ix].fd != fd) {
-		ix = res;
-		pr[ix].fd = fd;
-		pr[ix].events = (ErtsPollEvents) 0;
-	    }
-
-	    revents = ERTS_POLL_EV_N2E(ps->res_events[i].events);
-	    pr[ix].events |= revents;
-	    if (revents) {
-		if (res == ix) {
-		    ps->fds_status[fd].res_ev_ix = (unsigned short) ix;
-		    res++;
-		}
-	    }
-	}
-
-#elif ERTS_POLL_USE_KQUEUE	/* --- kqueue ------------------------------ */
-
-	struct kevent *ev;
-	int fd;
-	int ix;
-
-	ev = &ps->res_events[i];
-	fd = (int) ev->ident;
-	ASSERT(fd < ps->fds_status_len);
-	ASSERT(!(ps->fds_status[fd].flags & ERTS_POLL_FD_FLG_INFLBCK));
-	ix = (int) ps->fds_status[fd].res_ev_ix;
-
-	ASSERT(ix >= 0);
-	if (ix >= res || pr[ix].fd != fd) {
-	    ix = res;
-	    pr[ix].fd = (int) ev->ident;
-	    pr[ix].events = (ErtsPollEvents) 0;
-	}
-
-	if (ev->filter == EVFILT_READ) {
-#if ERTS_POLL_USE_WAKEUP_PIPE
-	    if (fd == wake_fd) {
-		cleanup_wakeup_pipe(ps);
-		continue;
-	    }
-#endif
-	    pr[ix].events |= ERTS_POLL_EV_IN;
-	}
-	else if (ev->filter == EVFILT_WRITE)
-	    pr[ix].events |= ERTS_POLL_EV_OUT;
-	if (ev->flags & (EV_ERROR|EV_EOF)) {
-	    if ((ev->flags & EV_ERROR) && (((int) ev->data) == EBADF))
-		pr[ix].events |= ERTS_POLL_EV_NVAL;
-	    else
-		pr[ix].events |= ERTS_POLL_EV_ERR;
-	}
-	if (pr[ix].events) {
-	    if (res == ix) {
-		ps->fds_status[fd].res_ev_ix = (unsigned short) ix;
-		res++;
-	    }
-	}
-
-#elif ERTS_POLL_USE_DEVPOLL	/* --- devpoll ----------------------------- */
-
-	if (ps->res_events[i].revents) {
-	    int fd = ps->res_events[i].fd;
-	    ErtsPollEvents revents;
-#if ERTS_POLL_USE_WAKEUP_PIPE
-	    if (fd == wake_fd) {
-		cleanup_wakeup_pipe(ps);
-		continue;
-	    }
-#endif
+            if (fd != wake_fd
 #if ERTS_POLL_USE_TIMERFD
-	    if (fd == timer_fd) {
-		continue;
-	    }
-#endif
-	    revents = ERTS_POLL_EV_N2E(ps->res_events[i].events);
-	    pr[res].fd = fd;
-	    pr[res].events = revents;
-	    res++;
-	}
-
+                && fd != ps->timer_fd
 #endif
-
-    }
-
-    return res;
-}
-
-#endif /* ERTS_POLL_USE_KERNEL_POLL */
-
-#if ERTS_POLL_USE_FALLBACK
-
-static int
-get_kp_results(ErtsPollSet ps, ErtsPollResFd pr[], int max_res)
-{
-    int res;
+                )
+                DEBUG_PRINT_FD("trig %s (%s)", ps, fd,
+                               ev2str(evts),
 #if ERTS_POLL_USE_KQUEUE
-    struct timespec ts = {0, 0};
+                               "kqueue"
+#elif ERTS_POLL_USE_EPOLL
+                               "epoll"
+#else
+                               "/dev/poll"
 #endif
-
-    if (max_res > ps->res_events_len)
-	grow_res_events(ps, max_res);
-
-    do {
-#if ERTS_POLL_USE_EPOLL
-	res = epoll_wait(ps->kp_fd, ps->res_events, max_res, 0);
-#elif ERTS_POLL_USE_KQUEUE
-	res = kevent(ps->kp_fd, NULL, 0, ps->res_events, max_res, &ts);
+                    );
 #endif
-    } while (res < 0 && errno == EINTR);
 
-    if (res < 0) {
-	fatal_error("%s:%d: %s() failed: %s (%d)\n",
-		    __FILE__, __LINE__,
-#if ERTS_POLL_USE_EPOLL
-		    "epoll_wait",
-#elif ERTS_POLL_USE_KQUEUE
-		    "kevent",
+            if (ERTS_POLL_USE_WAKEUP(ps) && fd == wake_fd) {
+                cleanup_wakeup_pipe(ps);
+                ERTS_POLL_RES_SET_FD(&pr[i], -1);
+                ERTS_POLL_RES_SET_EVTS(&pr[i], ERTS_POLL_EV_NONE);
+                res--;
+            }
+#if ERTS_POLL_USE_TIMERFD
+            else if (fd == ps->timer_fd) {
+                ERTS_POLL_RES_SET_FD(&pr[i], -1);
+                ERTS_POLL_RES_SET_EVTS(&pr[i], ERTS_POLL_EV_NONE);
+                res--;
+            }
 #endif
-		    erl_errno_id(errno), errno);
+#if !ERTS_POLL_USE_CONCURRENT_UPDATE
+            else {
+                /* Reset the events to emulate ONESHOT semantics */
+                ps->fds_status[fd].events = 0;
+                enqueue_update_request(ps, fd);
+            }
+#endif
+        }
     }
 
-    return save_kp_result(ps, pr, max_res, res);
+    if (res == 0)
+        return res;
+    else
+        return n;
 }
 
-#endif /* ERTS_POLL_USE_FALLBACK */
-
-
+#else /* !ERTS_POLL_USE_KERNEL_POLL */
 
 static ERTS_INLINE int
-save_poll_result(ErtsPollSet ps, ErtsPollResFd pr[], int max_res,
-		 int chk_fds_res, int ebadf)
+ERTS_POLL_EXPORT(save_result)(ErtsPollSet *ps, ErtsPollResFd pr[], int max_res, int chk_fds_res, int ebadf)
 {
-#if ERTS_POLL_USE_DEVPOLL
-    return save_kp_result(ps, pr, max_res, chk_fds_res);
-#elif ERTS_POLL_USE_FALLBACK
-    if (!ps->fallback_used)
-	return save_kp_result(ps, pr, max_res, chk_fds_res);
-    else
-#endif /* ERTS_POLL_USE_FALLBACK */
-    {
-
 #if ERTS_POLL_USE_POLL	/* --- poll -------------------------------- */
 	int res = 0;
-#if ERTS_POLL_USE_WAKEUP_PIPE && !ERTS_POLL_USE_FALLBACK 
 	int wake_fd = ps->wake_fds[0];
-#endif
 	int i, first_ix, end_ix;
 
 	/*
@@ -1933,23 +1493,30 @@ save_poll_result(ErtsPollSet ps, ErtsPollResFd pr[], int max_res,
 		if (ps->poll_fds[i].revents != (short) 0) {
 		    int fd = ps->poll_fds[i].fd;
 		    ErtsPollEvents revents;
-#if ERTS_POLL_USE_FALLBACK
-		    if (fd == ps->kp_fd) {
-			res += get_kp_results(ps, &pr[res], max_res-res);
-			i++;
-			continue;
-		    }
-#elif ERTS_POLL_USE_WAKEUP_PIPE
 		    if (fd == wake_fd) {
 			cleanup_wakeup_pipe(ps);
 			i++;
 			continue;
 		    }
-#endif
 		    revents = pollev2ev(ps->poll_fds[i].revents);
-		    pr[res].fd = fd;
-		    pr[res].events = revents;
+		    ERTS_POLL_RES_SET_FD(&pr[res], fd);
+		    ERTS_POLL_RES_SET_EVTS(&pr[res], revents);
+
+                    /* If an fd returns as error, we may want to check the
+                       update_requests queue to see if it has been reset
+                       before delivering the result?!?! This should allow
+                       the user to do driver_dselect + close without waiting
+                       for stop_select... */
+
+                    DEBUG_PRINT_FD("trig %s (poll)", ps, ERTS_POLL_RES_GET_FD(&pr[res]),
+                                   ev2str(ERTS_POLL_RES_GET_EVTS(&pr[res])));
+
 		    res++;
+
+                    /* Clear the events for this fd in order to mimic
+                       how epoll ONESHOT works */
+                    ps->fds_status[fd].events = 0;
+                    enqueue_update_request(ps, fd);
 		}
 		i++;
 	    }
@@ -1965,9 +1532,7 @@ save_poll_result(ErtsPollSet ps, ErtsPollResFd pr[], int max_res,
 
 #elif ERTS_POLL_USE_SELECT	/* --- select ------------------------------ */
 	int res = 0;
-#if ERTS_POLL_USE_WAKEUP_PIPE && !ERTS_POLL_USE_FALLBACK 
 	int wake_fd = ps->wake_fds[0];
-#endif
 	int fd, first_fd, end_fd;
 
 	/*
@@ -1980,29 +1545,23 @@ save_poll_result(ErtsPollSet ps, ErtsPollResFd pr[], int max_res,
 	if (!ebadf) {
 	    while (1) {
 		while (fd < end_fd && res < max_res) {
-
-		    pr[res].events = (ErtsPollEvents) 0;
+                    ErtsPollEvents events = 0;
 		    if (ERTS_FD_ISSET(fd, &ps->res_input_fds)) {
-#if ERTS_POLL_USE_FALLBACK
-			if (fd == ps->kp_fd) {
-			    res += get_kp_results(ps, &pr[res], max_res-res);
-			    fd++;
-			    continue;
-			}
-#elif ERTS_POLL_USE_WAKEUP_PIPE
 			if (fd == wake_fd) {
 			    cleanup_wakeup_pipe(ps);
 			    fd++;
 			    continue;
 			}
-#endif
-			pr[res].events |= ERTS_POLL_EV_IN;
+			events |= ERTS_POLL_EV_IN;
 		    }
 		    if (ERTS_FD_ISSET(fd, &ps->res_output_fds))
-			pr[res].events |= ERTS_POLL_EV_OUT;
-		    if (pr[res].events) {
-			pr[res].fd = fd;
+			events |= ERTS_POLL_EV_OUT;
+		    if (events) {
+                        ERTS_POLL_RES_SET_FD(&pr[res], fd);
+                        ERTS_POLL_RES_SET_EVTS(&pr[res], events);
 			res++;
+                        ps->fds_status[fd].events = 0;
+                        enqueue_update_request(ps, fd);
 		    }
 		    fd++;
 		}
@@ -2035,7 +1594,7 @@ save_poll_result(ErtsPollSet ps, ErtsPollResFd pr[], int max_res,
 			if (ps->fds_status[fd].events & ERTS_POLL_EV_OUT) {
 			    oset = &ps->res_output_fds;
 			    ERTS_FD_ZERO(oset);
-			    ERTS_FD_SET(fd, oset);			
+			    ERTS_FD_SET(fd, oset);
 			}
 			do {
 			    /* Initiate 'tv' each time;
@@ -2044,49 +1603,31 @@ save_poll_result(ErtsPollSet ps, ErtsPollResFd pr[], int max_res,
 			    sres = ERTS_SELECT(ps->max_fd+1, iset, oset, NULL, &tv);
 			} while (sres < 0 && errno == EINTR);
 			if (sres < 0) {
-#if ERTS_POLL_USE_FALLBACK
-			    if (fd == ps->kp_fd) {
-				res += get_kp_results(ps,
-						      &pr[res],
-						      max_res-res);
-				fd++;
-				continue;
-			    }
-#elif ERTS_POLL_USE_WAKEUP_PIPE
 			    if (fd == wake_fd) {
 				cleanup_wakeup_pipe(ps);
 				fd++;
 				continue;
 			    }
-#endif
-			    pr[res].fd = fd;
-			    pr[res].events = ERTS_POLL_EV_NVAL;
+                            ERTS_POLL_RES_SET_FD(&pr[res], fd);
+                            ERTS_POLL_RES_SET_EVTS(&pr[res], ERTS_POLL_EV_NVAL);
 			    res++;
 			}
 			else if (sres > 0) {
-			    pr[res].fd = fd;
+                            ErtsPollEvents events = 0;
+                            ERTS_POLL_RES_SET_FD(&pr[res], fd);
 			    if (iset && ERTS_FD_ISSET(fd, iset)) {
-#if ERTS_POLL_USE_FALLBACK
-				if (fd == ps->kp_fd) {
-				    res += get_kp_results(ps,
-							  &pr[res],
-							  max_res-res);
-				    fd++;
-				    continue;
-				}
-#elif ERTS_POLL_USE_WAKEUP_PIPE
 				if (fd == wake_fd) {
 				    cleanup_wakeup_pipe(ps);
 				    fd++;
 				    continue;
 				}
-#endif
-				pr[res].events |= ERTS_POLL_EV_IN;
+				events |= ERTS_POLL_EV_IN;
 			    }
 			    if (oset && ERTS_FD_ISSET(fd, oset)) {
-				pr[res].events |= ERTS_POLL_EV_OUT;
+				events |= ERTS_POLL_EV_OUT;
 			    }
-			    ASSERT(pr[res].events);
+			    ASSERT(events);
+                            ERTS_POLL_RES_SET_EVTS(&pr[res], events);
 			    res++;
 			}
 		    }
@@ -2101,68 +1642,64 @@ save_poll_result(ErtsPollSet ps, ErtsPollResFd pr[], int max_res,
 	}
 	ps->next_sel_fd = fd;
 	return res;
-#endif
-    }
+#endif /* ERTS_POLL_USE_SELECT */
 }
 
+#endif /* !ERTS_POLL_USE_KERNEL_POLL */
+
 static ERTS_INLINE ErtsMonotonicTime
-get_timeout(ErtsPollSet ps,
+get_timeout(ErtsPollSet *ps,
 	    int resolution,
 	    ErtsMonotonicTime timeout_time)
 {
-    ErtsMonotonicTime timeout, save_timeout_time;
+    ErtsMonotonicTime timeout;
 
     if (timeout_time == ERTS_POLL_NO_TIMEOUT) {
-	save_timeout_time = ERTS_MONOTONIC_TIME_MIN;
 	timeout = 0;
     }
+    else if (timeout_time == ERTS_POLL_INF_TIMEOUT) {
+        timeout = -1;
+    }
     else {
 	ErtsMonotonicTime diff_time, current_time;
 	current_time = erts_get_monotonic_time(NULL);
 	diff_time = timeout_time - current_time;
 	if (diff_time <= 0) {
-	    save_timeout_time = ERTS_MONOTONIC_TIME_MIN;
 	    timeout = 0;
 	}
 	else {
-	    save_timeout_time = current_time;
 	    switch (resolution) {
 	    case 1000:
 		/* Round up to nearest even milli second */
 		timeout = ERTS_MONOTONIC_TO_MSEC(diff_time - 1) + 1;
 		if (timeout > (ErtsMonotonicTime) INT_MAX)
 		    timeout = (ErtsMonotonicTime) INT_MAX;
-		save_timeout_time += ERTS_MSEC_TO_MONOTONIC(timeout);
 		timeout -= ERTS_PREMATURE_TIMEOUT(timeout, 1000);
 		break;
 	    case 1000000:
 		/* Round up to nearest even micro second */
 		timeout = ERTS_MONOTONIC_TO_USEC(diff_time - 1) + 1;
-		save_timeout_time += ERTS_USEC_TO_MONOTONIC(timeout);
 		timeout -= ERTS_PREMATURE_TIMEOUT(timeout, 1000*1000);
 		break;
 	    case 1000000000:
 		/* Round up to nearest even nano second */
 		timeout = ERTS_MONOTONIC_TO_NSEC(diff_time - 1) + 1;
-		save_timeout_time += ERTS_NSEC_TO_MONOTONIC(timeout);
 		timeout -= ERTS_PREMATURE_TIMEOUT(timeout, 1000*1000*1000);
 		break;
 	    default:
 		ERTS_INTERNAL_ERROR("Invalid resolution");
 		timeout = 0;
-		save_timeout_time = 0;
 		break;
 	    }
 	}
     }
-    set_timeout_time(ps, save_timeout_time);
     return timeout;
 }
 
 #if ERTS_POLL_USE_SELECT
 
 static ERTS_INLINE int
-get_timeout_timeval(ErtsPollSet ps,
+get_timeout_timeval(ErtsPollSet *ps,
 		    SysTimeval *tvp,
 		    ErtsMonotonicTime timeout_time)
 {
@@ -2176,6 +1713,9 @@ get_timeout_timeval(ErtsPollSet ps,
 
 	return 0;
     }
+    else if (timeout == -1) {
+        return -1;
+    }
     else {
 	ErtsMonotonicTime sec = timeout/(1000*1000);
 	tvp->tv_sec = sec;
@@ -2185,7 +1725,7 @@ get_timeout_timeval(ErtsPollSet ps,
 	ASSERT(tvp->tv_usec >= 0);
 	ASSERT(tvp->tv_usec < 1000*1000);
 
-	return !0;
+	return 1;
     }
 
 }
@@ -2195,7 +1735,7 @@ get_timeout_timeval(ErtsPollSet ps,
 #if ERTS_POLL_USE_KQUEUE || (ERTS_POLL_USE_POLL && defined(HAVE_PPOLL)) || ERTS_POLL_USE_TIMERFD
 
 static ERTS_INLINE int
-get_timeout_timespec(ErtsPollSet ps,
+get_timeout_timespec(ErtsPollSet *ps,
 		     struct timespec *tsp,
 		     ErtsMonotonicTime timeout_time)
 {
@@ -2208,6 +1748,9 @@ get_timeout_timespec(ErtsPollSet ps,
 	tsp->tv_nsec = 0;
 	return 0;
     }
+    else if (timeout == -1) {
+        return -1;
+    }
     else {
 	ErtsMonotonicTime sec = timeout/(1000*1000*1000);
 	tsp->tv_sec = sec;
@@ -2217,7 +1760,7 @@ get_timeout_timespec(ErtsPollSet ps,
 	ASSERT(tsp->tv_nsec >= 0);
 	ASSERT(tsp->tv_nsec < 1000*1000*1000);
 
-	return !0;
+	return 1;
     }
 }
 
@@ -2226,7 +1769,7 @@ get_timeout_timespec(ErtsPollSet ps,
 #if ERTS_POLL_USE_TIMERFD
 
 static ERTS_INLINE int
-get_timeout_itimerspec(ErtsPollSet ps,
+get_timeout_itimerspec(ErtsPollSet *ps,
                        struct itimerspec *itsp,
                        ErtsMonotonicTime timeout_time)
 {
@@ -2236,242 +1779,169 @@ get_timeout_itimerspec(ErtsPollSet ps,
 
     return get_timeout_timespec(ps, &itsp->it_value, timeout_time);
 }
-
+ 
 #endif
 
 static ERTS_INLINE int
-check_fd_events(ErtsPollSet ps, ErtsMonotonicTime timeout_time, int max_res)
+check_fd_events(ErtsPollSet *ps, ErtsPollResFd pr[], int max_res, ErtsMonotonicTime timeout_time)
 {
     int res;
-    ERTS_MSACC_PUSH_STATE_M();
-    if (erts_smp_atomic_read_nob(&ps->no_of_user_fds) == 0
-	&& timeout_time == ERTS_POLL_NO_TIMEOUT) {
-	/* Nothing to poll and zero timeout; done... */
-	return 0;
-    }
-    else {
-	int timeout;
-#if ERTS_POLL_USE_FALLBACK
-	if (!(ps->fallback_used = ERTS_POLL_NEED_FALLBACK(ps))) {
-
-#if ERTS_POLL_USE_EPOLL		/* --- epoll ------------------------------- */
-	    if (max_res > ps->res_events_len)
-		grow_res_events(ps, max_res);
+    int timeout;
+    DEBUG_PRINT_WAIT("Entering check_fd_events(), timeout=%d", ps, timeout_time);
+    {
+#if ERTS_POLL_USE_EPOLL                /* --- epoll ------------------------------- */
 #if ERTS_POLL_USE_TIMERFD
-            {
-                struct itimerspec its;
-                timeout = get_timeout_itimerspec(ps, &its, timeout_time);
-                if (timeout) {
-#ifdef ERTS_SMP
-                    erts_thr_progress_prepare_wait(NULL);
-#endif
-                    ERTS_MSACC_SET_STATE_CACHED_M(ERTS_MSACC_STATE_SLEEP);
-                    timerfd_set(ps, &its);
-                    res = epoll_wait(ps->kp_fd, ps->res_events, max_res, -1);
-                    res = timerfd_clear(ps, res, max_res);
-                } else {
-                    res = epoll_wait(ps->kp_fd, ps->res_events, max_res, 0);
-                }
-            }
+        struct itimerspec its;
+        timeout = get_timeout_itimerspec(ps, &its, timeout_time);
+        if (timeout > 0) {
+            timerfd_set(ps, &its);
+            res = epoll_wait(ps->kp_fd, pr, max_res, -1);
+            res = timerfd_clear(ps, pr, res, max_res);
+        } else {
+            res = epoll_wait(ps->kp_fd, pr, max_res, timeout);
+        }
 #else /* !ERTS_POLL_USE_TIMERFD */
-	    timeout = (int) get_timeout(ps, 1000, timeout_time);
-            if (timeout) {
-#ifdef ERTS_SMP
-		erts_thr_progress_prepare_wait(NULL);
-#endif
-                ERTS_MSACC_SET_STATE_CACHED_M(ERTS_MSACC_STATE_SLEEP);
-            }
-	    res = epoll_wait(ps->kp_fd, ps->res_events, max_res, timeout);
+        timeout = (int) get_timeout(ps, 1000, timeout_time);
+        res = epoll_wait(ps->kp_fd, pr, max_res, timeout);
 #endif /* !ERTS_POLL_USE_TIMERFD */
-#elif ERTS_POLL_USE_KQUEUE	/* --- kqueue ------------------------------ */
-	    struct timespec ts;
-	    if (max_res > ps->res_events_len)
-		grow_res_events(ps, max_res);
-	    timeout = get_timeout_timespec(ps, &ts, timeout_time);
-            if (timeout) {
-#ifdef ERTS_SMP
-		erts_thr_progress_prepare_wait(NULL);
-#endif
-		ERTS_MSACC_SET_STATE_CACHED_M(ERTS_MSACC_STATE_SLEEP);
-            }
-	    res = kevent(ps->kp_fd, NULL, 0, ps->res_events, max_res, &ts);
-#endif				/* ----------------------------------------- */
-	}
-	else /* use fallback (i.e. poll() or select()) */
-#endif /* ERTS_POLL_USE_FALLBACK */
-	{
-
-#if ERTS_POLL_USE_DEVPOLL	/* --- devpoll ----------------------------- */
-	    /*
-	     * The ioctl() will fail with EINVAL on Solaris 10 if dp_nfds
-	     * is set too high. dp_nfds should not be set greater than
-	     * the maximum number of file descriptors in the poll set.
-	     */
-	    struct dvpoll poll_res;
-	    int nfds = (int) erts_smp_atomic_read_nob(&ps->no_of_user_fds);
-#if ERTS_POLL_USE_WAKEUP_PIPE
-	    nfds++; /* Wakeup pipe */
-#endif
-	    timeout = (int) get_timeout(ps, 1000, timeout_time);
-	    poll_res.dp_nfds = nfds < max_res ? nfds : max_res;
-	    if (poll_res.dp_nfds > ps->res_events_len)
-		grow_res_events(ps, poll_res.dp_nfds);
-	    poll_res.dp_fds = ps->res_events;
-	    if (timeout) {
-#ifdef ERTS_SMP
-		erts_thr_progress_prepare_wait(NULL);
-#endif
-                ERTS_MSACC_SET_STATE_CACHED_M(ERTS_MSACC_STATE_SLEEP);
-            }
-	    poll_res.dp_timeout = timeout;
-	    res = ioctl(ps->kp_fd, DP_POLL, &poll_res);
+#elif ERTS_POLL_USE_KQUEUE     /* --- kqueue ------------------------------ */
+        struct timespec ts;
+        struct timespec *tsp;
+        timeout = get_timeout_timespec(ps, &ts, timeout_time);
+        tsp = timeout < 0 ? NULL : &ts;
+        res = kevent(ps->kp_fd, NULL, 0, pr, max_res, tsp);
+#elif ERTS_POLL_USE_DEVPOLL	/* --- devpoll ----------------------------- */
+        /*
+         * The ioctl() will fail with EINVAL on Solaris 10 if dp_nfds
+         * is set too high. dp_nfds should not be set greater than
+         * the maximum number of file descriptors in the poll set.
+         */
+        struct dvpoll poll_res;
+        int nfds = (int) erts_atomic_read_nob(&ps->no_of_user_fds) + 1 /* wakeup pipe */;
+        poll_res.dp_nfds = nfds < max_res ? nfds : max_res;
+        poll_res.dp_fds = pr;
+        poll_res.dp_timeout = (int) get_timeout(ps, 1000, timeout_time);
+        res = ioctl(ps->kp_fd, DP_POLL, &poll_res);
 #elif ERTS_POLL_USE_POLL && defined(HAVE_PPOLL)	/* --- ppoll ---------------- */
-            struct timespec ts;
-	    timeout = get_timeout_timespec(ps, &ts, timeout_time);
-            if (timeout) {
-#ifdef ERTS_SMP
-		erts_thr_progress_prepare_wait(NULL);
-#endif
-		ERTS_MSACC_SET_STATE_CACHED_M(ERTS_MSACC_STATE_SLEEP);
-            }
-            res = ppoll(ps->poll_fds, ps->no_poll_fds, &ts, NULL);
+        struct timespec ts;
+        struct timespec *tsp = &ts;
+        timeout = get_timeout_timespec(ps, &ts, timeout_time);
+        if (timeout < 0) tsp = NULL;
+        res = ppoll(ps->poll_fds, ps->no_poll_fds, tsp, NULL);
 #elif ERTS_POLL_USE_POLL        /* --- poll --------------------------------- */
-	    timeout = (int) get_timeout(ps, 1000, timeout_time);
-
-	    if (timeout) {
-#ifdef ERTS_SMP
-		erts_thr_progress_prepare_wait(NULL);
-#endif
-		ERTS_MSACC_SET_STATE_CACHED_M(ERTS_MSACC_STATE_SLEEP);
-            }
-	    res = poll(ps->poll_fds, ps->no_poll_fds, timeout);
+        timeout = (int) get_timeout(ps, 1000, timeout_time);
+        res = poll(ps->poll_fds, ps->no_poll_fds, timeout);
 #elif ERTS_POLL_USE_SELECT	/* --- select ------------------------------ */
-	    SysTimeval to;
-	    timeout = get_timeout_timeval(ps, &to, timeout_time);
-
-	    ERTS_FD_COPY(&ps->input_fds, &ps->res_input_fds);
-	    ERTS_FD_COPY(&ps->output_fds, &ps->res_output_fds);
-
-	    if (timeout) {
-#ifdef ERTS_SMP
-		erts_thr_progress_prepare_wait(NULL);
-#endif
-		ERTS_MSACC_SET_STATE_CACHED_M(ERTS_MSACC_STATE_SLEEP);
-	    }
-	    res = ERTS_SELECT(ps->max_fd + 1,
-			      &ps->res_input_fds,
-			      &ps->res_output_fds,
-			      NULL,
-			      &to);
-#ifdef ERTS_SMP
-	    if (timeout) {
-		erts_thr_progress_finalize_wait(NULL);
-		ERTS_MSACC_POP_STATE_M();
-	    }
-	    if (res < 0
-		&& errno == EBADF
-		&& ERTS_POLLSET_HAVE_UPDATE_REQUESTS(ps)) {
-		/*
-		 * This may have happened because another thread deselected
-		 * a fd in our poll set and then closed it, i.e. the driver
-		 * behaved correctly. We wan't to avoid looking for a bad
-		 * fd, that may even not exist anymore. Therefore, handle
-		 * update requests and try again.
-		 *
-		 * We don't know how much of the timeout is left; therfore,
-		 * we use a zero timeout. If no error occur and no events
-		 * have triggered, we fake an EAGAIN error and let the caller
-		 * restart us.
-		 */
-		to.tv_sec = 0;
-		to.tv_usec = 0;
-		ERTS_POLLSET_LOCK(ps);
-		handle_update_requests(ps);
-		ERTS_POLLSET_UNLOCK(ps);
-		res = ERTS_SELECT(ps->max_fd + 1,
-				  &ps->res_input_fds,
-				  &ps->res_output_fds,
-				  NULL,
-				  &to);
-		if (res == 0) {
-		    errno = EAGAIN;
-		    res = -1;
-		}
-	    }
-#endif /* ERTS_SMP */
-	    return res;
+        SysTimeval tv;
+        SysTimeval *tvp;
+        timeout = get_timeout_timeval(ps, &tv, timeout_time);
+        tvp = timeout < 0 ? NULL : &tv;
+
+        ERTS_FD_COPY(&ps->input_fds, &ps->res_input_fds);
+        ERTS_FD_COPY(&ps->output_fds, &ps->res_output_fds);
+
+        res = ERTS_SELECT(ps->max_fd + 1,
+                          &ps->res_input_fds,
+                          &ps->res_output_fds,
+                          NULL,
+                          tvp);
 #endif				/* ----------------------------------------- */
-	}
-	if (timeout) {
-#ifdef ERTS_SMP
-	    erts_thr_progress_finalize_wait(NULL);
-#endif
-	    ERTS_MSACC_POP_STATE_M();
-	}
-	return res;
     }
+    DEBUG_PRINT_WAIT("Leaving check_fd_events(), res=%d", ps, res);
+    return res;
 }
 
 int
-ERTS_POLL_EXPORT(erts_poll_wait)(ErtsPollSet ps,
+ERTS_POLL_EXPORT(erts_poll_wait)(ErtsPollSet *ps,
 				 ErtsPollResFd pr[],
 				 int *len,
-				 ErtsMonotonicTime timeout_time)
+                                 ErtsThrPrgrData *tpd,
+                                 ErtsMonotonicTime timeout_time)
 {
-    ErtsMonotonicTime to;
-    int res, no_fds;
+    int res, no_fds, used_fds = 0;
     int ebadf = 0;
-#ifdef ERTS_SMP
+    int do_wait;
     int ps_locked = 0;
-#endif
+    ERTS_MSACC_DECLARE_CACHE();
 
     no_fds = *len;
-#ifdef ERTS_POLL_MAX_RES
-    if (no_fds >= ERTS_POLL_MAX_RES)
-	no_fds = ERTS_POLL_MAX_RES;
-#endif
-
     *len = 0;
+    ASSERT(no_fds > 0);
 
-#ifdef ERTS_POLL_DEBUG_PRINT
-    erts_printf("Entering erts_poll_wait(), timeout_time=%bps\n",
-		timeout_time);
-#endif
-
-    if (ERTS_POLLSET_SET_POLLED_CHK(ps)) {
-	res = EINVAL; /* Another thread is in erts_poll_wait()
-			 on this pollset... */
-	goto done;
-    }
-
-    to = (is_woken(ps)
-	  ? ERTS_POLL_NO_TIMEOUT /* Use zero timeout */
-	  : timeout_time);
-
-#if ERTS_POLL_USE_UPDATE_REQUESTS_QUEUE
+#if !ERTS_POLL_USE_CONCURRENT_UPDATE
     if (ERTS_POLLSET_HAVE_UPDATE_REQUESTS(ps)) {
 	ERTS_POLLSET_LOCK(ps);
-	handle_update_requests(ps);
+	used_fds = handle_update_requests(ps, pr, no_fds);
 	ERTS_POLLSET_UNLOCK(ps);
+
+        if (used_fds == no_fds) {
+            *len = used_fds;
+            return 0;
+        }
     }
 #endif
 
+    do_wait = !is_woken(ps) && used_fds == 0 && timeout_time != ERTS_POLL_NO_TIMEOUT;
+
+    DEBUG_PRINT_WAIT("Entering %s(), do_wait=%d", ps, __FUNCTION__, do_wait);
+
+    if (do_wait) {
+        tpd = tpd ? tpd : erts_thr_prgr_data(NULL);
+        erts_thr_progress_prepare_wait(tpd);
+        ERTS_MSACC_SET_STATE_CACHED(ERTS_MSACC_STATE_SLEEP);
+    } else
+        timeout_time = ERTS_POLL_NO_TIMEOUT;
+
     while (1) {
-	res = check_fd_events(ps, to, no_fds);
-	if (res != 0)
-	    break;
-	if (to == ERTS_POLL_NO_TIMEOUT)
-	    break;
-	if (erts_get_monotonic_time(NULL) >= timeout_time)
+        res = check_fd_events(ps, pr + used_fds, no_fds - used_fds, timeout_time);
+        if (res != 0)
+            break;
+        if (timeout_time == ERTS_POLL_NO_TIMEOUT)
+            break;
+        if (erts_get_monotonic_time(NULL) >= timeout_time)
 	    break;
     }
 
-    woke_up(ps);
+#if !ERTS_POLL_USE_CONCURRENT_UPDATE
+    if (res < 0
+        && errno == EBADF
+        && ERTS_POLLSET_HAVE_UPDATE_REQUESTS(ps)) {
+        /*
+         * This may have happened because another thread deselected
+         * a fd in our poll set and then closed it, i.e. the driver
+         * behaved correctly. We wan't to avoid looking for a bad
+         * fd, that may even not exist anymore. Therefore, handle
+         * update requests and try again. This behaviour should only
+         * happen when using SELECT as the polling mechanism.
+         */
+        ERTS_POLLSET_LOCK(ps);
+        used_fds += handle_update_requests(ps, pr + used_fds, no_fds - used_fds);
+        if (used_fds == no_fds) {
+            *len = used_fds;
+            ERTS_POLLSET_UNLOCK(ps);
+            return 0;
+        }
+        res = check_fd_events(ps, pr + used_fds, no_fds - used_fds, ERTS_POLL_NO_TIMEOUT);
+        /* Keep the lock over the non-blocking poll in order to not
+           get any nasty races happening. */
+        ERTS_POLLSET_UNLOCK(ps);
+        if (res == 0) {
+            errno = EAGAIN;
+            res = -1;
+        }
+    }
+#endif
+
+    if (do_wait) {
+        erts_thr_progress_finalize_wait(tpd);
+        ERTS_MSACC_UPDATE_CACHE();
+        ERTS_MSACC_SET_STATE_CACHED(ERTS_MSACC_STATE_CHECK_IO);
+    }
+
+    if (ERTS_POLL_USE_WAKEUP(ps))
+        woke_up(ps);
 
-    if (res == 0) {
-	res = ETIMEDOUT;
-    }
-    else if (res < 0) {
+    if (res < 0) {
 #if ERTS_POLL_USE_SELECT
 	if (errno == EBADF) {
 	    ebadf = 1;
@@ -2480,38 +1950,34 @@ ERTS_POLL_EXPORT(erts_poll_wait)(ErtsPollSet ps,
 #endif
 	res = errno;
     }
-    else {
+    else if (res == 0) {
+        res = used_fds == 0 ? ETIMEDOUT : 0;
+#ifdef HARD_DEBUG
+	check_poll_result(pr, used_fds);
+#endif
+        *len = used_fds;
+    } else {
 #if ERTS_POLL_USE_SELECT
     save_results:
 #endif
-
-#ifdef ERTS_SMP
 	ps_locked = 1;
 	ERTS_POLLSET_LOCK(ps);
-#endif
 
-	no_fds = save_poll_result(ps, pr, no_fds, res, ebadf);
+	used_fds += ERTS_POLL_EXPORT(save_result)(ps, pr + used_fds, no_fds - used_fds, res, ebadf);
 
 #ifdef HARD_DEBUG
-	check_poll_result(pr, no_fds);
+	check_poll_result(pr, used_fds);
 #endif
 
-	res = (no_fds == 0 ? (is_interrupted_reset(ps) ? EINTR : EAGAIN) : 0);
-	*len = no_fds;
+	res = (used_fds == 0 ? (is_interrupted_reset(ps) ? EINTR : EAGAIN) : 0);
+	*len = used_fds;
     }
 
