erts: Move sys drivers to another file

3 files changed, 2003 insertions, 1910 deletions

diff --git a/erts/emulator/sys/unix/erl_unix_sys.h b/erts/emulator/sys/unix/erl_unix_sys.h
index 8d4e98bf3a..a11a44c259 100644
--- a/erts/emulator/sys/unix/erl_unix_sys.h
+++ b/erts/emulator/sys/unix/erl_unix_sys.h
@@ -470,4 +470,20 @@ extern jmp_buf erts_sys_sigsegv_jmp;
     } while(0)
 #endif
 
+#ifdef USE_THREADS
+#  ifdef ENABLE_CHILD_WAITER_THREAD
+#    define CHLDWTHR ENABLE_CHILD_WAITER_THREAD
+#  else
+#    define CHLDWTHR 0
+#  endif
+#  define FDBLOCK 1
+#else
+#  define CHLDWTHR 0
+#  define FDBLOCK 0
+#endif
+
+#define ERTS_SYS_SUSPEND_SIGNAL SIGUSR2
+
+int check_children(void);
+
 #endif /* #ifndef _ERL_UNIX_SYS_H */
diff --git a/erts/emulator/sys/unix/sys.c b/erts/emulator/sys/unix/sys.c
index 1cb7f72a2b..503ef5c2f6 100644
--- a/erts/emulator/sys/unix/sys.c
+++ b/erts/emulator/sys/unix/sys.c
@@ -67,7 +67,7 @@
 #include "erl_mseg.h"
 
 extern char **environ;
-static erts_smp_rwmtx_t environ_rwmtx;
+erts_smp_rwmtx_t environ_rwmtx;
 
 #define MAX_VSIZE 16		/* Max number of entries allowed in an I/O
 				 * vector sock_sendv().
@@ -76,91 +76,12 @@ static erts_smp_rwmtx_t environ_rwmtx;
  * Don't need global.h, but bif_table.h (included by bif.h),
  * won't compile otherwise
  */
-#include "global.h" 
+#include "global.h"
 #include "bif.h"
 
-#include "erl_sys_driver.h"
 #include "erl_check_io.h"
 #include "erl_cpu_topology.h"
 
-#ifndef DISABLE_VFORK
-#define DISABLE_VFORK 0
-#endif
-
-#if defined IOV_MAX
-#define MAXIOV IOV_MAX
-#elif defined UIO_MAXIOV
-#define MAXIOV UIO_MAXIOV
-#else
-#define MAXIOV 16
-#endif
-
-#ifdef USE_THREADS
-#  ifdef ENABLE_CHILD_WAITER_THREAD
-#    define CHLDWTHR ENABLE_CHILD_WAITER_THREAD
-#  else
-#    define CHLDWTHR 0
-#  endif
-#  define FDBLOCK 1
-#else
-#  define CHLDWTHR 0
-#  define FDBLOCK 0
-#endif
-/*
- * [OTP-3906]
- * Solaris signal management gets confused when threads are used and a
- * lot of child processes dies. The confusion results in that SIGCHLD
- * signals aren't delivered to the emulator which in turn results in
- * a lot of defunct processes in the system.
- *
- * The problem seems to appear when a signal is frequently
- * blocked/unblocked at the same time as the signal is frequently
- * propagated. The child waiter thread is a workaround for this problem.
- * The SIGCHLD signal is always blocked (in all threads), and the child
- * waiter thread fetches the signal by a call to sigwait(). See
- * child_waiter().
- */
-
-typedef struct ErtsSysReportExit_ ErtsSysReportExit;
-struct ErtsSysReportExit_ {
-    ErtsSysReportExit *next;
-    Eterm port;
-    int pid;
-    int ifd;
-    int ofd;
-#if CHLDWTHR && !defined(ERTS_SMP)
-    int status;
-#endif
-};
-
-/* Used by the fd driver iff the fd could not be set to non-blocking */
-typedef struct ErtsSysBlocking_ {
-    ErlDrvPDL pdl;
-    int res;
-    int err;
-    unsigned int pkey;
-} ErtsSysBlocking;
-
-
-/* This data is shared by these drivers - initialized by spawn_init() */
-typedef struct driver_data {
-    ErlDrvPort port_num;
-    int ofd, packet_bytes;
-    ErtsSysReportExit *report_exit;
-    int pid;
-    int alive;
-    int status;
-    int terminating;
-    ErtsSysBlocking *blocking;
-} ErtsSysDriverData;
-
-static ErtsSysDriverData *driver_data;			/* indexed by fd */
-
-static ErtsSysReportExit *report_exit_list;
-#if CHLDWTHR && !defined(ERTS_SMP)
-static ErtsSysReportExit *report_exit_transit_list;
-#endif
-
 extern int  driver_interrupt(int, int);
 extern void do_break(void);
 
@@ -172,32 +93,6 @@ extern void erts_sys_init_float(void);
 
 extern void erl_crash_dump(char* file, int line, char* fmt, ...);
 
-#define DIR_SEPARATOR_CHAR    '/'
-
-#if defined(__ANDROID__)
-#define SHELL "/system/bin/sh"
-#else
-#define SHELL "/bin/sh"
-#endif /* __ANDROID__ */
-
-
-#if defined(DEBUG)
-#define ERL_BUILD_TYPE_MARKER ".debug"
-#elif defined(PURIFY)
-#define ERL_BUILD_TYPE_MARKER ".purify"
-#elif defined(QUANTIFY)
-#define ERL_BUILD_TYPE_MARKER ".quantify"
-#elif defined(PURECOV)
-#define ERL_BUILD_TYPE_MARKER ".purecov"
-#elif defined(VALGRIND)
-#define ERL_BUILD_TYPE_MARKER ".valgrind"
-#else /* opt */
-#define ERL_BUILD_TYPE_MARKER
-#endif
-
-#define CHILD_SETUP_PROG_NAME	"erl_child_setup" ERL_BUILD_TYPE_MARKER
-static char *child_setup_prog;
-
 #ifdef DEBUG
 static int debug_log = 0;
 #endif
@@ -220,61 +115,18 @@ static volatile int have_prepared_crash_dump;
   (have_prepared_crash_dump++)
 #endif
 
-static erts_smp_atomic_t sys_misc_mem_sz;
+erts_smp_atomic_t sys_misc_mem_sz;
 
 #if defined(ERTS_SMP)
 static void smp_sig_notify(char c);
 static int sig_notify_fds[2] = {-1, -1};
 
 static int sig_suspend_fds[2] = {-1, -1};
-#define ERTS_SYS_SUSPEND_SIGNAL SIGUSR2
 
 #endif
 
 jmp_buf erts_sys_sigsegv_jmp;
 
-#if CHLDWTHR || defined(ERTS_SMP)
-erts_mtx_t chld_stat_mtx;
-#endif
-#if CHLDWTHR
-static erts_tid_t child_waiter_tid;
-/* chld_stat_mtx is used to protect against concurrent accesses
-   of the driver_data fields pid, alive, and status. */
-erts_cnd_t chld_stat_cnd;
-static long children_alive;
-#define CHLD_STAT_LOCK		erts_mtx_lock(&chld_stat_mtx)
-#define CHLD_STAT_UNLOCK	erts_mtx_unlock(&chld_stat_mtx)
-#define CHLD_STAT_WAIT		erts_cnd_wait(&chld_stat_cnd, &chld_stat_mtx)
-#define CHLD_STAT_SIGNAL	erts_cnd_signal(&chld_stat_cnd)
-#elif defined(ERTS_SMP) /* ------------------------------------------------- */
-#define CHLD_STAT_LOCK		erts_mtx_lock(&chld_stat_mtx)
-#define CHLD_STAT_UNLOCK	erts_mtx_unlock(&chld_stat_mtx)
-
-#else /* ------------------------------------------------------------------- */
-#define CHLD_STAT_LOCK
-#define CHLD_STAT_UNLOCK
-static volatile int children_died;
-#endif
-
-
-typedef struct ErtsSysFdData {
-    char  pbuf[4];   /* hold partial packet bytes */
-    int   psz;       /* size of pbuf */
-    char  *buf;
-    char  *cpos;
-    int   sz;
-    int   remain;  /* for input on fd */
-} ErtsSysFdData;
-
-static ErtsSysFdData *fd_data;			/* indexed by fd */
-
-/* static FUNCTION(int, write_fill, (int, char*, int)); unused? */
-static void note_child_death(int, int);
-
-#if CHLDWTHR
-static void* child_waiter(void *);
-#endif
-
 static int crashdump_companion_cube_fd = -1;
 
 /********************* General functions ****************************/
@@ -559,8 +411,6 @@ erts_sys_pre_init(void)
 
     erts_thr_init(&eid);
 
-    report_exit_list = NULL;
-
 #ifdef ERTS_ENABLE_LOCK_COUNT
     erts_lcnt_init();
 #endif
@@ -571,17 +421,6 @@ erts_sys_pre_init(void)
 
 #ifdef USE_THREADS
 
-#if CHLDWTHR || defined(ERTS_SMP)
-    erts_mtx_init(&chld_stat_mtx, "child_status");
-#endif
-#if CHLDWTHR
-#ifndef ERTS_SMP
-    report_exit_transit_list = NULL;
-#endif
-    erts_cnd_init(&chld_stat_cnd);
-    children_alive = 0;
-#endif
-
 #ifdef ERTS_SMP
     erts_smp_atomic32_init_nob(&erts_break_requested, 0);
     erts_smp_atomic32_init_nob(&erts_got_sigusr1, 0);
@@ -591,9 +430,6 @@ erts_sys_pre_init(void)
     erts_got_sigusr1 = 0;
     have_prepared_crash_dump = 0;
 #endif
-#if !CHLDWTHR && !defined(ERTS_SMP)
-    children_died = 0;
-#endif
 
