erts: Add enif_select & enif_open_resource_type_x

4 files changed, 728 insertions, 60 deletions

diff --git a/erts/emulator/sys/common/erl_check_io.c b/erts/emulator/sys/common/erl_check_io.c
index 2c138e1746..6f61fc8a28 100644
--- a/erts/emulator/sys/common/erl_check_io.c
+++ b/erts/emulator/sys/common/erl_check_io.c
@@ -53,6 +53,8 @@ typedef char EventStateType;
 #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 */
+#define ERTS_EV_TYPE_NIF      ((EventStateType) 4) /* enif_select */
+#define ERTS_EV_TYPE_STOP_NIF ((EventStateType) 5) /* pending nif stop */
 
 typedef char EventStateFlags;
 #define ERTS_EV_FLAG_USED         ((EventStateFlags) 1)   /* ERL_DRV_USE has been turned on */
@@ -122,7 +124,11 @@ typedef struct {
 #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 */
+            ErlNifResource* resource;   /* ERTS_EV_TYPE_STOP_NIF */
+        }stop;
     } driver;
     ErtsPollEvents events;
     unsigned short remove_cnt; /* number of removed_fd's referring to this fd */
@@ -212,11 +218,18 @@ static ERTS_INLINE void hash_erase_drv_ev_state(ErtsDrvEventState *state)
 
 static void stale_drv_select(Eterm id, ErtsDrvEventState *state, int mode);
 static void drv_select_steal(ErlDrvPort ix, ErtsDrvEventState *state,
-			 int mode, int on);
+                             int mode, int on);
+static void nif_select_steal(ErtsDrvEventState *state, int mode,
+                             ErlNifResource* 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, ErlNifResource*, Eterm ref);
+
 #ifdef ERTS_SYS_CONTINOUS_FD_NUMBERS
-static void select_large_fd_error(ErlDrvPort, ErtsSysFdType, int, int);
+static void drv_select_large_fd_error(ErlDrvPort, ErtsSysFdType, int, int);
+static void nif_select_large_fd_error(ErtsSysFdType, int, ErlNifResource*,Eterm ref);
 #endif
 #if ERTS_CIO_HAVE_DRV_EVENT
 static void drv_event_steal(ErlDrvPort ix, ErtsDrvEventState *state,
@@ -227,8 +240,12 @@ static void print_drv_event_op(erts_dsprintf_buf_t *dsbufp,
 static void event_large_fd_error(ErlDrvPort, ErtsSysFdType, ErlDrvEventData);
 #endif
 #endif
-static void steal_pending_stop_use(erts_dsprintf_buf_t*, ErlDrvPort,
-                                   ErtsDrvEventState*, int mode, int on);
+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, ErlNifResource*,
+                       ErtsDrvEventState *state, int mode, int on);
 
 #ifdef ERTS_SMP
 ERTS_SCHED_PREF_QUICK_ALLOC_IMPL(removed_fd, struct removed_fd, 64, ERTS_ALC_T_FD_LIST)
@@ -263,6 +280,18 @@ alloc_drv_select_data(void)
     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;
+    dsp->in.ddeselect_cnt = 0;
+    dsp->out.ddeselect_cnt = 0;
+    return dsp;
+}
+
 static ERTS_INLINE void
 free_drv_select_data(ErtsDrvSelectDataState *dsp)
 {
@@ -271,6 +300,12 @@ free_drv_select_data(ErtsDrvSelectDataState *dsp)
     erts_free(ERTS_ALC_T_DRV_SEL_D_STATE, dsp);   
 }
 
+static ERTS_INLINE void
+free_nif_select_data(ErtsNifSelectDataState *dsp)
+{
+    erts_free(ERTS_ALC_T_NIF_SEL_D_STATE, dsp);
+}
+
 #if ERTS_CIO_HAVE_DRV_EVENT
 
 static ERTS_INLINE ErtsDrvEventDataState *
@@ -352,6 +387,7 @@ forget_removed(struct pollset_info* psi)
     erts_smp_spin_unlock(&psi->removed_list_lock);
 