-#ifdef ERTS_SMP
     if (ps_locked)
 	ERTS_POLLSET_UNLOCK(ps);
-    ERTS_POLLSET_UNSET_POLLED(ps);
-#endif
 
- done:
-    set_timeout_time(ps, ERTS_MONOTONIC_TIME_MAX);
-#ifdef ERTS_POLL_DEBUG_PRINT
-    erts_printf("Leaving %s = erts_poll_wait()\n",
-		 res == 0 ? "0" : erl_errno_id(res));
-#endif
+    DEBUG_PRINT_WAIT("Leaving %s = %s(len = %d)", ps,
+                     res == 0 ? "0" : erl_errno_id(res), __FUNCTION__, *len);
 
     return res;
 }
@@ -2521,55 +1987,15 @@ ERTS_POLL_EXPORT(erts_poll_wait)(ErtsPollSet ps,
  */
 
 void
-ERTS_POLL_EXPORT(erts_poll_interrupt)(ErtsPollSet ps, int set)
-{
-#if defined(USE_THREADS) || ERTS_POLL_ASYNC_INTERRUPT_SUPPORT
-    if (!set)
-	reset_wakeup_state(ps);
-    else
-	wake_poller(ps, 1, 0);
-#endif
-}
-
-#if ERTS_POLL_ASYNC_INTERRUPT_SUPPORT
-void
-ERTS_POLL_EXPORT(erts_poll_async_sig_interrupt)(ErtsPollSet ps)
+ERTS_POLL_EXPORT(erts_poll_interrupt)(ErtsPollSet *ps, int set)
 {
-    /*
-     * NOTE: This function is called from signal handlers, it,
-     *       therefore, it has to be async-signal safe.
-     */
-    wake_poller(ps, 1, 1);
-}
-#endif
-
-/*
- * erts_poll_interrupt_timed():
- *   If 'set' != 0, interrupt thread blocked in erts_poll_wait() if it
- * is not guaranteed that it will timeout before 'msec' milli seconds.
- */
-void
-ERTS_POLL_EXPORT(erts_poll_interrupt_timed)(ErtsPollSet ps,
-					    int set,
-					    ErtsMonotonicTime timeout_time)
-{
-#if ERTS_POLL_ASYNC_INTERRUPT_SUPPORT || defined(ERTS_SMP)
-    if (!set)
-	reset_wakeup_state(ps);
-    else {
-	ErtsMonotonicTime max_wait_time = get_timeout_time(ps);
-	if (max_wait_time > timeout_time)
-	    wake_poller(ps, 1, 0);
-#ifdef ERTS_POLL_COUNT_AVOIDED_WAKEUPS
-	else {
-	    if (ERTS_POLLSET_IS_POLLED(ps))
-		erts_smp_atomic_inc_nob(&ps->no_avoided_wakeups);
-	    erts_smp_atomic_inc_nob(&ps->no_avoided_interrupts);
-	}
-	erts_smp_atomic_inc_nob(&ps->no_interrupt_timed);
-#endif
+    DEBUG_PRINT_WAIT("poll_interrupt(%d)", ps, set);
+    if (ERTS_POLL_USE_WAKEUP(ps)) {
+        if (!set)
+            reset_wakeup_state(ps);
+        else
+            wake_poller(ps, 1);
     }
-#endif
 }
 
 int
@@ -2582,13 +2008,19 @@ ERTS_POLL_EXPORT(erts_poll_max_fds)(void)
  */
 
 void
-ERTS_POLL_EXPORT(erts_poll_init)(void)
+ERTS_POLL_EXPORT(erts_poll_init)(int *concurrent_updates)
 {
-    erts_smp_spinlock_init(&pollsets_lock, "pollsets_lock");
-    pollsets = NULL;
 
     errno = 0;
 
+    if (concurrent_updates) {
+#if ERTS_POLL_USE_CONCURRENT_UPDATE
+        *concurrent_updates = 1;
+#else
+        *concurrent_updates = 0;
+#endif
+    }
+
 #if !defined(NO_SYSCONF)
     max_fds = sysconf(_SC_OPEN_MAX);
 #elif ERTS_POLL_USE_SELECT
@@ -2607,37 +2039,28 @@ ERTS_POLL_EXPORT(erts_poll_init)(void)
 	fatal_error("erts_poll_init(): Failed to get max number of files: %s\n",
 		    erl_errno_id(errno));
 
-#ifdef ERTS_POLL_DEBUG_PRINT
     print_misc_debug_info();
-#endif
 }
 
-ErtsPollSet
-ERTS_POLL_EXPORT(erts_poll_create_pollset)(void)
+ErtsPollSet *
+ERTS_POLL_EXPORT(erts_poll_create_pollset)(int id)
 {
 #if ERTS_POLL_USE_KERNEL_POLL
     int kp_fd;
 #endif
-    ErtsPollSet ps = erts_alloc(ERTS_ALC_T_POLLSET,
-				sizeof(struct ErtsPollSet_));
+    ErtsPollSet *ps = erts_alloc(ERTS_ALC_T_POLLSET,
+				sizeof(struct ERTS_POLL_EXPORT(erts_pollset)));
+    ps->id = id;
     ps->internal_fd_limit = 0;
-    ps->fds_status = NULL;
-    ps->fds_status_len = 0;
-    erts_smp_atomic_init_nob(&ps->no_of_user_fds, 0);
+    erts_atomic_init_nob(&ps->no_of_user_fds, 0);
 #if ERTS_POLL_USE_KERNEL_POLL
     ps->kp_fd = -1;
 #if ERTS_POLL_USE_EPOLL
     kp_fd = epoll_create(256);
-    ps->res_events_len = 0;
-    ps->res_events = NULL;
 #elif ERTS_POLL_USE_DEVPOLL
     kp_fd = open("/dev/poll", O_RDWR);
-    ps->res_events_len = 0;
-    ps->res_events = NULL;
 #elif ERTS_POLL_USE_KQUEUE
     kp_fd = kqueue();
-    ps->res_events_len = 0;
-    ps->res_events = NULL;
 #endif
     if (kp_fd < 0)
 	fatal_error("erts_poll_create_pollset(): Failed to "
@@ -2651,10 +2074,6 @@ ERTS_POLL_EXPORT(erts_poll_create_pollset)(void)
 		    ": %s (%d)\n",
 		    erl_errno_id(errno), errno);
 #endif /* ERTS_POLL_USE_KERNEL_POLL */
-#if ERTS_POLL_USE_BATCH_UPDATE_POLLSET
-    /* res_events is also used as write buffer */
-    grow_res_events(ps, ERTS_POLL_MIN_BATCH_BUF_SIZE);
-#endif
 #if ERTS_POLL_USE_POLL
     ps->next_poll_fds_ix = 0;
     ps->no_poll_fds = 0;
@@ -2663,9 +2082,6 @@ ERTS_POLL_EXPORT(erts_poll_create_pollset)(void)
 #elif ERTS_POLL_USE_SELECT
     ps->next_sel_fd = 0;
     ps->max_fd = -1;
-#if ERTS_POLL_USE_FALLBACK
-    ps->no_select_fds = 0;
-#endif
 #ifdef _DARWIN_UNLIMITED_SELECT
     ps->input_fds.sz = 0;
     ps->input_fds.ptr = NULL;
@@ -2682,133 +2098,76 @@ ERTS_POLL_EXPORT(erts_poll_create_pollset)(void)
     ERTS_FD_ZERO(&ps->res_output_fds);
 #endif
 #endif
-#if ERTS_POLL_USE_UPDATE_REQUESTS_QUEUE
+#if !ERTS_POLL_USE_CONCURRENT_UPDATE
+    ps->fds_status = NULL;
+    ps->fds_status_len = 0;
     ps->update_requests.next = NULL;
     ps->update_requests.len = 0;
     ps->curr_upd_req_block = &ps->update_requests;
-    erts_smp_atomic32_init_nob(&ps->have_update_requests, 0);
-#endif
-#ifdef ERTS_SMP
-    erts_atomic32_init_nob(&ps->polled, 0);
-    erts_smp_mtx_init(&ps->mtx, "pollset");
-#endif
-#if defined(USE_THREADS) || ERTS_POLL_ASYNC_INTERRUPT_SUPPORT
-    erts_atomic32_init_nob(&ps->wakeup_state, (erts_aint32_t) 0);
-#endif
-#if ERTS_POLL_USE_WAKEUP_PIPE
-    create_wakeup_pipe(ps);
-#endif
-#if ERTS_POLL_USE_TIMERFD
-    create_timerfd(ps);
-#endif
-#if ERTS_POLL_USE_FALLBACK
-    if (kp_fd >= ps->fds_status_len)
-	grow_fds_status(ps, kp_fd);
-    /* Force kernel poll fd into fallback (poll/select) set */
-    ps->fds_status[kp_fd].flags
-	|= ERTS_POLL_FD_FLG_INFLBCK|ERTS_POLL_FD_FLG_USEFLBCK;
-    {
-	int do_wake = 0;
-	ERTS_POLL_EXPORT(erts_poll_control)(ps, kp_fd, ERTS_POLL_EV_IN, 1,
-					    &do_wake);
-    }    
+    erts_atomic32_init_nob(&ps->have_update_requests, 0);
+    erts_mtx_init(&ps->mtx, "pollset", NIL, ERTS_LOCK_FLAGS_CATEGORY_IO);
 #endif
 #if ERTS_POLL_USE_KERNEL_POLL
     if (ps->internal_fd_limit <= kp_fd)
 	ps->internal_fd_limit = kp_fd + 1;
     ps->kp_fd = kp_fd;
+    if (ps->id == -1)
+        ps->oneshot = 0;
+    else
+        ps->oneshot = 1;
 #endif
-    init_timeout_time(ps);
-#ifdef ERTS_POLL_COUNT_AVOIDED_WAKEUPS
-    erts_smp_atomic_init_nob(&ps->no_avoided_wakeups, 0);
-    erts_smp_atomic_init_nob(&ps->no_avoided_interrupts, 0);
-    erts_smp_atomic_init_nob(&ps->no_interrupt_timed, 0);
-#endif
-#if ERTS_POLL_USE_UPDATE_REQUESTS_QUEUE
-    handle_update_requests(ps);
-#endif
-#if ERTS_POLL_USE_FALLBACK
-    ps->fallback_used = 0;
-#endif
-    erts_smp_atomic_set_nob(&ps->no_of_user_fds, 0); /* Don't count wakeup pipe and fallback fd */
-
-    erts_smp_spin_lock(&pollsets_lock);
-    ps->next = pollsets;
-    pollsets = ps;
-    erts_smp_spin_unlock(&pollsets_lock);
-
-    return ps;
-}
 
-void
-ERTS_POLL_EXPORT(erts_poll_destroy_pollset)(ErtsPollSet ps)
-{
-
-    if (ps->fds_status)
-	erts_free(ERTS_ALC_T_FD_STATUS, (void *) ps->fds_status);
+    erts_atomic32_init_nob(&ps->wakeup_state, (erts_aint32_t) 0);
+    create_wakeup_pipe(ps);
 
-#if ERTS_POLL_USE_EPOLL
-    if (ps->kp_fd >= 0)
-	close(ps->kp_fd);
-    if (ps->res_events)
-	erts_free(ERTS_ALC_T_POLL_RES_EVS, (void *) ps->res_events);
-#elif ERTS_POLL_USE_DEVPOLL
-    if (ps->kp_fd >= 0)
-	close(ps->kp_fd);
-    if (ps->res_events)
-	erts_free(ERTS_ALC_T_POLL_RES_EVS, (void *) ps->res_events);
-#elif ERTS_POLL_USE_POLL
-    if (ps->poll_fds)
-	erts_free(ERTS_ALC_T_POLL_FDS, (void *) ps->poll_fds);
-#elif ERTS_POLL_USE_SELECT
-#ifdef _DARWIN_UNLIMITED_SELECT
-    if (ps->input_fds.ptr)
-	erts_free(ERTS_ALC_T_SELECT_FDS, (void *) ps->input_fds.ptr);
-    if (ps->res_input_fds.ptr)
-	erts_free(ERTS_ALC_T_SELECT_FDS, (void *) ps->res_input_fds.ptr);
-    if (ps->output_fds.ptr)
-	erts_free(ERTS_ALC_T_SELECT_FDS, (void *) ps->output_fds.ptr);
-    if (ps->res_output_fds.ptr)
-	erts_free(ERTS_ALC_T_SELECT_FDS, (void *) ps->res_output_fds.ptr);
-#endif
-#endif
-#if ERTS_POLL_USE_UPDATE_REQUESTS_QUEUE
-    {
-	ErtsPollSetUpdateRequestsBlock *urqbp = ps->update_requests.next;
-	while (urqbp) {
-	    ErtsPollSetUpdateRequestsBlock *free_urqbp = urqbp;
-	    urqbp = urqbp->next;
-	    free_update_requests_block(ps, free_urqbp);
-	}
-    }
-#endif
-#ifdef ERTS_SMP
-    erts_smp_mtx_destroy(&ps->mtx);
-#endif
-#if ERTS_POLL_USE_WAKEUP_PIPE
-    if (ps->wake_fds[0] >= 0)
-	close(ps->wake_fds[0]);
-    if (ps->wake_fds[1] >= 0)
-	close(ps->wake_fds[1]);
-#endif
 #if ERTS_POLL_USE_TIMERFD
-    if (ps->timer_fd >= 0)
-        close(ps->timer_fd);
+    create_timerfd(ps);
 #endif
 
-    erts_smp_spin_lock(&pollsets_lock);
-    if (ps == pollsets)
-	pollsets = pollsets->next;
-    else {
-	ErtsPollSet prev_ps;
-	for (prev_ps = pollsets; ps != prev_ps->next; prev_ps = prev_ps->next)
-            ;
-	ASSERT(ps == prev_ps->next);
-	prev_ps->next = ps->next;
-    }
-    erts_smp_spin_unlock(&pollsets_lock);
+#if !ERTS_POLL_USE_CONCURRENT_UPDATE
+    handle_update_requests(ps, NULL, 0);
+    cleanup_wakeup_pipe(ps);
+#endif
+#if ERTS_POLL_USE_KERNEL_POLL && (defined(__DARWIN__) || defined(__APPLE__) && defined(__MACH__))
+    {
+        /*
+         * Using kqueue on OS X is a mess of brokenness...
+         *
+         * On OS X version older than 15.6 (i.e. OS X El Capitan released in July 2015),
+         * a thread waiting in kevent is not woken if an event is inserted into the kqueue
+         * by another thread and the event becomes ready. However if a new call to kevent
+         * is done by the waiting thread, the new event is found.
+         *
+         * So on effected OS X versions we could trigger the wakeup pipe so that
+         * the waiters will be woken and re-issue the kevent. However...
+         *
+         * On OS X version older then 16 (i.e. OS X Sierra released in September 2016),
+         * running the emulator driver_SUITE smp_select testcase consistently causes a
+         * kernel panic. I don't know why or what events that trigger it. But it seems
+         * like updates of the pollset while another thread is sleeping in it Creates
+         * some kind of race that triggers the kernel panic.
+         *
+         * So to deal with this, the erts configure check what OS X version is run
+         * and only enabled kernel poll on OS X 16 or newer. In addition, if someone
+         * attempts to compile Erlang on OS X 16 and then run it on OS X 15, we do the
+         * run-time check below to disallow this.
+         */
+        int major, minor, build;
+        os_version(&major,&minor,&build);
+        if (major < 16) {
+            erts_fprintf(stderr,"BROKEN KQUEUE!\n"
+                         "Erlang has been compiled with kernel-poll support,\n"
+                         "but this OS X version is known to have kernel bugs\n"
+                         "when using kernel-poll. You have two options:\n"
+                         " 1) update to a newer OS X version (OS X Sierra or newer)\n"
+                         " 2) recompile erlang without kernel-poll support\n");
+            erts_exit(1, "");
+        }
+    }
+#endif
+    erts_atomic_set_nob(&ps->no_of_user_fds, 0); /* Don't count wakeup pipe and fallback fd */
 
-    erts_free(ERTS_ALC_T_POLLSET, (void *) ps);
+    return ps;
 }
 
 /*
@@ -2816,24 +2175,18 @@ ERTS_POLL_EXPORT(erts_poll_destroy_pollset)(ErtsPollSet ps)
  */
 
 void
-ERTS_POLL_EXPORT(erts_poll_info)(ErtsPollSet ps, ErtsPollInfo *pip)
+ERTS_POLL_EXPORT(erts_poll_info)(ErtsPollSet *ps, ErtsPollInfo *pip)
 {
-#if ERTS_POLL_USE_UPDATE_REQUESTS_QUEUE
+#if !ERTS_POLL_USE_CONCURRENT_UPDATE
     int pending_updates;
 #endif
     Uint size = 0;
 
     ERTS_POLLSET_LOCK(ps);
 
-    size += sizeof(struct ErtsPollSet_);
+    size += sizeof(struct ERTS_POLL_EXPORT(erts_pollset));
+#if !ERTS_POLL_USE_CONCURRENT_UPDATE
     size += ps->fds_status_len*sizeof(ErtsFdStatus);
-
-#if ERTS_POLL_USE_EPOLL
-    size += ps->res_events_len*sizeof(struct epoll_event);
-#elif ERTS_POLL_USE_DEVPOLL
-    size += ps->res_events_len*sizeof(struct pollfd);
-#elif ERTS_POLL_USE_KQUEUE
-    size += ps->res_events_len*sizeof(struct kevent);
 #endif
 
 #if ERTS_POLL_USE_POLL
@@ -2845,7 +2198,7 @@ ERTS_POLL_EXPORT(erts_poll_info)(ErtsPollSet ps, ErtsPollInfo *pip)
 #endif
 #endif
 
-#if ERTS_POLL_USE_UPDATE_REQUESTS_QUEUE
+#if !ERTS_POLL_USE_CONCURRENT_UPDATE
     {
 	ErtsPollSetUpdateRequestsBlock *urqbp = ps->update_requests.next;
 	pending_updates = ps->update_requests.len;
@@ -2857,7 +2210,7 @@ ERTS_POLL_EXPORT(erts_poll_info)(ErtsPollSet ps, ErtsPollInfo *pip)
     }
 #endif
 
-    pip->primary = 
+    pip->primary =
 #if ERTS_POLL_USE_KQUEUE
 	"kqueue"
 #elif ERTS_POLL_USE_EPOLL
@@ -2871,17 +2224,7 @@ ERTS_POLL_EXPORT(erts_poll_info)(ErtsPollSet ps, ErtsPollInfo *pip)
 #endif
 	;
 
-    pip->fallback = 
-#if !ERTS_POLL_USE_FALLBACK
-	NULL
-#elif ERTS_POLL_USE_POLL
-	"poll"
-#elif ERTS_POLL_USE_SELECT
-	"select"
-#endif
-	;
-
-    pip->kernel_poll = 
+    pip->kernel_poll =
 #if !ERTS_POLL_USE_KERNEL_POLL
 	NULL
 #elif ERTS_POLL_USE_KQUEUE
@@ -2895,34 +2238,11 @@ ERTS_POLL_EXPORT(erts_poll_info)(ErtsPollSet ps, ErtsPollInfo *pip)
 
     pip->memory_size = size;
 
-    pip->poll_set_size = (int) erts_smp_atomic_read_nob(&ps->no_of_user_fds);
-#if ERTS_POLL_USE_WAKEUP_PIPE
+    pip->poll_set_size = (int) erts_atomic_read_nob(&ps->no_of_user_fds);
     pip->poll_set_size++; /* Wakeup pipe */
-#endif
-#if ERTS_POLL_USE_TIMERFD
-    pip->poll_set_size++; /* timerfd */
-#endif
-
-    pip->fallback_poll_set_size =
-#if !ERTS_POLL_USE_FALLBACK
-	0
-#elif ERTS_POLL_USE_POLL
-	ps->no_poll_fds
-#elif ERTS_POLL_USE_SELECT
-	ps->no_select_fds
-#endif
-	;
-
-#if ERTS_POLL_USE_FALLBACK
-    /* If only kp_fd is in fallback poll set we don't use fallback... */
-    if (pip->fallback_poll_set_size == 1)
-	pip->fallback_poll_set_size = 0;
-    else
-	pip->poll_set_size++; /* kp_fd */
-#endif
 
     pip->lazy_updates =
-#if ERTS_POLL_USE_UPDATE_REQUESTS_QUEUE
+#if !ERTS_POLL_USE_CONCURRENT_UPDATE
 	1
 #else
 	0
@@ -2930,21 +2250,13 @@ ERTS_POLL_EXPORT(erts_poll_info)(ErtsPollSet ps, ErtsPollInfo *pip)
 	;
 
     pip->pending_updates = 
-#if ERTS_POLL_USE_UPDATE_REQUESTS_QUEUE
+#if !ERTS_POLL_USE_CONCURRENT_UPDATE
 	pending_updates
 #else
 	0
 #endif
 	;
 
-    pip->batch_updates = 
-#if ERTS_POLL_USE_BATCH_UPDATE_POLLSET
-	1
-#else
-	0
-#endif
-	;
-
     pip->concurrent_updates =
 #if ERTS_POLL_USE_CONCURRENT_UPDATE
 	1
@@ -2953,13 +2265,23 @@ ERTS_POLL_EXPORT(erts_poll_info)(ErtsPollSet ps, ErtsPollInfo *pip)
 #endif
 	;
 
-    pip->max_fds = max_fds;
+    pip->is_fallback =
+#if ERTS_POLL_IS_FALLBACK
+        1
+#else
+        0
+#endif
+        ;
 
-#ifdef ERTS_POLL_COUNT_AVOIDED_WAKEUPS
-    pip->no_avoided_wakeups = erts_smp_atomic_read_nob(&ps->no_avoided_wakeups);
-    pip->no_avoided_interrupts = erts_smp_atomic_read_nob(&ps->no_avoided_interrupts);
-    pip->no_interrupt_timed = erts_smp_atomic_read_nob(&ps->no_interrupt_timed);
+    pip->batch_updates =
+#if ERTS_POLL_USE_DEVPOLL
+        1
+#else
+        0
 #endif
+        ;
+
+    pip->max_fds = max_fds;
 
     ERTS_POLLSET_UNLOCK(ps);
 
@@ -2995,35 +2317,61 @@ fatal_error(char *format, ...)
     abort();
 }
 
-static void
-fatal_error_async_signal_safe(char *error_str)
+/*
+ * --- Debug -----------------------------------------------------------------
+ */
+
+#if ERTS_POLL_USE_EPOLL
+uint32_t epoll_events(int kp_fd, int fd)
 {
-    if (ERTS_SOMEONE_IS_CRASH_DUMPING || ERTS_GOT_SIGUSR1) {
-	/* See comment above in fatal_error() */
-	return;
+    /* For epoll we read the information about what is selected upon from the proc fs.*/
+    char fname[30];
+    FILE *f;
+    unsigned int pos, flags, mnt_id;
+    int line = 0;
+    sprintf(fname,"/proc/%d/fdinfo/%d",getpid(), kp_fd);
+    f = fopen(fname,"r");
+    if (!f) {
+        fprintf(stderr,"failed to open file %s, errno = %d\n", fname, errno);
+        ASSERT(0);
+        return 0;
     }
-    if (error_str) {
-	int len = 0;
-	while (error_str[len])
-	    len++;
-	if (len) {
-	    /* async signal safe */
-	    erts_silence_warn_unused_result(write(2, error_str, len));
-	}
+    if (fscanf(f,"pos:\t%x\nflags:\t%x", &pos, &flags) != 2) {
+        fprintf(stderr,"failed to parse file %s, errno = %d\n", fname, errno);
+        ASSERT(0);
+        return 0;
     }
-    abort();
+    if (fscanf(f,"\nmnt_id:\t%x\n", &mnt_id));
+    line += 3;
+    while (!feof(f)) {
+        /* tfd:       10 events: 40000019 data:       180000000a */
+        int ev_fd;
+        uint32_t events;
+        uint64_t data;
+        if (fscanf(f,"tfd:%d events:%x data:%llx\n", &ev_fd, &events,
+                   (unsigned long long*)&data) != 3) {
+            fprintf(stderr,"failed to parse file %s on line %d, errno = %d\n", fname,
+                    line,
+                    errno);
+            return 0;
+        }
+        if (fd == ev_fd) {
+            fclose(f);
+            return events;
+        }
+    }
+    fclose(f);
+    return 0;
 }
- 
-/*
- * --- Debug -----------------------------------------------------------------
- */
+#endif
 
 void
-ERTS_POLL_EXPORT(erts_poll_get_selected_events)(ErtsPollSet ps,
+ERTS_POLL_EXPORT(erts_poll_get_selected_events)(ErtsPollSet *ps,
 						ErtsPollEvents ev[],
 						int len)
 {
     int fd;
+#if !ERTS_POLL_USE_CONCURRENT_UPDATE
     ERTS_POLLSET_LOCK(ps);
     for (fd = 0; fd < len; fd++) {
 	if (fd >= ps->fds_status_len)
@@ -3031,12 +2379,7 @@ ERTS_POLL_EXPORT(erts_poll_get_selected_events)(ErtsPollSet ps,
 	else {
 	    ev[fd] = ps->fds_status[fd].events;
             if (
-#if ERTS_POLL_USE_WAKEUP_PIPE
                 fd == ps->wake_fds[0] || fd == ps->wake_fds[1] ||
-#endif
-#if ERTS_POLL_USE_TIMERFD
-                fd == ps->timer_fd ||
-#endif
 #if ERTS_POLL_USE_KERNEL_POLL
                 fd == ps->kp_fd ||
 #endif
@@ -3045,7 +2388,57 @@ ERTS_POLL_EXPORT(erts_poll_get_selected_events)(ErtsPollSet ps,
 	}
     }
     ERTS_POLLSET_UNLOCK(ps);
+#elif ERTS_POLL_USE_EPOLL
 
+    /* For epoll we read the information about what is selected upon from the proc fs.*/
+    char fname[30];
+    FILE *f;
+    unsigned int pos, flags, mnt_id;
+    int line = 0;
+    sprintf(fname,"/proc/%d/fdinfo/%d",getpid(), ps->kp_fd);
+    for (fd = 0; fd < len; fd++)
+        ev[fd] = ERTS_POLL_EV_NONE;
+    f = fopen(fname,"r");
+    if (!f) {
+        fprintf(stderr,"failed to open file %s, errno = %d\n", fname, errno);
+        return;
+    }
+    if (fscanf(f,"pos:\t%x\nflags:\t%x", &pos, &flags) != 2) {
+        fprintf(stderr,"failed to parse file %s, errno = %d\n", fname, errno);
+        ASSERT(0);
+        return;
+    }
+    if (fscanf(f,"\nmnt_id:\t%x\n", &mnt_id));
+    line += 3;
+    while (!feof(f)) {
+        /* tfd:       10 events: 40000019 data:       180000000a */
+        int fd;
+        uint32_t events;
+        uint64_t data;
+        if (fscanf(f,"tfd:%d events:%x data:%llx\n", &fd, &events,
+                   (unsigned long long*)&data) != 3) {
+            fprintf(stderr,"failed to parse file %s on line %d, errno = %d\n",
+                    fname, line, errno);
+            ASSERT(0);
+            return;
+        }
+        if (fd == ps->wake_fds[0] || fd == ps->wake_fds[1])
+            continue;
+#if ERTS_POLL_USE_TIMERFD
+        if (fd == ps->timer_fd)
+            continue;
+#endif
+        data &= 0xFFFFFFFF;
+        ASSERT(fd == data);
+        /* Events are the events that are being monitored, which of course include
+           error and hup events, but we are only interested in IN/OUT events */
+        ev[fd] = (ERTS_POLL_EV_IN|ERTS_POLL_EV_OUT) & ERTS_POLL_EV_N2E(events);
+        line++;
+    }
+#else
+    for (fd = 0; fd < len; fd++)
+        ev[fd] = ERTS_POLL_EV_NONE;
+#endif
 }
 
 #ifdef HARD_DEBUG
@@ -3065,10 +2458,10 @@ check_poll_result(ErtsPollResFd pr[], int len)
 }
 
 
-#if ERTS_POLL_USE_DEVPOLL
+#if ERTS_POLL_USE_DEVPOLL && defined(DEBUG)
 
 static void
-check_poll_status(ErtsPollSet ps)
+check_poll_status(ErtsPollSet *ps)
 {
     int i;
     for (i = 0; i < ps->fds_status_len; i++) {
@@ -3100,34 +2493,24 @@ check_poll_status(ErtsPollSet ps)
 #endif /* ERTS_POLL_USE_DEVPOLL */
 #endif /* HARD_DEBUG */
 
-#ifdef ERTS_POLL_DEBUG_PRINT
 static void
 print_misc_debug_info(void)
 {
-    erts_printf("erts_poll using: %s lazy_updates:%s batch_updates:%s\n",
+#if ERTS_POLL_DEBUG_PRINT
+    erts_printf("erts_poll using: %s lazy_updates:%s\n",
 #if ERTS_POLL_USE_KQUEUE
 		"kqueue"
 #elif ERTS_POLL_USE_EPOLL
 		"epoll"
 #elif ERTS_POLL_USE_DEVPOLL
 		"/dev/poll"
-#endif
-#if ERTS_POLL_USE_FALLBACK
-		"-"
-#endif
-#if ERTS_POLL_USE_POLL
+#elif ERTS_POLL_USE_POLL
 		"poll"
 #elif ERTS_POLL_USE_SELECT
 		"select"
 #endif
 		,
-#if ERTS_POLL_USE_UPDATE_REQUESTS_QUEUE
-		"true"
-#else
-		"false"
-#endif
-		,
-#if ERTS_POLL_USE_BATCH_UPDATE_POLLSET
+#if !ERTS_POLL_USE_CONCURRENT_UPDATE
 		"true"
 #else
 		"false"
@@ -3146,6 +2529,20 @@ print_misc_debug_info(void)
 #ifdef FD_SETSIZE
     erts_printf("FD_SETSIZE=%d\n", FD_SETSIZE);
 #endif
+#endif
+}
+
+#ifdef ERTS_ENABLE_LOCK_COUNT
+void ERTS_POLL_EXPORT(erts_lcnt_enable_pollset_lock_count)(ErtsPollSet *pollset, int enable)
+{
+#if !ERTS_POLL_USE_CONCURRENT_UPDATE
+    if(enable) {
+        erts_lcnt_install_new_lock_info(&pollset->mtx.lcnt, "pollset_rm", NIL,
+            ERTS_LOCK_TYPE_MUTEX | ERTS_LOCK_FLAGS_CATEGORY_IO);
+    } else {
+        erts_lcnt_uninstall(&pollset->mtx.lcnt);
+    }
+#endif
+    return;
 }
-    
 #endif
diff --git a/erts/emulator/sys/common/erl_poll.h b/erts/emulator/sys/common/erl_poll.h
index c16122610d..d40dabc529 100644
--- a/erts/emulator/sys/common/erl_poll.h
+++ b/erts/emulator/sys/common/erl_poll.h
@@ -1,7 +1,7 @@
 /*
  * %CopyrightBegin%
  * 
- * Copyright Ericsson AB 2006-2016. All Rights Reserved.
+ * Copyright Ericsson AB 2006-2018. All Rights Reserved.
  * 
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -18,11 +18,31 @@
  * %CopyrightEnd%
  */
 
-/*
- * Description:	Poll interface suitable for ERTS with or without
- *              SMP support.
+/**
+ * @description: Poll interface suitable for ERTS with SMP support.
+ *
+ * @author: 	Rickard Green
+ * @author: 	Lukas Larsson
+ *
+ * This header file exports macros and functions that are used to
+ * react to I/O polling events from file descriptors or wait-able
+ * objects. The API exported is the following:
  *
- * Author: 	Rickard Green
+ * defines:
+ *   ERTS_POLL_EV_NONE - No events have been set. This is not the same as 0.
+ *   ERTS_POLL_EV_IN   - Represent an IN event
+ *   ERTS_POLL_EV_OUT  - Represent an OUT event
+ *   ERTS_POLL_EV_ERR  - Represent an error event
+ *   ERTS_POLL_EV_NVAL - Represent an invalid event
+ *
+ * macro functions:
+ *   ErtsSysFdType ERTS_POLL_RES_GET_FD(ErtsPollResFd *evt);
+ *   void ERTS_POLL_RES_SET_FD(ErtsPollResFd *evt, ErtsSysFdType fd);
+ *   ErtsPollEvents ERTS_POLL_RES_GET_EVTS(ErtsPollResFd *evt)
+ *   void ERTS_POLL_RES_SET_EVTS(ErtsPollResFd *evt, ErtsPollEvents fd);
+ *
+ * functions:
+ *   See erl_poll_api.h
  */
 
 #ifndef ERL_POLL_H__
@@ -31,34 +51,29 @@
 #include "sys.h"
 
 #define ERTS_POLL_NO_TIMEOUT ERTS_MONOTONIC_TIME_MIN
-
-#if 0
-#define ERTS_POLL_COUNT_AVOIDED_WAKEUPS
-#endif
+#define ERTS_POLL_INF_TIMEOUT ERTS_MONOTONIC_TIME_MAX
 
 #ifdef ERTS_ENABLE_KERNEL_POLL
-#  if defined(ERTS_KERNEL_POLL_VERSION)
-#    define ERTS_POLL_EXPORT(FUNC) FUNC ## _kp
+#  undef ERTS_ENABLE_KERNEL_POLL
+#  define ERTS_ENABLE_KERNEL_POLL 1
+#  if defined(ERTS_NO_KERNEL_POLL_VERSION)
+#    define ERTS_POLL_EXPORT(FUNC) FUNC ## _flbk
+#    undef ERTS_NO_KERNEL_POLL_VERSION
+#    define ERTS_NO_KERNEL_POLL_VERSION 1
+#    define ERTS_KERNEL_POLL_VERSION 0
 #  else
-#    define ERTS_POLL_EXPORT(FUNC) FUNC ## _nkp
-#    undef ERTS_POLL_DISABLE_KERNEL_POLL
-#    define ERTS_POLL_DISABLE_KERNEL_POLL
+#    undef ERTS_KERNEL_POLL_VERSION
+#    define ERTS_KERNEL_POLL_VERSION 1
+#    define ERTS_NO_KERNEL_POLL_VERSION 0
+#    define ERTS_POLL_EXPORT(FUNC) FUNC
 #  endif
 #else
 #    define ERTS_POLL_EXPORT(FUNC) FUNC
-#    undef ERTS_POLL_DISABLE_KERNEL_POLL
-#    define ERTS_POLL_DISABLE_KERNEL_POLL
+#    define ERTS_ENABLE_KERNEL_POLL 0
+#    define ERTS_NO_KERNEL_POLL_VERSION 1
+#    define ERTS_KERNEL_POLL_VERSION 0
 #endif
 
-#ifdef ERTS_POLL_DISABLE_KERNEL_POLL
-#  undef HAVE_SYS_EPOLL_H
-#  undef HAVE_SYS_EVENT_H
-#  undef HAVE_SYS_DEVPOLL_H
-#endif
-
-#undef ERTS_POLL_USE_KERNEL_POLL
-#define ERTS_POLL_USE_KERNEL_POLL 0
-
 #undef ERTS_POLL_USE_KQUEUE
 #define ERTS_POLL_USE_KQUEUE 0
 #undef ERTS_POLL_USE_EPOLL
@@ -70,68 +85,107 @@
 #undef ERTS_POLL_USE_SELECT
 #define ERTS_POLL_USE_SELECT 0
 