 #endif /* USE_THREADS */
 
@@ -630,39 +466,6 @@ erts_sys_pre_init(void)
 void
 erl_sys_init(void)
 {
-#if !DISABLE_VFORK
- {
-    int res;
-    char bindir[MAXPATHLEN];
-    size_t bindirsz = sizeof(bindir);
-    Uint csp_path_sz;
-
-    res = erts_sys_getenv_raw("BINDIR", bindir, &bindirsz);
-    if (res != 0) {
-	if (res < 0)
-	    erl_exit(-1,
-		     "Environment variable BINDIR is not set\n");
-	if (res > 0)
-	    erl_exit(-1,
-		     "Value of environment variable BINDIR is too large\n");
-    }
-    if (bindir[0] != DIR_SEPARATOR_CHAR)
-	erl_exit(-1,
-		 "Environment variable BINDIR does not contain an"
-		 " absolute path\n");
-    csp_path_sz = (strlen(bindir)
-		   + 1 /* DIR_SEPARATOR_CHAR */
-		   + sizeof(CHILD_SETUP_PROG_NAME)
-		   + 1);
-    child_setup_prog = erts_alloc(ERTS_ALC_T_CS_PROG_PATH, csp_path_sz);
-    erts_smp_atomic_add_nob(&sys_misc_mem_sz, csp_path_sz);
-    erts_snprintf(child_setup_prog, csp_path_sz,
-            "%s%c%s",
-            bindir,
-            DIR_SEPARATOR_CHAR,
-            CHILD_SETUP_PROG_NAME);
- }
-#endif
 
 #ifdef USE_SETLINEBUF
     setlinebuf(stdout);
@@ -980,43 +783,6 @@ int sys_max_files(void)
    return(max_files);
 }
 
-static void block_signals(void)
-{
-#if !CHLDWTHR
-   sys_sigblock(SIGCHLD);
-#endif
-#ifndef ERTS_SMP
-   sys_sigblock(SIGINT);
-#ifndef ETHR_UNUSABLE_SIGUSRX
-   sys_sigblock(SIGUSR1);
-#endif /* #ifndef ETHR_UNUSABLE_SIGUSRX */
-#endif /* #ifndef ERTS_SMP */
-
-#if defined(ERTS_SMP) && !defined(ETHR_UNUSABLE_SIGUSRX)
-   sys_sigblock(ERTS_SYS_SUSPEND_SIGNAL);
-#endif
-
-}
-
-static void unblock_signals(void)
-{
-    /* Update erl_child_setup.c if changed */
-#if !CHLDWTHR
-   sys_sigrelease(SIGCHLD);
-#endif
-#ifndef ERTS_SMP
-   sys_sigrelease(SIGINT);
-#ifndef ETHR_UNUSABLE_SIGUSRX
-   sys_sigrelease(SIGUSR1);
-#endif /* #ifndef ETHR_UNUSABLE_SIGUSRX */
-#endif /* #ifndef ERTS_SMP */
-
-#if defined(ERTS_SMP) && !defined(ETHR_UNUSABLE_SIGUSRX)
-   sys_sigrelease(ERTS_SYS_SUSPEND_SIGNAL);
-#endif
-
-}
-
 /************************** OS info *******************************/
 
 /* Used by erlang:info/1. */
@@ -1104,1502 +870,6 @@ void fini_getenv_state(GETENV_STATE *state)
    erts_smp_rwmtx_runlock(&environ_rwmtx);
 }
 