     while (fdlp) {
+        ErlNifResource* resource = NULL;
 	erts_driver_t* drv_ptr = NULL;
 	erts_smp_mtx_t* mtx;
 	ErtsSysFdType fd;
@@ -372,15 +408,25 @@ forget_removed(struct pollset_info* psi)
 	ASSERT(state->remove_cnt > 0);
 	if (--state->remove_cnt == 0) {
 	    switch (state->type) {
+	    case ERTS_EV_TYPE_STOP_NIF:
+		/* Now we can call stop */
+		resource = state->driver.stop.resource;
+                state->driver.stop.resource = NULL;
+                ASSERT(resource);
+		state->type = ERTS_EV_TYPE_NONE;
+		state->flags &= ~ERTS_EV_FLAG_USED;
+                goto case_ERTS_EV_TYPE_NONE;
+
 	    case ERTS_EV_TYPE_STOP_USE:
 		/* Now we can call stop_select */
-		drv_ptr = state->driver.drv_ptr;
+		drv_ptr = state->driver.stop.drv_ptr;
 		ASSERT(drv_ptr);
 		state->type = ERTS_EV_TYPE_NONE;
 		state->flags &= ~ERTS_EV_FLAG_USED;
-		state->driver.drv_ptr = NULL;  
+		state->driver.stop.drv_ptr = NULL;
 		/* Fall through */
-	    case ERTS_EV_TYPE_NONE:
+            case ERTS_EV_TYPE_NONE:
+            case_ERTS_EV_TYPE_NONE:
 #ifndef ERTS_SYS_CONTINOUS_FD_NUMBERS
 		hash_erase_drv_ev_state(state);
 #endif
@@ -403,6 +449,11 @@ forget_removed(struct pollset_info* psi)
 		erts_ddll_dereference_driver(drv_ptr->handle);
 	    }
 	}
+        if (resource) {
+            erts_resource_stop(resource);
+            enif_release_resource(resource->data);
+        }
+
 	tofree = fdlp;
 	fdlp = fdlp->next;
 	removed_fd_free(tofree);
@@ -440,7 +491,8 @@ grow_drv_ev_state(int min_ix)
 #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].driver.stop.drv_ptr = NULL;
+            drv_ev_state[i].driver.nif = NULL;
 	    drv_ev_state[i].events = 0;
 	    drv_ev_state[i].remove_cnt = 0;
 	    drv_ev_state[i].type = ERTS_EV_TYPE_NONE;
@@ -480,6 +532,7 @@ abort_tasks(ErtsDrvEventState *state, int mode)
 		       ERTS_EV_TYPE_DRV_EV);
 	    return;
 #endif
+        case ERTS_EV_TYPE_NIF:
 	case ERTS_EV_TYPE_NONE:
 	    return;
 	default:
@@ -534,6 +587,14 @@ deselect(ErtsDrvEventState *state, int mode)
 
     if (!(state->events)) {
 	switch (state->type) {
+        case ERTS_EV_TYPE_NIF:
+            state->driver.nif->in.pid = NIL;
+            state->driver.nif->out.pid = NIL;
+            state->driver.nif->in.ddeselect_cnt = 0;
+            state->driver.nif->out.ddeselect_cnt = 0;
+            enif_release_resource(state->driver.stop.resource);
+            state->driver.stop.resource = NULL;
+            break;
 	case ERTS_EV_TYPE_DRV_SEL:
 	    state->driver.select->inport = NIL;
 	    state->driver.select->outport = NIL;
@@ -569,7 +630,8 @@ 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;
 
@@ -586,6 +648,12 @@ check_fd_cleanup(ErtsDrvEventState *state,
 	state->driver.select = NULL;
     }
 
+    *free_nif = NULL;
+    if (state->driver.nif && (state->type != ERTS_EV_TYPE_NIF)) {
+        *free_nif = state->driver.nif;
+        state->driver.nif = NULL;
+    }
+
 #if ERTS_CIO_HAVE_DRV_EVENT
     *free_event = NULL;
     if (state->driver.event
@@ -617,12 +685,14 @@ check_cleanup_active_fd(ErtsSysFdType fd,
 			ErtsPollControlEntry *pce,
 			int *pce_ix,
 #endif
-			erts_aint_t current_cio_time)
+			erts_aint_t current_cio_time,
+                        int may_sleep)
 {
     ErtsDrvEventState *state;
     int active = 0;
     erts_smp_mtx_t *mtx = fd_mtx(fd);
     void *free_select = NULL;
+    void *free_nif = NULL;
 #if ERTS_CIO_HAVE_DRV_EVENT
     void *free_event = NULL;
 #endif
@@ -682,6 +752,41 @@ check_cleanup_active_fd(ErtsSysFdType fd,
 	    }
 	}
 