-#if defined(HAVE_SYS_EVENT_H)
-#  undef ERTS_POLL_USE_KQUEUE
-#  define ERTS_POLL_USE_KQUEUE 1
-#  undef ERTS_POLL_USE_KERNEL_POLL
-#  define ERTS_POLL_USE_KERNEL_POLL 1
-#elif defined(HAVE_SYS_EPOLL_H)
-#  undef ERTS_POLL_USE_EPOLL
-#  define ERTS_POLL_USE_EPOLL 1
-#  undef ERTS_POLL_USE_KERNEL_POLL
-#  define ERTS_POLL_USE_KERNEL_POLL 1
-#elif defined(HAVE_SYS_DEVPOLL_H)
-#  undef ERTS_POLL_USE_DEVPOLL
-#  define ERTS_POLL_USE_DEVPOLL 1
-#  undef ERTS_POLL_USE_KERNEL_POLL
-#  define ERTS_POLL_USE_KERNEL_POLL 1
+/* Defines which structure that erts_poll_wait should use to wait with
+   and how events should be represented */
+#define ERTS_POLL_USE_EPOLL_EVS 0
+#define ERTS_POLL_USE_KQUEUE_EVS 0
+#define ERTS_POLL_USE_DEVPOLL_EVS 0
+#define ERTS_POLL_USE_POLL_EVS 0
+#define ERTS_POLL_USE_SELECT_EVS 0
+
+#define ERTS_POLL_USE_KERNEL_POLL ERTS_KERNEL_POLL_VERSION
+
+#if ERTS_ENABLE_KERNEL_POLL
+#  if defined(HAVE_SYS_EVENT_H)
+#    undef ERTS_POLL_USE_KQUEUE_EVS
+#    define ERTS_POLL_USE_KQUEUE_EVS 1
+#    undef ERTS_POLL_USE_KQUEUE
+#    define ERTS_POLL_USE_KQUEUE ERTS_KERNEL_POLL_VERSION
+#  elif defined(HAVE_SYS_EPOLL_H)
+#    undef ERTS_POLL_USE_EPOLL_EVS
+#    define ERTS_POLL_USE_EPOLL_EVS 1
+#    undef ERTS_POLL_USE_EPOLL
+#    define ERTS_POLL_USE_EPOLL ERTS_KERNEL_POLL_VERSION
+#  elif defined(HAVE_SYS_DEVPOLL_H)
+#    undef ERTS_POLL_USE_DEVPOLL_EVS
+#    define ERTS_POLL_USE_DEVPOLL_EVS 1
+#    undef ERTS_POLL_USE_DEVPOLL
+#    define ERTS_POLL_USE_DEVPOLL ERTS_KERNEL_POLL_VERSION
+#  else
+#    error "Missing kernel poll implementation of erts_poll()"
+#  endif
 #endif
 
-#define ERTS_POLL_USE_FALLBACK (ERTS_POLL_USE_KQUEUE || ERTS_POLL_USE_EPOLL)
-
-#if !ERTS_POLL_USE_KERNEL_POLL || ERTS_POLL_USE_FALLBACK
+#if ERTS_NO_KERNEL_POLL_VERSION
 #  if defined(ERTS_USE_POLL)
+#    undef ERTS_POLL_USE_POLL_EVS
+#    define ERTS_POLL_USE_POLL_EVS 1
 #    undef ERTS_POLL_USE_POLL
 #    define ERTS_POLL_USE_POLL 1
 #  elif !defined(__WIN32__)
+#    undef ERTS_POLL_USE_SELECT_EVS
+#    define ERTS_POLL_USE_SELECT_EVS 1
 #    undef ERTS_POLL_USE_SELECT
 #    define ERTS_POLL_USE_SELECT 1
 #  endif
 #endif
 
+#define ERTS_POLL_USE_FALLBACK (ERTS_POLL_USE_KQUEUE || ERTS_POLL_USE_EPOLL)
+#define ERTS_POLL_USE_SCHEDULER_POLLING (ERTS_POLL_USE_KQUEUE || ERTS_POLL_USE_EPOLL)
+#define ERTS_POLL_SCHEDULER_POLLING_TIMEOUT 10
 #define ERTS_POLL_USE_TIMERFD 0
 
 typedef Uint32 ErtsPollEvents;
-#undef ERTS_POLL_EV_E2N
+
+typedef enum {
+    ERTS_POLL_OP_ADD = 0,          /* Add the FD to the pollset */
+    ERTS_POLL_OP_MOD = 1,          /* Modify the FD in the pollset */
+    ERTS_POLL_OP_DEL = 2           /* Delete the FD from the pollset */
+} ErtsPollOp;
+
+#define op2str(op) (op == ERTS_POLL_OP_ADD ? "add" :            \
+                    (op == ERTS_POLL_OP_MOD ? "mod" : "del"))
 
 #if defined(__WIN32__)	/* --- win32  --------------------------------------- */
 
-#define ERTS_POLL_EV_IN   1
-#define ERTS_POLL_EV_OUT  2
-#define ERTS_POLL_EV_ERR  4
-#define ERTS_POLL_EV_NVAL 8
+#define ERTS_POLL_EV_IN    1
+#define ERTS_POLL_EV_OUT   2
+#define ERTS_POLL_EV_ERR   4
+#define ERTS_POLL_EV_NVAL  8
+
+#define ERTS_POLL_EV_E2N(EV) 		(EV)
+#define ERTS_POLL_EV_N2E(EV) 		(EV)
 
-#elif ERTS_POLL_USE_EPOLL	/* --- epoll ------------------------------- */
+#elif ERTS_POLL_USE_EPOLL_EVS	/* --- epoll ------------------------------- */
 
 #include <sys/epoll.h>
 
+#if ERTS_POLL_USE_EPOLL
 #ifdef HAVE_SYS_TIMERFD_H
 #include <sys/timerfd.h>
 #undef ERTS_POLL_USE_TIMERFD
 #define ERTS_POLL_USE_TIMERFD 1
 #endif
+#endif
 
 #define ERTS_POLL_EV_E2N(EV) \
   ((uint32_t) (EV))
 #define ERTS_POLL_EV_N2E(EV) \
-  ((ErtsPollEvents) (EV))
+  ((ErtsPollEvents) (EV) & ~EPOLLONESHOT)
 
 #define ERTS_POLL_EV_IN			ERTS_POLL_EV_N2E(EPOLLIN)
 #define ERTS_POLL_EV_OUT		ERTS_POLL_EV_N2E(EPOLLOUT)
 #define ERTS_POLL_EV_NVAL		ERTS_POLL_EV_N2E(EPOLLET)
 #define ERTS_POLL_EV_ERR		ERTS_POLL_EV_N2E(EPOLLERR|EPOLLHUP)
 
-#elif ERTS_POLL_USE_DEVPOLL	/* --- devpoll ----------------------------- */
+typedef struct epoll_event ErtsPollResFd;
+
+#define ERTS_POLL_RES_GET_FD(evt) ((ErtsSysFdType)((evt)->data.fd))
+#define ERTS_POLL_RES_SET_FD(evt, ident) (evt)->data.fd = ident
+#define ERTS_POLL_RES_GET_EVTS(evt) ERTS_POLL_EV_N2E((evt)->events)
+#define ERTS_POLL_RES_SET_EVTS(evt, evts) (evt)->events = ERTS_POLL_EV_E2N(evts)
+
+#elif ERTS_POLL_USE_DEVPOLL_EVS	/* --- devpoll ----------------------------- */
 
 #include <sys/devpoll.h>
 
@@ -145,12 +199,37 @@ typedef Uint32 ErtsPollEvents;
 #define ERTS_POLL_EV_NVAL		ERTS_POLL_EV_N2E(POLLNVAL)
 #define ERTS_POLL_EV_ERR		ERTS_POLL_EV_N2E(POLLERR|POLLHUP)
 
-#elif ERTS_POLL_USE_KQUEUE	/* --- kqueue ------------------------------ */
+typedef struct pollfd ErtsPollResFd;
+
+#define ERTS_POLL_RES_GET_FD(evt) ((ErtsSysFdType)((evt)->fd))
+#define ERTS_POLL_RES_SET_FD(evt, ident) (evt)->fd = ident
+#define ERTS_POLL_RES_GET_EVTS(evt) ERTS_POLL_EV_N2E((evt)->revents)
+#define ERTS_POLL_RES_SET_EVTS(evt, evts) (evt)->revents = ERTS_POLL_EV_E2N(evts)
+
+#elif ERTS_POLL_USE_KQUEUE_EVS	/* --- kqueue ------------------------------ */
 /* Kqueue use fallback defines (poll() or select()) */
+
+#include <sys/event.h>
+
+#ifdef ERTS_USE_POLL
+#  undef ERTS_POLL_USE_POLL_EVS
+#  define ERTS_POLL_USE_POLL_EVS   1
+#elif !defined(__WIN32__)
+#  undef ERTS_POLL_USE_SELECT_EVS
+#  define ERTS_POLL_USE_SELECT_EVS 1
 #endif
 
-#if ERTS_POLL_USE_POLL	/* --- poll -------------------------------- */
+typedef struct kevent ErtsPollResFd;
+
+#define ERTS_POLL_RES_GET_FD(evt) ((ErtsSysFdType)((evt)->ident))
+#define ERTS_POLL_RES_SET_FD(evt, fd) (evt)->ident = fd
+#define ERTS_POLL_RES_GET_EVTS(evt) ERTS_POLL_EV_N2E((ErtsPollEvents)(evt)->udata)
+#define ERTS_POLL_RES_SET_EVTS(evt, evts) (evt)->udata = (void*)(UWord)(ERTS_POLL_EV_E2N(evts))
 
+#endif
+
+#if ERTS_POLL_USE_POLL_EVS
+				/* --- poll -------------------------------- */
 #include <poll.h>
 
 #define ERTS_POLL_EV_NKP_E2N(EV) \
@@ -169,7 +248,7 @@ typedef Uint32 ErtsPollEvents;
 #define ERTS_POLL_EV_NKP_NVAL		ERTS_POLL_EV_N2E(POLLNVAL)
 #define ERTS_POLL_EV_NKP_ERR		ERTS_POLL_EV_N2E(POLLERR|POLLHUP)
 
-#elif ERTS_POLL_USE_SELECT	/* --- select ------------------------------ */
+#elif ERTS_POLL_USE_SELECT_EVS	/* --- select ------------------------------ */
 
 #define ERTS_POLL_EV_NKP_E2N(EV) (EV)
 #define ERTS_POLL_EV_NKP_N2E(EV) (EV)
@@ -195,69 +274,65 @@ typedef Uint32 ErtsPollEvents;
 
 #endif
 
-typedef struct ErtsPollSet_ *ErtsPollSet;
-
-typedef struct {
-    ErtsSysFdType fd;
-    ErtsPollEvents events;
-    int on;
-} ErtsPollControlEntry;
+#if !ERTS_ENABLE_KERNEL_POLL
 
-typedef struct {
+typedef struct _ErtsPollResFd {
     ErtsSysFdType fd;
     ErtsPollEvents events;
 } ErtsPollResFd;
 
+#define ERTS_POLL_RES_GET_FD(evt) (evt)->fd
+#define ERTS_POLL_RES_SET_FD(evt, ident) (evt)->fd = (ident)
+#define ERTS_POLL_RES_GET_EVTS(evt) ERTS_POLL_EV_N2E((evt)->events)
+#define ERTS_POLL_RES_SET_EVTS(evt, evts) (evt)->events = ERTS_POLL_EV_E2N(evts)
+
+#endif
+
+#define ERTS_POLL_EV_NONE ERTS_POLL_EV_N2E((UINT_MAX & ~(ERTS_POLL_EV_IN|ERTS_POLL_EV_OUT|ERTS_POLL_EV_NVAL|ERTS_POLL_EV_ERR)))
+
+#define ev2str(ev)                                                     \
+    (((ev) == 0 || (ev) == ERTS_POLL_EV_NONE) ? "NONE" :               \
+     ((ev) == ERTS_POLL_EV_IN ? "IN" :                                 \
+      ((ev) == ERTS_POLL_EV_OUT ? "OUT" :                              \
+       ((ev) == (ERTS_POLL_EV_IN|ERTS_POLL_EV_OUT) ? "IN|OUT" :        \
+        ((ev) & ERTS_POLL_EV_ERR ? "ERR" :                             \
+         ((ev) & ERTS_POLL_EV_NVAL ? "NVAL" : "OTHER"))))))
+
+
+typedef struct ERTS_POLL_EXPORT(erts_pollset) ErtsPollSet;
+
 typedef struct {
     char *primary;
-    char *fallback;
     char *kernel_poll;
     Uint memory_size;
-    int poll_set_size;
-    int fallback_poll_set_size;
+    Uint poll_set_size;
     int lazy_updates;
-    int pending_updates;
+    Uint pending_updates;
     int batch_updates;
     int concurrent_updates;
-    int max_fds;
-#ifdef ERTS_POLL_COUNT_AVOIDED_WAKEUPS
-    long no_avoided_wakeups;
-    long no_avoided_interrupts;
-    long no_interrupt_timed;
-#endif
+    int is_fallback;
+    Uint max_fds;
+    Uint active_fds;
+    Uint poll_threads;
 } ErtsPollInfo;
 
-#ifdef ERTS_POLL_NEED_ASYNC_INTERRUPT_SUPPORT
-void		ERTS_POLL_EXPORT(erts_poll_async_sig_interrupt)(ErtsPollSet);
+#if defined(ERTS_POLL_USE_FALLBACK) && ERTS_KERNEL_POLL_VERSION
+#  undef ERTS_POLL_EXPORT
+#  define ERTS_POLL_EXPORT(FUNC) FUNC ## _flbk
+#  include "erl_poll_api.h"
+#  undef ERTS_POLL_EXPORT
+#  define ERTS_POLL_EXPORT(FUNC) FUNC
+#elif !defined(ERTS_POLL_USE_FALLBACK)
+#  define ERTS_POLL_USE_FALLBACK 0
 #endif
-void		ERTS_POLL_EXPORT(erts_poll_interrupt)(ErtsPollSet,
-						      int);
-void		ERTS_POLL_EXPORT(erts_poll_interrupt_timed)(ErtsPollSet,
-							    int,
-							    ErtsMonotonicTime);
-ErtsPollEvents	ERTS_POLL_EXPORT(erts_poll_control)(ErtsPollSet,
-						    ErtsSysFdType,
-						    ErtsPollEvents,
-						    int on,
-						    int* wake_poller
-						    );
-void		ERTS_POLL_EXPORT(erts_poll_controlv)(ErtsPollSet,
-						     ErtsPollControlEntry [],
-						     int on);
-int		ERTS_POLL_EXPORT(erts_poll_wait)(ErtsPollSet,
-						 ErtsPollResFd [],
-						 int *,
-						 ErtsMonotonicTime);
-int		ERTS_POLL_EXPORT(erts_poll_max_fds)(void);
-void		ERTS_POLL_EXPORT(erts_poll_info)(ErtsPollSet,
-						 ErtsPollInfo *);
-ErtsPollSet	ERTS_POLL_EXPORT(erts_poll_create_pollset)(void);
-void		ERTS_POLL_EXPORT(erts_poll_destroy_pollset)(ErtsPollSet);
-void		ERTS_POLL_EXPORT(erts_poll_init)(void);
-void		ERTS_POLL_EXPORT(erts_poll_get_selected_events)(ErtsPollSet,
-								ErtsPollEvents [],
-								int);
 
+#include "erl_poll_api.h"
+
+/**
+ * Get the next size of the array that holds the file descriptors.
+ * This function is used in order for the check io array and the
+ * pollset array to be of the same size.
+ */
 int erts_poll_new_table_len(int old_len, int need_len);
 
 #endif /* #ifndef ERL_POLL_H__ */
diff --git a/erts/emulator/sys/common/erl_poll_api.h b/erts/emulator/sys/common/erl_poll_api.h
new file mode 100644
index 0000000000..f3a91e54f7
--- /dev/null
+++ b/erts/emulator/sys/common/erl_poll_api.h
@@ -0,0 +1,126 @@
+/*
+ * %CopyrightBegin%
+ *
+ * Copyright Ericsson AB 2006-2018. All Rights Reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ * %CopyrightEnd%
+ */
+/**
+ * @description: Poll interface functions
+ * @author Lukas Larsson
+ *
+ * The functions in the header are used to interact with the poll
+ * implementation. Iff the kernel-poll implementation needs a fallback
+ * pollset, then all functions are exported twice. Once with a _flbk
+ * suffix and once without any suffix. If no fallback is needed, then
+ * only the non-suffix version is exported.
+ */
+
+/**
+ * Initialize the poll implementation. Has to be called before any other function.
+ * @param[out] concurrent_waiters if not NULL, set to 1 if more then one thread
+ * is allowed to wait in the pollsets at the same time.
+ */
+void ERTS_POLL_EXPORT(erts_poll_init)(int *concurrent_waiters);
+/**
+ * @brief Create a new pollset.
+ * @param id The unique debug id of this pollset.
+ */
+ErtsPollSet *ERTS_POLL_EXPORT(erts_poll_create_pollset)(int id);
+
+/**
+ * Modify the contents of a pollset. This function can be called while one
+ * (or possibly more) thread is waiting in the pollset.
+ *
+ * @param ps the pollset to modify
+ * @param fd the file descriptor to modify
+ * @param op the type of operation to do. Normal usage is ADD,MOD...MOD,DEL.
+ * @param evts the events that we are changing interest to. Ignored if op is DEL.
+ * @param[in] wake_poller if set to 1 any thread waiting in the pollset will be woken.
+ *   This parameter is ignored if the pollset supports concurrent waiters.
+ * @param[out] wake_poller set to 1 if the waiting thread was woken.
+ * @return The events set, or ERTS_POLL_EV_NVAL if it was not possible to add the
+ * fd to the pollset.
+ */
+ErtsPollEvents ERTS_POLL_EXPORT(erts_poll_control)(ErtsPollSet *ps,
+                                                   ErtsSysFdType fd,
+                                                   ErtsPollOp op,
+                                                   ErtsPollEvents evts,
+                                                   int *wake_poller);
+
+/**
+ * Wait for events to be ready in the pollset. If the erts_poll_init call
+ * set concurrent_waiters to 1, then multiple threads are allowed to call
+ * this function at the same time.
+ *
+ * When an event has been triggered on a fd, that event is disabled. To
+ * re-enable it the implementation has to call erts_poll_control again.
+ *
+ * @param ps the pollset to wait for events in
+ * @param res an array of fd results that the ready fds are put in.
+ * @param[in] length the length of the res array
+ * @param[out] length the number of ready events returned in res
+ * @param tpd the thread progress data to note sleep state in
+ * @param timeout_time the time in native to wake up at
+ * @return 0 on success, else the ERRNO of the error that happened.
+ */
+int ERTS_POLL_EXPORT(erts_poll_wait)(ErtsPollSet *ps,
+                                     ErtsPollResFd res[],
+                                     int *length,
+                                     ErtsThrPrgrData *tpd,
+                                     ErtsMonotonicTime timeout_time);
+/**
+ * Interrupt the thread waiting in the pollset. This function should be called
+ * with set = 0 before any thread calls erts_poll_wait in order to clear any
+ * interrupts that have happened while the thread was awake.
+ *
+ * This function has no effect on pollsets that support concurrent waiters.
+ *
+ * @param ps the pollset to wake
+ * @param set if 1, interrupt the pollset, if 0 clear the interrupt flag.
+ */
+void ERTS_POLL_EXPORT(erts_poll_interrupt)(ErtsPollSet *ps, int set);
+
+/* Debug functions */
+
+/**
+ * Get the maximum number of fds supported by the pollset
+ */
+int ERTS_POLL_EXPORT(erts_poll_max_fds)(void);
+/**
+ * Get information about the given pollset
+ */
+void ERTS_POLL_EXPORT(erts_poll_info)(ErtsPollSet *ps,
+                                      ErtsPollInfo *info);
+/**
+ * Get information about which events are currently selected.
+ *
+ * The unix fd is used to index into the array, so naturally this function does
+ * not work on windows. If the pollset cannot figure out what the selected
+ * events for a given fd is, it is set to ERTS_POLL_EV_NONE.
+ *
+ * @param ps the pollset to get events from
+ * @param evts an array of which events are selected on.
+ */
+void ERTS_POLL_EXPORT(erts_poll_get_selected_events)(ErtsPollSet *ps,
+                                                     ErtsPollEvents evts[],
+                                                     int length);
+
+#ifdef ERTS_ENABLE_LOCK_COUNT
+/**
+ * Enable lock counting of any locks within the pollset.
+ */
+void ERTS_POLL_EXPORT(erts_lcnt_enable_pollset_lock_count)(ErtsPollSet *, int enable);
+#endif
diff --git a/erts/emulator/sys/common/erl_sys_common_misc.c b/erts/emulator/sys/common/erl_sys_common_misc.c
index 79f87eb3a9..d34e1a9ec0 100644
--- a/erts/emulator/sys/common/erl_sys_common_misc.c
+++ b/erts/emulator/sys/common/erl_sys_common_misc.c
@@ -1,7 +1,7 @@
 /*
  * %CopyrightBegin%
  * 
- * Copyright Ericsson AB 2006-2016. All Rights Reserved.
+ * Copyright Ericsson AB 2006-2018. All Rights Reserved.
  * 
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -45,14 +45,6 @@
 #endif
 #endif
 
-/*
- * erts_check_io_time is used by the erl_check_io implementation. The
- * global erts_check_io_time variable is declared here since there
- * (often) exist two versions of erl_check_io (kernel-poll and
- * non-kernel-poll), and we dont want two versions of this variable.
- */
-erts_smp_atomic_t erts_check_io_time;
-
 /* Written once and only once */
 
 static int filename_encoding = ERL_FILENAME_UNKNOWN;
@@ -150,7 +142,16 @@ sys_double_to_chars(double fp, char *buffer, size_t buffer_size)
     return sys_double_to_chars_ext(fp, buffer, buffer_size, SYS_DEFAULT_FLOAT_DECIMALS);
 }
 
-/* Convert float to string using fixed point notation.
+
+#if SIZEOF_LONG == 8
+# define round_int64 lround
+#elif SIZEOF_LONG_LONG == 8
+# define round_int64 llround
+#else
+# error "No 64-bit integer type?"
+#endif
+
+/* Convert float to string
  *   decimals must be >= 0
  *   if compact != 0, the trailing 0's will be truncated
  */
@@ -158,93 +159,40 @@ int
 sys_double_to_chars_fast(double f, char *buffer, int buffer_size, int decimals,
 			 int compact)
 {
-    /* Note that some C compilers don't support "static const" propagation
-     * so we use a defines */
-    #define SYS_DOUBLE_RND_CONST 0.55555555555555555
+    #define SYS_DOUBLE_RND_CONST 0.5
     #define FRAC_SIZE            52
     #define EXP_SIZE             11
-    #define EXP_MASK             ((1ll << EXP_SIZE) - 1)
-    #define MAX_DECIMALS         (sizeof(cs_sys_double_pow10) \
-				   / sizeof(cs_sys_double_pow10[0]))
-    #define FRAC_MASK            ((1ll << FRAC_SIZE) - 1)
-    #define FRAC_MASK2           ((1ll << (FRAC_SIZE + 1)) - 1)
-    #define MAX_FLOAT            (1ll << (FRAC_SIZE+1))
-
-    static const double cs_sys_double_pow10[] = {
-        SYS_DOUBLE_RND_CONST / 1ll,
-        SYS_DOUBLE_RND_CONST / 10ll,
-        SYS_DOUBLE_RND_CONST / 100ll,
-        SYS_DOUBLE_RND_CONST / 1000ll,
-        SYS_DOUBLE_RND_CONST / 10000ll,
-        SYS_DOUBLE_RND_CONST / 100000ll,
-        SYS_DOUBLE_RND_CONST / 1000000ll,
-        SYS_DOUBLE_RND_CONST / 10000000ll,
-        SYS_DOUBLE_RND_CONST / 100000000ll,
-        SYS_DOUBLE_RND_CONST / 1000000000ll,
-        SYS_DOUBLE_RND_CONST / 10000000000ll,
-        SYS_DOUBLE_RND_CONST / 100000000000ll,
-        SYS_DOUBLE_RND_CONST / 1000000000000ll,
-        SYS_DOUBLE_RND_CONST / 10000000000000ll,
-        SYS_DOUBLE_RND_CONST / 100000000000000ll,
-        SYS_DOUBLE_RND_CONST / 1000000000000000ll,
-        SYS_DOUBLE_RND_CONST / 10000000000000000ll,
-        SYS_DOUBLE_RND_CONST / 100000000000000000ll,
-        SYS_DOUBLE_RND_CONST / 1000000000000000000ll
+    #define EXP_MASK             (((Uint64)1 << EXP_SIZE) - 1)
+    #define MAX_DECIMALS         (sizeof(pow10v) / sizeof(pow10v[0]))
+    #define FRAC_MASK            (((Uint64)1 << FRAC_SIZE) - 1)
+    #define FRAC_MASK2           (((Uint64)1 << (FRAC_SIZE + 1)) - 1)
+    #define MAX_FLOAT            ((Uint64)1 << (FRAC_SIZE+1))
+
+    static const double pow10v[] = {
+        1e0,  1e1,  1e2,  1e3,  1e4,  1e5,  1e6,  1e7,  1e8, 1e9,
+        1e10, 1e11, 1e12, 1e13, 1e14, 1e15, 1e16, 1e17, 1e18
     };
 
-    long long mantissa, int_part = 0, frac_part = 0;
-    short exp;
-    int max;
+    double af;
+    Uint64 int_part, frac_part;
     int neg;
-    double fr;
-    union { long long L; double F; } x;
+    int  has_decimals = decimals != 0;
     char *p = buffer;
 
     if (decimals < 0)
         return -1;
 
-    /* Round the number to given decimal places. The number of 5's in the
-     * SYS_DOUBLE_RND_CONST constant is chosen such that adding any more 5's doesn't
-     * change the double precision of the number, i.e.:
-     * 1> term_to_binary(0.55555555555555555, [{minor_version, 1}]).
-     * <<131,70,63,225,199,28,113,199,28,114>>
-     * 2> term_to_binary(0.5555555555555555555, [{minor_version, 1}]).
-     * <<131,70,63,225,199,28,113,199,28,114>>
-     */
-    if (f >= 0) {
-        neg = 0;
-        fr  = decimals < MAX_DECIMALS ? (f + cs_sys_double_pow10[decimals]) : f;
-        x.F = fr;
-    } else {
+    if (f < 0) {
         neg = 1;
-        fr  = decimals < MAX_DECIMALS ? (f - cs_sys_double_pow10[decimals]) : f;
-        x.F = -fr;
+        af = -f;
     }
-
-    exp      = (x.L >> FRAC_SIZE) & EXP_MASK;
-    mantissa = x.L & FRAC_MASK;
-
-    if (exp == EXP_MASK) {
-        if (mantissa == 0) {
-            if (neg)
-                *p++ = '-';
-            *p++ = 'i';
-            *p++ = 'n';
-            *p++ = 'f';
-        } else {
-            *p++ = 'n';
-            *p++ = 'a';
-            *p++ = 'n';
-        }
-        *p = '\0';
-        return p - buffer;
+    else {
+        neg = 0;
+        af = f;
     }
 
-    exp      -= EXP_MASK >> 1;
-    mantissa |= (1ll << FRAC_SIZE);
-
     /* Don't bother with optimizing too large numbers or too large precision */
-    if (x.F > MAX_FLOAT || decimals >= MAX_DECIMALS) {
+    if (af > MAX_FLOAT || decimals >= MAX_DECIMALS) {
         int len = erts_snprintf(buffer, buffer_size, "%.*f", decimals, f);
         char* p = buffer + len;
         if (len >= buffer_size)
@@ -254,62 +202,64 @@ sys_double_to_chars_fast(double f, char *buffer, int buffer_size, int decimals,
             p = find_first_trailing_zero(p);
         *p = '\0';
         return p - buffer;
-    } else if (exp >= FRAC_SIZE) {
-        int_part  = mantissa << (exp - FRAC_SIZE);
-    } else if (exp >= 0) {
-        int_part  = mantissa >> (FRAC_SIZE - exp);
-        frac_part = (mantissa << (exp + 1)) & FRAC_MASK2;
-    } else /* if (exp < 0) */ {
-        frac_part = (mantissa & FRAC_MASK2) >> -(exp + 1);
-    }
-
-    if (!int_part) {
-        if (neg)
-            *p++ = '-';
-        *p++ = '0';
-    } else {
-        int ret, i, n;
-        while (int_part != 0) {
-            long long j = int_part / 10;
-            *p++ = (char)(int_part - ((j << 3) + (j << 1)) + '0');
-            int_part = j;
-        }
-        if (neg)
-            *p++ = '-';
-        /* Reverse string */
-        ret = p - buffer;
-        for (i = 0, n = ret/2; i < n; i++) {
-            int  j = ret - i - 1;
-            char c = buffer[i];
-            buffer[i] = buffer[j];
-            buffer[j] = c;
-        }
     }
 
-    if (decimals > 0) {
-        int i;
-        *p++ = '.';
+    if (decimals) {
+        double int_f = floor(af);
+        double frac_f = round((af - int_f) * pow10v[decimals]);
 
-        max = buffer_size - (p - buffer) - 1 /* leave room for trailing '\0' */;
+        int_part = (Uint64)int_f;
+        frac_part = (Uint64)frac_f;
 
-        if (decimals > max)
-            return -1;  /* the number is not large enough to fit in the buffer */
+        if (frac_f >= pow10v[decimals]) {
+            /* rounding overflow carry into int_part */
+            int_part++;
+            frac_part = 0;
+        }
 
-        max = decimals;
+        do {
+            Uint64 n;
+            if (!frac_part) {
+                do {
+                    *p++ = '0';
+                } while (--decimals);
+                break;
+            }
+            n = frac_part / 10;
+            *p++ = (char)((frac_part - n*10) + '0');
+            frac_part = n;
+        } while (--decimals);
 
-        for (i = 0; i < max; i++) {
-            /* frac_part *= 10; */
-            frac_part = (frac_part << 3) + (frac_part << 1);
+        *p++ = '.';
+    }
+    else
+        int_part = (Uint64)round_int64(af);
 
-            *p++ = (char)((frac_part >> (FRAC_SIZE + 1)) + '0');
-            frac_part &= FRAC_MASK2;
+    if (!int_part) {
+        *p++ = '0';
+    } else {
+        do {
+            Uint64 n = int_part / 10;
+            *p++ = (char)((int_part - n*10) + '0');
+            int_part = n;
+        } while (int_part);
+    }
+    if (neg)
+        *p++ = '-';
+
+    {/* Reverse string */
+        int i = 0;
+        int j = p - buffer - 1;
+        for ( ; i < j; i++, j--) {
+            char tmp = buffer[i];
+            buffer[i] = buffer[j];
+            buffer[j] = tmp;
         }
-
-        /* Delete trailing zeroes */
-        if (compact)
-            p = find_first_trailing_zero(p);
     }
 
+    /* Delete trailing zeroes */
+    if (compact && has_decimals)
+        p = find_first_trailing_zero(p);
     *p = '\0';
     return p - buffer;
 }
diff --git a/erts/emulator/sys/unix/erl_child_setup.c b/erts/emulator/sys/unix/erl_child_setup.c
index 69fc6c2879..129861ebd5 100644
--- a/erts/emulator/sys/unix/erl_child_setup.c
+++ b/erts/emulator/sys/unix/erl_child_setup.c
@@ -1,7 +1,7 @@
 /*
  * %CopyrightBegin%
  * 
- * Copyright Ericsson AB 2002-2016. All Rights Reserved.
+ * Copyright Ericsson AB 2002-2018. All Rights Reserved.
  * 
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -56,6 +56,8 @@
 #include <stdio.h>
 #include <stdarg.h>
 #include <sys/wait.h>
+#include <sys/types.h>
+#include <sys/socket.h>
 
 #define WANT_NONBLOCKING
 
@@ -131,6 +133,7 @@ static int sigchld_pipe[2];
 static int
 start_new_child(int pipes[])
 {
+    struct sigaction sa;
     int errln = -1;
     int size, res, i, pos = 0;
     char *buff, *o_buff;
@@ -141,6 +144,16 @@ start_new_child(int pipes[])
 
     /* only child executes here */
 
+    /* Restore default handling of sigterm... */
+    sa.sa_handler = SIG_DFL;
+    sigemptyset(&sa.sa_mask);
+    sa.sa_flags = 0;
+
+    if (sigaction(SIGTERM, &sa, 0) == -1) {
+        perror(NULL);
+        exit(1);
+    }
+    
     do {
         res = read(pipes[0], (char*)&size, sizeof(size));
     } while(res < 0 && (errno == EINTR || errno == ERRNO_BLOCK));
@@ -437,6 +450,21 @@ main(int argc, char *argv[])
         exit(1);
     }
 
+    /* Ignore SIGTERM.
+       Some container environments send SIGTERM to all processes
+       when terminating. We don't want erl_child_setup to terminate
+       in these cases as that will prevent beam from properly
+       cleaning up.
+    */
+    sa.sa_handler = SIG_IGN;
+    sigemptyset(&sa.sa_mask);
+    sa.sa_flags = 0;
+
+    if (sigaction(SIGTERM, &sa, 0) == -1) {
+        perror(NULL);
+        exit(1);
+    }
+
     forker_hash_init();
 
     SET_CLOEXEC(uds_fd);
diff --git a/erts/emulator/sys/unix/erl_child_setup.h b/erts/emulator/sys/unix/erl_child_setup.h
index a28b136bfc..0058b92344 100644
--- a/erts/emulator/sys/unix/erl_child_setup.h
+++ b/erts/emulator/sys/unix/erl_child_setup.h
@@ -1,7 +1,7 @@
 /*
  * %CopyrightBegin%
  * 
- * Copyright Ericsson AB 2015-2015. All Rights Reserved.
+ * Copyright Ericsson AB 2015-2017. All Rights Reserved.
  * 
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -17,7 +17,7 @@
  * 
  * %CopyrightEnd%
  *
- * This file defines the interface inbetween erts and child_setup.
+ * This file defines the interface between erts and child_setup.
  */
 
 #ifndef _ERL_UNIX_FORKER_H
diff --git a/erts/emulator/sys/unix/erl_unix_sys.h b/erts/emulator/sys/unix/erl_unix_sys.h
index b64b0d87f6..ae7a3ea23e 100644
--- a/erts/emulator/sys/unix/erl_unix_sys.h
+++ b/erts/emulator/sys/unix/erl_unix_sys.h
@@ -1,7 +1,7 @@
 /*
  * %CopyrightBegin%
  * 
- * Copyright Ericsson AB 1997-2016. All Rights Reserved.
+ * Copyright Ericsson AB 1997-2018. All Rights Reserved.
  * 
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -46,10 +46,10 @@
 #include <signal.h>
 #include <setjmp.h>
 
-#if HAVE_SYS_SOCKETIO_H
+#ifdef HAVE_SYS_SOCKETIO_H
 #   include <sys/socketio.h>
 #endif
-#if HAVE_SYS_SOCKIO_H
+#ifdef HAVE_SYS_SOCKIO_H
 #   include <sys/sockio.h>
 #endif
 
@@ -86,6 +86,10 @@
 
 #include <sys/times.h>
 
+#ifdef HAVE_SYS_RESOURCE_H
+#  include <sys/resource.h>
+#endif
+
 #ifdef HAVE_IEEEFP_H
 #include <ieeefp.h>
 #endif
@@ -128,12 +132,8 @@
 /* File descriptors are numbers anc consecutively allocated on Unix */
 #define  ERTS_SYS_CONTINOUS_FD_NUMBERS
 
-#ifndef ERTS_SMP
-#  undef ERTS_POLL_NEED_ASYNC_INTERRUPT_SUPPORT
-#  define ERTS_POLL_NEED_ASYNC_INTERRUPT_SUPPORT
-#endif
 
-typedef void *GETENV_STATE;
+void erts_sys_env_init(void);
 
 /*
 ** For the erl_timer_sup module.
@@ -264,7 +264,7 @@ erts_os_monotonic_time(void)
 ERTS_GLB_INLINE void
 erts_os_times(ErtsMonotonicTime *mtimep, ErtsSystemTime *stimep)
 {
-    return (*erts_sys_time_data__.r.o.os_times)(mtimep, stimep);
+    (*erts_sys_time_data__.r.o.os_times)(mtimep, stimep);
 }
 