-
-/************************** Port I/O *******************************/
-
-
-
-/* I. Common stuff */
-
-/*
- * Decreasing the size of it below 16384 is not allowed.
- */
-
-/* II. The spawn/fd/vanilla drivers */
-
-#define ERTS_SYS_READ_BUF_SZ (64*1024)
-
-/* Driver interfaces */
-static ErlDrvData spawn_start(ErlDrvPort, char*, SysDriverOpts*);
-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 ErlDrvData vanilla_start(ErlDrvPort, char*, SysDriverOpts*);
-static int spawn_init(void);
-static void fd_stop(ErlDrvData);
-static void fd_flush(ErlDrvData);
-static void stop(ErlDrvData);
-static void ready_input(ErlDrvData, ErlDrvEvent);
-static void ready_output(ErlDrvData, ErlDrvEvent);
-static void output(ErlDrvData, char*, ErlDrvSizeT);
-static void outputv(ErlDrvData, ErlIOVec*);
-static void stop_select(ErlDrvEvent, void*);
-
-struct erl_drv_entry spawn_driver_entry = {
-    spawn_init,
-    spawn_start,
-    stop,
-    output,
-    ready_input,
-    ready_output,
-    "spawn",
-    NULL,
-    NULL,
-    NULL,
-    NULL,
-    NULL,
-    NULL,
-    NULL,
-    NULL,
-    NULL,
-    ERL_DRV_EXTENDED_MARKER,
-    ERL_DRV_EXTENDED_MAJOR_VERSION,
-    ERL_DRV_EXTENDED_MINOR_VERSION,
-    ERL_DRV_FLAG_USE_PORT_LOCKING,
-    NULL, NULL,
-    stop_select
-};
-struct erl_drv_entry fd_driver_entry = {
-    NULL,
-    fd_start,
-    fd_stop,
-    output,
-    ready_input,
-    ready_output, 
-    "fd",
-    NULL,
-    NULL,
-    fd_control,
-    NULL,
-    outputv,
-#if FDBLOCK
-    fd_ready_async, /* ready_async */
-#else
-    NULL,
-#endif
-    fd_flush, /* flush */
-    NULL, /* call */
-    NULL, /* event */
-    ERL_DRV_EXTENDED_MARKER,
-    ERL_DRV_EXTENDED_MAJOR_VERSION,
-    ERL_DRV_EXTENDED_MINOR_VERSION,
-    0, /* ERL_DRV_FLAGs */
-    NULL, /* handle2 */
-    NULL, /* process_exit */
-    stop_select
-};
-struct erl_drv_entry vanilla_driver_entry = {
-    NULL,
-    vanilla_start,
-    stop,
-    output,
-    ready_input,
-    ready_output,
-    "vanilla",
-    NULL,
-    NULL,
-    NULL,
-    NULL,
-    NULL,
-    NULL,
-    NULL, /* flush */
-    NULL, /* call */
-    NULL, /* event */
-    ERL_DRV_EXTENDED_MARKER,
-    ERL_DRV_EXTENDED_MAJOR_VERSION,
-    ERL_DRV_EXTENDED_MINOR_VERSION,
-    0, /* ERL_DRV_FLAGs */
-    NULL, /* handle2 */
-    NULL, /* process_exit */
-    stop_select
-};
-
-/* Handle SIGCHLD signals. */
-#if (defined(SIG_SIGSET) || defined(SIG_SIGNAL))
-static RETSIGTYPE onchld(void)
-#else
-static RETSIGTYPE onchld(int signum)
-#endif
-{
-#if CHLDWTHR
-    ASSERT(0); /* We should *never* catch a SIGCHLD signal */
-#elif defined(ERTS_SMP)
-    smp_sig_notify('C');
-#else
-    children_died = 1;
-    ERTS_CHK_IO_AS_INTR(); /* Make sure we don't sleep in poll */
-#endif
-}
-
-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));
-
-    dd->blocking->pdl = driver_pdl_create(dd->port_num);
-    dd->blocking->res = 0;
-    dd->blocking->err = 0;
-    dd->blocking->pkey = driver_async_port_key(dd->port_num);
-
-    return 1;
-}
-
-static int set_driver_data(ErlDrvPort port_num,
-			   int ifd,
-			   int ofd,
-			   int packet_bytes,
-			   int read_write,
-			   int exit_status,
-			   int pid,
-                           int is_blocking)
-{
-    Port *prt;
-    ErtsSysReportExit *report_exit;
-
-    if (!exit_status)
-	report_exit = NULL;
-    else {
-	report_exit = erts_alloc(ERTS_ALC_T_PRT_REP_EXIT,
-				 sizeof(ErtsSysReportExit));
-	report_exit->next = report_exit_list;
-	report_exit->port = erts_drvport2id(port_num);
-	report_exit->pid = pid;
-	report_exit->ifd = read_write & DO_READ ? ifd : -1;
-	report_exit->ofd = read_write & DO_WRITE ? ofd : -1;
-#if CHLDWTHR && !defined(ERTS_SMP)
-	report_exit->status = 0;
-#endif
-	report_exit_list = report_exit;
-    }
-
-    prt = erts_drvport2port(port_num);
-    if (prt != ERTS_INVALID_ERL_DRV_PORT)
-	prt->os_pid = pid;
-
-    if (read_write & DO_READ) {
-	driver_data[ifd].packet_bytes = packet_bytes;
-	driver_data[ifd].port_num = port_num;
-	driver_data[ifd].report_exit = report_exit;
-	driver_data[ifd].pid = pid;
-	driver_data[ifd].alive = 1;
-	driver_data[ifd].status = 0;
-        driver_data[ifd].terminating = 0;
-        driver_data[ifd].blocking = NULL;
-	if (read_write & DO_WRITE) {
-	    driver_data[ifd].ofd = ofd;
-            if (is_blocking && FDBLOCK)
-                if (!set_blocking_data(driver_data+ifd))
-                    return -1;
-	    if (ifd != ofd)
-		driver_data[ofd] = driver_data[ifd];  /* structure copy */
-	} else {		/* DO_READ only */
-	    driver_data[ifd].ofd = -1;
-	}
-	(void) driver_select(port_num, ifd, (ERL_DRV_READ|ERL_DRV_USE), 1);
-	return(ifd);
-    } else {			/* DO_WRITE only */
-	driver_data[ofd].packet_bytes = packet_bytes;
-	driver_data[ofd].port_num = port_num;
-	driver_data[ofd].report_exit = report_exit;
-	driver_data[ofd].ofd = ofd;
-	driver_data[ofd].pid = pid;
-	driver_data[ofd].alive = 1;
-	driver_data[ofd].status = 0;
-        driver_data[ofd].terminating = 0;
-        driver_data[ofd].blocking = NULL;
-        if (is_blocking && FDBLOCK)
-            if (!set_blocking_data(driver_data+ofd))
-                return -1;
-	return(ofd);
-    }
-}
-
-static int spawn_init()
-{
-   int i;
-#if CHLDWTHR
-   erts_thr_opts_t thr_opts = ERTS_THR_OPTS_DEFAULT_INITER;
-
-   thr_opts.detached = 0;
-   thr_opts.suggested_stack_size = 0; /* Smallest possible */
-   thr_opts.name = "child_waiter";
-#endif
-
-   sys_signal(SIGPIPE, SIG_IGN); /* Ignore - we'll handle the write failure */
-   driver_data = (ErtsSysDriverData *)
-       erts_alloc(ERTS_ALC_T_DRV_TAB, max_files * sizeof(ErtsSysDriverData));
-   erts_smp_atomic_add_nob(&sys_misc_mem_sz,
-			   max_files * sizeof(ErtsSysDriverData));
-
-   for (i = 0; i < max_files; i++)
-      driver_data[i].pid = -1;
-
-#if CHLDWTHR
-   sys_sigblock(SIGCHLD);
-#endif
-
-   sys_signal(SIGCHLD, onchld); /* Reap children */
-
-#if CHLDWTHR
-   erts_thr_create(&child_waiter_tid, child_waiter, NULL, &thr_opts);
-#endif
-
-   return 1;
-}
-
-static void close_pipes(int ifd[2], int ofd[2], int read_write)
-{
-    if (read_write & DO_READ) {
-	(void) close(ifd[0]);
-	(void) close(ifd[1]);
-    }
-    if (read_write & DO_WRITE) {
-	(void) close(ofd[0]);
-	(void) close(ofd[1]);
-    }
-}
-
-static void init_fd_data(int fd, ErlDrvPort port_num)
-{
-    fd_data[fd].buf = NULL;
-    fd_data[fd].cpos = NULL;
-    fd_data[fd].remain = 0;
-    fd_data[fd].sz = 0;
-    fd_data[fd].psz = 0;
-}
-
-static char **build_unix_environment(char *block)
-{
-    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;
-    }
-
-    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;
-
-	    s = cpp[j];
-	    t = old;
-	    while (*s == *t && *s != '=') {
-		s++, t++;
-	    }
-	    if (*s == '=' && *t == '=') {
-		break;
-	    }
-	}
-
-	if (j == len) {		/* New version not found */
-	    cpp[len++] = old;
-	}
-    }
-
-    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++;
-	}
-    }
-
-    cpp[len] = NULL;
-    return cpp;
-}
-
-/*
-  [arndt] In most Unix systems, including Solaris 2.5, 'fork' allocates memory
-  in swap space for the child of a 'fork', whereas 'vfork' does not do this.
-  The natural call to use here is therefore 'vfork'. Due to a bug in
-  'vfork' in Solaris 2.5 (apparently fixed in 2.6), using 'vfork'
-  can be dangerous in what seems to be these circumstances:
-      If the child code under a vfork sets the signal action to SIG_DFL
-      (or SIG_IGN)
-      for any signal which was previously set to a signal handler, the
-      state of the parent is clobbered, so that the later arrival of
-      such a signal yields a sigsegv in the parent. If the signal was
-      not set to a signal handler, but ignored, all seems to work.
-  If you change the forking code below, beware of this.
- */
-
-static ErlDrvData spawn_start(ErlDrvPort port_num, char* name, SysDriverOpts* opts)
-{
-#define CMD_LINE_PREFIX_STR "exec "
-#define CMD_LINE_PREFIX_STR_SZ (sizeof(CMD_LINE_PREFIX_STR) - 1)
-
-    int ifd[2], ofd[2], len, pid, i;
-    char **volatile new_environ; /* volatile since a vfork() then cannot
-				    cause 'new_environ' to be clobbered
-				    in the parent process. */
-    int saved_errno;
-    long res;
-    char *cmd_line;
-#ifndef QNX
-    int unbind;
-#endif
-#if !DISABLE_VFORK
-    int no_vfork;
-    size_t no_vfork_sz = sizeof(no_vfork);
-
-    no_vfork = (erts_sys_getenv_raw("ERL_NO_VFORK",
-				    (char *) &no_vfork,
-				    &no_vfork_sz) >= 0);
-#endif
-
-    switch (opts->read_write) {
-    case DO_READ:
-	if (pipe(ifd) < 0)
-	    return ERL_DRV_ERROR_ERRNO;
-	if (ifd[0] >= max_files) {
-	    close_pipes(ifd, ofd, opts->read_write);
-	    errno = EMFILE;
-	    return ERL_DRV_ERROR_ERRNO;
-	}
-	ofd[1] = -1;		/* keep purify happy */