+        if (state->driver.nif) {
+#if ERTS_CIO_DEFER_ACTIVE_EVENTS
+#  error Windows
+#endif
+            int do_wake = 0;
+            ErtsPollEvents rm_events = 0;
+            if (state->driver.nif->in.ddeselect_cnt) {
+                ASSERT(state->type == ERTS_EV_TYPE_NIF);
+                ASSERT(state->events & ERTS_POLL_EV_IN);
+                ASSERT(is_nil(state->driver.nif->in.pid));
+                if (may_sleep || state->driver.nif->in.ddeselect_cnt == 1) {
+                    rm_events = ERTS_POLL_EV_IN;
+                    state->driver.nif->in.ddeselect_cnt = 0;
+                }
+            }
+            if (state->driver.nif->out.ddeselect_cnt) {
+                ASSERT(state->type == ERTS_EV_TYPE_NIF);
+                ASSERT(state->events & ERTS_POLL_EV_OUT);
+                ASSERT(is_nil(state->driver.nif->out.pid));
+                if (may_sleep || state->driver.nif->out.ddeselect_cnt == 1) {
+                    rm_events |= ERTS_POLL_EV_OUT;
+                    state->driver.nif->out.ddeselect_cnt = 0;
+                }
+            }
+            if (rm_events) {
+                state->events = ERTS_CIO_POLL_CTL(pollset.ps, state->fd, rm_events, 0, &do_wake);
+            }
+            if (state->events)
+                active = 1;
+            else if (state->type != ERTS_EV_TYPE_NIF) {
+                free_nif = state->driver.nif;
+                state->driver.nif = NULL;
+            }
+        }
+
 #if ERTS_CIO_HAVE_DRV_EVENT
 	if (state->driver.event) {
 	    if (is_iotask_active(&state->driver.event->iotask, current_cio_time)) {
@@ -722,6 +827,8 @@ check_cleanup_active_fd(ErtsSysFdType fd,
 
     if (free_select)
 	free_drv_select_data(free_select);
+    if (free_nif)
+        free_nif_select_data(free_nif);
 #if ERTS_CIO_HAVE_DRV_EVENT
     if (free_event)
 	free_drv_event_data(free_event);
@@ -746,7 +853,7 @@ check_cleanup_active_fd(ErtsSysFdType fd,
 }
 
 static void
-check_cleanup_active_fds(erts_aint_t current_cio_time)
+check_cleanup_active_fds(erts_aint_t current_cio_time, int may_sleep)
 {
     int six = pollset.active_fd.six;
     int eix = pollset.active_fd.eix;
@@ -773,7 +880,8 @@ check_cleanup_active_fds(erts_aint_t current_cio_time)
 				     pctrl_entries,
 				     &pctrl_ix,
 #endif
-				     current_cio_time)) {
+				     current_cio_time,
+                                     may_sleep)) {
 	    no--;
 	    if (ix == six) {
 #ifdef DEBUG
@@ -831,7 +939,6 @@ 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,
@@ -867,6 +974,7 @@ ERTS_CIO_EXPORT(driver_select)(ErlDrvPort ix,
     ErtsDrvEventDataState *free_event = NULL;
 #endif
     ErtsDrvSelectDataState *free_select = NULL;
+    ErtsNifSelectDataState *free_nif = NULL;
 #ifdef USE_VM_PROBES
     DTRACE_CHARBUF(name, 64);
 #endif
@@ -882,7 +990,7 @@ ERTS_CIO_EXPORT(driver_select)(ErlDrvPort ix,
 	    return -1;    
 	}
 	if (fd >= max_fds) {
-	    select_large_fd_error(ix, fd, mode, on);
+	    drv_select_large_fd_error(ix, fd, mode, on);
 	    return -1;
 	}
 	grow_drv_ev_state(fd);
@@ -920,20 +1028,32 @@ ERTS_CIO_EXPORT(driver_select)(ErlDrvPort ix,
     }
 #endif
 
+    switch (state->type) {
 #if ERTS_CIO_HAVE_DRV_EVENT
-    if (state->type == ERTS_EV_TYPE_DRV_EV)
-	drv_select_steal(ix, state, mode, on);
+    case ERTS_EV_TYPE_DRV_EV:
 #endif
-    if (state->type == 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);
-    }
+    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;
+    }
+    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 (mode & ERL_DRV_READ) {
 	if (state->type == ERTS_EV_TYPE_DRV_SEL) {
@@ -1037,7 +1157,7 @@ ERTS_CIO_EXPORT(driver_select)(ErlDrvPort ix,
 		else {
 		    /* Not safe to close fd, postpone stop_select callback. */
 		    state->type = ERTS_EV_TYPE_STOP_USE;
-		    state->driver.drv_ptr = drv_ptr;
+		    state->driver.stop.drv_ptr = drv_ptr;
 		    if (drv_ptr->handle) {
 			erts_ddll_reference_referenced_driver(drv_ptr->handle);
 		    }
@@ -1054,7 +1174,8 @@ done:
 #if ERTS_CIO_HAVE_DRV_EVENT
 		     &free_event,
 #endif
-		     &free_select);
+		     &free_select,
+                     &free_nif);
 
 done_unknown:
     erts_smp_mtx_unlock(fd_mtx(fd));
@@ -1067,6 +1188,9 @@ done_unknown:
     }
     if (free_select)
 	free_drv_select_data(free_select);
+    if (free_nif)
+        free_nif_select_data(free_nif);
+
 #if ERTS_CIO_HAVE_DRV_EVENT
     if (free_event)
 	free_drv_event_data(free_event);
@@ -1075,6 +1199,269 @@ done_unknown:
 }
 