 #endif /* ERTS_OS_TIMES_INLINE_FUNC_PTR_CALL__ */
@@ -292,6 +292,8 @@ erts_sys_perf_counter()
 
 /*
  * Functions for measuring CPU time
+ *
+ * Note that gethrvtime is time per process and clock_gettime is per thread.
  */
 
 #if (defined(HAVE_GETHRVTIME) || defined(HAVE_CLOCK_GETTIME_CPU_TIME))
@@ -300,15 +302,15 @@ typedef struct timespec SysTimespec;
 
 #if defined(HAVE_GETHRVTIME)
 #define sys_gethrvtime() gethrvtime()
-#define sys_get_proc_cputime(t,tp) (t) = sys_gethrvtime(), \
-                                   (tp).tv_sec = (time_t)((t)/1000000000LL), \
-                                   (tp).tv_nsec = (long)((t)%1000000000LL)
+#define sys_get_cputime(t,tp) (t) = sys_gethrvtime(), \
+        (tp).tv_sec = (time_t)((t)/1000000000LL),     \
+        (tp).tv_nsec = (long)((t)%1000000000LL)
 int sys_start_hrvtime(void);
 int sys_stop_hrvtime(void);
 
 #elif defined(HAVE_CLOCK_GETTIME_CPU_TIME)
 #define sys_clock_gettime(cid,tp) clock_gettime((cid),&(tp))
-#define sys_get_proc_cputime(t,tp) sys_clock_gettime(CLOCK_PROCESS_CPUTIME_ID,(tp))
+#define sys_get_cputime(t,tp) sys_clock_gettime(CLOCK_THREAD_CPUTIME_ID,(tp))
 
 #endif
 #endif
@@ -322,6 +324,7 @@ extern SIGFUNC sys_signal(int, SIGFUNC);
 extern void sys_sigrelease(int);
 extern void sys_sigblock(int);
 extern void sys_init_suspend_handler(void);
+extern void erts_sys_unix_later_init(void);
 
 /*
  * Handling of floating point exceptions.
@@ -353,9 +356,7 @@ extern void sys_init_suspend_handler(void);
 #ifdef NO_FPE_SIGNALS
 
 #define erts_get_current_fp_exception() NULL
-#ifdef ERTS_SMP
 #define erts_thread_init_fp_exception() do{}while(0)
-#endif
 #  define __ERTS_FP_CHECK_INIT(fpexnp) do {} while (0)
 #  define __ERTS_FP_ERROR(fpexnp, f, Action) if (!isfinite(f)) { Action; } else {}
 #  define __ERTS_FP_ERROR_THOROUGH(fpexnp, f, Action) __ERTS_FP_ERROR(fpexnp, f, Action)
@@ -368,9 +369,7 @@ extern void sys_init_suspend_handler(void);
 #else /* !NO_FPE_SIGNALS */
 
 extern volatile unsigned long *erts_get_current_fp_exception(void);
-#ifdef ERTS_SMP
 extern void erts_thread_init_fp_exception(void);
-#endif
 #  if (defined(__i386__) || defined(__x86_64__)) && defined(__GNUC__)
 #    define erts_fwait(fpexnp,f) \
 	__asm__ __volatile__("fwait" : "=m"(*(fpexnp)) : "m"(f))
@@ -437,10 +436,8 @@ void erts_sys_unblock_fpe(int);
 
 
 /* Threads */
-#ifdef USE_THREADS
 extern int init_async(int);
 extern int exit_async(void);
-#endif
 
 #define ERTS_EXIT_AFTER_DUMP _exit
 
diff --git a/erts/emulator/sys/unix/sys.c b/erts/emulator/sys/unix/sys.c
index 089efec3e8..4823e549ea 100644
--- a/erts/emulator/sys/unix/sys.c
+++ b/erts/emulator/sys/unix/sys.c
@@ -1,7 +1,7 @@
 /*
  * %CopyrightBegin%
  *
- * Copyright Ericsson AB 1996-2016. All Rights Reserved.
+ * Copyright Ericsson AB 1996-2018. All Rights Reserved.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -50,7 +50,6 @@
 #endif
 
 #define ERTS_WANT_BREAK_HANDLING
-#define ERTS_WANT_GOT_SIGUSR1
 #define WANT_NONBLOCKING    /* must define this to pull in defs from sys.h */
 #include "sys.h"
 #include "erl_thr_progress.h"
@@ -59,15 +58,10 @@
 #define __DARWIN__ 1
 #endif
 
-#ifdef USE_THREADS
 #include "erl_threads.h"
-#endif
 
 #include "erl_mseg.h"
 
-extern char **environ;
-erts_smp_rwmtx_t environ_rwmtx;
-
 #define MAX_VSIZE 16		/* Max number of entries allowed in an I/O
 				 * vector sock_sendv().
 				 */
@@ -80,7 +74,7 @@ erts_smp_rwmtx_t environ_rwmtx;
 
 #include "erl_check_io.h"
 #include "erl_cpu_topology.h"
-
+#include "erl_osenv.h"
 extern int  driver_interrupt(int, int);
 extern void do_break(void);
 
@@ -90,43 +84,24 @@ extern void erl_sys_args(int*, char**);
 
 extern void erts_sys_init_float(void);
 
-extern void erl_crash_dump(char* file, int line, char* fmt, ...);
-
 
 #ifdef DEBUG
 static int debug_log = 0;
 #endif
 
-#ifdef ERTS_SMP
-erts_smp_atomic32_t erts_got_sigusr1;
-#define ERTS_SET_GOT_SIGUSR1 \
-  erts_smp_atomic32_set_mb(&erts_got_sigusr1, 1)
-#define ERTS_UNSET_GOT_SIGUSR1 \
-  erts_smp_atomic32_set_mb(&erts_got_sigusr1, 0)
-static erts_smp_atomic32_t have_prepared_crash_dump;
+static erts_atomic32_t have_prepared_crash_dump;
 #define ERTS_PREPARED_CRASH_DUMP \
-  ((int) erts_smp_atomic32_xchg_nob(&have_prepared_crash_dump, 1))
-#else
-volatile int erts_got_sigusr1;
-#define ERTS_SET_GOT_SIGUSR1 (erts_got_sigusr1 = 1)
-#define ERTS_UNSET_GOT_SIGUSR1 (erts_got_sigusr1 = 0)
-static volatile int have_prepared_crash_dump;
-#define ERTS_PREPARED_CRASH_DUMP \
-  (have_prepared_crash_dump++)
-#endif
+  ((int) erts_atomic32_xchg_nob(&have_prepared_crash_dump, 1))
 
-erts_smp_atomic_t sys_misc_mem_sz;
+erts_atomic_t sys_misc_mem_sz;
 
-#if defined(ERTS_SMP)
-static void smp_sig_notify(char c);
+static void smp_sig_notify(int signum);
 static int sig_notify_fds[2] = {-1, -1};
 
-#if !defined(ETHR_UNUSABLE_SIGUSRX) && defined(ERTS_THR_HAVE_SIG_FUNCS)
+#ifdef ERTS_SYS_SUSPEND_SIGNAL
 static int sig_suspend_fds[2] = {-1, -1};
-#define ERTS_SYS_SUSPEND_SIGNAL SIGUSR2
 #endif
 
-#endif
 
 jmp_buf erts_sys_sigsegv_jmp;
 
@@ -140,149 +115,36 @@ static int max_files = -1;
 /* 
  * a few variables used by the break handler 
  */
-#ifdef ERTS_SMP
-erts_smp_atomic32_t erts_break_requested;
+erts_atomic32_t erts_break_requested;
 #define ERTS_SET_BREAK_REQUESTED \
-  erts_smp_atomic32_set_nob(&erts_break_requested, (erts_aint32_t) 1)
+  erts_atomic32_set_nob(&erts_break_requested, (erts_aint32_t) 1)
 #define ERTS_UNSET_BREAK_REQUESTED \
-  erts_smp_atomic32_set_nob(&erts_break_requested, (erts_aint32_t) 0)
-#else
-volatile int erts_break_requested = 0;
-#define ERTS_SET_BREAK_REQUESTED (erts_break_requested = 1)
-#define ERTS_UNSET_BREAK_REQUESTED (erts_break_requested = 0)
-#endif
+  erts_atomic32_set_nob(&erts_break_requested, (erts_aint32_t) 0)
+
+
 /* set early so the break handler has access to initial mode */
 static struct termios initial_tty_mode;
 static int replace_intr = 0;
 /* assume yes initially, ttsl_init will clear it */
-int using_oldshell = 1; 
-
-#ifdef ERTS_ENABLE_KERNEL_POLL
-
-int erts_use_kernel_poll = 0;
-
-struct {
-    int (*select)(ErlDrvPort, ErlDrvEvent, int, int);
-    int (*event)(ErlDrvPort, ErlDrvEvent, ErlDrvEventData);
-    void (*check_io_as_interrupt)(void);
-    void (*check_io_interrupt)(int);
-    void (*check_io_interrupt_tmd)(int, ErtsMonotonicTime);
-    void (*check_io)(int);
-    Uint (*size)(void);
-    Eterm (*info)(void *);
-    int (*check_io_debug)(ErtsCheckIoDebugInfo *);
-} io_func = {0};
+int using_oldshell = 1;
 
-
-int
-driver_select(ErlDrvPort port, ErlDrvEvent event, int mode, int on)
-{
-    return (*io_func.select)(port, event, mode, on);
-}
-
-int
-driver_event(ErlDrvPort port, ErlDrvEvent event, ErlDrvEventData event_data)
-{
-    return (*io_func.event)(port, event, event_data);
-}
-
-Eterm erts_check_io_info(void *p)
-{
-    return (*io_func.info)(p);
-}
-
-int
-erts_check_io_debug(ErtsCheckIoDebugInfo *ip)
+UWord
+erts_sys_get_page_size(void)
 {
-    return (*io_func.check_io_debug)(ip);
-}
-
-
-static void
-init_check_io(void)
-{
-    if (erts_use_kernel_poll) {
-	io_func.select			= driver_select_kp;
-	io_func.event			= driver_event_kp;
-#ifdef ERTS_POLL_NEED_ASYNC_INTERRUPT_SUPPORT
-	io_func.check_io_as_interrupt	= erts_check_io_async_sig_interrupt_kp;
-#endif
-	io_func.check_io_interrupt	= erts_check_io_interrupt_kp;
-	io_func.check_io_interrupt_tmd	= erts_check_io_interrupt_timed_kp;
-	io_func.check_io		= erts_check_io_kp;
-	io_func.size			= erts_check_io_size_kp;
-	io_func.info			= erts_check_io_info_kp;
-	io_func.check_io_debug		= erts_check_io_debug_kp;
-	erts_init_check_io_kp();
-	max_files = erts_check_io_max_files_kp();
-    }
-    else {
-	io_func.select			= driver_select_nkp;
-	io_func.event			= driver_event_nkp;
-#ifdef ERTS_POLL_NEED_ASYNC_INTERRUPT_SUPPORT
-	io_func.check_io_as_interrupt	= erts_check_io_async_sig_interrupt_nkp;
-#endif
-	io_func.check_io_interrupt	= erts_check_io_interrupt_nkp;
-	io_func.check_io_interrupt_tmd	= erts_check_io_interrupt_timed_nkp;
-	io_func.check_io		= erts_check_io_nkp;
-	io_func.size			= erts_check_io_size_nkp;
-	io_func.info			= erts_check_io_info_nkp;
-	io_func.check_io_debug		= erts_check_io_debug_nkp;
-	erts_init_check_io_nkp();
-	max_files = erts_check_io_max_files_nkp();
-    }
-}
-
-#ifdef ERTS_POLL_NEED_ASYNC_INTERRUPT_SUPPORT
-#define ERTS_CHK_IO_AS_INTR()	(*io_func.check_io_as_interrupt)()
+#if defined(_SC_PAGESIZE)
+    return (UWord) sysconf(_SC_PAGESIZE);
+#elif defined(HAVE_GETPAGESIZE)
+    return (UWord) getpagesize();
 #else
-#define ERTS_CHK_IO_AS_INTR()	(*io_func.check_io_interrupt)(1)
+    return (UWord) 4*1024; /* Guess 4 KB */
 #endif
-#define ERTS_CHK_IO_INTR	(*io_func.check_io_interrupt)
-#define ERTS_CHK_IO_INTR_TMD	(*io_func.check_io_interrupt_tmd)
-#define ERTS_CHK_IO		(*io_func.check_io)
-#define ERTS_CHK_IO_SZ		(*io_func.size)
-
-#else /* !ERTS_ENABLE_KERNEL_POLL */
-
-static void
-init_check_io(void)
-{
-    erts_init_check_io();
-    max_files = erts_check_io_max_files();
 }
 
-#ifdef ERTS_POLL_NEED_ASYNC_INTERRUPT_SUPPORT
-#define ERTS_CHK_IO_AS_INTR()	erts_check_io_async_sig_interrupt()
-#else
-#define ERTS_CHK_IO_AS_INTR()	erts_check_io_interrupt(1)
-#endif
-#define ERTS_CHK_IO_INTR	erts_check_io_interrupt
-#define ERTS_CHK_IO_INTR_TMD	erts_check_io_interrupt_timed
-#define ERTS_CHK_IO		erts_check_io
-#define ERTS_CHK_IO_SZ		erts_check_io_size
-
-#endif
-
-void
-erts_sys_schedule_interrupt(int set)
-{
-    ERTS_CHK_IO_INTR(set);
-}
-
-#ifdef ERTS_SMP
-void
-erts_sys_schedule_interrupt_timed(int set, ErtsMonotonicTime timeout_time)
-{
-    ERTS_CHK_IO_INTR_TMD(set, timeout_time);
-}
-#endif
-
 Uint
 erts_sys_misc_mem_sz(void)
 {
-    Uint res = ERTS_CHK_IO_SZ();
-    res += erts_smp_atomic_read_mb(&sys_misc_mem_sz);
+    Uint res = erts_check_io_size();
+    res += erts_atomic_read_mb(&sys_misc_mem_sz);
     return res;
 }
 
@@ -307,7 +169,6 @@ MALLOC_USE_HASH(1);
 #endif
 #endif
 
-#ifdef USE_THREADS
 
 #ifdef ERTS_THR_HAVE_SIG_FUNCS
 
@@ -386,19 +247,15 @@ thr_create_prepare_child(void *vtcdp)
     erts_sched_bind_atthrcreate_child(tcdp->sched_bind_data);
 }
 
-#endif /* #ifdef USE_THREADS */
 
 void
 erts_sys_pre_init(void)
 {
-#ifdef USE_THREADS
     erts_thr_init_data_t eid = ERTS_THR_INIT_DATA_DEF_INITER;
-#endif
 
     erts_printf_add_cr_to_stdout = 1;
     erts_printf_add_cr_to_stderr = 1;
 
-#ifdef USE_THREADS
 
     eid.thread_create_child_func = thr_create_prepare_child;
     /* Before creation in parent */
@@ -406,37 +263,29 @@ erts_sys_pre_init(void)
     /* After creation in parent */
     eid.thread_create_parent_func = thr_create_cleanup,
 
-#ifdef ERTS_THR_HAVE_SIG_FUNCS
-    sigemptyset(&thr_create_sigmask);
-    sigaddset(&thr_create_sigmask, SIGINT);   /* block interrupt */
-    sigaddset(&thr_create_sigmask, SIGUSR1);  /* block user defined signal */
+#ifdef ERTS_ENABLE_LOCK_COUNT
+    erts_lcnt_pre_thr_init();
 #endif
 
     erts_thr_init(&eid);
 
 #ifdef ERTS_ENABLE_LOCK_COUNT
-    erts_lcnt_init();
+    erts_lcnt_post_thr_init();
+#endif
+
+#ifdef ERTS_ENABLE_LOCK_CHECK
+    erts_lc_init();
 #endif
 
-#endif /* USE_THREADS */
 
     erts_init_sys_time_sup();
 
-#ifdef USE_THREADS
 
-#ifdef ERTS_SMP
-    erts_smp_atomic32_init_nob(&erts_break_requested, 0);
-    erts_smp_atomic32_init_nob(&erts_got_sigusr1, 0);
-    erts_smp_atomic32_init_nob(&have_prepared_crash_dump, 0);
-#else
-    erts_break_requested = 0;
-    erts_got_sigusr1 = 0;
-    have_prepared_crash_dump = 0;
-#endif
+    erts_atomic32_init_nob(&erts_break_requested, 0);
+    erts_atomic32_init_nob(&have_prepared_crash_dump, 0);
 
-#endif /* USE_THREADS */
 
-    erts_smp_atomic_init_nob(&sys_misc_mem_sz, 0);
+    erts_atomic_init_nob(&sys_misc_mem_sz, 0);
 
     {
       /*
@@ -499,10 +348,8 @@ SIGFUNC sys_signal(int sig, SIGFUNC func)
     return(oact.sa_handler);
 }
 
-#ifdef USE_THREADS
 #undef  sigprocmask
 #define sigprocmask erts_thr_sigmask
-#endif
 
 void sys_sigblock(int sig)
 {
@@ -522,11 +369,13 @@ void sys_sigrelease(int sig)
     sigprocmask(SIG_UNBLOCK, &mask, (sigset_t *)NULL);
 }
 
+#ifdef ERTS_HAVE_TRY_CATCH
 void erts_sys_sigsegv_handler(int signo) {
     if (signo == SIGSEGV) {
         longjmp(erts_sys_sigsegv_jmp, 1);
     }
 }
+#endif
 
 /*
  * Function returns 1 if we can read from all values in between
@@ -602,10 +451,10 @@ prepare_crash_dump(int secs)
     close(crashdump_companion_cube_fd);
 
     envsz = sizeof(env);
-    i = erts_sys_getenv__("ERL_CRASH_DUMP_NICE", env, &envsz);
-    if (i >= 0) {
+    i = erts_sys_explicit_8bit_getenv("ERL_CRASH_DUMP_NICE", env, &envsz);
+    if (i != 0) {
 	int nice_val;
-	nice_val = i != 0 ? 0 : atoi(env);
+	nice_val = (i != 1) ? 0 : atoi(env);
 	if (nice_val > 39) {
 	    nice_val = 39;
 	}
@@ -622,6 +471,28 @@ int erts_sys_prepare_crash_dump(int secs)
     return prepare_crash_dump(secs);
 }
 
+static void signal_notify_requested(Eterm type) {
+    Process* p = NULL;
+    Eterm msg, *hp;
+    ErtsProcLocks locks = 0;
+    ErlOffHeap *ohp;
+
+    Eterm id = erts_whereis_name_to_id(NULL, am_erl_signal_server);
+
+    if ((p = (erts_pid2proc_opt(NULL, 0, id, 0, ERTS_P2P_FLG_INC_REFC))) != NULL) {
+        ErtsMessage *msgp = erts_alloc_message_heap(p, &locks, 3, &hp, &ohp);
+
+        /* erl_signal_server ! {notify, sighup} */
+        msg = TUPLE2(hp, am_notify, type);
+        erts_queue_message(p, locks, msgp, msg, am_system);
+
+        if (locks)
+            erts_proc_unlock(p, locks);
+        erts_proc_dec_refc(p);
+    }
+}
+
+
 static ERTS_INLINE void
 break_requested(void)
 {
@@ -629,50 +500,17 @@ break_requested(void)
    * just set a flag - checked for and handled by
    * scheduler threads erts_check_io() (not signal handler).
    */
-#ifdef DEBUG			
-  fprintf(stderr,"break!\n");
-#endif
   if (ERTS_BREAK_REQUESTED)
       erts_exit(ERTS_INTR_EXIT, "");
 
   ERTS_SET_BREAK_REQUESTED;
-  ERTS_CHK_IO_AS_INTR(); /* Make sure we don't sleep in poll */
+  /* Wake aux thread to get handle break */
+  erts_aux_thread_poke();
 }
 
-/* set up signal handlers for break and quit */
-#if (defined(SIG_SIGSET) || defined(SIG_SIGNAL))
-static RETSIGTYPE request_break(void)
-#else
 static RETSIGTYPE request_break(int signum)
-#endif
-{
-#ifdef ERTS_SMP
-    smp_sig_notify('I');
-#else
-    break_requested();
-#endif
-}
-
-static ERTS_INLINE void
-sigusr1_exit(void)
 {
-    char env[21]; /* enough to hold any 64-bit integer */
-    size_t envsz;
-    int i, secs = -1;
-
-    /* We do this at interrupt level, since the main reason for
-     * wanting to generate a crash dump in this way is that the emulator
-     * is hung somewhere, so it won't be able to poll any flag we set here.
-     */
-    ERTS_SET_GOT_SIGUSR1;
-
-    envsz = sizeof(env);
-    if ((i = erts_sys_getenv_raw("ERL_CRASH_DUMP_SECONDS", env, &envsz)) >= 0) {
-	secs = i != 0 ? 0 : atoi(env);
-    }
-
-    prepare_crash_dump(secs);
-    erts_exit(ERTS_ERROR_EXIT, "Received SIGUSR1\n");
+    smp_sig_notify(signum);
 }
 
 #ifdef ETHR_UNUSABLE_SIGUSRX
@@ -695,19 +533,6 @@ sys_thr_resume(erts_tid_t tid) {
 }
 #endif
 
-#if (defined(SIG_SIGSET) || defined(SIG_SIGNAL))
-static RETSIGTYPE user_signal1(void)
-#else
-static RETSIGTYPE user_signal1(int signum)
-#endif
-{
-#ifdef ERTS_SMP
-   smp_sig_notify('1');
-#else
-   sigusr1_exit();
-#endif
-}
-
 #ifdef ERTS_SYS_SUSPEND_SIGNAL
 #if (defined(SIG_SIGSET) || defined(SIG_SIGNAL))
 static RETSIGTYPE suspend_signal(void)
@@ -715,42 +540,115 @@ static RETSIGTYPE suspend_signal(void)
 static RETSIGTYPE suspend_signal(int signum)
 #endif
 {
-    int res, buf[1], __errno = errno;
+    int res, buf[1], tmp_errno = errno;
     do {
         res = read(sig_suspend_fds[0], buf, sizeof(int));
     } while (res < 0 && errno == EINTR);
 
     /* restore previous errno in case read changed it */
-    errno = __errno;
+    errno = tmp_errno;
 }
 #endif /* #ifdef ERTS_SYS_SUSPEND_SIGNAL */
 
 #endif /* #ifndef ETHR_UNUSABLE_SIGUSRX */
 
-static void
-quit_requested(void)
+/*
+ Signal      Action   Comment
+ ─────────────────────────────────────────────────────────────
+  SIGHUP     Term     Hangup detected on controlling terminal or death of controlling process
+ !SIGINT     Term     Interrupt from keyboard
+  SIGQUIT    Core     Quit from keyboard
+ !SIGILL     Core     Illegal Instruction
+  SIGABRT    Core     Abort signal from abort(3)
+ !SIGFPE     Core     Floating point exception
+ !SIGKILL    Term     Kill signal
+ !SIGSEGV    Core     Invalid memory reference
+ !SIGPIPE    Term     Broken pipe: write to pipe with no readers
+  SIGALRM    Term     Timer signal from alarm(2)
+  SIGTERM    Term     Termination signal
+  SIGUSR1    Term     User-defined signal 1
+  SIGUSR2    Term     User-defined signal 2
+ !SIGCHLD    Ign      Child stopped or terminated
+ !SIGCONT    Cont     Continue if stopped
+  SIGSTOP    Stop     Stop process
+  SIGTSTP    Stop     Stop typed at terminal
+ !SIGTTIN    Stop     Terminal input for background process
+ !SIGTTOU    Stop     Terminal output for background process
+*/
+
+
+static ERTS_INLINE int
+signalterm_to_signum(Eterm signal)
 {
-    erts_exit(ERTS_INTR_EXIT, "");
+    switch (signal) {
+    case am_sighup:  return SIGHUP;
+    /* case am_sigint:  return SIGINT; */
+    case am_sigquit: return SIGQUIT;
+    /* case am_sigill:  return SIGILL; */
+    case am_sigabrt: return SIGABRT;
+    /* case am_sigsegv: return SIGSEGV; */
+    case am_sigalrm: return SIGALRM;
+    case am_sigterm: return SIGTERM;
+    case am_sigusr1: return SIGUSR1;
+    case am_sigusr2: return SIGUSR2;
+    case am_sigchld: return SIGCHLD;
+    case am_sigstop: return SIGSTOP;
+    case am_sigtstp: return SIGTSTP;
+    default:         return 0;
+    }
 }
 
-#if (defined(SIG_SIGSET) || defined(SIG_SIGNAL))
-static RETSIGTYPE do_quit(void)
-#else
-static RETSIGTYPE do_quit(int signum)
-#endif
+static ERTS_INLINE Eterm
+signum_to_signalterm(int signum)
 {
-#ifdef ERTS_SMP
-    smp_sig_notify('Q');
-#else
-    quit_requested();
-#endif
+    switch (signum) {
+    case SIGHUP:  return am_sighup;
+    /* case SIGINT:  return am_sigint; */    /* ^c */
+    case SIGQUIT: return am_sigquit;   /* ^\ */
+    /* case SIGILL:  return am_sigill; */
+    case SIGABRT: return am_sigabrt;
+    /* case SIGSEGV: return am_sigsegv; */
+    case SIGALRM: return am_sigalrm;
+    case SIGTERM: return am_sigterm;
+    case SIGUSR1: return am_sigusr1;
+    case SIGUSR2: return am_sigusr2;
+    case SIGCHLD: return am_sigchld;
+    case SIGSTOP: return am_sigstop;
+    case SIGTSTP: return am_sigtstp;   /* ^z */
+    default:      return am_error;
+    }
+}
+
+static RETSIGTYPE generic_signal_handler(int signum)
+{
+    smp_sig_notify(signum);
+}
+
+int erts_set_signal(Eterm signal, Eterm type) {
+    int signum;
+    if ((signum = signalterm_to_signum(signal)) > 0) {
+        if (type == am_ignore) {
+            sys_signal(signum, SIG_IGN);
+        } else if (type == am_default) {
+            sys_signal(signum, SIG_DFL);
+        } else {
+            sys_signal(signum, generic_signal_handler);
+        }
+        return 1;
+    }
+    return 0;
 }
 
 /* Disable break */
 void erts_set_ignore_break(void) {
-    sys_signal(SIGINT,  SIG_IGN);
-    sys_signal(SIGQUIT, SIG_IGN);
-    sys_signal(SIGTSTP, SIG_IGN);
+    /*
+     * Ignore signals that can be sent to the VM by
+     * typing certain key combinations at the
+     * controlling terminal...
+     */
+    sys_signal(SIGINT,  SIG_IGN);       /* Ctrl-C */
+    sys_signal(SIGQUIT, SIG_IGN);       /* Ctrl-\ */
+    sys_signal(SIGTSTP, SIG_IGN);       /* Ctrl-Z */
 }
 
 /* Don't use ctrl-c for break handler but let it be 
@@ -760,11 +658,11 @@ void erts_replace_intr(void) {
 
   if (isatty(0)) {
     tcgetattr(0, &mode);
-    
+
     /* here's an example of how to replace ctrl-c with ctrl-u */
     /* mode.c_cc[VKILL] = 0;
        mode.c_cc[VINTR] = CKILL; */
-    
+
     mode.c_cc[VINTR] = 0;	/* disable ctrl-c */
     tcsetattr(0, TCSANOW, &mode);
     replace_intr = 1;
@@ -773,11 +671,11 @@ void erts_replace_intr(void) {
 
 void init_break_handler(void)
 {
-   sys_signal(SIGINT, request_break);
+   sys_signal(SIGINT,  request_break);
 #ifndef ETHR_UNUSABLE_SIGUSRX
-   sys_signal(SIGUSR1, user_signal1);
+   sys_signal(SIGUSR1, generic_signal_handler);
 #endif /* #ifndef ETHR_UNUSABLE_SIGUSRX */
-   sys_signal(SIGQUIT, do_quit);
+   sys_signal(SIGQUIT, generic_signal_handler);
 }
 
 void sys_init_suspend_handler(void)
@@ -787,9 +685,15 @@ void sys_init_suspend_handler(void)
 #endif
 }
 
+void
+erts_sys_unix_later_init(void)
+{
+    sys_signal(SIGTERM, generic_signal_handler);
+}
+
 int sys_max_files(void)
 {
-   return(max_files);
+   return max_files;
 }
 
 /************************** OS info *******************************/
@@ -817,10 +721,7 @@ get_number(char **str_ptr)
     }
 }
 
-void
-os_flavor(char* namebuf, 	/* Where to return the name. */
-	  unsigned size) 	/* Size of name buffer. */
-{
+void os_flavor(char* namebuf, unsigned size) {
     struct utsname uts;		/* Information about the system. */
     char* s;
 
@@ -833,63 +734,29 @@ os_flavor(char* namebuf, 	/* Where to return the name. */
     strcpy(namebuf, uts.sysname);
 }
 
-void
-os_version(pMajor, pMinor, pBuild)
-int* pMajor;			/* Pointer to major version. */
-int* pMinor;			/* Pointer to minor version. */
-int* pBuild;			/* Pointer to build number. */
-{
+void os_version(int *pMajor, int *pMinor, int *pBuild) {
     struct utsname uts;		/* Information about the system. */
     char* release;		/* Pointer to the release string:
-				 * X.Y or X.Y.Z.
-				 */
+				 * X.Y or X.Y.Z.  */
 
     (void) uname(&uts);
     release = uts.release;
-    *pMajor = get_number(&release);
-    *pMinor = get_number(&release);
-    *pBuild = get_number(&release);
-}
-
-void init_getenv_state(GETENV_STATE *state)
-{
-   erts_smp_rwmtx_rlock(&environ_rwmtx);
-   *state = NULL;
-}
-
-char *getenv_string(GETENV_STATE *state0)
-{
-   char **state = (char **) *state0;
-   char *cp;
-
-   ERTS_SMP_LC_ASSERT(erts_smp_lc_rwmtx_is_rlocked(&environ_rwmtx));
-
-   if (state == NULL)
-      state = environ;
-
-   cp = *state++;
-   *state0 = (GETENV_STATE) state;
-
-   return cp;
-}
-
-void fini_getenv_state(GETENV_STATE *state)
-{
-   *state = NULL;
-   erts_smp_rwmtx_runlock(&environ_rwmtx);
+    *pMajor = get_number(&release); /* Pointer to major version. */
+    *pMinor = get_number(&release); /* Pointer to minor version. */
+    *pBuild = get_number(&release); /* Pointer to build number. */
 }
 
 void erts_do_break_handling(void)
 {
     struct termios temp_mode;
     int saved = 0;
-    
+
     /*
      * Most functions that do_break() calls are intentionally not thread safe;
      * therefore, make sure that all threads but this one are blocked before
      * proceeding!
      */
-    erts_smp_thr_progress_block();
+    erts_thr_progress_block();
 
     /* during break we revert to initial settings */
     /* this is done differently for oldshell */
@@ -901,14 +768,14 @@ void erts_do_break_handling(void)
       tcsetattr(0,TCSANOW,&initial_tty_mode);
       saved = 1;
     }
-    
+
     /* call the break handling function, reset the flag */
     do_break();
 
     ERTS_UNSET_BREAK_REQUESTED;
 
     fflush(stdout);
-    
+
     /* after break we go back to saved settings */
     if (using_oldshell && !replace_intr) {
       SET_NONBLOCKING(1);
@@ -917,9 +784,10 @@ void erts_do_break_handling(void)
       tcsetattr(0,TCSANOW,&temp_mode);
     }
 
-    erts_smp_thr_progress_unblock();
+    erts_thr_progress_unblock();
 }
 
+
 /* Fills in the systems representation of the jam/beam process identifier.
 ** The Pid is put in STRING representation in the supplied buffer,
 ** no interpretatione of this should be done by the rest of the
@@ -931,122 +799,13 @@ void sys_get_pid(char *buffer, size_t buffer_size){
     erts_snprintf(buffer, buffer_size, "%lu",(unsigned long) p);
 }
 
-int
-erts_sys_putenv_raw(char *key, char *value) {
-    return erts_sys_putenv(key, value);
-}
-int
-erts_sys_putenv(char *key, char *value)
-{
-    int res;
-    char *env;
-    Uint need = strlen(key) + strlen(value) + 2;
-
-#ifdef HAVE_COPYING_PUTENV
-    env = erts_alloc(ERTS_ALC_T_TMP, need);
-#else
-    env = erts_alloc(ERTS_ALC_T_PUTENV_STR, need);
-    erts_smp_atomic_add_nob(&sys_misc_mem_sz, need);
-#endif
-    strcpy(env,key);
-    strcat(env,"=");
-    strcat(env,value);
-    erts_smp_rwmtx_rwlock(&environ_rwmtx);
-    res = putenv(env);
-    erts_smp_rwmtx_rwunlock(&environ_rwmtx);
-#ifdef HAVE_COPYING_PUTENV
-    erts_free(ERTS_ALC_T_TMP, env);
-#endif
-    return res;
-}
 
-int
-erts_sys_getenv__(char *key, char *value, size_t *size)
-{
-    int res;
-    char *orig_value = getenv(key);
-    if (!orig_value)
-	res = -1;
-    else {
-	size_t len = sys_strlen(orig_value);
-	if (len >= *size) {
-	    *size = len + 1;
-	    res = 1;
-	}
-	else {
-	    *size = len;
-	    sys_memcpy((void *) value, (void *) orig_value, len+1);
-	    res = 0;
-	}
-    }
-    return res;
-}
-
-int
-erts_sys_getenv_raw(char *key, char *value, size_t *size) {
-    return erts_sys_getenv(key, value, size);
-}
-
-/*
- * erts_sys_getenv
- * returns:
- *  -1, if environment key is not set with a value
- *   0, if environment key is set and value fits into buffer size
- *   1, if environment key is set but does not fit into buffer size
- *      size is set with the needed buffer size value
- */
-
-int
-erts_sys_getenv(char *key, char *value, size_t *size)
-{
-    int res;
-    erts_smp_rwmtx_rlock(&environ_rwmtx);
-    res = erts_sys_getenv__(key, value, size);
-    erts_smp_rwmtx_runlock(&environ_rwmtx);
-    return res;
-}
-
-int
-erts_sys_unsetenv(char *key)
-{
-    int res;
-    erts_smp_rwmtx_rwlock(&environ_rwmtx);
-    res = unsetenv(key);
-    erts_smp_rwmtx_rwunlock(&environ_rwmtx);
-    return res;
-}
-
-void
-sys_init_io(void)
-{
-}
-
-#if (0) /* unused? */
-static int write_fill(fd, buf, len)
-int fd, len;
-char *buf;
-{
-    int i, done = 0;
-    
-    do {
-	if ((i = write(fd, buf+done, len-done)) < 0) {
-	    if (errno != EINTR)
-		return (i);
-	    i = 0;
-	}
-	done += i;
-    } while (done < len);
-    return (len);
-}
-#endif
+void sys_init_io(void) { }
+void erts_sys_alloc_init(void) { }
 
 extern const char pre_loaded_code[];
 extern Preload pre_loaded[];
 
-void erts_sys_alloc_init(void)
-{
-}
-
 #if ERTS_HAVE_ERTS_SYS_ALIGNED_ALLOC
 void *erts_sys_aligned_alloc(UWord alignment, UWord size)
 {
@@ -1147,9 +906,7 @@ void sys_preload_end(Preload* p)
    Here we assume that all schedulers are stopped so that erl_poll
    does not interfere with the select below.
 */
-int sys_get_key(fd)
-int fd;
-{
+int sys_get_key(int fd) {
     int c, ret;
     unsigned char rbuf[64];
     fd_set fds;
@@ -1168,29 +925,18 @@ int fd;
         if (c <= 0)
             return c;
     }
-
-    return rbuf[0]; 
+    return rbuf[0];
 }
 
 
 extern int erts_initialized;
 void
 erl_assert_error(const char* expr, const char* func, const char* file, int line)
-{   
+{
     fflush(stdout);
     fprintf(stderr, "%s:%d:%s() Assertion failed: %s\n",
             file, line, func, expr);
     fflush(stderr);
-#if !defined(ERTS_SMP) && 0
-    /* Writing a crashdump from a failed assertion when smp support
-     * is enabled almost a guaranteed deadlocking, don't even bother.
-     *
-     * It could maybe be useful (but I'm not convinced) to write the
-     * crashdump if smp support is disabled...
-     */
-    if (erts_initialized)
-	erl_crash_dump(file, line, "Assertion failed: %s\n", expr);
-#endif
     abort();
 }
 
@@ -1201,7 +947,7 @@ erl_debug(char* fmt, ...)
 {
     char sbuf[1024];		/* Temporary buffer. */
     va_list va;
-    
+
     if (debug_log) {
 	va_start(va, fmt);
 	vsprintf(sbuf, fmt, va);
@@ -1212,32 +958,17 @@ erl_debug(char* fmt, ...)
 