-	break;
-    case DO_WRITE:
-	if (pipe(ofd) < 0) return ERL_DRV_ERROR_ERRNO;
-	if (ofd[1] >= max_files) {
-	    close_pipes(ifd, ofd, opts->read_write);
-	    errno = EMFILE;
-	    return ERL_DRV_ERROR_ERRNO;
-	}
-	ifd[0] = -1;		/* keep purify happy */
-	break;
-    case DO_READ|DO_WRITE:
-	if (pipe(ifd) < 0) return ERL_DRV_ERROR_ERRNO;
-	errno = EMFILE;		/* default for next two conditions */
-	if (ifd[0] >= max_files || pipe(ofd) < 0) {
-	    close_pipes(ifd, ofd, DO_READ);
-	    return ERL_DRV_ERROR_ERRNO;
-	}
-	if (ofd[1] >= max_files) {
-	    close_pipes(ifd, ofd, opts->read_write);
-	    errno = EMFILE;
-	    return ERL_DRV_ERROR_ERRNO;
-	}
-	break;
-    default:
-	ASSERT(0);
-	return ERL_DRV_ERROR_GENERAL;
-    }
-
-    if (opts->spawn_type == ERTS_SPAWN_EXECUTABLE) {
-	/* started with spawn_executable, not with spawn */
-	len = strlen(name);
-	cmd_line = (char *) erts_alloc_fnf(ERTS_ALC_T_TMP, len + 1);
-	if (!cmd_line) {
-	    close_pipes(ifd, ofd, opts->read_write);
-	    errno = ENOMEM;
-	    return ERL_DRV_ERROR_ERRNO;
-	}
-	memcpy((void *) cmd_line,(void *) name, len);
-	cmd_line[len] = '\0';
-	if (access(cmd_line,X_OK) != 0) {
-	    int save_errno = errno;
-	    erts_free(ERTS_ALC_T_TMP, cmd_line);
-	    errno = save_errno;
-	    return ERL_DRV_ERROR_ERRNO;
-	}
-    } else {
-	/* make the string suitable for giving to "sh" */
-	len = strlen(name);
-	cmd_line = (char *) erts_alloc_fnf(ERTS_ALC_T_TMP,
-					   CMD_LINE_PREFIX_STR_SZ + len + 1);
-	if (!cmd_line) {
-	    close_pipes(ifd, ofd, opts->read_write);
-	    errno = ENOMEM;
-	    return ERL_DRV_ERROR_ERRNO;
-	}
-	memcpy((void *) cmd_line,
-	       (void *) CMD_LINE_PREFIX_STR,
-	       CMD_LINE_PREFIX_STR_SZ);
-	memcpy((void *) (cmd_line + CMD_LINE_PREFIX_STR_SZ), (void *) name, len);
-	cmd_line[CMD_LINE_PREFIX_STR_SZ + len] = '\0';
-    }
-
-    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);
-	erts_free(ERTS_ALC_T_TMP, (void *) cmd_line);
-	errno = ENOMEM;
-	return ERL_DRV_ERROR_ERRNO;
-    } 
-
-#ifndef QNX
-    /* Block child from SIGINT and SIGUSR1. Must be before fork()
-       to be safe. */
-    block_signals();
-
-    CHLD_STAT_LOCK;
-
-    unbind = erts_sched_bind_atfork_prepare();
-
-#if !DISABLE_VFORK
-    /* See fork/vfork discussion before this function. */
-    if (no_vfork) {
-#endif
-
-	DEBUGF(("Using fork\n"));
-	pid = fork();
-
-	if (pid == 0) {
-	    /* The child! Setup child... */
-
-	    if (erts_sched_bind_atfork_child(unbind) != 0)
-		goto child_error;
-
-	    /* OBSERVE!
-	     * Keep child setup after vfork() (implemented below and in
-	     * erl_child_setup.c) up to date if changes are made here.
-	     */
-
-	    if (opts->use_stdio) {
-		if (opts->read_write & DO_READ) {
-		    /* stdout for process */
-		    if (dup2(ifd[1], 1) < 0)
-			goto child_error;
-		    if(opts->redir_stderr)
-			/* stderr for process */
-			if (dup2(ifd[1], 2) < 0)
-			    goto child_error;
-		}
-		if (opts->read_write & DO_WRITE)
-		    /* stdin for process */
-		    if (dup2(ofd[0], 0) < 0)
-			goto child_error;
-	    }
-	    else {	/* XXX will fail if ofd[0] == 4 (unlikely..) */
-		if (opts->read_write & DO_READ)
-		    if (dup2(ifd[1], 4) < 0)
-			goto child_error;
-		if (opts->read_write & DO_WRITE)
-		    if (dup2(ofd[0], 3) < 0)
-			goto child_error;
-	    }
-
-#if defined(HAVE_CLOSEFROM)
-	    closefrom(opts->use_stdio ? 3 : 5);
-#else
-	    for (i = opts->use_stdio ? 3 : 5; i < max_files; i++)
-		(void) close(i);
-#endif
-
-	    if (opts->wd && chdir(opts->wd) < 0)
-		goto child_error;
-
-#if defined(USE_SETPGRP_NOARGS)		/* SysV */
-	    (void) setpgrp();
-#elif defined(USE_SETPGRP)		/* BSD */
-	    (void) setpgrp(0, getpid());
-#else					/* POSIX */
-	    (void) setsid();
-#endif
-	    
-	    unblock_signals();
-
-	    if (opts->spawn_type == ERTS_SPAWN_EXECUTABLE) {
-		if (opts->argv == NULL) {
-		    execle(cmd_line,cmd_line,(char *) NULL, new_environ);
-		} else {
-		    if (opts->argv[0] == erts_default_arg0) {
-			opts->argv[0] = cmd_line;
-		    }
-		    execve(cmd_line, opts->argv, new_environ);
-		    if (opts->argv[0] == cmd_line) {
-			opts->argv[0] = erts_default_arg0;
-		    }
-		}
-	    } else {
-		execle(SHELL, "sh", "-c", cmd_line, (char *) NULL, new_environ);
-	    }
-	child_error:
-	    _exit(1);
-	}
-#if !DISABLE_VFORK
-    }
-#define ENOUGH_BYTES (44)
-    else { /* Use vfork() */
-	char **cs_argv= erts_alloc(ERTS_ALC_T_TMP,(CS_ARGV_NO_OF_ARGS + 1)*
-				   sizeof(char *));
-	char fd_close_range[ENOUGH_BYTES];                  /* 44 bytes are enough to  */
-	char dup2_op[CS_ARGV_NO_OF_DUP2_OPS][ENOUGH_BYTES]; /* hold any "%d:%d" string */
-                                                            /* on a 64-bit machine.    */
-
-	/* Setup argv[] for the child setup program (implemented in
-	   erl_child_setup.c) */
-	i = 0;
-	if (opts->use_stdio) {
-	    if (opts->read_write & DO_READ){
-		/* stdout for process */
-		erts_snprintf(&dup2_op[i++][0], ENOUGH_BYTES, "%d:%d", ifd[1], 1);
-		if(opts->redir_stderr)
-		    /* stderr for process */
-		    erts_snprintf(&dup2_op[i++][0], ENOUGH_BYTES, "%d:%d", ifd[1], 2);
-	    }
-	    if (opts->read_write & DO_WRITE)
-		/* stdin for process */
-		erts_snprintf(&dup2_op[i++][0], ENOUGH_BYTES, "%d:%d", ofd[0], 0);
-	} else {	/* XXX will fail if ofd[0] == 4 (unlikely..) */
-	    if (opts->read_write & DO_READ)
-		erts_snprintf(&dup2_op[i++][0], ENOUGH_BYTES, "%d:%d", ifd[1], 4);
-	    if (opts->read_write & DO_WRITE)
-		erts_snprintf(&dup2_op[i++][0], ENOUGH_BYTES, "%d:%d", ofd[0], 3);
-	}
-	for (; i < CS_ARGV_NO_OF_DUP2_OPS; i++)
-	    strcpy(&dup2_op[i][0], "-");
-	erts_snprintf(fd_close_range, ENOUGH_BYTES, "%d:%d", opts->use_stdio ? 3 : 5, max_files-1);
-
-	cs_argv[CS_ARGV_PROGNAME_IX] = child_setup_prog;
-	cs_argv[CS_ARGV_WD_IX] = opts->wd ? opts->wd : ".";
-	cs_argv[CS_ARGV_UNBIND_IX] = erts_sched_bind_atvfork_child(unbind);
-	cs_argv[CS_ARGV_FD_CR_IX] = fd_close_range;
-	for (i = 0; i < CS_ARGV_NO_OF_DUP2_OPS; i++)
-	    cs_argv[CS_ARGV_DUP2_OP_IX(i)] = &dup2_op[i][0];
-
-	if (opts->spawn_type == ERTS_SPAWN_EXECUTABLE) {
-	    int num = 0;
-	    int j = 0;
-	    if (opts->argv != NULL) {
-		for(; opts->argv[num] != NULL; ++num)
-		    ;
-	    }
-	    cs_argv = erts_realloc(ERTS_ALC_T_TMP,cs_argv, (CS_ARGV_NO_OF_ARGS + 1 + num + 1) * sizeof(char *));
-	    cs_argv[CS_ARGV_CMD_IX] = "-";
-	    cs_argv[CS_ARGV_NO_OF_ARGS] = cmd_line;
-	    if (opts->argv != NULL) {
-		for (;opts->argv[j] != NULL; ++j) {
-		    if (opts->argv[j] == erts_default_arg0) {
-			cs_argv[CS_ARGV_NO_OF_ARGS + 1 + j] = cmd_line;
-		    } else {
-			cs_argv[CS_ARGV_NO_OF_ARGS + 1 + j] = opts->argv[j];
-		    }
-		}
-	    }
-	    cs_argv[CS_ARGV_NO_OF_ARGS + 1 + j] = NULL;
-	} else {
-	    cs_argv[CS_ARGV_CMD_IX] = cmd_line; /* Command */
-	    cs_argv[CS_ARGV_NO_OF_ARGS] = NULL;
-	}
-	DEBUGF(("Using vfork\n"));
-	pid = vfork();
-
-	if (pid == 0) {
-	    /* The child! */
-
-	    /* Observe!
-	     * OTP-4389: The child setup program (implemented in
-	     * erl_child_setup.c) will perform the necessary setup of the
-	     * child before it execs to the user program. This because
-	     * vfork() only allow an *immediate* execve() or _exit() in the
-	     * child.
-	     */
-	    execve(child_setup_prog, cs_argv, new_environ);
-	    _exit(1);
-	}
-	erts_free(ERTS_ALC_T_TMP,cs_argv);
-    }
-#undef ENOUGH_BYTES
-#endif
-
-    erts_sched_bind_atfork_parent(unbind);
-
-    if (pid == -1) {
-        saved_errno = errno;
-	CHLD_STAT_UNLOCK;
-	erts_smp_rwmtx_runlock(&environ_rwmtx);
-	erts_free(ERTS_ALC_T_TMP, (void *) cmd_line);
-        unblock_signals();
-        close_pipes(ifd, ofd, opts->read_write);
-	errno = saved_errno;
-	return ERL_DRV_ERROR_ERRNO;
-    }
-#else /* QNX */
-    if (opts->use_stdio) {
-	if (opts->read_write & DO_READ)
-	    qnx_spawn_options.iov[1] = ifd[1];  /* stdout for process */
-	if (opts->read_write & DO_WRITE)
-	    qnx_spawn_options.iov[0] = ofd[0];  /* stdin for process */
-	} 
-    else {
-	if (opts->read_write & DO_READ)
-	    qnx_spawn_options.iov[4] = ifd[1];
-	if (opts->read_write & DO_WRITE)
-	    qnx_spawn_options.iov[3] = ofd[0];
-    }
-    /* Close fds on exec */
-    for (i = 3; i < max_files; i++)
-	fcntl(i, F_SETFD, 1);
-
-    qnx_spawn_options.flags = _SPAWN_SETSID;
-    if ((pid = spawnl(P_NOWAIT, SHELL, SHELL, "-c", cmd_line, 
-                      (char *) 0)) < 0) {
-	erts_free(ERTS_ALC_T_TMP, (void *) cmd_line);
-        reset_qnx_spawn();
-	erts_smp_rwmtx_runlock(&environ_rwmtx);
-	close_pipes(ifd, ofd, opts->read_write);
-	return ERL_DRV_ERROR_GENERAL;
-    }
-    reset_qnx_spawn();
-#endif /* QNX */
-
-    erts_free(ERTS_ALC_T_TMP, (void *) cmd_line);
-
-    if (new_environ != environ)
-	erts_free(ERTS_ALC_T_ENVIRONMENT, (void *) new_environ);