 int
+ERTS_CIO_EXPORT(enif_select)(ErlNifEnv* env,
+                             ErlNifEvent e,
+                             enum ErlNifSelectFlags mode,
+                             void* obj,
+                             Eterm ref)
+{
+    int on;
+    const Eterm id = env->proc->common.id;
+    ErlNifResource* resource = DATA_TO_RESOURCE(obj);
+    ErtsSysFdType fd = (ErtsSysFdType) e;
+    ErtsPollEvents ctl_events = (ErtsPollEvents) 0;
+    ErtsPollEvents new_events, old_events;
+    ErtsDrvEventState *state;
+    int wake_poller;
+    int ret;
+    enum { NO_STOP=0, CALL_STOP, CALL_STOP_AND_RELEASE } call_stop = NO_STOP;
+#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
+
+#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) {
+	    nif_select_large_fd_error(fd, mode, resource, ref);
+            return -1;
+	}
+	grow_drv_ev_state(fd);
+    }
+#endif
+
+    erts_smp_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
+
+    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 = 0;
+            goto done_unknown;
+        }
+        on = 0;
+        mode = ERL_DRV_READ | ERL_DRV_WRITE | ERL_DRV_USE;
+        wake_poller = 1; /* to eject fd from pollset (if needed) */
+    }
+    else {
+        on = 1;
+        ASSERT(mode);
+        wake_poller = 0;
+    }
+
+#ifndef ERTS_SYS_CONTINOUS_FD_NUMBERS
+    if (state == NULL) {
+	state = hash_new_drv_ev_state(fd);
+    }
+#endif
+
+    switch (state->type) {
+    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;
+#if ERTS_CIO_HAVE_DRV_EVENT
+    case ERTS_EV_TYPE_DRV_EV:
+#endif
+    case ERTS_EV_TYPE_DRV_SEL:
+        nif_select_steal(state, mode, resource, ref);
+        break;
+    case ERTS_EV_TYPE_STOP_USE: {
+        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 = 0;
+            goto done;
+        }
+        ASSERT(state->type == ERTS_EV_TYPE_NONE);
+        break;
+    }}
+
+    ASSERT(state->type == ERTS_EV_TYPE_NONE ||
+           state->type == ERTS_EV_TYPE_NIF);
+
+    if (mode & ERL_DRV_READ) {
+	ctl_events |= ERTS_POLL_EV_IN;
+    }
+    if (mode & ERL_DRV_WRITE) {
+	ctl_events |= ERTS_POLL_EV_OUT;
+    }
+
+    ASSERT((state->type == ERTS_EV_TYPE_NIF) ||
+	   (state->type == ERTS_EV_TYPE_NONE && !state->events));
+
+    new_events = ERTS_CIO_POLL_CTL(pollset.ps, state->fd, ctl_events, on, &wake_poller);
+
+    if (new_events & (ERTS_POLL_EV_ERR|ERTS_POLL_EV_NVAL)) {
+	if (state->type == ERTS_EV_TYPE_NIF && !state->events) {
+	    state->type = ERTS_EV_TYPE_NONE;
+	    state->flags &= ~ERTS_EV_FLAG_USED;
+	    state->driver.nif->in.pid = NIL;
+	    state->driver.nif->out.pid = NIL;
+            state->driver.nif->in.ddeselect_cnt = 0;
+            state->driver.nif->out.ddeselect_cnt = 0;
+            state->driver.stop.resource = NULL;
+	}
+	ret = -1;
+	goto done;
+    }
+
+    old_events = state->events;
+
+    ASSERT(on
+	   ? (new_events == (state->events | ctl_events))
+	   : (new_events == (state->events & ~ctl_events)));
+
+    ASSERT(state->type == ERTS_EV_TYPE_NIF
+	   || state->type == ERTS_EV_TYPE_NONE);
+
+    state->events = new_events;
+    if (ctl_events) {
+	if (on) {
+            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 (ctl_events & ERTS_POLL_EV_IN) {
+                ASSERT(is_nil(state->driver.nif->in.pid));
+		state->driver.nif->in.pid = id;
+                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;
+                    state->driver.nif->in.refn[0] = refn[0];
+                    state->driver.nif->in.refn[1] = refn[1];
+                    state->driver.nif->in.refn[2] = refn[2];
+                }
+                state->driver.nif->in.ddeselect_cnt = 0;
+            }
+	    if (ctl_events & ERTS_POLL_EV_OUT) {
+                ASSERT(is_nil(state->driver.nif->out.pid));
+		state->driver.nif->out.pid = id;
+                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;
+                    state->driver.nif->out.refn[0] = refn[0];
+                    state->driver.nif->out.refn[1] = refn[1];
+                    state->driver.nif->out.refn[2] = refn[2];
+                }
+                state->driver.nif->out.ddeselect_cnt = 0;
+            }
+            state->flags |= ERTS_EV_FLAG_USED;
+	}
+	else { /* off */
+	    if (state->type == ERTS_EV_TYPE_NIF) {
+                //erts_fprintf(stderr, "SVERK: enif select clear fd=%d inpid=%T inrsrc=%p\n",
+                //             state->fd, state->driver.nif->inpid,
+                //             state->driver.nif->in.resource);
+                state->driver.nif->in.pid = NIL;
+                state->driver.nif->out.pid = NIL;
+                state->driver.nif->in.ddeselect_cnt = 0;
+                state->driver.nif->out.ddeselect_cnt = 0;
+                state->flags &= ~ERTS_EV_FLAG_USED;
+                if (old_events != 0) {
+                    remember_removed(state, &pollset);
+                }
+	    }
+            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) */
+                //erts_fprintf(stderr, "SVERK : enif_select calling stop before return\n");
+                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;
+            }
+            else {
+                /* Not safe to close fd, postpone stop_select callback. */
+                //erts_fprintf(stderr, "SVERK: enif_select schedule stop\n");
+                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 = 0;
+
+done:
+
+    check_fd_cleanup(state,
+#if ERTS_CIO_HAVE_DRV_EVENT
+		     &free_event,
+#endif
+		     &free_select,
+                     &free_nif);
+
+done_unknown:
+    erts_smp_mtx_unlock(fd_mtx(fd));
+    if (call_stop) {
+        erts_resource_stop(resource);
+        if (call_stop == CALL_STOP_AND_RELEASE) {
+            enif_release_resource(resource->data);
+        }
+    }
+    if (free_select)
+	free_drv_select_data(free_select);
+    if (free_nif)
+        free_nif_select_data(free_nif);
+
+#if ERTS_CIO_HAVE_DRV_EVENT
+    if (free_event)
+	free_drv_event_data(free_event);
+#endif
+    return ret;
+}
+
+
+int
 ERTS_CIO_EXPORT(driver_event)(ErlDrvPort ix,
 			      ErlDrvEvent e,
 			      ErlDrvEventData event_data)
@@ -1094,6 +1481,7 @@ ERTS_CIO_EXPORT(driver_event)(ErlDrvPort ix,
     ErtsDrvEventDataState *free_event;
 #endif
     ErtsDrvSelectDataState *free_select;
+    ErtsNifSelectDataState *free_nif;
     Port *prt = erts_drvport2port(ix);
 