 #endif /* DEBUG */
 
-/*
- * Called from schedule() when it runs out of runnable processes,
- * or when Erlang code has performed INPUT_REDUCTIONS reduction
- * steps. runnable == 0 iff there are no runnable Erlang processes.
- */
-void
-erl_sys_schedule(int runnable)
-{
-    ERTS_CHK_IO(!runnable);
-    ERTS_SMP_LC_ASSERT(!erts_thr_progress_is_blocking());
-}
-
-
-#ifdef ERTS_SMP
-
-static erts_smp_tid_t sig_dispatcher_tid;
+static erts_tid_t sig_dispatcher_tid;
 
 static void
-smp_sig_notify(char c)
+smp_sig_notify(int signum)
 {
     int res;
     do {
 	/* write() is async-signal safe (according to posix) */
-	res = write(sig_notify_fds[1], &c, 1);
+	res = write(sig_notify_fds[1], &signum, sizeof(int));
     } while (res < 0 && errno == EINTR);
-    if (res != 1) {
+    if (res != sizeof(int)) {
 	char msg[] =
 	    "smp_sig_notify(): Failed to notify signal-dispatcher thread "
 	    "about received signal";
@@ -1253,57 +984,55 @@ signal_dispatcher_thread_func(void *unused)
     erts_lc_set_thread_name("signal_dispatcher");
 #endif
     while (1) {
-	char buf[32];
-	int res, i;
+        union {int signum; char buf[4];} sb;
+        Eterm signal;
+	int res, i = 0;
 	/* Block on read() waiting for a signal notification to arrive... */
-	res = read(sig_notify_fds[0], (void *) &buf[0], 32);
+
+        do {
+            res = read(sig_notify_fds[0], (void *) &sb.buf[i], sizeof(int) - i);
+            i += res > 0 ? res : 0;
+        } while ((i < sizeof(int) && res >= 0) || (res < 0 && errno == EINTR));
+
 	if (res < 0) {
-	    if (errno == EINTR)
-		continue;
 	    erts_exit(ERTS_ABORT_EXIT,
 		     "signal-dispatcher thread got unexpected error: %s (%d)\n",
 		     erl_errno_id(errno),
 		     errno);
 	}
-	for (i = 0; i < res; i++) {
-	    /*
-	     * NOTE 1: The signal dispatcher thread should not do work
-	     *         that takes a substantial amount of time (except
-	     *         perhaps in test and debug builds). It needs to
-	     *         be responsive, i.e, it should only dispatch work
-	     *         to other threads.
-	     *
-	     * NOTE 2: The signal dispatcher thread is not a blockable
-	     *         thread (i.e., not a thread managed by the
-	     *         erl_thr_progress module). This is intentional.
-	     *         We want to be able to interrupt writing of a crash
-	     *         dump by hitting C-c twice. Since it isn't a
-	     *         blockable thread it is important that it doesn't
-	     *         change the state of any data that a blocking thread
-	     *         expects to have exclusive access to (unless the
-	     *         signal dispatcher itself explicitly is blocking all
-	     *         blockable threads).
-	     */
-	    switch (buf[i]) {
-	    case 0: /* Emulator initialized */
+        /*
+         * NOTE 1: The signal dispatcher thread should not do work
+         *         that takes a substantial amount of time (except
+         *         perhaps in test and debug builds). It needs to
+         *         be responsive, i.e, it should only dispatch work
+         *         to other threads.
+         *
+         * NOTE 2: The signal dispatcher thread is not a blockable
+         *         thread (i.e., not a thread managed by the
+         *         erl_thr_progress module). This is intentional.
+         *         We want to be able to interrupt writing of a crash
+         *         dump by hitting C-c twice. Since it isn't a
+         *         blockable thread it is important that it doesn't
+         *         change the state of any data that a blocking thread
+         *         expects to have exclusive access to (unless the
+         *         signal dispatcher itself explicitly is blocking all
+         *         blockable threads).
+         */
+        switch (sb.signum) {
+            case 0: continue;
+            case SIGINT:
+                break_requested();
                 break;
-	    case 'I': /* SIGINT */
-		break_requested();
-		break;
-	    case 'Q': /* SIGQUIT */
-		quit_requested();
-		break;
-	    case '1': /* SIGUSR1 */
-		sigusr1_exit();
-		break;
-	    default:
-		erts_exit(ERTS_ABORT_EXIT,
-			 "signal-dispatcher thread received unknown "
-			 "signal notification: '%c'\n",
-			 buf[i]);
-	    }
-	}
-	ERTS_SMP_LC_ASSERT(!erts_thr_progress_is_blocking());
+            default:
+                if ((signal = signum_to_signalterm(sb.signum)) == am_error) {
+                    erts_exit(ERTS_ABORT_EXIT,
+                            "signal-dispatcher thread received unknown "
+                            "signal notification: '%d'\n",
+                            sb.signum);
+                }
+                signal_notify_requested(signal);
+        }
+        ERTS_LC_ASSERT(!erts_thr_progress_is_blocking());
     }
     return NULL;
 }
@@ -1311,7 +1040,7 @@ signal_dispatcher_thread_func(void *unused)
 static void
 init_smp_sig_notify(void)
 {
-    erts_smp_thr_opts_t thr_opts = ERTS_SMP_THR_OPTS_DEFAULT_INITER;
+    erts_thr_opts_t thr_opts = ERTS_THR_OPTS_DEFAULT_INITER;
     thr_opts.detached = 1;
     thr_opts.name = "sys_sig_dispatcher";
 
@@ -1323,7 +1052,7 @@ init_smp_sig_notify(void)
     }
 
     /* Start signal handler thread */
-    erts_smp_thr_create(&sig_dispatcher_tid,
+    erts_thr_create(&sig_dispatcher_tid,
 			signal_dispatcher_thread_func,
 			NULL,
 			&thr_opts);
@@ -1346,9 +1075,9 @@ init_smp_sig_suspend(void) {
 int erts_darwin_main_thread_pipe[2];
 int erts_darwin_main_thread_result_pipe[2];
 
-static void initialize_darwin_main_thread_pipes(void) 
+static void initialize_darwin_main_thread_pipes(void)
 {
-    if (pipe(erts_darwin_main_thread_pipe) < 0 || 
+    if (pipe(erts_darwin_main_thread_pipe) < 0 ||
 	pipe(erts_darwin_main_thread_result_pipe) < 0) {
 	erts_exit(ERTS_ERROR_EXIT,"Fatal error initializing Darwin main thread stealing");
     }
@@ -1361,12 +1090,12 @@ erts_sys_main_thread(void)
     erts_thread_disable_fpe();
 #ifdef __DARWIN__
     initialize_darwin_main_thread_pipes();
-#endif
+#else
     /* Become signal receiver thread... */
 #ifdef ERTS_ENABLE_LOCK_CHECK
     erts_lc_set_thread_name("signal_receiver");
 #endif
-
+#endif
     smp_sig_notify(0); /* Notify initialized */
 
     /* Wait for a signal to arrive... */
@@ -1416,103 +1145,15 @@ erts_sys_main_thread(void)
     }
 }
 
-#endif /* ERTS_SMP */
-
-#ifdef ERTS_ENABLE_KERNEL_POLL /* get_value() is currently only used when
-				  kernel-poll is enabled */
-
-/* Get arg marks argument as handled by
-   putting NULL in argv */
-static char *
-get_value(char* rest, char** argv, int* ip)
-{
-    char *param = argv[*ip]+1;
-    argv[*ip] = NULL;
-    if (*rest == '\0') {
-	char *next = argv[*ip + 1];
-	if (next[0] == '-'
-	    && next[1] == '-'
-	    &&  next[2] == '\0') {
-	    erts_fprintf(stderr, "bad \"%s\" value: \n", param);
-	    erts_usage();
-	}
-	(*ip)++;
-	argv[*ip] = NULL;
-	return next;
-    }
-    return rest;
-}
-
-#endif /* ERTS_ENABLE_KERNEL_POLL */
-
 void
 erl_sys_args(int* argc, char** argv)
 {
-    int i, j;
-
-    erts_smp_rwmtx_init(&environ_rwmtx, "environ");
-
-    i = 1;
-
     ASSERT(argc && argv);
 
-    while (i < *argc) {
-	if(argv[i][0] == '-') {
-	    switch (argv[i][1]) {
-#ifdef ERTS_ENABLE_KERNEL_POLL
-	    case 'K': {
-		char *arg = get_value(argv[i] + 2, argv, &i);
-		if (strcmp("true", arg) == 0) {
-		    erts_use_kernel_poll = 1;
-		}
-		else if (strcmp("false", arg) == 0) {
-		    erts_use_kernel_poll = 0;
-		}
-		else {
-		    erts_fprintf(stderr, "bad \"K\" value: %s\n", arg);
-		    erts_usage();
-		}
-		break;
-	    }
-#endif
-	    case '-':
-		goto done_parsing;
-	    default:
-		break;
-	    }
-	}
-	i++;
-    }
-
- done_parsing:
-
-#ifdef ERTS_ENABLE_KERNEL_POLL
-    if (erts_use_kernel_poll) {
-	char no_kp[10];
-	size_t no_kp_sz = sizeof(no_kp);
-	int res = erts_sys_getenv_raw("ERL_NO_KERNEL_POLL", no_kp, &no_kp_sz);
-	if (res > 0
-	    || (res == 0
-		&& sys_strcmp("false", no_kp) != 0
-		&& sys_strcmp("FALSE", no_kp) != 0)) {
-	    erts_use_kernel_poll = 0;
-	}
-    }
-#endif
-
-    init_check_io();
+    max_files = erts_check_io_max_files();
 
-#ifdef ERTS_SMP
     init_smp_sig_notify();
     init_smp_sig_suspend();
-#endif
-
-    /* Handled arguments have been marked with NULL. Slide arguments
-       not handled towards the beginning of argv. */
-    for (i = 0, j = 0; i < *argc; i++) {
-	if (argv[i])
-	    argv[j++] = argv[i];
-    }
-    *argc = j;
 
+    erts_sys_env_init();
 }
diff --git a/erts/emulator/sys/unix/sys_drivers.c b/erts/emulator/sys/unix/sys_drivers.c
index 400f163652..816bdea9c5 100644
--- a/erts/emulator/sys/unix/sys_drivers.c
+++ b/erts/emulator/sys/unix/sys_drivers.c
@@ -1,7 +1,7 @@
 /*
  * %CopyrightBegin%
  *
- * Copyright Ericsson AB 1996-2016. All Rights Reserved.
+ * Copyright Ericsson AB 1996-2018. All Rights Reserved.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -50,17 +50,15 @@
 #include <sys/ioctl.h>
 #endif
 
+#include <sys/types.h>
+#include <sys/socket.h>
+
 #define WANT_NONBLOCKING    /* must define this to pull in defs from sys.h */
 #include "sys.h"
 
-#ifdef USE_THREADS
 #include "erl_threads.h"
-#endif
-
-extern char **environ;
-extern erts_smp_rwmtx_t environ_rwmtx;
 
-extern erts_smp_atomic_t sys_misc_mem_sz;
+extern erts_atomic_t sys_misc_mem_sz;
 
 static Eterm forker_port;
 
@@ -86,12 +84,6 @@ static Eterm forker_port;
 #define MAXIOV 16
 #endif
 
-#ifdef USE_THREADS
-#  define FDBLOCK 1
-#else
-#  define FDBLOCK 0
-#endif
-
 /* Used by the fd driver iff the fd could not be set to non-blocking */
 typedef struct ErtsSysBlocking_ {
     ErlDrvPDL pdl;
@@ -178,9 +170,7 @@ void
 erl_sys_late_init(void)
 {
     SysDriverOpts opts;
-#ifdef ERTS_SMP
     Port *port;
-#endif
 
     sys_signal(SIGPIPE, SIG_IGN); /* Ignore - we'll handle the write failure */
 
@@ -190,20 +180,17 @@ erl_sys_late_init(void)
     opts.read_write = 0;
     opts.hide_window = 0;
     opts.wd = NULL;
-    opts.envir = NULL;
+    erts_osenv_init(&opts.envir);
     opts.exit_status = 0;
     opts.overlapped_io = 0;
     opts.spawn_type = ERTS_SPAWN_ANY;
     opts.argv = NULL;
     opts.parallelism = erts_port_parallelism;
 
-#ifdef ERTS_SMP
     port =
-#endif
         erts_open_driver(&forker_driver, make_internal_pid(0), "forker", &opts, NULL, NULL);
-#ifdef ERTS_SMP
     erts_mtx_unlock(port->lock);
-#endif
+    erts_sys_unix_later_init(); /* Need to be called after forker has been started */
 }
 
 /* II. Prototypes */
@@ -219,10 +206,8 @@ static ErlDrvData vanilla_start(ErlDrvPort, char*, SysDriverOpts*);
 
 /* II.III FD prototypes */
 static ErlDrvData fd_start(ErlDrvPort, char*, SysDriverOpts*);
-#if FDBLOCK
 static void fd_async(void *);
 static void fd_ready_async(ErlDrvData drv_data, ErlDrvThreadData thread_data);
-#endif
 static ErlDrvSSizeT fd_control(ErlDrvData, unsigned int, char *, ErlDrvSizeT,
 			       char **, ErlDrvSizeT);
 static void fd_stop(ErlDrvData);
@@ -286,11 +271,7 @@ struct erl_drv_entry fd_driver_entry = {
     fd_control,
     NULL,
     outputv,
-#if FDBLOCK
     fd_ready_async, /* ready_async */
-#else
-    NULL,
-#endif
     fd_flush, /* flush */
     NULL, /* call */
     NULL, /* event */
@@ -362,7 +343,7 @@ static int set_blocking_data(ErtsSysDriverData *dd) {
 
     dd->blocking = erts_alloc(ERTS_ALC_T_SYS_BLOCKING, sizeof(ErtsSysBlocking));
 
-    erts_smp_atomic_add_nob(&sys_misc_mem_sz, sizeof(ErtsSysBlocking));
+    erts_atomic_add_nob(&sys_misc_mem_sz, sizeof(ErtsSysBlocking));
 
     dd->blocking->pdl = driver_pdl_create(dd->port_num);
     dd->blocking->res = 0;
@@ -405,7 +386,7 @@ create_driver_data(ErlDrvPort port_num,
         size += sizeof(ErtsSysFdData);
 
     data = erts_alloc(ERTS_ALC_T_DRV_TAB,size);
-    erts_smp_atomic_add_nob(&sys_misc_mem_sz, size);
+    erts_atomic_add_nob(&sys_misc_mem_sz, size);
 
     driver_data = (ErtsSysDriverData*)data;
     data += sizeof(*driver_data);
@@ -440,7 +421,7 @@ create_driver_data(ErlDrvPort port_num,
             data += sizeof(*driver_data->ofd);
             init_fd_data(driver_data->ofd, ofd);
         }
-        if (is_blocking && FDBLOCK)
+        if (is_blocking)
             if (!set_blocking_data(driver_data)) {
                 erts_free(ERTS_ALC_T_DRV_TAB, driver_data);
                 return NULL;
@@ -462,85 +443,55 @@ static void close_pipes(int ifd[2], int ofd[2])
     close(ofd[1]);
 }
 
-static char **build_unix_environment(char *block)
+struct __add_spawn_env_state {
+    struct iovec *iov;
+    int *iov_index;
+
+    Sint32 *payload_size;
+    char *env_block;
+};
+
+static void add_spawn_env_block_foreach(void *_state,
+                                        const erts_osenv_data_t *key,
+                                        const erts_osenv_data_t *value)
 {
-    int i;
-    int j;
-    int len;
-    char *cp;
-    char **cpp;
-    char** old_env;
-    
-    ERTS_SMP_LC_ASSERT(erts_smp_lc_rwmtx_is_rlocked(&environ_rwmtx));
-
-    cp = block;
-    len = 0;
-    while (*cp != '\0') {
-	cp += strlen(cp) + 1;
-	len++;
-    }
-    old_env = environ;
-    while (*old_env++ != NULL) {
-	len++;
-    }
-    
-    cpp = (char **) erts_alloc_fnf(ERTS_ALC_T_ENVIRONMENT,
-				   sizeof(char *) * (len+1));
-    if (cpp == NULL) {
-	return NULL;
-    }
+    struct __add_spawn_env_state *state;
+    struct iovec *iov;
 
-    cp = block;
-    len = 0;
-    while (*cp != '\0') {
-	cpp[len] = cp;
-	cp += strlen(cp) + 1;
-	len++;
-    }
-    
-    i = len;
-    for (old_env = environ; *old_env; old_env++) {
-	char* old = *old_env;
-
-	for (j = 0; j < len; j++) {
-	    char *s, *t;
-
-	    /* check if cpp[j] equals old
-	       before the = sign,
-	       i.e.
-	       "TMPDIR=/tmp/" */
-	    s = cpp[j];
-	    t = old;
-	    while (*s == *t && *s != '=') {
-		s++, t++;
-	    }
-	    if (*s == '=' && *t == '=') {
-		break;
-	    }
-	}
+    state = (struct __add_spawn_env_state*)(_state);
+    iov = &state->iov[*state->iov_index];
 
-	if (j == len) {		/* New version not found */
-	    cpp[len++] = old;
-	}
-    }
+    iov->iov_base = state->env_block;
 
-    for (j = 0; j < i; ) {
-        size_t last = strlen(cpp[j])-1;
-	if (cpp[j][last] == '=' && strchr(cpp[j], '=') == cpp[j]+last) {
-	    cpp[j] = cpp[--len];
-	    if (len < i) {
-		i--;
-	    } else {
-		j++;
-	    }
-	}
-	else {
-	    j++;
-	}
-    }
+    sys_memcpy(state->env_block, key->data, key->length);
+    state->env_block += key->length;
+    *state->env_block++ = '=';
+    sys_memcpy(state->env_block, value->data, value->length);
+    state->env_block += value->length;
+    *state->env_block++ = '\0';
+
+    iov->iov_len = state->env_block - (char*)iov->iov_base;
 
-    cpp[len] = NULL;
-    return cpp;
+    (*state->payload_size) += iov->iov_len;
+    (*state->iov_index)++;
+}
+
+static void *add_spawn_env_block(const erts_osenv_t *env, struct iovec *iov,
+                                  int *iov_index, Sint32 *payload_size) {
+    struct __add_spawn_env_state add_state;
+    char *env_block;
+
+    env_block = erts_alloc(ERTS_ALC_T_TMP, env->content_size +
+        env->variable_count * sizeof("=\0"));
+
+    add_state.iov = iov;
+    add_state.iov_index = iov_index;
+    add_state.env_block = env_block;
+    add_state.payload_size = payload_size;
+
+    erts_osenv_foreach_native(env, &add_state, add_spawn_env_block_foreach);
+
+    return env_block;
 }
 
 static ErlDrvData spawn_start(ErlDrvPort port_num, char* name,
@@ -550,7 +501,6 @@ static ErlDrvData spawn_start(ErlDrvPort port_num, char* name,
 #define CMD_LINE_PREFIX_STR_SZ (sizeof(CMD_LINE_PREFIX_STR) - 1)
 
     int len;
-    char **new_environ;
     ErtsSysDriverData *dd;
     char *cmd_line;
     char wd_buff[MAXPATHLEN+1];
@@ -617,19 +567,7 @@ static ErlDrvData spawn_start(ErlDrvPort port_num, char* name,
 	memcpy((void *) (cmd_line + CMD_LINE_PREFIX_STR_SZ), (void *) name, len);
 	cmd_line[CMD_LINE_PREFIX_STR_SZ + len] = '\0';
 	len = CMD_LINE_PREFIX_STR_SZ + len + 1;
-    }
-
-    erts_smp_rwmtx_rlock(&environ_rwmtx);
-
-    if (opts->envir == NULL) {
-	new_environ = environ;
-    } else if ((new_environ = build_unix_environment(opts->envir)) == NULL) {
-	erts_smp_rwmtx_runlock(&environ_rwmtx);
-        close_pipes(ifd, ofd);
-	erts_free(ERTS_ALC_T_TMP, (void *) cmd_line);
-	errno = ENOMEM;
-	return ERL_DRV_ERROR_ERRNO;
-    }
+}
 
     if ((cwd = getcwd(wd_buff, MAXPATHLEN+1)) == NULL) {
         /* on some OSs this call opens a fd in the
@@ -638,9 +576,6 @@ static ErlDrvData spawn_start(ErlDrvPort port_num, char* name,
         int err = errno;
         close_pipes(ifd, ofd);
         erts_free(ERTS_ALC_T_TMP, (void *) cmd_line);
-        if (new_environ != environ)
-            erts_free(ERTS_ALC_T_ENVIRONMENT, (void *) new_environ);
-        erts_smp_rwmtx_runlock(&environ_rwmtx);
         errno = err;
         return ERL_DRV_ERROR_ERRNO;
     }
@@ -648,6 +583,7 @@ static ErlDrvData spawn_start(ErlDrvPort port_num, char* name,
     wd = opts->wd;
 
     {
+        void *environment_block;
         struct iovec *io_vector;
         int iov_len = 5;
         char nullbuff[] = "\0";
@@ -660,10 +596,8 @@ static ErlDrvData spawn_start(ErlDrvPort port_num, char* name,
 
         if (wd) iov_len++;
 
-        /* count number of elements in environment */
-        while(new_environ[env_len] != NULL)
-            env_len++;
-        iov_len += 1 + env_len; /* num envs including size int */
+        /* num envs including size int */
+        iov_len += 1 + opts->envir.variable_count;
 
         /* count number of element in argument list */
         if (opts->spawn_type == ERTS_SPAWN_EXECUTABLE) {
@@ -680,10 +614,7 @@ static ErlDrvData spawn_start(ErlDrvPort port_num, char* name,
 
         if (!io_vector) {
             close_pipes(ifd, ofd);
-            erts_smp_rwmtx_runlock(&environ_rwmtx);
             erts_free(ERTS_ALC_T_TMP, (void *) cmd_line);
-            if (new_environ != environ)
-                erts_free(ERTS_ALC_T_ENVIRONMENT, (void *) new_environ);
             errno = ENOMEM;
             return ERL_DRV_ERROR_ERRNO;
         }
@@ -718,16 +649,13 @@ static ErlDrvData spawn_start(ErlDrvPort port_num, char* name,
         io_vector[i++].iov_len = 1;
         buffsz += io_vector[i-1].iov_len;
 
+        env_len = htonl(opts->envir.variable_count);
         io_vector[i].iov_base = (void*)&env_len;
-        env_len = htonl(env_len);
         io_vector[i++].iov_len = sizeof(env_len);
         buffsz += io_vector[i-1].iov_len;
 
-        for (j = 0; new_environ[j] != NULL; j++) {
-            io_vector[i].iov_base = new_environ[j];
-            io_vector[i++].iov_len = strlen(new_environ[j]) + 1;
-            buffsz += io_vector[i-1].iov_len;
-        }
+        environment_block = add_spawn_env_block(&opts->envir, io_vector, &i,
+            &buffsz);
 
         /* only append arguments if this was a spawn_executable */
         if (opts->spawn_type == ERTS_SPAWN_EXECUTABLE) {
@@ -757,15 +685,12 @@ static ErlDrvData spawn_start(ErlDrvPort port_num, char* name,
 
         /* we send the request to do the fork */
         if ((res = writev(ofd[1], io_vector, iov_len > MAXIOV ? MAXIOV : iov_len)) < 0) {
-            if (errno == ERRNO_BLOCK) {
+            if (errno == ERRNO_BLOCK || errno == EINTR) {
                 res = 0;
             } else {
                 int err = errno;
                 close_pipes(ifd, ofd);
                 erts_free(ERTS_ALC_T_TMP, io_vector);
-                if (new_environ != environ)
-                    erts_free(ERTS_ALC_T_ENVIRONMENT, (void *) new_environ);
-                erts_smp_rwmtx_runlock(&environ_rwmtx);
                 erts_free(ERTS_ALC_T_TMP, (void *) cmd_line);
                 errno = err;
                 return ERL_DRV_ERROR_ERRNO;
@@ -786,16 +711,12 @@ static ErlDrvData spawn_start(ErlDrvPort port_num, char* name,
             driver_select(port_num, ofd[1], ERL_DRV_WRITE|ERL_DRV_USE, 1);
         }
 
+        erts_free(ERTS_ALC_T_TMP, environment_block);
         erts_free(ERTS_ALC_T_TMP, io_vector);
     }
 
     erts_free(ERTS_ALC_T_TMP, (void *) cmd_line);
 
-    if (new_environ != environ)
-	erts_free(ERTS_ALC_T_ENVIRONMENT, (void *) new_environ);
-
-    erts_smp_rwmtx_runlock(&environ_rwmtx);
-
     dd = create_driver_data(port_num, ifd[0], ofd[1], opts->packet_bytes,
                              DO_WRITE | DO_READ, opts->exit_status,
                              0, 0);
@@ -1067,8 +988,8 @@ static void clear_fd_data(ErtsSysFdData *fdd)
 {
     if (fdd->sz > 0) {
 	erts_free(ERTS_ALC_T_FD_ENTRY_BUF, (void *) fdd->buf);
-	ASSERT(erts_smp_atomic_read_nob(&sys_misc_mem_sz) >= fdd->sz);
-	erts_smp_atomic_add_nob(&sys_misc_mem_sz, -1*fdd->sz);
+	ASSERT(erts_atomic_read_nob(&sys_misc_mem_sz) >= fdd->sz);
+	erts_atomic_add_nob(&sys_misc_mem_sz, -1*fdd->sz);
     }
     fdd->buf = NULL;
     fdd->sz = 0;
@@ -1079,7 +1000,7 @@ static void clear_fd_data(ErtsSysFdData *fdd)
 
 static void nbio_stop_fd(ErlDrvPort prt, ErtsSysFdData *fdd)
 {
-    driver_select(prt, abs(fdd->fd), DO_READ|DO_WRITE, 0);
+    driver_select(prt, abs(fdd->fd), ERL_DRV_USE_NO_CALLBACK|DO_READ|DO_WRITE, 0);
     clear_fd_data(fdd);
     SET_BLOCKING(abs(fdd->fd));
 
@@ -1091,13 +1012,11 @@ static void fd_stop(ErlDrvData ev)  /* Does not close the fds */
     ErlDrvPort prt = dd->port_num;
     int sz = sizeof(ErtsSysDriverData);
 
-#if FDBLOCK
     if (dd->blocking) {
         erts_free(ERTS_ALC_T_SYS_BLOCKING, dd->blocking);
         dd->blocking = NULL;
         sz += sizeof(ErtsSysBlocking);
     }
-#endif
 
     if (dd->ifd) {
         sz += sizeof(ErtsSysFdData);
@@ -1109,7 +1028,7 @@ static void fd_stop(ErlDrvData ev)  /* Does not close the fds */
     }
 
      erts_free(ERTS_ALC_T_DRV_TAB, dd);
-     erts_smp_atomic_add_nob(&sys_misc_mem_sz, -sz);
+     erts_atomic_add_nob(&sys_misc_mem_sz, -sz);
 }
 
 static void fd_flush(ErlDrvData ev)
@@ -1190,19 +1109,19 @@ static void outputv(ErlDrvData e, ErlIOVec* ev)
     ev->iov[0].iov_len = pb;
     ev->size += pb;
 
-    if (dd->blocking && FDBLOCK)
+    if (dd->blocking)
         driver_pdl_lock(dd->blocking->pdl);
 
     if ((sz = driver_sizeq(ix)) > 0) {
 	driver_enqv(ix, ev, 0);
 
-        if (dd->blocking && FDBLOCK)
+        if (dd->blocking)
             driver_pdl_unlock(dd->blocking->pdl);
 
 	if (sz + ev->size >= (1 << 13))
 	    set_busy_port(ix, 1);
     }
-    else if (!dd->blocking || !FDBLOCK) {
+    else if (!dd->blocking) {
         /* We try to write directly if the fd in non-blocking */
 	int vsize = ev->vsize > MAX_VSIZE ? MAX_VSIZE : ev->vsize;
 
@@ -1219,7 +1138,6 @@ static void outputv(ErlDrvData e, ErlIOVec* ev)
 	driver_enqv(ix, ev, n);  /* n is the skip value */
 	driver_select(ix, ofd, ERL_DRV_WRITE|ERL_DRV_USE, 1);
     }
-#if FDBLOCK
     else {
         if (ev->size != 0) {
             driver_enqv(ix, ev, 0);
@@ -1230,7 +1148,6 @@ static void outputv(ErlDrvData e, ErlIOVec* ev)
             driver_pdl_unlock(dd->blocking->pdl);
         }
     }
-#endif
     /* return 0;*/
 }
 
@@ -1302,7 +1219,7 @@ static int port_inp_failure(ErtsSysDriverData *dd, int res)
         clear_fd_data(dd->ifd);
     }
 
-    if (dd->blocking && FDBLOCK) {
+    if (dd->blocking) {
         driver_pdl_lock(dd->blocking->pdl);
         if (driver_sizeq(dd->port_num) > 0) {
             driver_pdl_unlock(dd->blocking->pdl);
@@ -1340,6 +1257,8 @@ static int port_inp_failure(ErtsSysDriverData *dd, int res)
         }
        driver_failure_eof(dd->port_num);
     } else if (dd->ifd) {
+        if (dd->alive == -1)
+            errno = dd->status;
         erl_drv_init_ack(dd->port_num, ERL_DRV_ERROR_ERRNO);
     } else {
 	driver_failure_posix(dd->port_num, err);
@@ -1370,10 +1289,10 @@ static void ready_input(ErlDrvData e, ErlDrvEvent ready_fd)
         int res;
 
         if((res = read(ready_fd, &proto, sizeof(proto))) <= 0) {
+            if (res < 0 && (errno == ERRNO_BLOCK || errno == EINTR))
+                return;
             /* hmm, child setup seems to have closed the pipe too early...
                we close the port as there is not much else we can do */
-            if (res < 0 && errno == ERRNO_BLOCK)
-                return;
             driver_select(port_num, ready_fd, ERL_DRV_READ, 0);
             if (res == 0)
                 errno = EPIPE;
@@ -1407,7 +1326,7 @@ static void ready_input(ErlDrvData e, ErlDrvEvent ready_fd)
 
             if (dd->ifd->fd < 0) {
                 driver_select(port_num, abs(dd->ifd->fd), ERL_DRV_READ|ERL_DRV_USE, 0);
-                erts_smp_atomic_add_nob(&sys_misc_mem_sz, -sizeof(ErtsSysFdData));
+                erts_atomic_add_nob(&sys_misc_mem_sz, -sizeof(ErtsSysFdData));
                 dd->ifd = NULL;
             }
 
@@ -1507,13 +1426,13 @@ static void ready_input(ErlDrvData e, ErlDrvEvent ready_fd)
 		    continue;
 		}
 		else {		/* The last message we got was split */
-		        char *buf = erts_alloc_fnf(ERTS_ALC_T_FD_ENTRY_BUF, h);
+                    char *buf = erts_alloc_fnf(ERTS_ALC_T_FD_ENTRY_BUF, h);
 		    if (!buf) {
 			errno = ENOMEM;
 			port_inp_failure(dd, -1);
 		    }
 		    else {
-			erts_smp_atomic_add_nob(&sys_misc_mem_sz, h);
+			erts_atomic_add_nob(&sys_misc_mem_sz, h);
 			sys_memcpy(buf, cpos, bytes_left);
 			dd->ifd->buf = buf;
 			dd->ifd->sz = h;
@@ -1548,7 +1467,7 @@ static void ready_output(ErlDrvData e, ErlDrvEvent ready_fd)
                should close the output fd as soon as the command has
                been sent. */
             driver_select(ix, ready_fd, ERL_DRV_WRITE|ERL_DRV_USE, 0);
-            erts_smp_atomic_add_nob(&sys_misc_mem_sz, -sizeof(ErtsSysFdData));
+            erts_atomic_add_nob(&sys_misc_mem_sz, -sizeof(ErtsSysFdData));
             dd->ofd = NULL;
         }
         if (dd->terminating)
@@ -1578,7 +1497,6 @@ static void stop_select(ErlDrvEvent fd, void* _)
     close((int)fd);
 }
 
-#if FDBLOCK
 
 static void
 fd_async(void *async_data)
@@ -1657,7 +1575,6 @@ void fd_ready_async(ErlDrvData drv_data,
     return; /* 0; */
 }
 
-#endif
 
 /* Forker driver */
 
@@ -1677,15 +1594,13 @@ static ErlDrvData forker_start(ErlDrvPort port_num, char* name,
 
     forker_port = erts_drvport2id(port_num);
 
-    res = erts_sys_getenv_raw("BINDIR", bindir, &bindirsz);
-    if (res != 0) {
-        if (res < 0)
-            erts_exit(1,
-                     "Environment variable BINDIR is not set\n");
-        if (res > 0)
-            erts_exit(1,
-                     "Value of environment variable BINDIR is too large\n");
+    res = erts_sys_explicit_8bit_getenv("BINDIR", bindir, &bindirsz);
+    if (res == 0) {
+        erts_exit(1, "Environment variable BINDIR is not set\n");
+    } else if(res < 0) {
+        erts_exit(1, "Value of environment variable BINDIR is too large\n");
     }
+
     if (bindir[0] != DIR_SEPARATOR_CHAR)
         erts_exit(1,
                  "Environment variable BINDIR does not contain an"
@@ -1748,8 +1663,6 @@ static ErlDrvData forker_start(ErlDrvPort port_num, char* name,
 
     SET_NONBLOCKING(forker_fd);
 
-    driver_select(port_num, forker_fd, ERL_DRV_READ|ERL_DRV_USE, 1);
-
     return (ErlDrvData)port_num;
 }
 
@@ -1759,15 +1672,37 @@ static void forker_stop(ErlDrvData e)
        the port has been closed by the user. */
 }
 
+static ErlDrvSizeT forker_deq(ErlDrvPort port_num, ErtsSysForkerProto *proto)
+{
+    close(proto->u.start.fds[0]);
+    close(proto->u.start.fds[1]);
+    if (proto->u.start.fds[1] != proto->u.start.fds[2])
+        close(proto->u.start.fds[2]);
+
+    return driver_deq(port_num, sizeof(*proto));
+}
+
+static void forker_sigchld(Eterm port_id, int error)
+{
+    ErtsSysForkerProto *proto = erts_alloc(ERTS_ALC_T_DRV_CTRL_DATA, sizeof(*proto));
+    proto->action = ErtsSysForkerProtoAction_SigChld;
+    proto->u.sigchld.error_number = error;
+    proto->u.sigchld.port_id = port_id;
+
+    /* ideally this would be a port_command call, but as command is
+       already used by the spawn_driver, we use control instead.
+       Note that when using erl_drv_port_control it is an asynchronous
+       control. */
+    erl_drv_port_control(port_id, 'S', (char*)proto, sizeof(*proto));
+}
+
 static void forker_ready_input(ErlDrvData e, ErlDrvEvent fd)
 {
     int res;
-    ErtsSysForkerProto *proto;
-
-    proto = erts_alloc(ERTS_ALC_T_DRV_CTRL_DATA, sizeof(*proto));
+    ErtsSysForkerProto proto;
 