-
-    if (opts->read_write & DO_READ) 
-	(void) close(ifd[1]);
-    if (opts->read_write & DO_WRITE)
-	(void) close(ofd[0]);
-	
-    if (opts->read_write & DO_READ) {
-	SET_NONBLOCKING(ifd[0]);
-	init_fd_data(ifd[0], port_num);
-    }
-    if (opts->read_write & DO_WRITE) {
-	SET_NONBLOCKING(ofd[1]);
-        init_fd_data(ofd[1], port_num);
-    }
-
-    res = set_driver_data(port_num, ifd[0], ofd[1], opts->packet_bytes,
-			  opts->read_write, opts->exit_status, pid, 0);
-    /* Don't unblock SIGCHLD until now, since the call above must
-       first complete putting away the info about our new subprocess. */
-    unblock_signals();
-
-#if CHLDWTHR
-    ASSERT(children_alive >= 0);
-
-    if (!(children_alive++))
-	CHLD_STAT_SIGNAL; /* Wake up child waiter thread if no children
-			     was alive before we fork()ed ... */
-#endif
-    /* Don't unlock chld_stat_mtx until now of the same reason as above */
-    CHLD_STAT_UNLOCK;
-
-    erts_smp_rwmtx_runlock(&environ_rwmtx);
-
-    return (ErlDrvData)res;
-#undef CMD_LINE_PREFIX_STR
-#undef CMD_LINE_PREFIX_STR_SZ
-}
-
-#ifdef QNX
-static reset_qnx_spawn()
-{
-    int i;
-
-    /* Reset qnx_spawn_options */
-    qnx_spawn_options.flags = 0; 
-    qnx_spawn_options.iov[0] = 0xff;
-    qnx_spawn_options.iov[1] = 0xff;
-    qnx_spawn_options.iov[2] = 0xff;
-    qnx_spawn_options.iov[3] = 0xff;
-}
-#endif
-
-#define FD_DEF_HEIGHT 24
-#define FD_DEF_WIDTH 80
-/* Control op */
-#define FD_CTRL_OP_GET_WINSIZE 100
-
-static int fd_get_window_size(int fd, Uint32 *width, Uint32 *height)
-{
-#ifdef TIOCGWINSZ 
-    struct winsize ws;
-    if (ioctl(fd,TIOCGWINSZ,&ws) == 0) {
-	*width = (Uint32) ws.ws_col;
-	*height = (Uint32) ws.ws_row;
-	return 0;
-    }
-#endif
-    return -1;
-}
-
-static ErlDrvSSizeT fd_control(ErlDrvData drv_data,
-			       unsigned int command,
-			       char *buf, ErlDrvSizeT len,
-			       char **rbuf, ErlDrvSizeT rlen)
-{
-    int fd = (int)(long)drv_data;
-    char resbuff[2*sizeof(Uint32)];
-    switch (command) {
-    case FD_CTRL_OP_GET_WINSIZE:
-	{
-	    Uint32 w,h;
-	    if (fd_get_window_size(fd,&w,&h)) 
-		return 0;
-	    memcpy(resbuff,&w,sizeof(Uint32));
-	    memcpy(resbuff+sizeof(Uint32),&h,sizeof(Uint32));
-	}
-	break;
-    default:
-	return 0;
-    }
-    if (rlen < 2*sizeof(Uint32)) {
-	*rbuf = driver_alloc(2*sizeof(Uint32));
-    }
-    memcpy(*rbuf,resbuff,2*sizeof(Uint32));
-    return 2*sizeof(Uint32);
-}
-
-static ErlDrvData fd_start(ErlDrvPort port_num, char* name,
-			   SysDriverOpts* opts)
-{
-    ErlDrvData res;
-    int non_blocking = 0;
-
-    if (((opts->read_write & DO_READ) && opts->ifd >= max_files) ||
-	((opts->read_write & DO_WRITE) && opts->ofd >= max_files))
-	return ERL_DRV_ERROR_GENERAL;
-
-    /*
-     * Historical:
-     *
-     * "Note about nonblocking I/O.
-     *
-     * At least on Solaris, setting the write end of a TTY to nonblocking,
-     * will set the input end to nonblocking as well (and vice-versa).
-     * If erl is run in a pipeline like this:  cat | erl
-     * the input end of the TTY will be the standard input of cat.
-     * And cat is not prepared to handle nonblocking I/O."
-     *
-     * Actually, the reason for this is not that the tty itself gets set
-     * in non-blocking mode, but that the "input end" (cat's stdin) and
-     * the "output end" (erlang's stdout) are typically the "same" file
-     * descriptor, dup()'ed from a single fd by one of this process'
-     * ancestors.
-     *
-     * The workaround for this problem used to be a rather bad kludge,
-     * interposing an extra process ("internal cat") between erlang's
-     * stdout and the original stdout, allowing erlang to set its stdout
-     * in non-blocking mode without affecting the stdin of the preceding
-     * process in the pipeline - and being a kludge, it caused all kinds
-     * of weird problems.
-     *
-     * So, this is the current logic:
-     *
-     * The only reason to set non-blocking mode on the output fd at all is
-     * if it's something that can cause a write() to block, of course,
-     * i.e. primarily if it points to a tty, socket, pipe, or fifo. 
-     *
-     * If we don't set non-blocking mode when we "should" have, and output
-     * becomes blocked, the entire runtime system will be suspended - this
-     * is normally bad of course, and can happen fairly "easily" - e.g. user
-     * hits ^S on tty - but doesn't necessarily happen.
-     * 
-     * If we do set non-blocking mode when we "shouldn't" have, the runtime
-     * system will end up seeing EOF on the input fd (due to the preceding
-     * process dying), which typically will cause the entire runtime system
-     * to terminate immediately (due to whatever erlang process is seeing
-     * the EOF taking it as a signal to halt the system). This is *very* bad.
-     * 
-     * I.e. we should take a conservative approach, and only set non-
-     * blocking mode when we a) need to, and b) are reasonably certain
-     * that it won't be a problem. And as in the example above, the problem
-     * occurs when input fd and output fd point to different "things".
-     *
-     * However, determining that they are not just the same "type" of
-     * "thing", but actually the same instance of that type of thing, is
-     * unreasonably complex in many/most cases.
-     *
-     * Also, with pipes, sockets, and fifos it's far from obvious that the
-     * user *wants* non-blocking output: If you're running erlang inside
-     * some complex pipeline, you're probably not running a real-time system
-     * that must never stop, but rather *want* it to suspend if the output
-     * channel is "full".
-     *
-     * So, the bottom line: We will only set the output fd non-blocking if
-     * it points to a tty, and either a) the input fd also points to a tty,
-     * or b) we can make sure that setting the output fd non-blocking
-     * doesn't interfere with someone else's input, via a somewhat milder
-     * kludge than the above.
-     *
-     * Also keep in mind that while this code is almost exclusively run as
-     * a result of an erlang open_port({fd,0,1}, ...), that isn't the only
-     * case - it can be called with any old pre-existing file descriptors,
-     * the relations between which (if they're even two) we can only guess
-     * at - still, we try our best...
-     *
-     * Added note OTP 18: Some systems seem to use stdout/stderr to log data
-     * using unix pipes, so we cannot allow the system to block on a write.
-     * Therefore we use an async thread to write the data to fd's that could
-     * not be set to non-blocking. When no async threads are available we
-     * fall back on the old behaviour.
-     *
-     * Also the guarantee about what is delivered to the OS has changed.
-     * Pre 18 the fd driver did no flushing of data before terminating.
-     * Now it does. This is because we want to be able to guarantee that things
-     * such as escripts and friends really have outputted all data before
-     * terminating. This could potentially block the termination of the system
-     * for a very long time, but if the user wants to terminate fast she should
-     * use erlang:halt with flush=false.
-     */
-
-    if (opts->read_write & DO_READ) {
-	init_fd_data(opts->ifd, port_num);
-    }
-    if (opts->read_write & DO_WRITE) {
-	init_fd_data(opts->ofd, port_num);
-
-	/* If we don't have a read end, all bets are off - no non-blocking. */
-	if (opts->read_write & DO_READ) {
-
-	    if (isatty(opts->ofd)) { /* output fd is a tty:-) */
-
-		if (isatty(opts->ifd)) { /* input fd is also a tty */
-
-		    /* To really do this "right", we should also check that
-		       input and output fd point to the *same* tty - but
-		       this seems like overkill; ttyname() isn't for free,
-		       and this is a very common case - and it's hard to
-		       imagine a scenario where setting non-blocking mode
-		       here would cause problems - go ahead and do it. */
-
-                    non_blocking = 1;
-		    SET_NONBLOCKING(opts->ofd);
-
-		} else {	/* output fd is a tty, input fd isn't */
-
-		    /* This is a "problem case", but also common (see the
-		       example above) - i.e. it makes sense to try a bit
-		       harder before giving up on non-blocking mode: Try to
-		       re-open the tty that the output fd points to, and if
-		       successful replace the original one with the "new" fd
-		       obtained this way, and set *that* one in non-blocking
-		       mode. (Yes, this is a kludge.)
-
-		       However, re-opening the tty may fail in a couple of
-		       (unusual) cases:
-
-		       1) The name of the tty (or an equivalent one, i.e.
-			  same major/minor number) can't be found, because