     if (prt == ERTS_INVALID_ERL_DRV_PORT)
@@ -1203,12 +1591,15 @@ done:
 #if ERTS_CIO_HAVE_DRV_EVENT
 		     &free_event,
 #endif
-		     &free_select);
+		     &free_select,
+                     &free_nif);
 
     erts_smp_mtx_unlock(fd_mtx(fd));
 
     if (free_select)
 	free_drv_select_data(free_select);
+    if (free_nif)
+        free_nif_select_data(free_nif);
 #if ERTS_CIO_HAVE_DRV_EVENT
     if (free_event)
 	free_drv_event_data(free_event);
@@ -1244,13 +1635,19 @@ need2steal(ErtsDrvEventState *state, int mode)
 				  state,
 				  ERL_DRV_WRITE);
 	break;
+    case ERTS_EV_TYPE_NIF:
+        ASSERT(state->driver.stop.resource);
+        do_steal = 1;
+        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_STOP_USE:
-	ASSERT(0);
+    case ERTS_EV_TYPE_STOP_NIF:
+        ASSERT(0);
 	break;
     default:
 	break;
@@ -1311,6 +1708,25 @@ steal(erts_dsprintf_buf_t *dsbufp, ErtsDrvEventState *state, int mode)
 	erts_dsprintf(dsbufp, "\n");
 	break;
     }
+    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;
+    }
 #if ERTS_CIO_HAVE_DRV_EVENT
     case ERTS_EV_TYPE_DRV_EV: {
 	Eterm eid = state->driver.event->port;
@@ -1328,7 +1744,8 @@ steal(erts_dsprintf_buf_t *dsbufp, ErtsDrvEventState *state, int mode)
 	break;
     }
 #endif
-    case ERTS_EV_TYPE_STOP_USE: {
+    case ERTS_EV_TYPE_STOP_USE:
+    case ERTS_EV_TYPE_STOP_NIF: {
 	ASSERT(0);
 	break;
     }
@@ -1358,6 +1775,23 @@ print_drv_select_op(erts_dsprintf_buf_t *dsbufp,
 }
 
 static void
+print_nif_select_op(erts_dsprintf_buf_t *dsbufp,
+                    ErtsSysFdType fd, int mode,
+                    ErlNifResource* resource, Eterm ref)
+{
+    erts_dsprintf(dsbufp,
+		  "enif_select(_, %d,%s%s%s, %T:%T, %T) ",
+		  (int) GET_FD(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)) {
@@ -1368,6 +1802,18 @@ drv_select_steal(ErlDrvPort ix, ErtsDrvEventState *state, int mode, int on)
     }
 }
 