-    if ((res = read(fd, proto, sizeof(*proto))) < 0) {
-        if (errno == ERRNO_BLOCK)
+    if ((res = read(fd, &proto, sizeof(proto))) < 0) {
+        if (errno == ERRNO_BLOCK || errno == EINTR)
             return;
         erts_exit(ERTS_DUMP_EXIT, "Failed to read from erl_child_setup: %d\n", errno);
     }
@@ -1775,10 +1710,10 @@ static void forker_ready_input(ErlDrvData e, ErlDrvEvent fd)
     if (res == 0)
         erts_exit(ERTS_DUMP_EXIT, "erl_child_setup closed\n");
 
-    ASSERT(res == sizeof(*proto));
+    ASSERT(res == sizeof(proto));
 
 #ifdef FORKER_PROTO_START_ACK
-    if (proto->action == ErtsSysForkerProtoAction_StartAck) {
+    if (proto.action == ErtsSysForkerProtoAction_StartAck) {
         /* Ideally we would like to not have to ack each Start
            command being sent over the uds, but it would seem
            that some operating systems (only observed on FreeBSD)
@@ -1788,28 +1723,15 @@ static void forker_ready_input(ErlDrvData e, ErlDrvEvent fd)
         ErlDrvPort port_num = (ErlDrvPort)e;
         int vlen;
         SysIOVec *iov = driver_peekq(port_num, &vlen);
-        ErtsSysForkerProto *proto = (ErtsSysForkerProto *)iov[0].iov_base;
-
-        close(proto->u.start.fds[0]);
-        close(proto->u.start.fds[1]);
-        if (proto->u.start.fds[1] != proto->u.start.fds[2])
-            close(proto->u.start.fds[2]);
+        ErtsSysForkerProto *qproto = (ErtsSysForkerProto *)iov[0].iov_base;
 
-        driver_deq(port_num, sizeof(*proto));
-
-        if (driver_sizeq(port_num) > 0)
+        if (forker_deq(port_num, qproto))
             driver_select(port_num, forker_fd, ERL_DRV_WRITE|ERL_DRV_USE, 1);
     } else
 #endif
     {
-        ASSERT(proto->action == ErtsSysForkerProtoAction_SigChld);
-
-        /* ideally this would be a port_command call, but as command is
-           already used by the spawn_driver, we use control instead.
-           Note that when using erl_drv_port_control it is an asynchronous
-           control. */
-        erl_drv_port_control(proto->u.sigchld.port_id, 'S',
-                             (char*)proto, sizeof(*proto));
+        ASSERT(proto.action == ErtsSysForkerProtoAction_SigChld);
+        forker_sigchld(proto.u.sigchld.port_id, proto.u.sigchld.error_number);
     }
 
 }
@@ -1819,7 +1741,8 @@ static void forker_ready_output(ErlDrvData e, ErlDrvEvent fd)
     ErlDrvPort port_num = (ErlDrvPort)e;
 
 #ifndef FORKER_PROTO_START_ACK
-    while (driver_sizeq(port_num) > 0) {
+    int loops = 10;
+    while (driver_sizeq(port_num) > 0 && --loops) {
 #endif
         int vlen;
         SysIOVec *iov = driver_peekq(port_num, &vlen);
@@ -1827,29 +1750,42 @@ static void forker_ready_output(ErlDrvData e, ErlDrvEvent fd)
         ASSERT(iov[0].iov_len >= (sizeof(*proto)));
         if (sys_uds_write(forker_fd, (char*)proto, sizeof(*proto),
                           proto->u.start.fds, 3, 0) < 0) {
-            if (errno == ERRNO_BLOCK)
+            if (errno == ERRNO_BLOCK || errno == EINTR) {
                 return;
-            erts_exit(ERTS_DUMP_EXIT, "Failed to write to erl_child_setup: %d\n", errno);
+            } else if (errno == EMFILE) {
+                forker_sigchld(proto->u.start.port_id, errno);
+                if (forker_deq(port_num, proto) == 0)
+                    driver_select(port_num, forker_fd, ERL_DRV_WRITE, 0);
+                return;
+            } else {
+                erts_exit(ERTS_DUMP_EXIT, "Failed to write to erl_child_setup: %d\n", errno);
+            }
         }
 #ifndef FORKER_PROTO_START_ACK
-        close(proto->u.start.fds[0]);
-        close(proto->u.start.fds[1]);
-        if (proto->u.start.fds[1] != proto->u.start.fds[2])
-            close(proto->u.start.fds[2]);
-        driver_deq(port_num, sizeof(*proto));
+        if (forker_deq(port_num, proto) == 0)
+            driver_select(port_num, forker_fd, ERL_DRV_WRITE, 0);
     }
-#endif
-
+#else
     driver_select(port_num, forker_fd, ERL_DRV_WRITE, 0);
+#endif
 }
 
 static ErlDrvSSizeT forker_control(ErlDrvData e, unsigned int cmd, char *buf,
                                    ErlDrvSizeT len, char **rbuf, ErlDrvSizeT rlen)
 {
+    static int first_call = 1;
     ErtsSysForkerProto *proto = (ErtsSysForkerProto *)buf;
     ErlDrvPort port_num = (ErlDrvPort)e;
     int res;
 
+    if (first_call) {
+        /*
+         * Do driver_select here when schedulers and their pollsets have started.
+         */
+        driver_select(port_num, forker_fd, ERL_DRV_READ|ERL_DRV_USE, 1);
+        first_call = 0;
+    }
+
     driver_enq(port_num, buf, len);
     if (driver_sizeq(port_num) > sizeof(*proto)) {
         return 0;
@@ -1857,20 +1793,21 @@ static ErlDrvSSizeT forker_control(ErlDrvData e, unsigned int cmd, char *buf,
 
     if ((res = sys_uds_write(forker_fd, (char*)proto, sizeof(*proto),
                              proto->u.start.fds, 3, 0)) < 0) {
-        if (errno == ERRNO_BLOCK) {
+        if (errno == ERRNO_BLOCK || errno == EINTR) {
             driver_select(port_num, forker_fd, ERL_DRV_WRITE|ERL_DRV_USE, 1);
             return 0;
+        } else if (errno == EMFILE) {
+            forker_sigchld(proto->u.start.port_id, errno);
+            forker_deq(port_num, proto);
+            return 0;
+        } else {
+            erts_exit(ERTS_DUMP_EXIT, "Failed to write to erl_child_setup: %d\n", errno);
         }
-        erts_exit(ERTS_DUMP_EXIT, "Failed to write to erl_child_setup: %d\n", errno);
     }
 
 #ifndef FORKER_PROTO_START_ACK
     ASSERT(res == sizeof(*proto));
-    close(proto->u.start.fds[0]);
-    close(proto->u.start.fds[1]);
-    if (proto->u.start.fds[1] != proto->u.start.fds[2])
-        close(proto->u.start.fds[2]);
-    driver_deq(port_num, sizeof(*proto));
+    forker_deq(port_num, proto);
 #endif
 
     return 0;
diff --git a/erts/emulator/sys/unix/sys_env.c b/erts/emulator/sys/unix/sys_env.c
new file mode 100644
index 0000000000..4d8301f985
--- /dev/null
+++ b/erts/emulator/sys/unix/sys_env.c
@@ -0,0 +1,133 @@
+
+#ifdef HAVE_CONFIG_H
+#  include "config.h"
+#endif
+
+#include "sys.h"
+#include "erl_osenv.h"
+#include "erl_alloc.h"
+
+#include "erl_thr_progress.h"
+
+static erts_osenv_t sysenv_global_env;
+static erts_rwmtx_t sysenv_rwmtx;
+
+extern char **environ;
+
+static void import_initial_env(void);
+
+void erts_sys_env_init() {
+    erts_rwmtx_init(&sysenv_rwmtx, "environ", NIL,
+        ERTS_LOCK_FLAGS_PROPERTY_STATIC | ERTS_LOCK_FLAGS_CATEGORY_GENERIC);
+
+    erts_osenv_init(&sysenv_global_env);
+    import_initial_env();
+}
+
+const erts_osenv_t *erts_sys_rlock_global_osenv() {
+    erts_rwmtx_rlock(&sysenv_rwmtx);
+    return &sysenv_global_env;
+}
+
+erts_osenv_t *erts_sys_rwlock_global_osenv() {
+    erts_rwmtx_rwlock(&sysenv_rwmtx);
+    return &sysenv_global_env;
+}
+
+void erts_sys_rwunlock_global_osenv() {
+    erts_rwmtx_rwunlock(&sysenv_rwmtx);
+}
+
+void erts_sys_runlock_global_osenv() {
+    erts_rwmtx_runlock(&sysenv_rwmtx);
+}
+
+int erts_sys_explicit_8bit_putenv(char *key, char *value) {
+    erts_osenv_data_t env_key, env_value;
+    int result;
+
+    env_key.length = sys_strlen(key);
+    env_key.data = key;
+
+    env_value.length = sys_strlen(value);
+    env_value.data = value;
+
+    {
+        erts_osenv_t *env = erts_sys_rwlock_global_osenv();
+        result = erts_osenv_put_native(env, &env_key, &env_value);
+        erts_sys_rwunlock_global_osenv();
+    }
+
+    return result;
+}
+
+int erts_sys_explicit_8bit_getenv(char *key, char *value, size_t *size) {
+    erts_osenv_data_t env_key, env_value;
+    int result;
+
+    env_key.length = sys_strlen(key);
+    env_key.data = key;
+
+    /* Reserve space for NUL termination. */
+    env_value.length = *size - 1;
+    env_value.data = value;
+
+    {
+        const erts_osenv_t *env = erts_sys_rlock_global_osenv();
+        result = erts_osenv_get_native(env, &env_key, &env_value);
+        erts_sys_runlock_global_osenv();
+    }
+
+    if(result == 1) {
+        value[env_value.length] = '\0';
+    }
+
+    *size = env_value.length;
+
+    return result;
+}
+
+int erts_sys_explicit_host_getenv(char *key, char *value, size_t *size) {
+    char *orig_value;
+    size_t length;
+    
+    orig_value = getenv(key);
+
+    if(orig_value == NULL) {
+        return 0;
+    }
+
+    length = sys_strlen(orig_value);
+
+    if (length >= *size) {
+        *size = length + 1;
+        return -1;
+    }
+
+    sys_memcpy((void*)value, (void*)orig_value, length + 1);
+    *size = length;
+
+    return 1;
+}
+
+static void import_initial_env(void) {
+    char **environ_iterator, *environ_variable;
+
+    environ_iterator = environ;
+
+    while ((environ_variable = *(environ_iterator++)) != NULL) {
+        char *separator_index = strchr(environ_variable, '=');
+
+        if (separator_index != NULL) {
+            erts_osenv_data_t env_key, env_value;
+
+            env_key.length = separator_index - environ_variable;
+            env_key.data = environ_variable;
+    
+            env_value.length = sys_strlen(separator_index) - 1;
+            env_value.data = separator_index + 1;
+
+            erts_osenv_put_native(&sysenv_global_env, &env_key, &env_value);
+        }
+    }
+}
diff --git a/erts/emulator/sys/unix/sys_float.c b/erts/emulator/sys/unix/sys_float.c
index 6435da086f..832074f679 100644
--- a/erts/emulator/sys/unix/sys_float.c
+++ b/erts/emulator/sys/unix/sys_float.c
@@ -1,7 +1,7 @@
 /*
  * %CopyrightBegin%
  *
- * Copyright Ericsson AB 2001-2016. All Rights Reserved.
+ * Copyright Ericsson AB 2001-2018. All Rights Reserved.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -39,7 +39,6 @@ erts_sys_init_float(void)
 
 #else  /* !NO_FPE_SIGNALS */
 
-#ifdef ERTS_SMP
 static erts_tsd_key_t fpe_key;
 
 /* once-only initialisation early in the main thread (via erts_sys_init_float()) */
@@ -61,11 +60,6 @@ static ERTS_INLINE volatile unsigned long *erts_thread_get_fp_exception(void)
 {
     return (volatile unsigned long*)erts_tsd_get(fpe_key);
 }
-#else /* !SMP */
-#define erts_init_fp_exception()	/*empty*/
-static volatile unsigned long fp_exception;
-#define erts_thread_get_fp_exception()	(&fp_exception)
-#endif /* SMP */
 
 volatile unsigned long *erts_get_current_fp_exception(void)
 {
@@ -659,11 +653,9 @@ void erts_sys_init_float(void)
 
 void erts_thread_init_float(void)
 {
-#ifdef ERTS_SMP
     /* This allows Erlang schedulers to leave Erlang-process context
        and still have working FP exceptions. XXX: is this needed? */
     erts_thread_init_fp_exception();
-#endif
 
 #ifndef NO_FPE_SIGNALS
     /* NOTE:
diff --git a/erts/emulator/sys/unix/sys_time.c b/erts/emulator/sys/unix/sys_time.c
index 4f26639703..8ba575b7b6 100644
--- a/erts/emulator/sys/unix/sys_time.c
+++ b/erts/emulator/sys/unix/sys_time.c
@@ -1,7 +1,7 @@
 /*
  * %CopyrightBegin%
  * 
- * Copyright Ericsson AB 2005-2016. All Rights Reserved.
+ * Copyright Ericsson AB 2005-2018. All Rights Reserved.
  * 
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -160,7 +160,7 @@ struct sys_time_internal_state_read_mostly__ {
 
 #ifdef ERTS_SYS_TIME_INTERNAL_STATE_WRITE_FREQ__
 struct sys_time_internal_state_write_freq__ {
-    erts_smp_mtx_t mtx;
+    erts_mtx_t mtx;
 #if defined(__linux__) && defined(OS_MONOTONIC_TIME_USING_CLOCK_GETTIME)
     ErtsMonotonicTime last_delivered;
 #endif
@@ -304,8 +304,8 @@ sys_init_time(ErtsSysInitTimeResult *init_resp)
 	    erts_sys_time_data__.r.o.os_times =
 		clock_gettime_times_verified;
 #endif
-	    erts_smp_mtx_init(&internal_state.w.f.mtx,
-			      "os_monotonic_time");
+            erts_mtx_init(&internal_state.w.f.mtx, "os_monotonic_time", NIL,
+                ERTS_LOCK_FLAGS_PROPERTY_STATIC | ERTS_LOCK_FLAGS_CATEGORY_IO);
 	    internal_state.w.f.last_delivered
 		= clock_gettime_monotonic();
 	    init_resp->os_monotonic_time_info.locked_use = 1;
@@ -525,12 +525,12 @@ static ErtsMonotonicTime clock_gettime_monotonic_verified(void)
     mtime = (ErtsMonotonicTime) posix_clock_gettime(MONOTONIC_CLOCK_ID,
 						    MONOTONIC_CLOCK_ID_STR);
 
-    erts_smp_mtx_lock(&internal_state.w.f.mtx);
+    erts_mtx_lock(&internal_state.w.f.mtx);
     if (mtime < internal_state.w.f.last_delivered)
 	mtime = internal_state.w.f.last_delivered;
     else
 	internal_state.w.f.last_delivered = mtime;
-    erts_smp_mtx_unlock(&internal_state.w.f.mtx);
+    erts_mtx_unlock(&internal_state.w.f.mtx);
 
     return mtime;
 }
@@ -547,12 +547,12 @@ static void clock_gettime_times_verified(ErtsMonotonicTime *mtimep,
 			      WALL_CLOCK_ID_STR,
 			      stimep);
 
-    erts_smp_mtx_lock(&internal_state.w.f.mtx);
+    erts_mtx_lock(&internal_state.w.f.mtx);
     if (*mtimep < internal_state.w.f.last_delivered)
 	*mtimep = internal_state.w.f.last_delivered;
     else
 	internal_state.w.f.last_delivered = *mtimep;
-    erts_smp_mtx_unlock(&internal_state.w.f.mtx);
+    erts_mtx_unlock(&internal_state.w.f.mtx);
 }
 
 #endif /* defined(OS_SYSTEM_TIME_USING_CLOCK_GETTIME) */
@@ -878,8 +878,6 @@ ErtsMonotonicTime
 erts_os_monotonic_time(void)
 {
     Uint32 ticks = get_tick_count();
-    ERTS_CHK_EXTEND_OS_MONOTONIC_TIME(&internal_state.wr.m.os_mtime_xtnd,
-				      ticks);
     return ERTS_EXTEND_OS_MONOTONIC_TIME(&internal_state.wr.m.os_mtime_xtnd,
 					 ticks) << internal_state.r.o.times_shift;
 }
diff --git a/erts/emulator/sys/unix/sys_uds.c b/erts/emulator/sys/unix/sys_uds.c
index dd0a3b03ff..c9f73622ba 100644
--- a/erts/emulator/sys/unix/sys_uds.c
+++ b/erts/emulator/sys/unix/sys_uds.c
@@ -1,7 +1,7 @@
 /*
  * %CopyrightBegin%
  * 
- * Copyright Ericsson AB 2002-2016. All Rights Reserved.
+ * Copyright Ericsson AB 2002-2018. All Rights Reserved.
  * 
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -18,6 +18,42 @@
  * %CopyrightEnd%
  */
 
+#ifdef HAVE_CONFIG_H
+#  include "config.h"
+#endif
+
+#if defined(__sun__) && !defined(_XOPEN_SOURCE)
+#define _XOPEN_SOURCE 500
+#endif
+
+#include <limits.h>
+
+#include <sys/types.h>
+#include <sys/socket.h>
+
+#ifdef HAVE_SYS_SOCKETIO_H
+#   include <sys/socketio.h>
+#endif
+#ifdef HAVE_SYS_SOCKIO_H
+#   include <sys/sockio.h>
+#endif
+
+#ifdef HAVE_NET_ERRNO_H
+#include <net/errno.h>
+#endif
+
+#ifdef HAVE_DIRENT_H
+#  include <dirent.h>
+#endif
+
+#ifdef HAVE_UNISTD_H
+#   include <unistd.h>
+#endif
+
+#include <stdlib.h>
+#include <string.h>
+#include <errno.h>
+
 #include "sys_uds.h"
 
 int
@@ -52,8 +88,9 @@ sys_uds_readv(int fd, struct iovec *iov, size_t iov_len,
     if((msg.msg_flags & MSG_CTRUNC) == MSG_CTRUNC)
     {
         /* We assume that we have given enough space for any header
-           that are sent to us. So the only remaining reason to get
-           this flag set is if the caller has run out of file descriptors.
+           that are sent to us. So the only remaining reasons to get
+           this flag set is if the caller has run out of file descriptors
+           or an SELinux policy prunes the response (eg. O_APPEND on STDERR).
         */
         errno = EMFILE;
         return -1;
@@ -96,7 +133,7 @@ sys_uds_writev(int fd, struct iovec *iov, size_t iov_len,
 
     struct msghdr msg;
     struct cmsghdr *cmsg = NULL;
-    int res, i;
+    int res, i, error;
 
     /* initialize socket message */
     memset(&msg, 0, sizeof(struct msghdr));
@@ -137,11 +174,22 @@ sys_uds_writev(int fd, struct iovec *iov, size_t iov_len,
 
     res = sendmsg(fd, &msg, flags);
 
+#ifdef ETOOMANYREFS
+    /* Linux may give ETOOMANYREFS when there are too many fds in transit.
+       We map this to EMFILE as bsd and other use this error code and we want
+       the behaviour to be the same on all OSs */
+    if (errno == ETOOMANYREFS)
+        errno = EMFILE;
+#endif
+    error = errno;
+
     if (iov_len > MAXIOV)
         free(iov[0].iov_base);
 
     free(msg.msg_control);
 
+    errno = error;
+
     return res;
 }
 
diff --git a/erts/emulator/sys/unix/sys_uds.h b/erts/emulator/sys/unix/sys_uds.h
index a598102d5c..49a4b39250 100644
--- a/erts/emulator/sys/unix/sys_uds.h
+++ b/erts/emulator/sys/unix/sys_uds.h
@@ -1,7 +1,7 @@
 /*
  * %CopyrightBegin%
  *
- * Copyright Ericsson AB 2002-2016. All Rights Reserved.
+ * Copyright Ericsson AB 2002-2018. All Rights Reserved.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -21,18 +21,6 @@
 #ifndef _ERL_UNIX_UDS_H
 #define _ERL_UNIX_UDS_H
 
-#ifdef HAVE_CONFIG_H
-#  include "config.h"
-#endif
-
-#if defined(__sun__) && !defined(_XOPEN_SOURCE)
-#define _XOPEN_SOURCE 500
-#endif
-
-#include <limits.h>
-
-#include <sys/types.h>
-#include <sys/socket.h>
 #include <sys/uio.h>
 
 #if defined IOV_MAX
@@ -43,8 +31,6 @@
 #define MAXIOV 16
 #endif
 
-#include "sys.h"
-
 int sys_uds_readv(int fd, struct iovec *iov, size_t iov_len,
                   int *fds, int fd_count, int flags);
 int sys_uds_read(int fd, char *buff, size_t len,
diff --git a/erts/emulator/sys/win32/erl_poll.c b/erts/emulator/sys/win32/erl_poll.c
index f23c7ab03d..3843a27a6e 100644
--- a/erts/emulator/sys/win32/erl_poll.c
+++ b/erts/emulator/sys/win32/erl_poll.c
@@ -1,7 +1,7 @@
 /*
  * %CopyrightBegin%
  *
- * Copyright Ericsson AB 2007-2016. All Rights Reserved.
+ * Copyright Ericsson AB 2007-2018. All Rights Reserved.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -34,6 +34,7 @@
  */
 
 /*#define HARDDEBUG */
+/*#define HARDTRACE */
 #ifdef HARDDEBUG
 #ifdef HARDTRACE
 #define HARDTRACEF(X) my_debug_printf##X
@@ -50,7 +51,7 @@ static void my_debug_printf(char *fmt, ...)
     va_start(args, fmt);
     erts_vsnprintf(buffer,1024,fmt,args);
     va_end(args);
-    erts_fprintf(stderr,"%s\r\n",buffer);
+    erts_printf("%s\r\n",buffer);
 }
 #else
 #define HARDTRACEF(X)
@@ -142,7 +143,8 @@ static erts_mtx_t save_ops_mtx;
 
 static void poll_debug_init(void)
 {
-    erts_mtx_init(&save_ops_mtx, "save_ops_lock");
+    erts_mtx_init(&save_ops_mtx, "save_ops_lock", NIL,
+        ERTS_LOCK_FLAGS_PROPERTY_STATIC | ERTS_LOCK_FLAGS_CATEGORY_DEBUG);
 }
 
 void poll_debug_set_active_fd(ErtsSysFdType fd)
@@ -273,53 +275,35 @@ typedef struct _Waiter {
 /*
  * The structure for a pollset. There can currently be only one...
  */
-struct ErtsPollSet_ {
+struct erts_pollset {
     Waiter** waiter;
     int allocated_waiters;  /* Size ow waiter array */ 
     int num_waiters;	    /* Number of waiter threads. */
-    int restore_events;        /* Tells us to restore waiters events 
-				  next time around */
     HANDLE event_io_ready;     /* To be used when waiting for io */
     /* These are used to wait for workers to enter standby */
     volatile int standby_wait_counter; /* Number of threads to wait for */
     CRITICAL_SECTION standby_crit;     /* CS to guard the counter */
-    HANDLE standby_wait_event;         /* Event signalled when counte == 0 */
+    HANDLE standby_wait_event;         /* Event signalled when counter == 0 */
     erts_atomic32_t wakeup_state;
-#ifdef ERTS_SMP
-    erts_smp_mtx_t mtx;
-#endif
-    erts_atomic64_t timeout_time;
+    erts_mtx_t mtx;
 };
 
-#ifdef ERTS_SMP
 
 #define ERTS_POLLSET_LOCK(PS) \
-  erts_smp_mtx_lock(&(PS)->mtx)
+  erts_mtx_lock(&(PS)->mtx)
 #define ERTS_POLLSET_UNLOCK(PS) \
-  erts_smp_mtx_unlock(&(PS)->mtx)
-
-#else
+  erts_mtx_unlock(&(PS)->mtx)
 
-#define ERTS_POLLSET_LOCK(PS)
-#define ERTS_POLLSET_UNLOCK(PS)
-
-#endif
 
 /*
  * Communication with sys_interrupt
  */
 
-#ifdef ERTS_SMP
-extern erts_smp_atomic32_t erts_break_requested;
+extern erts_atomic32_t erts_break_requested;
 #define ERTS_SET_BREAK_REQUESTED \
-  erts_smp_atomic32_set_nob(&erts_break_requested, (erts_aint32_t) 1)
+  erts_atomic32_set_nob(&erts_break_requested, (erts_aint32_t) 1)
 #define ERTS_UNSET_BREAK_REQUESTED \
-  erts_smp_atomic32_set_nob(&erts_break_requested, (erts_aint32_t) 0)
-#else
-extern volatile int erts_break_requested;
-#define ERTS_SET_BREAK_REQUESTED (erts_break_requested = 1)
-#define ERTS_UNSET_BREAK_REQUESTED (erts_break_requested = 0)
-#endif
+  erts_atomic32_set_nob(&erts_break_requested, (erts_aint32_t) 0)
 
 static erts_mtx_t break_waiter_lock;
 static HANDLE break_happened_event;
@@ -366,43 +350,23 @@ do { \
     wait_standby(PS); \
  } while(0)
 
-static ERTS_INLINE void
-init_timeout_time(ErtsPollSet ps)
-{
-    erts_atomic64_init_nob(&ps->timeout_time,
-			   (erts_aint64_t) ERTS_MONOTONIC_TIME_MAX);
-}
-
-static ERTS_INLINE void
-set_timeout_time(ErtsPollSet ps, ErtsMonotonicTime time)
-{
-    erts_atomic64_set_relb(&ps->timeout_time,
-			   (erts_aint64_t) time);
-}
-
-static ERTS_INLINE ErtsMonotonicTime
-get_timeout_time(ErtsPollSet ps)
-{
-    return (ErtsMonotonicTime) erts_atomic64_read_acqb(&ps->timeout_time);
-}
-
 #define ERTS_POLL_NOT_WOKEN		((erts_aint32_t) 0)
 #define ERTS_POLL_WOKEN_IO_READY	((erts_aint32_t) 1)
 #define ERTS_POLL_WOKEN_INTR		((erts_aint32_t) 2)
 #define ERTS_POLL_WOKEN_TIMEDOUT	((erts_aint32_t) 3)
 
 static ERTS_INLINE int
-is_io_ready(ErtsPollSet ps)
+is_io_ready(ErtsPollSet *ps)
 {
     return erts_atomic32_read_nob(&ps->wakeup_state) == ERTS_POLL_WOKEN_IO_READY;
 }
 
 static ERTS_INLINE void
-woke_up(ErtsPollSet ps)
+woke_up(ErtsPollSet *ps, int waketype)
 {
     if (erts_atomic32_read_nob(&ps->wakeup_state) == ERTS_POLL_NOT_WOKEN)
 	erts_atomic32_cmpxchg_nob(&ps->wakeup_state,
-				  ERTS_POLL_WOKEN_TIMEDOUT,
+				  waketype,
 				  ERTS_POLL_NOT_WOKEN);
 #ifdef DEBUG
     {
@@ -421,7 +385,7 @@ woke_up(ErtsPollSet ps)
 }
 
 static ERTS_INLINE int
-wakeup_cause(ErtsPollSet ps)
+wakeup_cause(ErtsPollSet *ps)
 {
     int res;
     erts_aint32_t wakeup_state = erts_atomic32_read_acqb(&ps->wakeup_state);
@@ -444,46 +408,8 @@ wakeup_cause(ErtsPollSet ps)
     return res;
 }
 
-static ERTS_INLINE DWORD
-poll_wait_timeout(ErtsPollSet ps, ErtsMonotonicTime timeout_time)
-{
-    ErtsMonotonicTime current_time, diff_time, timeout;
-
-    if (timeout_time == ERTS_POLL_NO_TIMEOUT) {
-    no_timeout:
-	set_timeout_time(ps, ERTS_MONOTONIC_TIME_MIN);
-	woke_up(ps);
-	return (DWORD) 0;
-    }
-
-    current_time = erts_get_monotonic_time(NULL);
-    diff_time = timeout_time - current_time;
-    if (diff_time <= 0)
-	goto no_timeout;
-
-    /* Round up to nearest milli second */
-    timeout = (ERTS_MONOTONIC_TO_MSEC(diff_time - 1) + 1);
-    if (timeout > INT_MAX)
-	timeout = INT_MAX; /* Also prevents DWORD overflow */
-
-    set_timeout_time(ps, current_time + ERTS_MSEC_TO_MONOTONIC(timeout));
-
-    ResetEvent(ps->event_io_ready);
-    /*
-     * Since we don't know the internals of ResetEvent() we issue
-     * a memory barrier as a safety precaution ensuring that
-     * the load of wakeup_state wont be reordered with stores made
-     * by ResetEvent().
-     */
-    ERTS_THR_MEMORY_BARRIER;
-    if (erts_atomic32_read_nob(&ps->wakeup_state) != ERTS_POLL_NOT_WOKEN)
-	return (DWORD) 0;
-
-    return (DWORD) timeout;
-}
-
 static ERTS_INLINE void
-wake_poller(ErtsPollSet ps, int io_ready)
+wake_poller(ErtsPollSet *ps, int io_ready)
 {
     erts_aint32_t wakeup_state;
     if (io_ready) {
@@ -518,13 +444,13 @@ wake_poller(ErtsPollSet ps, int io_ready)
 }
 
 static ERTS_INLINE void
-reset_io_ready(ErtsPollSet ps)
+reset_io_ready(ErtsPollSet *ps)
 {
     erts_atomic32_set_nob(&ps->wakeup_state, ERTS_POLL_NOT_WOKEN);
 }
 
 static ERTS_INLINE void
-restore_io_ready(ErtsPollSet ps)
+restore_io_ready(ErtsPollSet *ps)
 {
     erts_atomic32_set_nob(&ps->wakeup_state, ERTS_POLL_WOKEN_IO_READY);
 }
@@ -534,13 +460,13 @@ restore_io_ready(ErtsPollSet ps)
  * notifying a poller thread about I/O ready.
  */
 static ERTS_INLINE void
-notify_io_ready(ErtsPollSet ps)
+notify_io_ready(ErtsPollSet *ps)
 {
     wake_poller(ps, 1);
 }
 
 static ERTS_INLINE void
-reset_interrupt(ErtsPollSet ps)
+reset_interrupt(ErtsPollSet *ps)
 {
     /* We need to keep io-ready if set */
     erts_aint32_t wakeup_state = erts_atomic32_read_nob(&ps->wakeup_state);
@@ -557,12 +483,12 @@ reset_interrupt(ErtsPollSet ps)
 }
 
 static ERTS_INLINE void
-set_interrupt(ErtsPollSet ps)
+set_interrupt(ErtsPollSet *ps)
 {
     wake_poller(ps, 0);
 }
 
-static void setup_standby_wait(ErtsPollSet ps, int num_threads)
+static void setup_standby_wait(ErtsPollSet *ps, int num_threads)
 {
     EnterCriticalSection(&(ps->standby_crit));
     ps->standby_wait_counter = num_threads;
@@ -570,7 +496,7 @@ static void setup_standby_wait(ErtsPollSet ps, int num_threads)
     LeaveCriticalSection(&(ps->standby_crit));
 }
 
-static void signal_standby(ErtsPollSet ps) 
+static void signal_standby(ErtsPollSet *ps)
 {
     EnterCriticalSection(&(ps->standby_crit));
     --(ps->standby_wait_counter);
@@ -584,7 +510,7 @@ static void signal_standby(ErtsPollSet ps)
     LeaveCriticalSection(&(ps->standby_crit));
 }
 
-static void wait_standby(ErtsPollSet ps)
+static void wait_standby(ErtsPollSet *ps)
 {
     WaitForSingleObject(ps->standby_wait_event,INFINITE);
 }
@@ -652,7 +578,7 @@ static void consistency_check(Waiter* w)
 
 #endif
 
-static void new_waiter(ErtsPollSet ps)
+static void new_waiter(ErtsPollSet *ps)
 {
     register Waiter* w;
     DWORD tid;			/* Id for thread. */
@@ -677,7 +603,7 @@ static void new_waiter(ErtsPollSet ps)
     w->active_events = 1;
     w->highwater = 1;
     w->total_events = 1;
-    erts_mtx_init(&w->mtx, "pollwaiter");
+    erts_mtx_init(&w->mtx, "pollwaiter", NIL, ERTS_LOCK_FLAGS_CATEGORY_IO);
 
 
     /*
@@ -746,7 +672,7 @@ static void *break_waiter(void *param)
 static void *threaded_waiter(void *param)
 {
     register Waiter* w = (Waiter *) param;
-    ErtsPollSet ps = (ErtsPollSet) w->xdata;
+    ErtsPollSet *ps = (ErtsPollSet*) w->xdata;
 #ifdef HARD_POLL_DEBUG2
     HANDLE oold_fired[64];
     int num_oold_fired;
@@ -842,16 +768,16 @@ event_happened:
 	    ASSERT(WAIT_OBJECT_0 < i && i < WAIT_OBJECT_0+w->active_events);
 	    notify_io_ready(ps);
 
-	    /* 
-	     * The main thread wont start working on our arrays untill we're
-	     * stopped, so we can work in peace although the main thread runs 
+	    /*
+	     * The main thread wont start working on our arrays until we're
+	     * stopped, so we can work in peace although the main thread runs
 	     */
 	    ASSERT(i >= WAIT_OBJECT_0+1);
 	    i -= WAIT_OBJECT_0;
 	    ASSERT(i >= 1);
-	    w->active_events--;
 	    HARDDEBUGF(("i = %d, a,h,t = %d,%d,%d",i,
 			w->active_events, w->highwater, w->total_events));
+	    w->active_events--;
 #ifdef HARD_POLL_DEBUG2
 	    fired[num_fired++] = w->events[i];
 #endif
@@ -881,7 +807,7 @@ event_happened:
  * The actual adding and removing from pollset utilities 
  */
 
-static int set_driver_select(ErtsPollSet ps, HANDLE event, ErtsPollEvents mode)
+static int set_driver_select(ErtsPollSet *ps, HANDLE event, ErtsPollEvents mode)
 {
     int i;
     int best_waiter = -1;	/* The waiter with lowest number of events. */
@@ -971,13 +897,13 @@ static int set_driver_select(ErtsPollSet ps, HANDLE event, ErtsPollEvents mode)
 #endif
     erts_mtx_unlock(&w->mtx);
     START_WAITER(ps,w);
-    HARDDEBUGF(("add select %d %d %d %d",best_waiter,
+    HARDDEBUGF(("%d: add select %d %d %d %d", event, best_waiter,
 		w->active_events,w->highwater,w->total_events));
     return mode;
 }
 
 
-static int cancel_driver_select(ErtsPollSet ps, HANDLE event)
+static int cancel_driver_select(ErtsPollSet *ps, HANDLE event)
 {
     int i;
 
@@ -1032,26 +958,14 @@ static int cancel_driver_select(ErtsPollSet ps, HANDLE event)
  * Interface functions
  */
 
-void  erts_poll_interrupt(ErtsPollSet ps, int set /* bool */)
+void  erts_poll_interrupt(ErtsPollSet *ps, int set /* bool */)
 {
-    HARDTRACEF(("In erts_poll_interrupt(%d)",set));
+    HARDTRACEF(("In erts_poll_interrupt(%p, %d)",ps,set));
     if (!set)
 	reset_interrupt(ps);
     else
 	set_interrupt(ps);
-    HARDTRACEF(("Out erts_poll_interrupt(%d)",set));
-}
-
-void erts_poll_interrupt_timed(ErtsPollSet ps,
-			       int set /* bool */,
-			       ErtsMonotonicTime timeout_time)
-{
-    HARDTRACEF(("In erts_poll_interrupt_timed(%d,%ld)",set,timeout_time));
-    if (!set)
-	reset_interrupt(ps);
-    else if (get_timeout_time(ps) > timeout_time)
-	set_interrupt(ps);
-    HARDTRACEF(("Out erts_poll_interrupt_timed"));
+    HARDTRACEF(("Out erts_poll_interrupt(%p, %d)",ps,set));
 }
 