-			  it actually lives somewhere other than /dev (or
-			  wherever ttyname() looks for it), and isn't
-			  equivalent to any of those that do live in the
-			  "standard" place - this should be *very* unusual.
-
-		       2) Permissions on the tty don't allow us to open it -
-			  it's perfectly possible to have an fd open to an
-			  object whose permissions wouldn't allow us to open
-			  it. This is not as unusual as it sounds, one case
-			  is if the user has su'ed to someone else (not
-			  root) - we have a read/write fd open to the tty
-			  (because it has been inherited all the way down
-			  here), but we have neither read nor write
-			  permission for the tty.
-
-		       In these cases, we finally give up, and don't set the
-		       output fd in non-blocking mode. */
-
-		    char *tty;
-		    int nfd;
-
-		    if ((tty = ttyname(opts->ofd)) != NULL &&
-			(nfd = open(tty, O_WRONLY)) != -1) {
-			dup2(nfd, opts->ofd);
-			close(nfd);
-                        non_blocking = 1;
-			SET_NONBLOCKING(opts->ofd);
-		    }
-		}
-	    }
-	}
-    }
-    CHLD_STAT_LOCK;
-    res = (ErlDrvData)(long)set_driver_data(port_num, opts->ifd, opts->ofd,
-                                            opts->packet_bytes,
-                                            opts->read_write, 0, -1,
-                                            !non_blocking);
-    CHLD_STAT_UNLOCK;
-    return res;
-}
-
-static void clear_fd_data(int fd) 
-{
-    if (fd_data[fd].sz > 0) {
-	erts_free(ERTS_ALC_T_FD_ENTRY_BUF, (void *) fd_data[fd].buf);
-	ASSERT(erts_smp_atomic_read_nob(&sys_misc_mem_sz) >= fd_data[fd].sz);
-	erts_smp_atomic_add_nob(&sys_misc_mem_sz, -1*fd_data[fd].sz);
-    }
-    fd_data[fd].buf = NULL;
-    fd_data[fd].sz = 0;
-    fd_data[fd].remain = 0;
-    fd_data[fd].cpos = NULL;
-    fd_data[fd].psz = 0;
-}
-
-static void nbio_stop_fd(ErlDrvPort prt, int fd)
-{
-    driver_select(prt,fd,DO_READ|DO_WRITE,0);
-    clear_fd_data(fd);
-    SET_BLOCKING(fd);
-}
-
-static void fd_stop(ErlDrvData ev)  /* Does not close the fds */
-{
-    int ofd;
-    int fd = (int)(long)ev;
-    ErlDrvPort prt = driver_data[fd].port_num;
-    
-#if FDBLOCK
-    if (driver_data[fd].blocking) {
-        erts_free(ERTS_ALC_T_SYS_BLOCKING,driver_data[fd].blocking);
-        driver_data[fd].blocking = NULL;
-        erts_smp_atomic_add_nob(&sys_misc_mem_sz, -1*sizeof(ErtsSysBlocking));
-    }
-#endif
-
-    nbio_stop_fd(prt, fd);
-    ofd = driver_data[fd].ofd;
-    if (ofd != fd && ofd != -1)
-	nbio_stop_fd(prt, ofd);
-}
-
-static void fd_flush(ErlDrvData fd)
-{
-    if (!driver_data[(int)(long)fd].terminating)
-        driver_data[(int)(long)fd].terminating = 1;
-}
-
-static ErlDrvData vanilla_start(ErlDrvPort port_num, char* name,
-				SysDriverOpts* opts)
-{
-    int flags, fd;
-    ErlDrvData res;
-
-    flags = (opts->read_write == DO_READ ? O_RDONLY :
-	     opts->read_write == DO_WRITE ? O_WRONLY|O_CREAT|O_TRUNC :
-	     O_RDWR|O_CREAT);
-    if ((fd = open(name, flags, 0666)) < 0)
-	return ERL_DRV_ERROR_GENERAL;
-    if (fd >= max_files) {
-	close(fd);
-	return ERL_DRV_ERROR_GENERAL;
-    }
-    SET_NONBLOCKING(fd);
-    init_fd_data(fd, port_num);
-
-    CHLD_STAT_LOCK;
-    res = (ErlDrvData)(long)set_driver_data(port_num, fd, fd,
-                                            opts->packet_bytes,
-                                            opts->read_write, 0, -1, 0);
-    CHLD_STAT_UNLOCK;
-    return res;
-}
-
-/* Note that driver_data[fd].ifd == fd if the port was opened for reading, */
-/* otherwise (i.e. write only) driver_data[fd].ofd = fd.  */
-
-static void stop(ErlDrvData fd)
-{
-    ErlDrvPort prt;
-    int ofd;
-
-    prt = driver_data[(int)(long)fd].port_num;
-    nbio_stop_fd(prt, (int)(long)fd);
-
-    ofd = driver_data[(int)(long)fd].ofd;
-    if (ofd != (int)(long)fd && (int)(long)ofd != -1)
-	nbio_stop_fd(prt, ofd);
-    else
-	ofd = -1;
-
-    CHLD_STAT_LOCK;
-
-    /* Mark as unused. */
-    driver_data[(int)(long)fd].pid = -1;
-
-    CHLD_STAT_UNLOCK;
-
-    /* SMP note: Close has to be last thing done (open file descriptors work
-       as locks on driver_data[] entries) */
-    driver_select(prt, (int)(long)fd, ERL_DRV_USE, 0);  /* close(fd); */
-    if (ofd >= 0) {
-	driver_select(prt, (int)(long)ofd, ERL_DRV_USE, 0);  /* close(ofd); */
-    }
-}
-
-/* used by fd_driver */
-static void outputv(ErlDrvData e, ErlIOVec* ev)
-{
-    int fd = (int)(long)e;
-    ErlDrvPort ix = driver_data[fd].port_num;
-    int pb = driver_data[fd].packet_bytes;
-    int ofd = driver_data[fd].ofd;
-    ssize_t n;
-    ErlDrvSizeT sz;
-    char lb[4];
-    char* lbp;
-    ErlDrvSizeT len = ev->size;
-
-    /* (len > ((unsigned long)-1 >> (4-pb)*8)) */
-    /*    if (pb >= 0 && (len & (((ErlDrvSizeT)1 << (pb*8))) - 1) != len) {*/
-    if (((pb == 2) && (len > 0xffff)) || (pb == 1 && len > 0xff)) {
-	driver_failure_posix(ix, EINVAL);
-	return; /* -1; */
-    }
-    /* Handles 0 <= pb <= 4 only */
-    put_int32((Uint32) len, lb);
-    lbp = lb + (4-pb);
-
-    ev->iov[0].iov_base = lbp;
-    ev->iov[0].iov_len = pb;
-    ev->size += pb;
-
-    if (driver_data[fd].blocking && FDBLOCK)
-        driver_pdl_lock(driver_data[fd].blocking->pdl);
-
-    if ((sz = driver_sizeq(ix)) > 0) {
-	driver_enqv(ix, ev, 0);
-
-        if (driver_data[fd].blocking && FDBLOCK)
-            driver_pdl_unlock(driver_data[fd].blocking->pdl);
-
-	if (sz + ev->size >= (1 << 13))
-	    set_busy_port(ix, 1);
-    }
-    else if (!driver_data[fd].blocking || !FDBLOCK) {
-        /* We try to write directly if the fd in non-blocking */
-	int vsize = ev->vsize > MAX_VSIZE ? MAX_VSIZE : ev->vsize;
-
-	n = writev(ofd, (const void *) (ev->iov), vsize);
-	if (n == ev->size)
-	    return; /* 0;*/
-	if (n < 0) {
-	    if ((errno != EINTR) && (errno != ERRNO_BLOCK)) {
-		driver_failure_posix(ix, errno);
-		return; /* -1;*/
-	    }
-	    n = 0;
-	}
-	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);
-            driver_pdl_unlock(driver_data[fd].blocking->pdl);
-            driver_async(ix, &driver_data[fd].blocking->pkey,
-                         fd_async, driver_data+fd, NULL);
-        } else {
-            driver_pdl_unlock(driver_data[fd].blocking->pdl);
-        }
-    }
-#endif
-    /* return 0;*/
-}
-
-/* Used by spawn_driver and vanilla driver */
-static void output(ErlDrvData e, char* buf, ErlDrvSizeT len)
-{
-    int fd = (int)(long)e;
-    ErlDrvPort ix = driver_data[fd].port_num;
-    int pb = driver_data[fd].packet_bytes;
-    int ofd = driver_data[fd].ofd;
-    ssize_t n;
-    ErlDrvSizeT sz;
-    char lb[4];
-    char* lbp;
-    struct iovec iv[2];
-
-    /* (len > ((unsigned long)-1 >> (4-pb)*8)) */
-    if (((pb == 2) && (len > 0xffff)) || (pb == 1 && len > 0xff)) {
-	driver_failure_posix(ix, EINVAL);
-	return; /* -1; */
-    }
-    put_int32(len, lb);
-    lbp = lb + (4-pb);
-
-    if ((sz = driver_sizeq(ix)) > 0) {
-	driver_enq(ix, lbp, pb);
-	driver_enq(ix, buf, len);
-	if (sz + len + pb >= (1 << 13))
-	    set_busy_port(ix, 1);
-    }
-    else {
-	iv[0].iov_base = lbp;
-	iv[0].iov_len = pb;  /* should work for pb=0 */
-	iv[1].iov_base = buf;
-	iv[1].iov_len = len;
-	n = writev(ofd, iv, 2);
-	if (n == pb+len)
-	    return; /* 0; */
-	if (n < 0) {
-	    if ((errno != EINTR) && (errno != ERRNO_BLOCK)) {
-		driver_failure_posix(ix, errno);
-		return; /* -1; */
-	    }
-	    n = 0;
-	}
-	if (n < pb) {
-	    driver_enq(ix, lbp+n, pb-n);
-	    driver_enq(ix, buf, len);
-	}
-	else {
-	    n -= pb;
-	    driver_enq(ix, buf+n, len-n);
-	}
-	driver_select(ix, ofd, ERL_DRV_WRITE|ERL_DRV_USE, 1);
-    }
-    return; /* 0; */
-}
-
-static int port_inp_failure(ErlDrvPort port_num, int ready_fd, int res)
-				/* Result: 0 (eof) or -1 (error) */
-{
-    int err = errno;
-
-    ASSERT(res <= 0);
-    (void) driver_select(port_num, ready_fd, ERL_DRV_READ|ERL_DRV_WRITE, 0); 
-    clear_fd_data(ready_fd);
-
-    if (driver_data[ready_fd].blocking && FDBLOCK) {
-        driver_pdl_lock(driver_data[ready_fd].blocking->pdl);
-        if (driver_sizeq(driver_data[ready_fd].port_num) > 0) {
-            driver_pdl_unlock(driver_data[ready_fd].blocking->pdl);
-            /* We have stuff in the output queue, so we just
-               set the state to terminating and wait for fd_async_ready
-               to terminate the port */
-            if (res == 0)
-                driver_data[ready_fd].terminating = 2;
-            else
-                driver_data[ready_fd].terminating = -err;
-            return 0;
-        }
-        driver_pdl_unlock(driver_data[ready_fd].blocking->pdl);
-    }
-
-    if (res == 0) {
-	if (driver_data[ready_fd].report_exit) {
-	    CHLD_STAT_LOCK;
-
-	    if (driver_data[ready_fd].alive) {
-		/*