+static void
+nif_select_steal(ErtsDrvEventState *state, int mode,
+                 ErlNifResource* 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);
+    }
+}
+
 #ifdef ERTS_SYS_CONTINOUS_FD_NUMBERS
 static void
 large_fd_error_common(erts_dsprintf_buf_t *dsbufp, ErtsSysFdType fd)
@@ -1378,7 +1824,7 @@ large_fd_error_common(erts_dsprintf_buf_t *dsbufp, ErtsSysFdType fd)
 }
 
 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_drv_select_op(dsbufp, ix, fd, mode, on);
@@ -1386,6 +1832,16 @@ select_large_fd_error(ErlDrvPort ix, ErtsSysFdType fd, int mode, int on)
     large_fd_error_common(dsbufp, fd);
     erts_send_error_to_logger_nogl(dsbufp);
 }
+static void
+nif_select_large_fd_error(ErtsSysFdType fd, int mode,
+                          ErlNifResource* 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);
+}
 #endif /* ERTS_SYS_CONTINOUS_FD_NUMBERS */
 
 
@@ -1394,38 +1850,78 @@ static void
 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 &= ~ERTS_EV_FLAG_USED;
+        state->driver.stop.drv_ptr = NULL;
+    }
+    else {
+        erts_dsprintf(dsbufp, "ignored repeated call\n");
+    }
+    erts_send_error_to_logger_nogl(dsbufp);
+}
+
+static void
+steal_pending_stop_nif(erts_dsprintf_buf_t *dsbufp, ErlNifResource* resource,
+                       ErtsDrvEventState *state, int mode, int on)
+{
+    int cancel = 0;
+
+    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 ((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;
+    }
+
+    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);
+        state->type = ERTS_EV_TYPE_NONE;
+        state->flags &= ~ERTS_EV_FLAG_USED;
+        state->driver.stop.resource = NULL;
+    }
+    else {
+        erts_dsprintf(dsbufp, "ignored repeated call\n");
+    }
+    erts_send_error_to_logger_nogl(dsbufp);
 
 }
 
@@ -1557,6 +2053,48 @@ oready(Eterm id, ErtsDrvEventState *state, erts_aint_t current_cio_time)
     }
 }
 
+static ERTS_INLINE void
+send_event_tuple(struct erts_nif_select_event* e, ErlNifResource* resource,
+                 Eterm event_atom)
+{
+    Process* rp = erts_proc_lookup(e->pid);
+    ErtsProcLocks rp_locks = 0;
+    ErtsMessage* mp;
+    ErlOffHeap* ohp;
+    ErtsBinary* bin;
+    Eterm* hp;
+    Uint hsz = 5 + PROC_BIN_SIZE + REF_THING_SIZE; /* {select, Resource, Ref, EventAtom} */
+    Eterm resource_term, ref_term, tuple;
+
+    if (!rp) {
+        erts_fprintf(stderr, "SVERK: Process %T not alive for msg %T\n", e->pid, event_atom);
+        return;
+    }
+
+    bin = ERTS_MAGIC_BIN_FROM_UNALIGNED_DATA(resource);
+
+    mp = erts_alloc_message_heap(rp, &rp_locks, hsz, &hp, &ohp);
+
+    resource_term = erts_mk_magic_binary_term(&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 += REF_THING_SIZE;
+    tuple = TUPLE4(hp, am_select, resource_term, ref_term, event_atom);
+
+    ERL_MESSAGE_TOKEN(mp) = am_undefined;
+    erts_queue_message(rp, rp_locks, mp, tuple, am_system);
+
+    if (rp_locks)
+        erts_smp_proc_unlock(rp, rp_locks);
+}
+
+
 #if ERTS_CIO_HAVE_DRV_EVENT
 static ERTS_INLINE void
 eready(Eterm id, ErtsDrvEventState *state, ErlDrvEventData event_data,
@@ -1602,6 +2140,8 @@ ERTS_CIO_EXPORT(erts_check_io_interrupt_timed)(int set,
     ERTS_CIO_POLL_INTR_TMD(pollset.ps, set, timeout_time);
 }
 