 
@@ -1060,17 +974,17 @@ void erts_poll_interrupt_timed(ErtsPollSet ps,
  * the only difference between ERTS_POLL_EV_IN and ERTS_POLL_EV_OUT
  * is which driver callback will eventually be called.
  */
-static ErtsPollEvents do_poll_control(ErtsPollSet ps,
-				      ErtsSysFdType fd,
-				      ErtsPollEvents pe,
-				      int on /* bool */)
+static ErtsPollEvents do_poll_control(ErtsPollSet *ps,
+                                      ErtsSysFdType fd,
+                                      ErtsPollOp op,
+                                      ErtsPollEvents pe)
 {
     HANDLE event = (HANDLE) fd;
     ErtsPollEvents mode;
     ErtsPollEvents result;
     ASSERT(event != INVALID_HANDLE_VALUE);
 
-    if (on) {
+    if (op != ERTS_POLL_OP_DEL) {
 	if (pe & ERTS_POLL_EV_IN || !(pe & ERTS_POLL_EV_OUT )) {
 	    mode = ERTS_POLL_EV_IN;
 	} else {
@@ -1083,51 +997,32 @@ static ErtsPollEvents do_poll_control(ErtsPollSet ps,
     return result;
 }
 
-ErtsPollEvents erts_poll_control(ErtsPollSet ps,
+ErtsPollEvents erts_poll_control(ErtsPollSet *ps,
 				 ErtsSysFdType fd,
+                                 ErtsPollOp op,
 				 ErtsPollEvents pe,
-				 int on,
 				 int* do_wake) /* In: Wake up polling thread */
 				               /* Out: Poller is woken */
 {
     ErtsPollEvents result;
-    HARDTRACEF(("In erts_poll_control(0x%08X, %u, %d)",(unsigned long) fd, (unsigned) pe, on));
+    HARDTRACEF(("In erts_poll_control(0x%08X, %s, %s)",
+                (unsigned long) fd, op2str(op), ev2str(pe)));
     ERTS_POLLSET_LOCK(ps);
-    result=do_poll_control(ps,fd,pe,on);
+    result=do_poll_control(ps, fd, op, pe);
     ERTS_POLLSET_UNLOCK(ps);
     *do_wake = 0; /* Never any need to wake polling threads on windows */
     HARDTRACEF(("Out erts_poll_control -> %u",(unsigned) result));
     return result;
 }
 
-void erts_poll_controlv(ErtsPollSet ps,
-			ErtsPollControlEntry pcev[],
-			int len)
-{
-    int i;
-    int hshur = 0;
-    int do_wake = 0;
-
-    HARDTRACEF(("In erts_poll_controlv(%d)",len));
-    ERTS_POLLSET_LOCK(ps);
-
-    for (i = 0; i < len; i++) {
-	pcev[i].events = do_poll_control(ps,
-					 pcev[i].fd,
-					 pcev[i].events,
-					 pcev[i].on);
-    }
-    ERTS_POLLSET_UNLOCK(ps);
-    HARDTRACEF(("Out erts_poll_controlv"));
-}
-
-int erts_poll_wait(ErtsPollSet ps,
+int erts_poll_wait(ErtsPollSet *ps,
 		   ErtsPollResFd pr[],
 		   int *len,
-		   ErtsMonotonicTime timeout_time)
+                   ErtsThrPrgrData *tpd,
+                   Sint64 timeout_in)
 {
     int no_fds;
-    DWORD timeout;
+    DWORD timeout = timeout_in == -1 ? INFINITE : timeout_in;
     EventData* ev;
     int res = 0;
     int num = 0;
@@ -1138,42 +1033,6 @@ int erts_poll_wait(ErtsPollSet ps,
     HARDTRACEF(("In erts_poll_wait"));
     ERTS_POLLSET_LOCK(ps);
 
-    if (!is_io_ready(ps) && ps->restore_events) {
-	HARDDEBUGF(("Restore events: %d",ps->num_waiters));
-	ps->restore_events = 0;
-	for (i = 0; i < ps->num_waiters; ++i) {
-	   Waiter* w = ps->waiter[i];
-	   erts_mtx_lock(&w->mtx);
-	   HARDDEBUGF(("Maybe reset %d %d %d %d",i,
-		       w->active_events,w->highwater,w->total_events));
-	   if (w->active_events < w->total_events) {
-	       erts_mtx_unlock(&w->mtx);
-	       STOP_WAITER(ps,w);
-	       HARDDEBUGF(("Need reset %d %d %d %d",i,
-			   w->active_events,w->highwater,w->total_events));
-	       erts_mtx_lock(&w->mtx);	       
-	       /* Need reset, just check that it doesn't have got more to tell */
-	       if (w->highwater != w->active_events) {
-		   HARDDEBUGF(("Oups!"));
-		   /* Oups, got signalled before we took the lock, can't reset */
-		   if(!is_io_ready(ps)) {
-		       erts_exit(ERTS_ERROR_EXIT,"Internal error: "
-				"Inconsistent io structures in erl_poll.\n");
-		   }
-		   START_WAITER(ps,w);
-		   erts_mtx_unlock(&w->mtx);
-		   ps->restore_events = 1; 
-		   continue;
-	       }
-	       w->active_events = w->highwater =  w->total_events;
-	       START_WAITER(ps,w);
-	       erts_mtx_unlock(&w->mtx);
-	   } else {
-	       erts_mtx_unlock(&w->mtx);
-	   }
-	}
-    }
-
     no_fds = *len;
 
 #ifdef ERTS_POLL_MAX_RES
@@ -1181,29 +1040,33 @@ int erts_poll_wait(ErtsPollSet ps,
 	no_fds = ERTS_POLL_MAX_RES;
 #endif
 
-    timeout = poll_wait_timeout(ps, timeout_time);
-
-    /*HARDDEBUGF(("timeout = %ld",(long) timeout));*/
+    ResetEvent(ps->event_io_ready);
+    /*
+     * Since we don't know the internals of ResetEvent() we issue
+     * a memory barrier as a safety precaution ensuring that
+     * the load of wakeup_state wont be reordered with stores made
+     * by ResetEvent().
+     */
+    ERTS_THR_MEMORY_BARRIER;
+    if (erts_atomic32_read_nob(&ps->wakeup_state) != ERTS_POLL_NOT_WOKEN)
+       timeout = (DWORD) 0;
 
-    if (timeout > 0 && !erts_atomic32_read_nob(&break_waiter_state)) {
+    if (!erts_atomic32_read_nob(&break_waiter_state)) {
 	HANDLE harr[2] = {ps->event_io_ready, break_happened_event};
-	int num_h = 2;
-        ERTS_MSACC_PUSH_STATE_M();
+	int num_h = 2, handle;
+        ERTS_MSACC_PUSH_STATE();
 
 	HARDDEBUGF(("Start waiting %d [%d]",num_h, (int) timeout));
 	ERTS_POLLSET_UNLOCK(ps);
-#ifdef ERTS_SMP
-	erts_thr_progress_prepare_wait(NULL);
-#endif
-        ERTS_MSACC_SET_STATE_CACHED_M(ERTS_MSACC_STATE_SLEEP);
-	WaitForMultipleObjects(num_h, harr, FALSE, timeout);
-#ifdef ERTS_SMP
-	erts_thr_progress_finalize_wait(NULL);
-#endif
-        ERTS_MSACC_POP_STATE_M();
+	erts_thr_progress_prepare_wait(tpd);
+        ERTS_MSACC_SET_STATE_CACHED(ERTS_MSACC_STATE_SLEEP);
+	handle = WaitForMultipleObjects(num_h, harr, FALSE, timeout);
+	erts_thr_progress_finalize_wait(tpd);
+        ERTS_MSACC_POP_STATE();
 	ERTS_POLLSET_LOCK(ps);
 	HARDDEBUGF(("Stop waiting %d [%d]",num_h, (int) timeout));
-	woke_up(ps);
+        if (handle == WAIT_OBJECT_0)
+            woke_up(ps, ERTS_POLL_WOKEN_TIMEDOUT);
     }
 
     ERTS_UNSET_BREAK_REQUESTED;
@@ -1215,7 +1078,10 @@ int erts_poll_wait(ErtsPollSet ps,
 	erts_mtx_unlock(&break_waiter_lock);
 	switch (break_state) {
 	case  BREAK_WAITER_GOT_BREAK:
+            woke_up(ps, ERTS_POLL_WOKEN_INTR);
 	    ERTS_SET_BREAK_REQUESTED;
+            /* Wake aux thread to get handle break */
+            erts_aux_thread_poke();
 	    break;
 	case  BREAK_WAITER_GOT_HALT:
 	    erts_exit(0,"");
@@ -1233,7 +1099,7 @@ int erts_poll_wait(ErtsPollSet ps,
 
     reset_io_ready(ps);
 
-    n = ps->num_waiters;	
+    n = ps->num_waiters;
 
     for (i = 0; i < n; i++) {
 	Waiter* w = ps->waiter[i];
@@ -1259,11 +1125,10 @@ int erts_poll_wait(ErtsPollSet ps,
 		HARDDEBUGF(("To many FD's to report!"));
 		goto done;
 	    }
-	    HARDDEBUGF(("SET! Restore events"));
-	    ps->restore_events = 1;
 	    HARDDEBUGF(("Report %d,%d",i,j));
-	    pr[num].fd = (ErtsSysFdType) w->events[j];
-	    pr[num].events = w->evdata[j]->mode;
+	    ERTS_POLL_RES_SET_FD(&pr[num], w->events[j]);
+	    ERTS_POLL_RES_SET_EVTS(&pr[num], w->evdata[j]->mode);
+            remove_event_from_set(w, j);
 #ifdef HARD_POLL_DEBUG
 	    poll_debug_reported(w->events[j],w->highwater | (j << 16));
 	    poll_debug_reported(w->events[j],first | (last << 16));
@@ -1271,13 +1136,14 @@ int erts_poll_wait(ErtsPollSet ps,
 	    ++num;
 	}
 
+        w->total_events = w->highwater = w->active_events;
+
 #ifdef DEBUG
 	consistency_check(w);
 #endif
 	erts_mtx_unlock(&w->mtx);
     }
  done:
-    set_timeout_time(ps, ERTS_MONOTONIC_TIME_MAX);
     *len = num;
     ERTS_POLLSET_UNLOCK(ps);
     HARDTRACEF(("Out erts_poll_wait"));
@@ -1292,7 +1158,7 @@ int erts_poll_max_fds(void)
     return res;
 }
 
-void erts_poll_info(ErtsPollSet ps,
+void erts_poll_info(ErtsPollSet *ps,
 		    ErtsPollInfo *pip)
 {
     Uint size = 0;
@@ -1302,7 +1168,7 @@ void erts_poll_info(ErtsPollSet ps,
     HARDTRACEF(("In erts_poll_info"));
     ERTS_POLLSET_LOCK(ps);
 
-    size += sizeof(struct ErtsPollSet_);
+    size += sizeof(struct erts_pollset);
     size += sizeof(Waiter *) * ps->allocated_waiters;
     for (i = 0; i < ps->num_waiters; ++i) {
 	Waiter *w = ps->waiter[i];
@@ -1317,16 +1183,12 @@ void erts_poll_info(ErtsPollSet ps,
 
     pip->primary = "WaitForMultipleObjects"; 
 
-    pip->fallback = NULL;
-
     pip->kernel_poll = NULL;
 
     pip->memory_size = size;
 
     pip->poll_set_size = num_events;
 
-    pip->fallback_poll_set_size = 0;
-
     pip->lazy_updates = 0;
 
     pip->pending_updates = 0;
@@ -1334,6 +1196,8 @@ void erts_poll_info(ErtsPollSet ps,
     pip->batch_updates = 0;
 
     pip->concurrent_updates = 0;
+
+    pip->is_fallback = 0;
     ERTS_POLLSET_UNLOCK(ps);
 
     pip->max_fds = erts_poll_max_fds();
@@ -1341,10 +1205,10 @@ void erts_poll_info(ErtsPollSet ps,
 
 }
 
-ErtsPollSet erts_poll_create_pollset(void)
+ErtsPollSet *erts_poll_create_pollset(int no)
 {
-    ErtsPollSet ps = SEL_ALLOC(ERTS_ALC_T_POLLSET,
-			       sizeof(struct ErtsPollSet_));
+    ErtsPollSet *ps = SEL_ALLOC(ERTS_ALC_T_POLLSET,
+			       sizeof(struct erts_pollset));
     HARDTRACEF(("In erts_poll_create_pollset"));
 
     ps->num_waiters = 0;
@@ -1355,19 +1219,15 @@ ErtsPollSet erts_poll_create_pollset(void)
     ps->standby_wait_counter = 0;
     ps->event_io_ready = CreateManualEvent(FALSE);
     ps->standby_wait_event = CreateManualEvent(FALSE); 
-    ps->restore_events = 0;
 
     erts_atomic32_init_nob(&ps->wakeup_state, ERTS_POLL_NOT_WOKEN);
-#ifdef ERTS_SMP
-    erts_smp_mtx_init(&ps->mtx, "pollset");
-#endif
-    init_timeout_time(ps);
+    erts_mtx_init(&ps->mtx, "pollset", NIL, ERTS_LOCK_FLAGS_CATEGORY_IO);
 
     HARDTRACEF(("Out erts_poll_create_pollset"));
     return ps;
 }
 
-void erts_poll_destroy_pollset(ErtsPollSet ps)
+void erts_poll_destroy_pollset(ErtsPollSet *ps)
 {
     int i;
     HARDTRACEF(("In erts_poll_destroy_pollset"));
@@ -1390,9 +1250,7 @@ void erts_poll_destroy_pollset(ErtsPollSet ps)
     CloseHandle(ps->event_io_ready);
     CloseHandle(ps->standby_wait_event);
     ERTS_POLLSET_UNLOCK(ps);
-#ifdef ERTS_SMP
-    erts_smp_mtx_destroy(&ps->mtx);
-#endif
+    erts_mtx_destroy(&ps->mtx);
     SEL_FREE(ERTS_ALC_T_POLLSET, (void *) ps);
     HARDTRACEF(("Out erts_poll_destroy_pollset"));
 }
@@ -1400,36 +1258,44 @@ void erts_poll_destroy_pollset(ErtsPollSet ps)
 /*
  * Actually mostly initializes the friend module sys_interrupt...
  */
-void  erts_poll_init(void)
+void  erts_poll_init(int *concurrent_updates)
 {
-    erts_tid_t thread;
 
 #ifdef HARD_POLL_DEBUG
     poll_debug_init();
 #endif
 
+    if (concurrent_updates)
+        *concurrent_updates = 0;
+
     HARDTRACEF(("In erts_poll_init"));
     erts_sys_break_event = CreateManualEvent(FALSE);
 
-    erts_mtx_init(&break_waiter_lock,"break_waiter_lock");
+    erts_mtx_init(&break_waiter_lock, "break_waiter_lock", NIL,
+        ERTS_LOCK_FLAGS_PROPERTY_STATIC | ERTS_LOCK_FLAGS_CATEGORY_IO);
     break_happened_event = CreateManualEvent(FALSE);
     erts_atomic32_init_nob(&break_waiter_state, 0); 
 
+    HARDTRACEF(("Out erts_poll_init"));
+}
+
+void erts_poll_late_init(void)
+{
+    erts_tid_t thread;
     erts_thr_create(&thread, &break_waiter, NULL, NULL);
     ERTS_UNSET_BREAK_REQUESTED;
-    HARDTRACEF(("Out erts_poll_init"));
 }
 
 /*
  * Non windows friendly interface, not used when fd's are not continous
  */
-void  erts_poll_get_selected_events(ErtsPollSet ps,
+void  erts_poll_get_selected_events(ErtsPollSet *ps,
 				    ErtsPollEvents ev[],
 				    int len)
 {
     int i;
     HARDTRACEF(("In erts_poll_get_selected_events"));
     for (i = 0; i < len; ++i)
-	ev[i] = 0;
+	ev[i] = ERTS_POLL_EV_NONE;
     HARDTRACEF(("Out erts_poll_get_selected_events"));
 }
diff --git a/erts/emulator/sys/win32/erl_win32_sys_ddll.c b/erts/emulator/sys/win32/erl_win32_sys_ddll.c
index 274133a346..7fe1f5cc78 100644
--- a/erts/emulator/sys/win32/erl_win32_sys_ddll.c
+++ b/erts/emulator/sys/win32/erl_win32_sys_ddll.c
@@ -1,7 +1,7 @@
 /*
  * %CopyrightBegin%
  * 
- * Copyright Ericsson AB 2006-2016. All Rights Reserved.
+ * Copyright Ericsson AB 2006-2018. All Rights Reserved.
  * 
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -46,9 +46,17 @@ static TWinDynDriverCallbacks wddc;
 static TWinDynNifCallbacks nif_callbacks;
 
 void erl_sys_ddll_init(void) {
+    WCHAR cwd_buffer[MAX_PATH];
+
     tls_index = TlsAlloc();
     ERL_INIT_CALLBACK_STRUCTURE(wddc);
 
+    /* LOAD_WITH_ALTERED_SEARCH_PATH removes the startup directory from the
+     * search path, so we add it separately to be backwards compatible. */
+    if (GetCurrentDirectoryW(sizeof(cwd_buffer), cwd_buffer)) {
+        SetDllDirectoryW(cwd_buffer);
+    }
+
 #define ERL_NIF_API_FUNC_DECL(RET,NAME,ARGS) nif_callbacks.NAME = NAME
 #include "erl_nif_api_funcs.h"
 #undef ERL_NIF_API_FUNC_DECL
@@ -81,7 +89,10 @@ int erts_sys_ddll_open(const char *full_name, void **handle, ErtsSysDdllError* e
 						   ERTS_ALC_T_TMP, &used, EXT_LEN);
     wcscpy(&wcp[used/2 - 1], FILE_EXT_WCHAR);
 
-    if ((hinstance = LoadLibraryW(wcp)) == NULL) {
+    /* LOAD_WITH_ALTERED_SEARCH_PATH adds the specified DLL's directory to the
+     * dependency search path. This also removes the directory we started in,
+     * but we've explicitly added that in in erl_sys_ddll_init. */
+    if ((hinstance = LoadLibraryExW(wcp, NULL, LOAD_WITH_ALTERED_SEARCH_PATH)) == NULL) {
 	code = ERL_DE_DYNAMIC_ERROR_OFFSET - GetLastError();
 	if (err != NULL) {
 	    err->str = erts_sys_ddll_error(code);
diff --git a/erts/emulator/sys/win32/erl_win_dyn_driver.h b/erts/emulator/sys/win32/erl_win_dyn_driver.h
index 6f28d513c2..c683e8cf49 100644
--- a/erts/emulator/sys/win32/erl_win_dyn_driver.h
+++ b/erts/emulator/sys/win32/erl_win_dyn_driver.h
@@ -1,7 +1,7 @@
 /*
  * %CopyrightBegin%
  * 
- * Copyright Ericsson AB 2003-2016. All Rights Reserved.
+ * Copyright Ericsson AB 2003-2018. All Rights Reserved.
  * 
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -40,7 +40,6 @@ WDD_TYPEDEF(int, driver_exit, (ErlDrvPort, int));
 WDD_TYPEDEF(int, driver_failure_eof, (ErlDrvPort));
 WDD_TYPEDEF(void, erl_drv_busy_msgq_limits, (ErlDrvPort, ErlDrvSizeT *, ErlDrvSizeT *));
 WDD_TYPEDEF(int, driver_select, (ErlDrvPort, ErlDrvEvent, int, int));
-WDD_TYPEDEF(int, driver_event, (ErlDrvPort, ErlDrvEvent,ErlDrvEventData));
 WDD_TYPEDEF(int, driver_output, (ErlDrvPort, char *, ErlDrvSizeT));
 WDD_TYPEDEF(int, driver_output2, (ErlDrvPort, char *, ErlDrvSizeT ,char *, ErlDrvSizeT));
 WDD_TYPEDEF(int, driver_output_binary, (ErlDrvPort, char *, ErlDrvSizeT, ErlDrvBinary*, ErlDrvSizeT, ErlDrvSizeT));
@@ -162,7 +161,7 @@ typedef struct {
     WDD_FTYPE(driver_failure_eof) *driver_failure_eof;
     WDD_FTYPE(erl_drv_busy_msgq_limits) *erl_drv_busy_msgq_limits;
     WDD_FTYPE(driver_select) *driver_select;
-    WDD_FTYPE(driver_event) *driver_event;
+    void *REMOVED_driver_event;
     WDD_FTYPE(driver_output) *driver_output;
     WDD_FTYPE(driver_output2) *driver_output2;
     WDD_FTYPE(driver_output_binary) *driver_output_binary;
@@ -276,7 +275,6 @@ extern TWinDynDriverCallbacks WinDynDriverCallbacks;
 #define driver_failure_eof (WinDynDriverCallbacks.driver_failure_eof)
 #define erl_drv_busy_msgq_limits (WinDynDriverCallbacks.erl_drv_busy_msgq_limits)
 #define driver_select (WinDynDriverCallbacks.driver_select)
-#define driver_event (WinDynDriverCallbacks.driver_event)
 #define driver_output (WinDynDriverCallbacks.driver_output)
 #define driver_output2 (WinDynDriverCallbacks.driver_output2)
 #define driver_output_binary (WinDynDriverCallbacks.driver_output_binary)
@@ -414,7 +412,7 @@ do {				                        \
 ((W).driver_failure_eof) = driver_failure_eof;		\
 ((W).erl_drv_busy_msgq_limits) = erl_drv_busy_msgq_limits;\
 ((W).driver_select) = driver_select;			\
-((W).driver_event) = driver_event;			\
+((W).REMOVED_driver_event) = NULL;			\
 ((W).driver_output) = driver_output;			\
 ((W).driver_output2) = driver_output2;			\
 ((W).driver_output_binary) = driver_output_binary;	\
diff --git a/erts/emulator/sys/win32/erl_win_sys.h b/erts/emulator/sys/win32/erl_win_sys.h
index 04fbf23109..b00ba287e2 100644
--- a/erts/emulator/sys/win32/erl_win_sys.h
+++ b/erts/emulator/sys/win32/erl_win_sys.h
@@ -1,7 +1,7 @@
 /*
  * %CopyrightBegin%
  * 
- * Copyright Ericsson AB 1997-2016. All Rights Reserved.
+ * Copyright Ericsson AB 1997-2018. All Rights Reserved.
  * 
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -182,6 +182,8 @@ typedef LONGLONG ErtsMonotonicTime;
 typedef LONGLONG ErtsSysHrTime;
 #endif
 
+#define ErtsStrToSint64 _strtoi64
+
 typedef ErtsMonotonicTime ErtsSystemTime;
 typedef ErtsMonotonicTime ErtsSysPerfCounter;
 
@@ -309,10 +311,8 @@ typedef long ssize_t;
 #endif
 
 /* Threads */
-#ifdef USE_THREADS
 int init_async(int);
 int exit_async(void);
-#endif
 
 #define ERTS_HAVE_TRY_CATCH 1
 
diff --git a/erts/emulator/sys/win32/sys.c b/erts/emulator/sys/win32/sys.c
index cf821b05cb..a1c630d68a 100644
--- a/erts/emulator/sys/win32/sys.c
+++ b/erts/emulator/sys/win32/sys.c
@@ -1,7 +1,7 @@
 /*
  * %CopyrightBegin%
  *
- * Copyright Ericsson AB 1996-2016. All Rights Reserved.
+ * Copyright Ericsson AB 1996-2017. All Rights Reserved.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -40,7 +40,6 @@ void erts_sys_init_float(void);
 void erl_start(int, char**);
 void erts_exit(int n, char*, ...);
 void erl_error(char*, va_list);
-void erl_crash_dump(char*, int, char*, ...);
 
 /*
  * Microsoft-specific function to map a WIN32 error code to a Posix errno.
@@ -78,14 +77,13 @@ static int create_pipe(LPHANDLE, LPHANDLE, BOOL, BOOL);
 static int application_type(const wchar_t* originalName, wchar_t fullPath[MAX_PATH],
 			   BOOL search_in_path, BOOL handle_quotes,
 			   int *error_return);
+static void *build_env_block(const erts_osenv_t *env);
 
 HANDLE erts_service_event;
 
-#ifdef ERTS_SMP
-static erts_smp_tsd_key_t win32_errstr_key;
-#endif
+static erts_tsd_key_t win32_errstr_key;
 
-static erts_smp_atomic_t pipe_creation_counter;
+static erts_atomic_t pipe_creation_counter;
 
 /* Results from application_type(_w) is one of */
 #define APPL_NONE 0
@@ -95,10 +93,8 @@ static erts_smp_atomic_t pipe_creation_counter;
 
 static int driver_write(long, HANDLE, byte*, int);
 static int create_file_thread(struct async_io* aio, int mode);
-#ifdef ERTS_SMP
 static void close_active_handle(DriverData *, HANDLE handle);
 static DWORD WINAPI threaded_handle_closer(LPVOID param);
-#endif
 static DWORD WINAPI threaded_reader(LPVOID param);
 static DWORD WINAPI threaded_writer(LPVOID param);
 static DWORD WINAPI threaded_exiter(LPVOID param);
@@ -137,7 +133,7 @@ static OSVERSIONINFO int_os_version;	/* Version information for Win32. */
     Disabled the use of CancelIoEx as its been seen to cause problem with some
     drivers. Not sure what to blame; faulty drivers or some form of invalid use.
 */
-#if defined(ERTS_SMP) && defined(USE_CANCELIOEX)
+#if defined(USE_CANCELIOEX)
 static BOOL (WINAPI *fpCancelIoEx)(HANDLE,LPOVERLAPPED);
 #endif
 
@@ -146,7 +142,7 @@ static BOOL (WINAPI *fpCancelIoEx)(HANDLE,LPOVERLAPPED);
    - call erl_start() to parse arguments and do other init
 */
 
-static erts_smp_atomic_t sys_misc_mem_sz;
+static erts_atomic_t sys_misc_mem_sz;
 
 HMODULE beam_module = NULL;
 
@@ -187,11 +183,17 @@ void sys_primitive_init(HMODULE beam)
     beam_module = (HMODULE) beam;
 }
 
+UWord
+erts_sys_get_page_size(void)
+{
+    return (UWord) 4*1024; /* Guess 4 KB */
+}
+
 Uint
 erts_sys_misc_mem_sz(void)
 {
     Uint res = (Uint) erts_check_io_size();
-    res += (Uint) erts_smp_atomic_read_mb(&sys_misc_mem_sz);
+    res += (Uint) erts_atomic_read_mb(&sys_misc_mem_sz);
     return res;
 }
 
@@ -295,6 +297,10 @@ int erts_sys_prepare_crash_dump(int secs)
     return 0;
 }
 
+int erts_set_signal(Eterm signal, Eterm type) {
+    return 0;
+}
+
 static void
 init_console(void)
 {
@@ -441,9 +447,7 @@ typedef struct async_io {
 				 * the console for Windows NT).
 				 */
   HANDLE fd;			/* Handle for file or pipe. */
-#ifdef ERTS_SMP
   int async_io_active;          /* if true, a close of the file will signal the event in ov */
-#endif
   OVERLAPPED ov;		/* Control structure for overlapped reading.
 				 * When overlapped reading is simulated with
 				 * a thread, the fields are used as follows:
@@ -493,7 +497,7 @@ struct driver_data {
     int outBufSize;		/* Size of output buffer. */
     byte *outbuf;		/* Buffer to use for overlapped write. */
     ErlDrvPort port_num;	/* The port handle. */
-    int packet_bytes;		/* 0: continous stream, 1, 2, or 4: the number
+    int packet_bytes;		/* 0: continuous stream, 1, 2, or 4: the number
 				 * of bytes in the packet header.
 				 */
     HANDLE port_pid;		/* PID of the port process. */
@@ -656,7 +660,7 @@ new_driver_data(ErlDrvPort port_num, int packet_bytes, int wait_objs_required, i
     dp->inbuf = DRV_BUF_ALLOC(dp->inBufSize);
     if (dp->inbuf == NULL)
 	goto buf_alloc_error;
-    erts_smp_atomic_add_nob(&sys_misc_mem_sz, dp->inBufSize);
+    erts_atomic_add_nob(&sys_misc_mem_sz, dp->inBufSize);
     dp->outBufSize = 0;
     dp->outbuf = NULL;
     dp->port_num = port_num;
@@ -682,7 +686,6 @@ buf_alloc_error:
 static void
 release_driver_data(DriverData* dp)
 {
-#ifdef ERTS_SMP
 #ifdef USE_CANCELIOEX
     if (fpCancelIoEx != NULL) {
 	if (dp->in.thread == (HANDLE) -1 && dp->in.fd != INVALID_HANDLE_VALUE) {
@@ -725,18 +728,10 @@ release_driver_data(DriverData* dp)
 	    DEBUGF(("...done\n"));
 	}
     }
-#else
-	if (dp->in.thread == (HANDLE) -1 && dp->in.fd != INVALID_HANDLE_VALUE) {
-	     CancelIo(dp->in.fd); 
-	}
-	if (dp->out.thread == (HANDLE) -1 && dp->out.fd != INVALID_HANDLE_VALUE) {
-	    CancelIo(dp->out.fd); 
-	}
-#endif
 
     if (dp->inbuf != NULL) {
-	ASSERT(erts_smp_atomic_read_nob(&sys_misc_mem_sz) >= dp->inBufSize);
-	erts_smp_atomic_add_nob(&sys_misc_mem_sz, -1*dp->inBufSize);
+	ASSERT(erts_atomic_read_nob(&sys_misc_mem_sz) >= dp->inBufSize);
+	erts_atomic_add_nob(&sys_misc_mem_sz, -1*dp->inBufSize);
 	DRV_BUF_FREE(dp->inbuf);
 	dp->inBufSize = 0;
 	dp->inbuf = NULL;
@@ -744,8 +739,8 @@ release_driver_data(DriverData* dp)
     ASSERT(dp->inBufSize == 0);
 
     if (dp->outbuf != NULL) {
-	ASSERT(erts_smp_atomic_read_nob(&sys_misc_mem_sz) >= dp->outBufSize);
-	erts_smp_atomic_add_nob(&sys_misc_mem_sz, -1*dp->outBufSize);
+	ASSERT(erts_atomic_read_nob(&sys_misc_mem_sz) >= dp->outBufSize);
+	erts_atomic_add_nob(&sys_misc_mem_sz, -1*dp->outBufSize);
 	DRV_BUF_FREE(dp->outbuf);
 	dp->outBufSize = 0;
 	dp->outbuf = NULL;
@@ -768,7 +763,6 @@ release_driver_data(DriverData* dp)
     unrefer_driver_data(dp);
 }
 
-#ifdef ERTS_SMP
 
 struct handles_to_be_closed {
     HANDLE handles[MAXIMUM_WAIT_OBJECTS];
@@ -861,7 +855,6 @@ threaded_handle_closer(LPVOID param)
     DEBUGF(("threaded_handle_closer %p terminating\r\n", htbc));
     return 0;
 }
-#endif /* ERTS_SMP */
 
 /*
  * Stores input and output file descriptors in the DriverData structure,
@@ -937,9 +930,7 @@ init_async_io(DriverData *dp, AsyncIo* aio, int use_threads)
     aio->flushReplyEvent = NULL;
     aio->pendingError = 0;
     aio->bytesTransferred = 0;
-#ifdef ERTS_SMP
     aio->async_io_active = 0;
-#endif
     aio->ov.hEvent = CreateManualEvent(FALSE);
     if (aio->ov.hEvent == NULL)
 	return -1;
@@ -1020,9 +1011,7 @@ async_read_file(AsyncIo* aio, LPVOID buf, DWORD numToRead)
 	ResetEvent(aio->ov.hEvent);
 	SetEvent(aio->ioAllowed);
     } else {
-#ifdef ERTS_SMP
 	aio->async_io_active = 1; /* Will get 0 when the event actually happened */
-#endif
 	if (ReadFile(aio->fd, buf, numToRead,
 		     &aio->bytesTransferred, &aio->ov)) {
 	    DEBUGF(("async_read_file: ReadFile() suceeded: %d bytes\n",
@@ -1070,16 +1059,12 @@ async_write_file(AsyncIo* aio,		/* Pointer to async control block. */
 	ResetEvent(aio->ov.hEvent);
 	SetEvent(aio->ioAllowed);
     } else {
-#ifdef ERTS_SMP
 	aio->async_io_active = 1; /* Will get 0 when the event actually happened */
-#endif
 	if (WriteFile(aio->fd, buf, numToWrite,
 		      &aio->bytesTransferred, &aio->ov)) {
 	    DEBUGF(("async_write_file: WriteFile() suceeded: %d bytes\n",
 		    aio->bytesTransferred));
-#ifdef ERTS_SMP
 	    aio->async_io_active = 0; /* The event will not be signalled */
-#endif
 	    ResetEvent(aio->ov.hEvent);
 	    return TRUE;
 	} else {
@@ -1181,7 +1166,7 @@ static int
 spawn_init(void)
 {
     int i;
-#if defined(ERTS_SMP) && defined(USE_CANCELIOEX)
+#if defined(USE_CANCELIOEX)
     HMODULE module = GetModuleHandle("kernel32");
     fpCancelIoEx = (BOOL (WINAPI *)(HANDLE,LPOVERLAPPED))
 	((module != NULL) ? GetProcAddress(module,"CancelIoEx") : NULL);
@@ -1206,7 +1191,6 @@ spawn_start(ErlDrvPort port_num, char* utf8_name, SysDriverOpts* opts)
     int ok;
     int neededSelects = 0;
     SECURITY_ATTRIBUTES sa = {sizeof(SECURITY_ATTRIBUTES), NULL, TRUE};
-    char* envir = opts->envir;
     int errno_return = -1;
     wchar_t *name;
     int len;
@@ -1281,29 +1265,33 @@ spawn_start(ErlDrvPort port_num, char* utf8_name, SysDriverOpts* opts)
 	name[i] = L'\0';
     }
     DEBUGF(("Spawning \"%S\"\n", name));
-    envir = win_build_environment(envir); /* Always a unicode environment */ 
-    ok = create_child_process(name,
-			      hChildStdin,
-			      hChildStdout,
-			      hChildStderr,
-			      &dp->port_pid,
-			      &pid,
-			      opts->hide_window,
-			      (LPVOID) envir,
-			      (wchar_t *) opts->wd,
-			      opts->spawn_type,
-			      (wchar_t **) opts->argv,
-			      &errno_return);
-    CloseHandle(hChildStdin);
-    CloseHandle(hChildStdout);
-    if (close_child_stderr && hChildStderr != INVALID_HANDLE_VALUE &&
-	hChildStderr != 0) {
-	CloseHandle(hChildStderr);
-    }
-    erts_free(ERTS_ALC_T_TMP, name);
-
-    if (envir != NULL) {
-	erts_free(ERTS_ALC_T_ENVIRONMENT, envir);
+
+    {
+        void *environment_block = build_env_block(&opts->envir);
+
+        ok = create_child_process(name,
+                                  hChildStdin,
+                                  hChildStdout,
+                                  hChildStderr,
+                                  &dp->port_pid,
+                                  &pid,
+                                  opts->hide_window,
+                                  environment_block,
+                                  (wchar_t *) opts->wd,
+                                  opts->spawn_type,
+                                  (wchar_t **) opts->argv,
+                                  &errno_return);
+
+        CloseHandle(hChildStdin);
+        CloseHandle(hChildStdout);
+
+        if (close_child_stderr && hChildStderr != INVALID_HANDLE_VALUE &&
+            hChildStderr != 0) {
+            CloseHandle(hChildStderr);
+        }
+
+        erts_free(ERTS_ALC_T_TMP, environment_block);
+        erts_free(ERTS_ALC_T_TMP, name);
     }
 
     if (!ok) {
@@ -1354,6 +1342,41 @@ spawn_start(ErlDrvPort port_num, char* utf8_name, SysDriverOpts* opts)
     return retval;
 }
 