-		 * We have eof and want to report exit status, but the process
-		 * hasn't exited yet. When it does report_exit_status() will
-		 * driver_select() this fd which will make sure that we get
-		 * back here with driver_data[ready_fd].alive == 0 and
-		 * driver_data[ready_fd].status set.
-		 */
-		CHLD_STAT_UNLOCK;
-		return 0;
-	    }
-	    else {
-		int status = driver_data[ready_fd].status;
-		CHLD_STAT_UNLOCK;
-
-		/* We need not be prepared for stopped/continued processes. */
-		if (WIFSIGNALED(status))
-		    status = 128 + WTERMSIG(status);
-		else
-		    status = WEXITSTATUS(status);
-
-		driver_report_exit(driver_data[ready_fd].port_num, status);
-	    }
-       }
-       driver_failure_eof(port_num);
-    } else {
-	driver_failure_posix(port_num, err);
-    }
-    return 0;
-}
-
-/* fd is the drv_data that is returned from the */
-/* initial start routine                        */
-/* ready_fd is the descriptor that is ready to read */
-
-static void ready_input(ErlDrvData e, ErlDrvEvent ready_fd)
-{
-    int fd = (int)(long)e;
-    ErlDrvPort port_num;
-    int packet_bytes;
-    int res;
-    Uint h;
-
-    port_num = driver_data[fd].port_num;
-    packet_bytes = driver_data[fd].packet_bytes;
-
-
-    if (packet_bytes == 0) {
-	byte *read_buf = (byte *) erts_alloc(ERTS_ALC_T_SYS_READ_BUF,
-					     ERTS_SYS_READ_BUF_SZ);
-	res = read(ready_fd, read_buf, ERTS_SYS_READ_BUF_SZ);
-	if (res < 0) {
-	    if ((errno != EINTR) && (errno != ERRNO_BLOCK))
-		port_inp_failure(port_num, ready_fd, res);
-	}
-	else if (res == 0)
-	    port_inp_failure(port_num, ready_fd, res);
-	else 
-	    driver_output(port_num, (char*) read_buf, res);
-	erts_free(ERTS_ALC_T_SYS_READ_BUF, (void *) read_buf);
-    }
-    else if (fd_data[ready_fd].remain > 0) { /* We try to read the remainder */
-	/* space is allocated in buf */
-	res = read(ready_fd, fd_data[ready_fd].cpos, 
-		   fd_data[ready_fd].remain);
-	if (res < 0) {
-	    if ((errno != EINTR) && (errno != ERRNO_BLOCK))
-		port_inp_failure(port_num, ready_fd, res);
-	}
-	else if (res == 0) {
-	    port_inp_failure(port_num, ready_fd, res);
-	}
-	else if (res == fd_data[ready_fd].remain) { /* we're done  */
-	    driver_output(port_num, fd_data[ready_fd].buf, 
-			  fd_data[ready_fd].sz);
-	    clear_fd_data(ready_fd);
-	}
-	else { /*  if (res < fd_data[ready_fd].remain) */
-	    fd_data[ready_fd].cpos += res;
-	    fd_data[ready_fd].remain -= res;
-	}
-    }
-    else if (fd_data[ready_fd].remain == 0) { /* clean fd */
-	byte *read_buf = (byte *) erts_alloc(ERTS_ALC_T_SYS_READ_BUF,
-					     ERTS_SYS_READ_BUF_SZ);
-	/* We make one read attempt and see what happens */
-	res = read(ready_fd, read_buf, ERTS_SYS_READ_BUF_SZ);
-	if (res < 0) {  
-	    if ((errno != EINTR) && (errno != ERRNO_BLOCK))
-		port_inp_failure(port_num, ready_fd, res);
-	}
-	else if (res == 0) {     	/* eof */
-	    port_inp_failure(port_num, ready_fd, res);
-	} 
-	else if (res < packet_bytes - fd_data[ready_fd].psz) { 
-	    memcpy(fd_data[ready_fd].pbuf+fd_data[ready_fd].psz,
-		   read_buf, res);
-	    fd_data[ready_fd].psz += res;
-	}
-	else  { /* if (res >= packet_bytes) */
-	    unsigned char* cpos = read_buf;
-	    int bytes_left = res;
-
-	    while (1) {
-		int psz = fd_data[ready_fd].psz;
-		char* pbp = fd_data[ready_fd].pbuf + psz;
-
-		while(bytes_left && (psz < packet_bytes)) {
-		    *pbp++ = *cpos++;
-		    bytes_left--;
-		    psz++;
-		}
-		
-		if (psz < packet_bytes) {
-		    fd_data[ready_fd].psz = psz;
-		    break;
-		}
-		fd_data[ready_fd].psz = 0;
-
-		switch (packet_bytes) {
-		case 1: h = get_int8(fd_data[ready_fd].pbuf);  break;
-		case 2: h = get_int16(fd_data[ready_fd].pbuf); break;
-		case 4: h = get_int32(fd_data[ready_fd].pbuf); break;
-		default: ASSERT(0); return; /* -1; */
-		}
-
-		if (h <= (bytes_left)) {
-		    driver_output(port_num, (char*) cpos, h);
-		    cpos += h;
-		    bytes_left -= h;
-		    continue;
-		}
-		else {		/* The last message we got was split */
-		        char *buf = erts_alloc_fnf(ERTS_ALC_T_FD_ENTRY_BUF, h);
-		    if (!buf) {
-			errno = ENOMEM;
-			port_inp_failure(port_num, ready_fd, -1);
-		    }
-		    else {
-			erts_smp_atomic_add_nob(&sys_misc_mem_sz, h);
-			sys_memcpy(buf, cpos, bytes_left);
-			fd_data[ready_fd].buf = buf;
-			fd_data[ready_fd].sz = h;
-			fd_data[ready_fd].remain = h - bytes_left;
-			fd_data[ready_fd].cpos = buf + bytes_left;
-		    }
-		    break;
-		}
-	    }
-	}
-	erts_free(ERTS_ALC_T_SYS_READ_BUF, (void *) read_buf);
-    }
-}
-
-
-/* fd is the drv_data that is returned from the */
-/* initial start routine                        */
-/* ready_fd is the descriptor that is ready to read */
-
-static void ready_output(ErlDrvData e, ErlDrvEvent ready_fd)
-{
-    int fd = (int)(long)e;
-    ErlDrvPort ix = driver_data[fd].port_num;
-    int n;
-    struct iovec* iv;
-    int vsize;
-    
-
-    if ((iv = (struct iovec*) driver_peekq(ix, &vsize)) == NULL) {
-	driver_select(ix, ready_fd, ERL_DRV_WRITE, 0);
-        if (driver_data[fd].terminating)
-            driver_failure_atom(driver_data[fd].port_num,"normal");
-	return; /* 0; */
-    }
-    vsize = vsize > MAX_VSIZE ? MAX_VSIZE : vsize;
-    if ((n = writev(ready_fd, iv, vsize)) > 0) {
-	if (driver_deq(ix, n) == 0)
-	    set_busy_port(ix, 0);
-    }
-    else if (n < 0) {
-	if (errno == ERRNO_BLOCK || errno == EINTR)
-	    return; /* 0; */
-	else {
-	    int res = errno;
-	    driver_select(ix, ready_fd, ERL_DRV_WRITE, 0);
-	    driver_failure_posix(ix, res);
-	    return; /* -1; */
-	}
-    }
-    return; /* 0; */
-}
-
-static void stop_select(ErlDrvEvent fd, void* _)
-{
-    close((int)fd);
-}
-
-#if FDBLOCK
-
-static void
-fd_async(void *async_data)
-{
-    int res;
-    ErtsSysDriverData *dd = (ErtsSysDriverData*)async_data;
-    SysIOVec      *iov0;
-    SysIOVec      *iov;
-    int            iovlen;
-    int            err = 0;
-    /* much of this code is stolen from efile_drv:invoke_writev */
-    driver_pdl_lock(dd->blocking->pdl);
-    iov0 = driver_peekq(dd->port_num, &iovlen);
-    iovlen = iovlen < MAXIOV ? iovlen : MAXIOV;
-    iov = erts_alloc_fnf(ERTS_ALC_T_SYS_WRITE_BUF,
-                         sizeof(SysIOVec)*iovlen);
-    if (!iov) {
-        res = -1;
-        err = ENOMEM;
-        driver_pdl_unlock(dd->blocking->pdl);
-    } else {
-        memcpy(iov,iov0,iovlen*sizeof(SysIOVec));
-        driver_pdl_unlock(dd->blocking->pdl);
-
-        do {
-            res = writev(dd->ofd, iov, iovlen);
-        } while (res < 0 && errno == EINTR);
-        if (res < 0)
-            err = errno;
-
-        erts_free(ERTS_ALC_T_SYS_WRITE_BUF, iov);
-    }
-    dd->blocking->res = res;
-    dd->blocking->err = err;
-}
-
-void fd_ready_async(ErlDrvData drv_data,
-                    ErlDrvThreadData thread_data) {
-    ErtsSysDriverData *dd = (ErtsSysDriverData *)thread_data;
-    ErlDrvPort port_num = dd->port_num;
-
-    ASSERT(dd->blocking);
-    ASSERT(dd == (driver_data + (int)(long)drv_data));
-
-    if (dd->blocking->res > 0) {
-        driver_pdl_lock(dd->blocking->pdl);
-        if (driver_deq(port_num, dd->blocking->res) == 0) {
-            driver_pdl_unlock(dd->blocking->pdl);
-            set_busy_port(port_num, 0);
-            if (dd->terminating) {
-                /* The port is has been ordered to terminate
-                   from either fd_flush or port_inp_failure */
-                if (dd->terminating == 1)
-                    driver_failure_atom(port_num, "normal");
-                else if (dd->terminating == 2)
-                    driver_failure_eof(port_num);
-                else if (dd->terminating < 0)
-                    driver_failure_posix(port_num, -dd->terminating);
-                return; /* -1; */
-            }
-        } else {
-            driver_pdl_unlock(dd->blocking->pdl);
-            /* still data left to write in queue */
-            driver_async(port_num, &dd->blocking->pkey, fd_async, dd, NULL);
-            return /* 0; */;
-        }
-    } else if (dd->blocking->res < 0) {
-        if (dd->blocking->err == ERRNO_BLOCK) {
-            set_busy_port(port_num, 1);
-            /* still data left to write in queue */
-            driver_async(port_num, &dd->blocking->pkey, fd_async, dd, NULL);
-        } else
-            driver_failure_posix(port_num, dd->blocking->err);
-        return; /* -1; */
-    }
-    return; /* 0; */
-}
-
-#endif
-
 void erts_do_break_handling(void)
 {
     struct termios temp_mode;
@@ -2740,10 +1010,7 @@ erts_sys_unsetenv(char *key)
 void
 sys_init_io(void)
 {
-    fd_data = (ErtsSysFdData *)
-	erts_alloc(ERTS_ALC_T_FD_TAB, max_files * sizeof(ErtsSysFdData));
-    erts_smp_atomic_add_nob(&sys_misc_mem_sz,
-			    max_files * sizeof(ErtsSysFdData));
+
 }
 