+#define ERTS_NIF_DELAYED_DESELECT 20
+
 void
 ERTS_CIO_EXPORT(erts_check_io)(int do_wait)
 {
@@ -1635,7 +2175,8 @@ ERTS_CIO_EXPORT(erts_check_io)(int do_wait)
     current_cio_time++;
     erts_smp_atomic_set_relb(&erts_check_io_time, current_cio_time);
 
-    check_cleanup_active_fds(current_cio_time);
+    check_cleanup_active_fds(current_cio_time,
+                             timeout_time != ERTS_POLL_NO_TIMEOUT);
 
 #ifdef ERTS_ENABLE_LOCK_CHECK
     erts_lc_check_exact(NULL, 0); /* No locks should be locked */
@@ -1741,6 +2282,69 @@ ERTS_CIO_EXPORT(erts_check_io)(int do_wait)
 	    break;
 	}
 
+        case ERTS_EV_TYPE_NIF: { /* Requested via enif_select()... */
+            struct erts_nif_select_event in = {NIL};
+            struct erts_nif_select_event out = {NIL};
+            ErlNifResource* resource;
+            ErtsPollEvents revents = pollres[i].events;
+
+            if (revents & ERTS_POLL_EV_ERR) {
+                /*
+                 * Handle error events by triggering all in/out events
+                 * that the NIF has selected.
+                 * We *do not* want to send a message that corresponds
+		 * to an event not selected.
+                 */
+                revents = state->events;
+            }
+            else {
+                revents &= (state->events | ERTS_POLL_EV_NVAL);
+            }
+
+            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.ddeselect_cnt = ERTS_NIF_DELAYED_DESELECT;
+                        state->driver.nif->out.pid = NIL;
+                        add_active_fd(state->fd);
+                    }
+                    else {
+                        ASSERT(state->driver.nif->out.ddeselect_cnt >= 2);
+                        state->driver.nif->out.ddeselect_cnt--;
+                    }
+                }
+                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.ddeselect_cnt = ERTS_NIF_DELAYED_DESELECT;
+                        state->driver.nif->in.pid = NIL;
+                        add_active_fd(state->fd);
+                    }
+                    else {
+                        ASSERT(state->driver.nif->in.ddeselect_cnt >= 2);
+                        state->driver.nif->in.ddeselect_cnt--;
+                    }
+                }
+            }
+            else if (revents & ERTS_POLL_EV_NVAL) {
+                abort();
+            }
+
+#ifdef ERTS_SMP
+            erts_smp_mtx_unlock(fd_mtx(fd));
+#endif
+            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);
+            }
+            goto next_pollres_unlocked;
+        }
+
 #if ERTS_CIO_HAVE_DRV_EVENT
 	case ERTS_EV_TYPE_DRV_EV: { /* Requested via driver_event()... */
 	    ErlDrvEventData event_data;
@@ -1781,6 +2385,7 @@ ERTS_CIO_EXPORT(erts_check_io)(int do_wait)
 #ifdef ERTS_SMP
 	erts_smp_mtx_unlock(fd_mtx(fd));
 #endif
+        next_pollres_unlocked:;
     }
 
     erts_smp_atomic_set_nob(&pollset.in_poll_wait, 0);
@@ -2306,6 +2911,39 @@ static void doit_erts_check_io_debug(void *vstate, void *vcounters)
 		}
 	    }
 	}
+        else if (state->type == ERTS_EV_TYPE_NIF) {
+            ErlNifResource* r;
+            erts_printf("enif_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);
+            }
+#else
+            if (print_events(cio_events) != 0)
+                err = 1;
+#endif
+            erts_printf(" inpid=%T dd_cnt=%b32d", state->driver.nif->in.pid,
+                        state->driver.nif->in.ddeselect_cnt);
+            erts_printf(" outpid=%T dd_cnt=%b32d", state->driver.nif->out.pid,
+                        state->driver.nif->out.ddeselect_cnt);
+            r = state->driver.stop.resource;
+            erts_printf(" resource=%p(%T:%T)", r, r->type->module, r->type->name);
+        }
 #if ERTS_CIO_HAVE_DRV_EVENT
 	else if (state->type == ERTS_EV_TYPE_DRV_EV) {
 	    Eterm id;
@@ -2362,11 +3000,12 @@ static void doit_erts_check_io_debug(void *vstate, void *vcounters)
 	    erts_printf("control_type=%d ", (int)state->type);
 #ifdef ERTS_SYS_CONTINOUS_FD_NUMBERS
 	    if (cio_events == ep_events) {
-		erts_printf("ev=0x%b32x", (Uint32) cio_events);
+                erts_printf("ev=");
+                print_events(cio_events);
 	    }
 	    else {
-		erts_printf("cio_ev=0x%b32x", (Uint32) cio_events);
-		erts_printf(" ep_ev=0x%b32x", (Uint32) ep_events);
+		erts_printf("cio_ev="); print_events(cio_events);
+		erts_printf(" ep_ev="); print_events(ep_events);
 	    }
 #else
 	    erts_printf("ev=0x%b32x", (Uint32) cio_events);
@@ -2395,7 +3034,7 @@ ERTS_CIO_EXPORT(erts_check_io_debug)(ErtsCheckIoDebugInfo *ciodip)
 #if ERTS_CIO_HAVE_DRV_EVENT
     null_des.driver.event = NULL;
 #endif
-    null_des.driver.drv_ptr = NULL;
+    null_des.driver.stop.drv_ptr = NULL;
     null_des.events = 0;
     null_des.remove_cnt = 0;
     null_des.type = ERTS_EV_TYPE_NONE;
diff --git a/erts/emulator/sys/common/erl_check_io.h b/erts/emulator/sys/common/erl_check_io.h
index 14f1ea3f43..242e7cfcf5 100644
--- a/erts/emulator/sys/common/erl_check_io.h
+++ b/erts/emulator/sys/common/erl_check_io.h
@@ -34,6 +34,8 @@
 