+struct __build_env_state {
+    WCHAR *next_variable;
+};
+
+static void build_env_foreach(void *_state, const erts_osenv_data_t *key,
+                              const erts_osenv_data_t *value)
+{
+    struct __build_env_state *state = (struct __build_env_state*)(_state);
+
+    sys_memcpy(state->next_variable, key->data, key->length);
+    state->next_variable += (int)key->length / sizeof(WCHAR);
+    *state->next_variable++ = L'=';
+
+    sys_memcpy(state->next_variable, value->data, value->length);
+    state->next_variable += (int)value->length / sizeof(WCHAR);
+    *state->next_variable++ = L'\0';
+}
+
+/* Builds an environment block suitable for CreateProcessW. */
+static void *build_env_block(const erts_osenv_t *env) {
+    struct __build_env_state build_state;
+    WCHAR *env_block;
+
+    env_block = erts_alloc(ERTS_ALC_T_TMP, env->content_size +
+        (env->variable_count * sizeof(L"=\0") + sizeof(L'\0')));
+
+    build_state.next_variable = env_block;
+
+    erts_osenv_foreach_native(env, &build_state, build_env_foreach);
+
+    (*build_state.next_variable) = L'\0';
+
+    return env_block;
+}
+
 static int
 create_file_thread(AsyncIo* aio, int mode)
 {
@@ -1424,7 +1447,7 @@ int parse_command(wchar_t* cmd){
  *
  * If new == NULL we just calculate the length.
  *
- * The reason for having to quote all of the is becasue CreateProcessW removes
+ * The reason for having to quote all of the is because CreateProcessW removes
  * one level of escaping since it takes a single long command line rather
  * than the argument chunks that unix uses.
  */
@@ -1753,7 +1776,7 @@ static int create_pipe(HANDLE *phRead, HANDLE *phWrite, BOOL inheritRead, BOOL o
      * Otherwise, create named pipes.
      */
 
-    calls = (UWord) erts_smp_atomic_inc_read_nob(&pipe_creation_counter);
+    calls = (UWord) erts_atomic_inc_read_nob(&pipe_creation_counter);
     erts_snprintf(pipe_name, sizeof(pipe_name),
 		  "\\\\.\\pipe\\erlang44_%d_%bpu", getpid(), calls);
 
@@ -2438,7 +2461,7 @@ output(ErlDrvData drv_data, char* buf, ErlDrvSizeT len)
     }
 
     dp->outBufSize = pb+len;
-    erts_smp_atomic_add_nob(&sys_misc_mem_sz, dp->outBufSize);
+    erts_atomic_add_nob(&sys_misc_mem_sz, dp->outBufSize);
 
     /*
      * Store header bytes (if any).
@@ -2467,8 +2490,8 @@ output(ErlDrvData drv_data, char* buf, ErlDrvSizeT len)
     } else {
 	dp->out.ov.Offset += pb+len; /* For vanilla driver. */
 	/* XXX OffsetHigh should be changed too. */
-	ASSERT(erts_smp_atomic_read_nob(&sys_misc_mem_sz) >= dp->outBufSize);
-	erts_smp_atomic_add_nob(&sys_misc_mem_sz, -1*dp->outBufSize);
+	ASSERT(erts_atomic_read_nob(&sys_misc_mem_sz) >= dp->outBufSize);
+	erts_atomic_add_nob(&sys_misc_mem_sz, -1*dp->outBufSize);
 	DRV_BUF_FREE(dp->outbuf);
 	dp->outBufSize = 0;
 	dp->outbuf = NULL;
@@ -2483,7 +2506,7 @@ output(ErlDrvData drv_data, char* buf, ErlDrvSizeT len)
  *	event object has been signaled, indicating that there is
  *	something to read on the corresponding file handle.
  *
- *	If the port is working in the continous stream mode (packet_bytes == 0),
+ *	If the port is working in the continuous stream mode (packet_bytes == 0),
  *	whatever data read will be sent straight to Erlang.
  *
  * Results:
@@ -2502,11 +2525,9 @@ ready_input(ErlDrvData drv_data, ErlDrvEvent ready_event)
     int pb;
 
     pb = dp->packet_bytes;
-#ifdef ERTS_SMP
     if(dp->in.thread == (HANDLE) -1) {
 	dp->in.async_io_active = 0;
     }
-#endif
     DEBUGF(("ready_input: dp %p, event 0x%x\n", dp, ready_event));
 
     /*
@@ -2524,7 +2545,7 @@ ready_input(ErlDrvData drv_data, ErlDrvEvent ready_event)
 #endif
 
     if (error == NO_ERROR) {
-	if (pb == 0) { /* Continous stream. */
+	if (pb == 0) { /* Continuous stream. */
 #ifdef DEBUG
 	    DEBUGF(("ready_input: %d: ", bytesRead));
 	    erl_bin_write(dp->inbuf, 16, bytesRead);
@@ -2581,8 +2602,8 @@ ready_input(ErlDrvData drv_data, ErlDrvEvent ready_event)
 			    error = ERROR_NOT_ENOUGH_MEMORY;
 			    break; /* Break out of loop into error handler. */
 			}
-			ASSERT(erts_smp_atomic_read_nob(&sys_misc_mem_sz) >= dp->inBufSize);
-			erts_smp_atomic_add_nob(&sys_misc_mem_sz,
+			ASSERT(erts_atomic_read_nob(&sys_misc_mem_sz) >= dp->inBufSize);
+			erts_atomic_add_nob(&sys_misc_mem_sz,
 						dp->totalNeeded - dp->inBufSize);
 			dp->inBufSize = dp->totalNeeded;
 			dp->inbuf = new_buf;
@@ -2671,11 +2692,9 @@ ready_output(ErlDrvData drv_data, ErlDrvEvent ready_event)
     DriverData *dp = (DriverData *) drv_data;
     int error;
 
-#ifdef ERTS_SMP
     if(dp->out.thread == (HANDLE) -1) {
 	dp->out.async_io_active = 0;
     }
-#endif
     DEBUGF(("ready_output(%p, 0x%x)\n", drv_data, ready_event));
     set_busy_port(dp->port_num, 0);
     if (!(dp->outbuf)) {
@@ -2683,8 +2702,8 @@ ready_output(ErlDrvData drv_data, ErlDrvEvent ready_event)
 	   write... */
 	return;
     }
-    ASSERT(erts_smp_atomic_read_nob(&sys_misc_mem_sz) >= dp->outBufSize);
-    erts_smp_atomic_add_nob(&sys_misc_mem_sz, -1*dp->outBufSize);
+    ASSERT(erts_atomic_read_nob(&sys_misc_mem_sz) >= dp->outBufSize);
+    erts_atomic_add_nob(&sys_misc_mem_sz, -1*dp->outBufSize);
     DRV_BUF_FREE(dp->outbuf);
     dp->outBufSize = 0;
     dp->outbuf = NULL;
@@ -2734,7 +2753,6 @@ sys_init_io(void)
     max_files = 2*erts_ptab_max(&erts_port);
 }
 
-#ifdef ERTS_SMP
 void
 erts_sys_main_thread(void)
 {
@@ -2747,7 +2765,6 @@ erts_sys_main_thread(void)
 	WaitForSingleObject(dummy, INFINITE);
     }
 }
-#endif
 
 void erts_sys_alloc_init(void)
 {
@@ -2834,7 +2851,7 @@ Preload* sys_preloaded(void)
 			   (num_preloaded+1)*sizeof(Preload));
     res_name = erts_alloc(ERTS_ALC_T_PRELOADED,
 			  (num_preloaded+1)*sizeof(unsigned));
-    erts_smp_atomic_add_nob(&sys_misc_mem_sz,
+    erts_atomic_add_nob(&sys_misc_mem_sz,
 			    (num_preloaded+1)*sizeof(Preload)
 			    + (num_preloaded+1)*sizeof(unsigned));
     for (i = 0; i < num_preloaded; i++) {
@@ -2847,7 +2864,7 @@ Preload* sys_preloaded(void)
 	n = GETWORD(data);
 	data += 2;
 	preloaded[i].name = erts_alloc(ERTS_ALC_T_PRELOADED, n+1);
-	erts_smp_atomic_add_nob(&sys_misc_mem_sz, n+1);
+	erts_atomic_add_nob(&sys_misc_mem_sz, n+1);
 	sys_memcpy(preloaded[i].name, data, n);
 	preloaded[i].name[n] = '\0';
 	data += n;
@@ -2929,11 +2946,7 @@ sys_get_key(int fd)
 
 char* win32_errorstr(int error)
 {
-#ifdef SMP
-  LPTSTR lpBufPtr = erts_smp_tsd_get(win32_errstr_key);
-#else
-  static LPTSTR lpBufPtr = NULL;
-#endif
+  LPTSTR lpBufPtr = erts_tsd_get(win32_errstr_key);
   if (lpBufPtr) {
       LocalFree(lpBufPtr);
   }
@@ -2947,9 +2960,7 @@ char* win32_errorstr(int error)
 		0,
 		NULL);
   SetLastError(error);
-#ifdef ERTS_SMP
-  erts_smp_tsd_set(win32_errstr_key,lpBufPtr);
-#endif
+  erts_tsd_set(win32_errstr_key,lpBufPtr);
   return lpBufPtr;
 }
 
@@ -3122,7 +3133,6 @@ check_supported_os_version(void)
 #endif
 }
 
-#ifdef USE_THREADS
 
 typedef struct {
     int sched_bind_data;
@@ -3167,37 +3177,39 @@ thr_create_prepare_child(void *vtcdp)
     erts_sched_bind_atthrcreate_child(tcdp->sched_bind_data);
 }
 
-#endif /* USE_THREADS */
 
 void
 erts_sys_pre_init(void)
 {
-#ifdef USE_THREADS
     erts_thr_init_data_t eid = ERTS_THR_INIT_DATA_DEF_INITER;
-#endif
     int_os_version.dwOSVersionInfoSize = sizeof(OSVERSIONINFO);
     GetVersionEx(&int_os_version);
     check_supported_os_version();
 
-#ifdef USE_THREADS
     eid.thread_create_child_func = thr_create_prepare_child;
     /* Before creation in parent */
     eid.thread_create_prepare_func = thr_create_prepare;
     /* After creation in parent */
     eid.thread_create_parent_func = thr_create_cleanup;
 
-    erts_thr_init(&eid);
+#ifdef ERTS_ENABLE_LOCK_COUNT
+    erts_lcnt_pre_thr_init();
 #endif
 
-    erts_init_sys_time_sup();
+    erts_thr_init(&eid);
 
-#ifdef USE_THREADS
 #ifdef ERTS_ENABLE_LOCK_COUNT
-    erts_lcnt_init();
+    erts_lcnt_post_thr_init();
 #endif
+
+#ifdef ERTS_ENABLE_LOCK_CHECK
+    erts_lc_init();
 #endif
 
-    erts_smp_atomic_init_nob(&sys_misc_mem_sz, 0);
+
+    erts_init_sys_time_sup();
+
+    erts_atomic_init_nob(&sys_misc_mem_sz, 0);
 }
 
 void noinherit_std_handle(DWORD type)
@@ -3217,11 +3229,9 @@ void erl_sys_init(void)
     noinherit_std_handle(STD_INPUT_HANDLE);
     noinherit_std_handle(STD_ERROR_HANDLE);
 
-#ifdef ERTS_SMP
-    erts_smp_tsd_key_create(&win32_errstr_key,"win32_errstr_key");
+    erts_tsd_key_create(&win32_errstr_key,"win32_errstr_key");
     InitializeCriticalSection(&htbc_lock);
-#endif
-    erts_smp_atomic_init_nob(&pipe_creation_counter,0);
+    erts_atomic_init_nob(&pipe_creation_counter,0);
     /*
      * Test if we have named pipes or not.
      */
@@ -3264,42 +3274,16 @@ void erl_sys_init(void)
 	SetStdHandle(STD_ERROR_HANDLE, GetStdHandle(STD_OUTPUT_HANDLE));
     }
     erts_sys_init_float();
-    erts_init_check_io();
 
     /* Suppress windows error message popups */
     SetErrorMode(SetErrorMode(0) |
 		 SEM_FAILCRITICALERRORS | SEM_NOOPENFILEERRORBOX); 
 }
+void erts_poll_late_init(void);
 
 void
 erl_sys_late_init(void)
 {
     /* do nothing */
+    erts_poll_late_init();
 }
-
-void
-erts_sys_schedule_interrupt(int set)
-{
-    erts_check_io_interrupt(set);
-}
-
-#ifdef ERTS_SMP
-void
-erts_sys_schedule_interrupt_timed(int set, ErtsMonotonicTime timeout_time)
-{
-    erts_check_io_interrupt_timed(set, timeout_time);
-}
-#endif
-
-/*
- * Called from schedule() when it runs out of runnable processes,
- * or when Erlang code has performed INPUT_REDUCTIONS reduction
- * steps. runnable == 0 iff there are no runnable Erlang processes.
- */
-void
-erl_sys_schedule(int runnable)
-{
-    erts_check_io(!runnable);
-    ERTS_SMP_LC_ASSERT(!erts_thr_progress_is_blocking());
-}
-
diff --git a/erts/emulator/sys/win32/sys_env.c b/erts/emulator/sys/win32/sys_env.c
index 21ef71ad9a..c78161b344 100644
--- a/erts/emulator/sys/win32/sys_env.c
+++ b/erts/emulator/sys/win32/sys_env.c
@@ -1,318 +1,212 @@
-/*

- * %CopyrightBegin%

- *

- * Copyright Ericsson AB 2002-2016. All Rights Reserved.

- *

- * Licensed under the Apache License, Version 2.0 (the "License");

- * you may not use this file except in compliance with the License.

- * You may obtain a copy of the License at

- *

- *     http://www.apache.org/licenses/LICENSE-2.0

- *

- * Unless required by applicable law or agreed to in writing, software

- * distributed under the License is distributed on an "AS IS" BASIS,

- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

- * See the License for the specific language governing permissions and

- * limitations under the License.

- *

- * %CopyrightEnd%

- */

-

-#ifdef HAVE_CONFIG_H

-#  include "config.h"

-#endif

-

-#include "sys.h"

-#include "erl_sys_driver.h"

-#include "erl_alloc.h"

-

-static WCHAR *merge_environment(WCHAR *current, WCHAR *add);

-static WCHAR *arg_to_env(WCHAR **arg);

-static WCHAR **env_to_arg(WCHAR *env);

-static WCHAR **find_arg(WCHAR **arg, WCHAR *str);

-static int compare(const void *a, const void *b);

-

-static erts_smp_rwmtx_t environ_rwmtx;

-

-void

-erts_sys_env_init(void)

-{

-    erts_smp_rwmtx_init(&environ_rwmtx, "environ");

-}

-

-int

-erts_sys_putenv_raw(char *key, char *value)

-{

-    int res;

-    erts_smp_rwmtx_rwlock(&environ_rwmtx);

-    res = (SetEnvironmentVariable((LPCTSTR) key,

-				  (LPCTSTR) value) ? 0 : 1);

-    erts_smp_rwmtx_rwunlock(&environ_rwmtx);

-    return res;

-}

-

-int

-erts_sys_putenv(char *key, char *value)

-{

-    int res;

-    WCHAR *wkey = (WCHAR *) key;

-    WCHAR *wvalue = (WCHAR *) value;

-    erts_smp_rwmtx_rwlock(&environ_rwmtx);

-    res = (SetEnvironmentVariableW(wkey,

-				   wvalue) ? 0 : 1);

-    erts_smp_rwmtx_rwunlock(&environ_rwmtx);

-    return res;

-}

-

-int

-erts_sys_getenv(char *key, char *value, size_t *size)

-{

-    size_t req_size = 0;

-    int res = 0;

-    DWORD new_size;

-    WCHAR *wkey = (WCHAR *) key;

-    WCHAR *wvalue = (WCHAR *) value;

-    DWORD wsize = *size / (sizeof(WCHAR) / sizeof(char));

-

-    SetLastError(0);

-    erts_smp_rwmtx_rlock(&environ_rwmtx);

-    new_size = GetEnvironmentVariableW(wkey,

-				       wvalue,

-				      (DWORD) wsize);

-    res = !new_size && GetLastError() == ERROR_ENVVAR_NOT_FOUND ? -1 : 0;

-    erts_smp_rwmtx_runlock(&environ_rwmtx);

-    if (res < 0)

-	return res;

-    res = new_size > wsize ? 1 : 0;

-    *size = new_size * (sizeof(WCHAR) / sizeof(char));

-    return res;

-}

-int

-erts_sys_getenv__(char *key, char *value, size_t *size)

-{

-    size_t req_size = 0;

-    int res = 0;

-    DWORD new_size;

-

-    SetLastError(0);

-    new_size = GetEnvironmentVariable((LPCTSTR) key,

-				      (LPTSTR) value,

-				      (DWORD) *size);

-    res = !new_size && GetLastError() == ERROR_ENVVAR_NOT_FOUND ? -1 : 0;

-    if (res < 0)

-	return res;

-    res = new_size > *size ? 1 : 0;

-    *size = new_size;

-    return res;

-}

-

-int

-erts_sys_getenv_raw(char *key, char *value, size_t *size)

-{

-    int res;

-    erts_smp_rwmtx_rlock(&environ_rwmtx);

-    res = erts_sys_getenv__(key, value, size);

-    erts_smp_rwmtx_runlock(&environ_rwmtx);

-    return res;

-}

-

-void init_getenv_state(GETENV_STATE *state)

-{

-    erts_smp_rwmtx_rlock(&environ_rwmtx);

-    state->environment_strings = GetEnvironmentStringsW();

-    state->next_string = state->environment_strings;

-}

-

-char *getenv_string(GETENV_STATE *state)

-{

-    ERTS_SMP_LC_ASSERT(erts_smp_lc_rwmtx_is_rlocked(&environ_rwmtx));

-    if (state->next_string[0] == L'\0') {

-	return NULL;

-    } else {

-	WCHAR *res = state->next_string;

-	state->next_string += wcslen(res) + 1;

-	return (char *) res;

-    }

-}

-

-void fini_getenv_state(GETENV_STATE *state)

-{

-    FreeEnvironmentStringsW(state->environment_strings);

-    state->environment_strings = state->next_string = NULL;

-    erts_smp_rwmtx_runlock(&environ_rwmtx);

-}

-

-int erts_sys_unsetenv(char *key)

-{

-    int res = 0;

-    WCHAR *wkey = (WCHAR *) key;

-

-    SetLastError(0);

-    erts_smp_rwmtx_rlock(&environ_rwmtx);

-    GetEnvironmentVariableW(wkey,

-                            NULL,

-                            0);

-    if (GetLastError() != ERROR_ENVVAR_NOT_FOUND) {

-        res = (SetEnvironmentVariableW(wkey,

-                                       NULL) ? 0 : 1);

-    }

-    erts_smp_rwmtx_runlock(&environ_rwmtx);

-    return res;

-}

-

-char*

-win_build_environment(char* new_env)

-{

-    if (new_env == NULL) {

-	return NULL;

-    } else {

-	WCHAR *tmp, *merged, *tmp_new;

-

-	tmp_new = (WCHAR *) new_env;

-	

-	erts_smp_rwmtx_rlock(&environ_rwmtx);

-	tmp = GetEnvironmentStringsW();

-	merged = merge_environment(tmp, tmp_new);

-

-	FreeEnvironmentStringsW(tmp);

-	erts_smp_rwmtx_runlock(&environ_rwmtx);

-	return (char *) merged;

-    }

-}

-

-static WCHAR *

-merge_environment(WCHAR *old, WCHAR *add)

-{

-    WCHAR **a_arg = env_to_arg(add);

-    WCHAR **c_arg = env_to_arg(old);

-    WCHAR *ret;

-    int i, j;

-    

-    for(i = 0; c_arg[i] != NULL; ++i)

-	;

-

-    for(j = 0; a_arg[j] != NULL; ++j)

-	;

-

-    c_arg = erts_realloc(ERTS_ALC_T_TMP,

-			 c_arg, (i+j+1) * sizeof(WCHAR *));

-

-    for(j = 0; a_arg[j] != NULL; ++j){

-	WCHAR **tmp;

-	WCHAR *current = a_arg[j];

-	WCHAR *eq_p = wcschr(current,L'=');

-	int unset = (eq_p!=NULL && eq_p[1]==L'\0');

-

-	if ((tmp = find_arg(c_arg, current)) != NULL) {

-	    if (!unset) {

-		*tmp = current;

-	    } else {

-		*tmp = c_arg[--i];

-		c_arg[i] = NULL;

-	    }

-	} else if (!unset) {

-	    c_arg[i++] = current;

-	    c_arg[i] = NULL;

-	}

-    }

-    ret = arg_to_env(c_arg);

-    erts_free(ERTS_ALC_T_TMP, c_arg);

-    erts_free(ERTS_ALC_T_TMP, a_arg);

-    return ret;

-}

-

-static WCHAR**

-find_arg(WCHAR **arg, WCHAR *str)

-{

-    WCHAR *tmp;

-    int len;

-

-    if ((tmp = wcschr(str, L'=')) != NULL) {

-	tmp++;

-	len = tmp - str;

-	while (*arg != NULL){

-	    if (_wcsnicmp(*arg, str, len) == 0){

-		return arg;

-	    }

-	    ++arg;

-	}

-    }

-    return NULL;

-}

-

-static int

-compare(const void *a, const void *b)

-{

-    WCHAR *s1 = *((WCHAR **) a);

-    WCHAR *s2 = *((WCHAR **) b);

-    WCHAR *e1 = wcschr(s1,L'=');

-    WCHAR *e2 = wcschr(s2,L'=');

-    int ret;

-    int len;

-  

-    if(!e1)

-	e1 = s1 + wcslen(s1);

-    if(!e2)

-	e2 = s2 + wcslen(s2);

-  

-    if((e1 - s1) > (e2 - s2))

-	len = (e2 - s2);

-    else

-	len = (e1 - s1);

-  

-    ret = _wcsnicmp(s1,s2,len);

-    if (ret == 0)

-	return ((e1 - s1) - (e2 - s2));

-    else

-	return ret;

-}

-

-static WCHAR**

-env_to_arg(WCHAR *env)

-{

-    WCHAR **ret;

-    WCHAR *tmp;

-    int i;

-    int num_strings = 0;

-

-    for(tmp = env; *tmp != '\0'; tmp += wcslen(tmp)+1) {

-	++num_strings;

-    }

-    ret = erts_alloc(ERTS_ALC_T_TMP, sizeof(WCHAR *) * (num_strings + 1));

-    i = 0;

-    for(tmp = env; *tmp != '\0'; tmp += wcslen(tmp)+1){

-	ret[i++] = tmp;

-    }

-    ret[i] = NULL;

-    return ret;

-}

-

-static WCHAR *

-arg_to_env(WCHAR **arg)

-{

-    WCHAR *block;

-    WCHAR *ptr;

-    int i;

-    int totlen = 1;		/* extra '\0' */

-

-    for(i = 0; arg[i] != NULL; ++i) {

-	totlen += wcslen(arg[i])+1;

-    }

-

-    /* sort the environment vector */

-    qsort(arg, i, sizeof(WCHAR *), &compare);

-

-    if (totlen == 1){

-	block = erts_alloc(ERTS_ALC_T_ENVIRONMENT, 2 * sizeof(WCHAR));

-	block[0] = block[1] = '\0'; 

-    } else {

-	block = erts_alloc(ERTS_ALC_T_ENVIRONMENT, totlen * sizeof(WCHAR));

-	ptr = block;

-	for(i=0; arg[i] != NULL; ++i){

-	    wcscpy(ptr, arg[i]);

-	    ptr += wcslen(ptr)+1;

-	}

-	*ptr = '\0';

-    }

-    return block;

-}

+/*
+ * %CopyrightBegin%
+ *
+ * Copyright Ericsson AB 2002-2017. All Rights Reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ * %CopyrightEnd%
+ */
+
+#ifdef HAVE_CONFIG_H
+#  include "config.h"
+#endif
+
+#include "sys.h"
+#include "erl_sys_driver.h"
+#include "erl_alloc.h"
+
+static erts_osenv_t sysenv_global_env;
+static erts_rwmtx_t sysenv_rwmtx;
+
+static void import_initial_env(void);
+
+void erts_sys_env_init() {
+    erts_rwmtx_init(&sysenv_rwmtx, "environ", NIL,
+        ERTS_LOCK_FLAGS_PROPERTY_STATIC | ERTS_LOCK_FLAGS_CATEGORY_GENERIC);
+
+    erts_osenv_init(&sysenv_global_env);
+    import_initial_env();
+}
+
+const erts_osenv_t *erts_sys_rlock_global_osenv() {
+    erts_rwmtx_rlock(&sysenv_rwmtx);
+    return &sysenv_global_env;
+}
+
+erts_osenv_t *erts_sys_rwlock_global_osenv() {
+    erts_rwmtx_rwlock(&sysenv_rwmtx);
+    return &sysenv_global_env;
+}
+
+void erts_sys_runlock_global_osenv() {
+    erts_rwmtx_runlock(&sysenv_rwmtx);
+}
+
+void erts_sys_rwunlock_global_osenv() {
+    erts_rwmtx_rwunlock(&sysenv_rwmtx);
+}
+
+int erts_sys_explicit_host_getenv(char *key, char *value, size_t *size) {
+    size_t new_size = GetEnvironmentVariableA(key, value, (DWORD)*size);
+
+    if(new_size == 0 && GetLastError() == ERROR_ENVVAR_NOT_FOUND) {
+        return 0;
+    } else if(new_size > *size) {
+        return -1;
+    }
+
+    *size = new_size;
+    return 1;
+}
+
+int erts_sys_explicit_8bit_putenv(char *key, char *value) {
+    WCHAR *wide_key, *wide_value;
+    int key_length, value_length;
+    int result;
+
+    /* Note that we do *NOT* honor the filename encoding flags (+fnu/+fnl)
+     * here; the previous implementation used SetEnvironmentVariableA and
+     * things may break if we step away from that. */
+
+    key_length = MultiByteToWideChar(CP_ACP, 0, key, -1, NULL, 0);
+    value_length = MultiByteToWideChar(CP_ACP, 0, value, -1, NULL, 0);
+
+    /* Report "not found" if either string isn't convertible. */
+    if(key_length == 0 || value_length == 0) {
+        return 0;
+    }
+
+    wide_key = erts_alloc(ERTS_ALC_T_TMP, key_length * sizeof(WCHAR));
+    wide_value = erts_alloc(ERTS_ALC_T_TMP, value_length * sizeof(WCHAR));
+
+    MultiByteToWideChar(CP_ACP, 0, key, -1, wide_key, key_length);
+    MultiByteToWideChar(CP_ACP, 0, value, -1, wide_value, value_length);
+
+    {
+        erts_osenv_data_t env_key, env_value;
+        erts_osenv_t *env;
+
+        env = erts_sys_rwlock_global_osenv();
+
+        /* -1 to exclude the NUL terminator. */
+        env_key.length = (key_length - 1) * sizeof(WCHAR);
+        env_key.data = wide_key;
+
+        env_value.length = (value_length - 1) * sizeof(WCHAR);
+        env_value.data = wide_value;
+
+        result = erts_osenv_put_native(env, &env_key, &env_value);
+        erts_sys_rwunlock_global_osenv();
+    }
+
+    erts_free(ERTS_ALC_T_TMP, wide_key);
+    erts_free(ERTS_ALC_T_TMP, wide_value);
+
+    return result;
+}
+
+int erts_sys_explicit_8bit_getenv(char *key, char *value, size_t *size) {
+    erts_osenv_data_t env_key, env_value;
+    int key_length, value_length, result;
+    WCHAR *wide_key, *wide_value;
+
+    key_length = MultiByteToWideChar(CP_ACP, 0, key, -1, NULL, 0);
+
+    /* Report "not found" if the string isn't convertible. */
+    if(key_length == 0) {
+        return 0;
+    }
+
+    wide_key = erts_alloc(ERTS_ALC_T_TMP, key_length * sizeof(WCHAR));
+    MultiByteToWideChar(CP_ACP, 0, key, -1, wide_key, key_length);
+
+    /* We assume that the worst possible size is twice the output buffer width,
+     * as we could theoretically be on a code page that requires surrogates. */
+    value_length = (*size) * 2;
+    wide_value = erts_alloc(ERTS_ALC_T_TMP, value_length * sizeof(WCHAR));
+
+    {
+        const erts_osenv_t *env = erts_sys_rlock_global_osenv();
+
+        /* -1 to exclude the NUL terminator. */
+        env_key.length = (key_length - 1) * sizeof(WCHAR);
+        env_key.data = wide_key;
+
+        env_value.length = value_length * sizeof(WCHAR);
+        env_value.data = wide_value;
+
+        result = erts_osenv_get_native(env, &env_key, &env_value);
+        erts_sys_runlock_global_osenv();
+    }
+
+    if(result == 1 && env_value.length > 0) {
+        /* This function doesn't NUL-terminate if the provided size is >= 0,
+         * so we pass (*size - 1) to reserve space for it and then do it
+         * manually. */
+        *size = WideCharToMultiByte(CP_ACP, 0, env_value.data,
+            env_value.length / sizeof(WCHAR), value, *size - 1, NULL, NULL);
+
+        if(*size == 0) {
+            if(GetLastError() == ERROR_INSUFFICIENT_BUFFER) {
+                result = -1;
+            } else {
+                result = 0;
+            }
+        }
+    } else {
+        *size = 0;
+    }
+
+    if(*size > 0) {
+        value[*size] = '\0';
+    }
+
+    erts_free(ERTS_ALC_T_TMP, wide_key);
+    erts_free(ERTS_ALC_T_TMP, wide_value);
+
+    return result;
+}
+
+static void import_initial_env(void) {
+    WCHAR *environment_block, *current_variable;
+
+    environment_block = GetEnvironmentStringsW();
+    current_variable = environment_block;
+
+    while(wcslen(current_variable) > 0) {
+        WCHAR *separator_index = wcschr(current_variable, L'=');
+
+        /* We tolerate environment variables starting with '=' as the per-drive
+         * working directories are stored this way. */
+        if(separator_index == current_variable) {
+            separator_index = wcschr(separator_index + 1, L'=');
+        }
+
+        if(separator_index != NULL && separator_index != current_variable) {
+            erts_osenv_data_t env_key, env_value;
+
+            env_key.length = (separator_index - current_variable) * sizeof(WCHAR);
+            env_key.data = current_variable;
+
+            env_value.length = (wcslen(separator_index) - 1) * sizeof(WCHAR);
+            env_value.data = separator_index + 1;
+
+            erts_osenv_put_native(&sysenv_global_env, &env_key, &env_value);
+        }
+
+        current_variable += wcslen(current_variable) + 1;
+    }
+
+    FreeEnvironmentStringsW(environment_block);
+}
diff --git a/erts/emulator/sys/win32/sys_interrupt.c b/erts/emulator/sys/win32/sys_interrupt.c
index df838960eb..cee269eed4 100644
--- a/erts/emulator/sys/win32/sys_interrupt.c
+++ b/erts/emulator/sys/win32/sys_interrupt.c
@@ -1,7 +1,7 @@
 /*
  * %CopyrightBegin%
  * 
- * Copyright Ericsson AB 1997-2016. All Rights Reserved.
+ * Copyright Ericsson AB 1997-2018. All Rights Reserved.
  * 
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -35,17 +35,11 @@
 #  define WIN_SYS_INLINE __forceinline
 #endif
 
-#ifdef ERTS_SMP
-erts_smp_atomic32_t erts_break_requested;
+erts_atomic32_t erts_break_requested;
 #define ERTS_SET_BREAK_REQUESTED \
-  erts_smp_atomic32_set_nob(&erts_break_requested, (erts_aint32_t) 1)
+  erts_atomic32_set_nob(&erts_break_requested, (erts_aint32_t) 1)
 #define ERTS_UNSET_BREAK_REQUESTED \
-  erts_smp_atomic32_set_nob(&erts_break_requested, (erts_aint32_t) 0)
-#else
-volatile int erts_break_requested = 0;
-#define ERTS_SET_BREAK_REQUESTED (erts_break_requested = 1)
-#define ERTS_UNSET_BREAK_REQUESTED (erts_break_requested = 0)
-#endif
+  erts_atomic32_set_nob(&erts_break_requested, (erts_aint32_t) 0)
 
 extern int nohup;
 HANDLE erts_sys_break_event = NULL;
@@ -57,14 +51,14 @@ void erts_do_break_handling(void)
      * therefore, make sure that all threads but this one are blocked before
      * proceeding!
      */
-    erts_smp_thr_progress_block();
+    erts_thr_progress_block();
     /* call the break handling function, reset the flag */
     do_break();
 
     ResetEvent(erts_sys_break_event);
     ERTS_UNSET_BREAK_REQUESTED;
 
-    erts_smp_thr_progress_unblock();
+    erts_thr_progress_unblock();
 }
 
 
diff --git a/erts/emulator/sys/win32/sys_time.c b/erts/emulator/sys/win32/sys_time.c
index e8c67b3928..a1dd14f871 100644
--- a/erts/emulator/sys/win32/sys_time.c
+++ b/erts/emulator/sys/win32/sys_time.c
@@ -1,7 +1,7 @@
 /*
  * %CopyrightBegin%
  * 
- * Copyright Ericsson AB 1997-2016. All Rights Reserved.
+ * Copyright Ericsson AB 1997-2018. All Rights Reserved.
  * 
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -95,7 +95,7 @@ struct sys_time_internal_state_read_mostly__ {
 };
 
 struct sys_time_internal_state_write_freq__ {
-    erts_smp_mtx_t mtime_mtx;
+    erts_mtx_t mtime_mtx;
     ULONGLONG wrap;
     ULONGLONG last_tick_count;
 };
@@ -187,8 +187,6 @@ os_monotonic_time_gtc32(void)
 {
     ErtsMonotonicTime mtime;
     Uint32 ticks = (Uint32) GetTickCount();
-    ERTS_CHK_EXTEND_OS_MONOTONIC_TIME(&internal_state.wr.m.os_mtime_xtnd,
-				      ticks);
     mtime = ERTS_EXTEND_OS_MONOTONIC_TIME(&internal_state.wr.m.os_mtime_xtnd,
 					  ticks);
     mtime <<= ERTS_GET_TICK_COUNT_TIME_UNIT_SHIFT;
@@ -205,8 +203,6 @@ os_times_gtc32(ErtsMonotonicTime *mtimep, ErtsSystemTime *stimep)
     ticks = (Uint32) GetTickCount();
     GetSystemTime(&st);
 
-    ERTS_CHK_EXTEND_OS_MONOTONIC_TIME(&internal_state.wr.m.os_mtime_xtnd,
-				      ticks);
     mtime = ERTS_EXTEND_OS_MONOTONIC_TIME(&internal_state.wr.m.os_mtime_xtnd,
 					  ticks);
     mtime <<= ERTS_GET_TICK_COUNT_TIME_UNIT_SHIFT;
@@ -265,8 +261,6 @@ sys_hrtime_gtc32(void)
 {
     ErtsSysHrTime time;
     Uint32 ticks = (Uint32) GetTickCount();
-    ERTS_CHK_EXTEND_OS_MONOTONIC_TIME(&internal_state.wr.m.os_mtime_xtnd,
-				      tick_count);
     time = (ErtsSysHrTime) ERTS_EXTEND_OS_MONOTONIC_TIME(&internal_state.wr.m.os_mtime_xtnd,
 							 ticks);
     time *= (ErtsSysHrTime) (1000 * 1000);
@@ -300,8 +294,8 @@ sys_init_time(ErtsSysInitTimeResult *init_resp)
     module = GetModuleHandle(kernel_dll_name);
     if (!module) {
     get_tick_count:
-	erts_smp_mtx_init(&internal_state.w.f.mtime_mtx,
-			  "os_monotonic_time");
+        erts_mtx_init(&internal_state.w.f.mtime_mtx, "os_monotonic_time", NIL,
+            ERTS_LOCK_FLAGS_PROPERTY_STATIC | ERTS_LOCK_FLAGS_CATEGORY_GENERIC);
 	internal_state.w.f.wrap = 0;
 	internal_state.w.f.last_tick_count = 0;