 int driver_select_kp(ErlDrvPort, ErlDrvEvent, int, int);
 int driver_select_nkp(ErlDrvPort, ErlDrvEvent, int, int);
+int enif_select_kp(ErlNifEnv*, ErlNifEvent, enum ErlNifSelectFlags, void*, Eterm);
+int enif_select_nkp(ErlNifEnv*, ErlNifEvent, enum ErlNifSelectFlags, void*, Eterm);
 int driver_event_kp(ErlDrvPort, ErlDrvEvent, ErlDrvEventData);
 int driver_event_nkp(ErlDrvPort, ErlDrvEvent, ErlDrvEventData);
 Uint erts_check_io_size_kp(void);
@@ -136,4 +138,20 @@ typedef struct {
     ErtsIoTask iniotask;
     ErtsIoTask outiotask;
 } ErtsDrvSelectDataState;
+
+struct erts_nif_select_event {
+    Eterm pid;
+    Eterm immed;
+    Uint32 refn[ERTS_REF_NUMBERS];
+    Sint32 ddeselect_cnt; /* 0:  No delayed deselect in progress
+                           * 1:  Do deselect before next poll
+                           * >1: Countdown of ignored events
+                           */
+};
+
+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_poll.c b/erts/emulator/sys/common/erl_poll.c
index b8a28bcc18..0c4df3e13a 100644
--- a/erts/emulator/sys/common/erl_poll.c
+++ b/erts/emulator/sys/common/erl_poll.c
@@ -3030,6 +3030,7 @@ ERTS_POLL_EXPORT(erts_poll_get_selected_events)(ErtsPollSet ps,
 	    ev[fd] = 0;
 	else {
 	    ev[fd] = ps->fds_status[fd].events;
+            ASSERT(ps->fds_status[fd].used_events == ev[fd]);
             if (
 #if ERTS_POLL_USE_WAKEUP_PIPE
                 fd == ps->wake_fds[0] || fd == ps->wake_fds[1] ||
diff --git a/erts/emulator/sys/unix/sys.c b/erts/emulator/sys/unix/sys.c
index 4b2edace0a..789b455f2d 100644
--- a/erts/emulator/sys/unix/sys.c
+++ b/erts/emulator/sys/unix/sys.c
@@ -161,6 +161,7 @@ int erts_use_kernel_poll = 0;
 
 struct {
     int (*select)(ErlDrvPort, ErlDrvEvent, int, int);
+    int (*enif_select)(ErlNifEnv*, ErlNifEvent, enum ErlNifSelectFlags, void*, Eterm);
     int (*event)(ErlDrvPort, ErlDrvEvent, ErlDrvEventData);
     void (*check_io_as_interrupt)(void);
     void (*check_io_interrupt)(int);
@@ -184,6 +185,13 @@ driver_event(ErlDrvPort port, ErlDrvEvent event, ErlDrvEventData event_data)
     return (*io_func.event)(port, event, event_data);
 }
 
+int enif_select(ErlNifEnv* env, ErlNifEvent event,
+                enum ErlNifSelectFlags flags, void* obj, Eterm ref)
+{
+    return (*io_func.enif_select)(env, event, flags, obj, ref);
+}
+
+
 Eterm erts_check_io_info(void *p)
 {
     return (*io_func.info)(p);
@@ -201,6 +209,7 @@ init_check_io(void)
 {
     if (erts_use_kernel_poll) {
 	io_func.select			= driver_select_kp;
+        io_func.enif_select		= enif_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;
@@ -216,6 +225,7 @@ init_check_io(void)
     }
     else {
 	io_func.select			= driver_select_nkp;
+        io_func.enif_select		= enif_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;