 #if (0) /* unused? */
@@ -2937,178 +1204,6 @@ erl_debug(char* fmt, ...)
 
 #endif /* DEBUG */
 
-static ERTS_INLINE void
-report_exit_status(ErtsSysReportExit *rep, int status)
-{
-    Port *pp;
-#ifdef ERTS_SMP
-    CHLD_STAT_UNLOCK;
-    pp = erts_thr_id2port_sflgs(rep->port,
-				ERTS_PORT_SFLGS_INVALID_DRIVER_LOOKUP);
-    CHLD_STAT_LOCK;
-#else
-    pp = erts_id2port_sflgs(rep->port,
-			    NULL,
-			    0,
-			    ERTS_PORT_SFLGS_INVALID_DRIVER_LOOKUP);
-#endif
-    if (pp) {
-	if (rep->ifd >= 0) {
-	    driver_data[rep->ifd].alive = 0;
-	    driver_data[rep->ifd].status = status;
-	    (void) driver_select(ERTS_Port2ErlDrvPort(pp),
-				 rep->ifd,
-				 (ERL_DRV_READ|ERL_DRV_USE),
-				 1);
-	}
-	if (rep->ofd >= 0) {
-	    driver_data[rep->ofd].alive = 0;
-	    driver_data[rep->ofd].status = status;
-	    (void) driver_select(ERTS_Port2ErlDrvPort(pp),
-				 rep->ofd,
-				 (ERL_DRV_WRITE|ERL_DRV_USE),
-				 1);
-	}
-#ifdef ERTS_SMP
-	erts_thr_port_release(pp);
-#else
-	erts_port_release(pp);
-#endif
-    }
-    erts_free(ERTS_ALC_T_PRT_REP_EXIT, rep);
-}
-
-#if !CHLDWTHR  /* ---------------------------------------------------------- */
-
-#define ERTS_REPORT_EXIT_STATUS report_exit_status
-
-static int check_children(void)
-{
-    int res = 0;
-    int pid;
-    int status;
-
-#ifndef ERTS_SMP
-    if (children_died)
-#endif
-    {
-	sys_sigblock(SIGCHLD);
-	CHLD_STAT_LOCK;
-	while ((pid = waitpid(-1, &status, WNOHANG)) > 0)
-	    note_child_death(pid, status);
-#ifndef ERTS_SMP
-	children_died = 0;
-#endif
-	CHLD_STAT_UNLOCK;
-	sys_sigrelease(SIGCHLD);
-	res = 1;
-    }
-    return res;
-}
-
-#ifdef ERTS_SMP
-
-void
-erts_check_children(void)
-{
-    (void) check_children();
-}
-
-#endif
-
-#elif CHLDWTHR && defined(ERTS_SMP) /* ------------------------------------- */
-
-#define ERTS_REPORT_EXIT_STATUS report_exit_status
-
-#define check_children() (0)
-
-
-#else /* CHLDWTHR && !defined(ERTS_SMP) ------------------------------------ */
-
-#define ERTS_REPORT_EXIT_STATUS initiate_report_exit_status
-
-static ERTS_INLINE void
-initiate_report_exit_status(ErtsSysReportExit *rep, int status)
-{
-    rep->next = report_exit_transit_list;
-    rep->status = status;
-    report_exit_transit_list = rep;
-    erts_sys_schedule_interrupt(1);
-}
-
-static int check_children(void)
-{
-    int res;
-    ErtsSysReportExit *rep;
-    CHLD_STAT_LOCK;
-    rep = report_exit_transit_list;
-    res = rep != NULL;
-    while (rep) {
-	ErtsSysReportExit *curr_rep = rep;
-	rep = rep->next;
-	report_exit_status(curr_rep, curr_rep->status);
-    }
-    report_exit_transit_list = NULL;
-    CHLD_STAT_UNLOCK;
-    return res;
-}
-
-#endif /* ------------------------------------------------------------------ */
-
-static void note_child_death(int pid, int status)
-{
-    ErtsSysReportExit **repp = &report_exit_list;
-    ErtsSysReportExit *rep = report_exit_list;
-
-    while (rep) {
-	if (pid == rep->pid) {
-	    *repp = rep->next;
-	    ERTS_REPORT_EXIT_STATUS(rep, status);
-	    break;
-	}
-	repp = &rep->next;
-	rep = rep->next;
-    }
-}
-
-#if CHLDWTHR
-
-static void *
-child_waiter(void *unused)
-{
-  int pid;
-  int status;
-
-#ifdef ERTS_ENABLE_LOCK_CHECK
-  erts_lc_set_thread_name("child waiter");
-#endif
-
-  while(1) {
-#ifdef DEBUG
-      int waitpid_errno;
-#endif
-      pid = waitpid(-1, &status, 0);
-#ifdef DEBUG
-      waitpid_errno = errno;
-#endif
-      CHLD_STAT_LOCK;
-      if (pid < 0) {
-	  ASSERT(waitpid_errno == ECHILD);
-      }
-      else {
-	  children_alive--;
-	  ASSERT(children_alive >= 0);
-	  note_child_death(pid, status);
-      }
-      while (!children_alive)
-	  CHLD_STAT_WAIT; /* Wait for children to wait on... :) */
-      CHLD_STAT_UNLOCK;
-  }
-
-  return NULL;
-}
-
-#endif
 
 /*
  * Called from schedule() when it runs out of runnable processes,
@@ -3127,7 +1222,6 @@ erl_sys_schedule(int runnable)
     (void) check_children();
 }
 
-
 #ifdef ERTS_SMP
 
 static erts_smp_tid_t sig_dispatcher_tid;
diff --git a/erts/emulator/sys/unix/sys_drivers.c b/erts/emulator/sys/unix/sys_drivers.c
new file mode 100644
index 0000000000..e3f089fc0f
--- /dev/null
+++ b/erts/emulator/sys/unix/sys_drivers.c
@@ -0,0 +1,1983 @@
+/*
+ * %CopyrightBegin%
+ *
+ * Copyright Ericsson AB 1996-2014. 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
+
+#ifdef ISC32
+#define _POSIX_SOURCE
+#define _XOPEN_SOURCE
+#endif
+
+#include <sys/times.h>		/* ! */
+#include <time.h>
+#include <signal.h>
+#include <sys/wait.h>
+#include <sys/uio.h>
+#include <termios.h>
+#include <ctype.h>
+#include <sys/utsname.h>
+#include <sys/select.h>
+
+#ifdef ISC32
+#include <sys/bsdtypes.h>
+#endif
+
+#include <termios.h>
+#ifdef HAVE_FCNTL_H
+#include <fcntl.h>
+#endif
+#ifdef HAVE_SYS_IOCTL_H
+#include <sys/ioctl.h>
+#endif
+
+#define NEED_CHILD_SETUP_DEFINES
+#define WANT_NONBLOCKING    /* must define this to pull in defs from sys.h */
+#include "sys.h"
+#include "erl_thr_progress.h"
+
+#if defined(__APPLE__) && defined(__MACH__) && !defined(__DARWIN__)
+#define __DARWIN__ 1
+#endif
+
+#ifdef USE_THREADS
+#include "erl_threads.h"
+#endif
+
+#include "erl_mseg.h"
+
+extern char **environ;
+extern erts_smp_rwmtx_t environ_rwmtx;
+
+extern erts_smp_atomic_t sys_misc_mem_sz;
+
+#define MAX_VSIZE 16		/* Max number of entries allowed in an I/O
+				 * vector sock_sendv().
+				 */
+/*
+ * Don't need global.h, but erl_cpu_topology.h won't compile otherwise
+ */
+#include "global.h"
+
+#include "erl_sys_driver.h"
+#include "erl_check_io.h"
+#include "erl_cpu_topology.h"
+
+#ifndef DISABLE_VFORK
+#define DISABLE_VFORK 0
+#endif
+
+#if defined IOV_MAX
+#define MAXIOV IOV_MAX
+#elif defined UIO_MAXIOV
+#define MAXIOV UIO_MAXIOV
+#else
+#define MAXIOV 16
+#endif
+
+/*
+ * [OTP-3906]
+ * Solaris signal management gets confused when threads are used and a
+ * lot of child processes dies. The confusion results in that SIGCHLD
+ * signals aren't delivered to the emulator which in turn results in
+ * a lot of defunct processes in the system.
+ *
+ * The problem seems to appear when a signal is frequently
+ * blocked/unblocked at the same time as the signal is frequently
+ * propagated. The child waiter thread is a workaround for this problem.
+ * The SIGCHLD signal is always blocked (in all threads), and the child
+ * waiter thread fetches the signal by a call to sigwait(). See
+ * child_waiter().
+ */
+
+typedef struct ErtsSysReportExit_ ErtsSysReportExit;
+struct ErtsSysReportExit_ {
+    ErtsSysReportExit *next;
+    Eterm port;
+    int pid;
+    int ifd;
+    int ofd;
+#if CHLDWTHR && !defined(ERTS_SMP)
+    int status;
+#endif
+};
+
+/* Used by the fd driver iff the fd could not be set to non-blocking */
+typedef struct ErtsSysBlocking_ {
+    ErlDrvPDL pdl;
+    int res;
+    int err;
+    unsigned int pkey;
+} ErtsSysBlocking;
+
+
+/* This data is shared by these drivers - initialized by spawn_init() */
+typedef struct driver_data {
+    ErlDrvPort port_num;
+    int ofd, packet_bytes;
+    ErtsSysReportExit *report_exit;
+    int pid;
+    int alive;
+    int status;
+    int terminating;
+    ErtsSysBlocking *blocking;
+} ErtsSysDriverData;
+
+static ErtsSysDriverData *driver_data;			/* indexed by fd */
+
+static ErtsSysReportExit *report_exit_list;
+#if CHLDWTHR && !defined(ERTS_SMP)
+static ErtsSysReportExit *report_exit_transit_list;
+#endif
+
+#define DIR_SEPARATOR_CHAR    '/'
+
+#if defined(__ANDROID__)
+#define SHELL "/system/bin/sh"
+#else
+#define SHELL "/bin/sh"
+#endif /* __ANDROID__ */
+
+
+#if defined(DEBUG)
+#define ERL_BUILD_TYPE_MARKER ".debug"
+#elif defined(PURIFY)
+#define ERL_BUILD_TYPE_MARKER ".purify"
+#elif defined(QUANTIFY)
+#define ERL_BUILD_TYPE_MARKER ".quantify"
+#elif defined(PURECOV)
+#define ERL_BUILD_TYPE_MARKER ".purecov"
+#elif defined(VALGRIND)
+#define ERL_BUILD_TYPE_MARKER ".valgrind"
+#else /* opt */
+#define ERL_BUILD_TYPE_MARKER
+#endif
+
+#define CHILD_SETUP_PROG_NAME	"erl_child_setup" ERL_BUILD_TYPE_MARKER
+static char *child_setup_prog;
+
+#if CHLDWTHR || defined(ERTS_SMP)
+erts_mtx_t chld_stat_mtx;
+#endif
+#if CHLDWTHR
+static erts_tid_t child_waiter_tid;
+/* chld_stat_mtx is used to protect against concurrent accesses
+   of the driver_data fields pid, alive, and status. */
+erts_cnd_t chld_stat_cnd;
+static long children_alive;
+#define CHLD_STAT_LOCK		erts_mtx_lock(&chld_stat_mtx)
+#define CHLD_STAT_UNLOCK	erts_mtx_unlock(&chld_stat_mtx)
+#define CHLD_STAT_WAIT		erts_cnd_wait(&chld_stat_cnd, &chld_stat_mtx)
+#define CHLD_STAT_SIGNAL	erts_cnd_signal(&chld_stat_cnd)
+#elif defined(ERTS_SMP) /* ------------------------------------------------- */
+#define CHLD_STAT_LOCK		erts_mtx_lock(&chld_stat_mtx)
+#define CHLD_STAT_UNLOCK	erts_mtx_unlock(&chld_stat_mtx)
+
+#else /* ------------------------------------------------------------------- */
+#define CHLD_STAT_LOCK
+#define CHLD_STAT_UNLOCK
+static volatile int children_died;
+#endif
+
+typedef struct ErtsSysFdData {
+    char  pbuf[4];   /* hold partial packet bytes */
+    int   psz;       /* size of pbuf */
+    char  *buf;
+    char  *cpos;
+    int   sz;
+    int   remain;  /* for input on fd */
+} ErtsSysFdData;
+
+static ErtsSysFdData *fd_data;			/* indexed by fd */
+
+/* static FUNCTION(int, write_fill, (int, char*, int)); unused? */
+static void note_child_death(int, int);
+
+#if CHLDWTHR
+static void* child_waiter(void *);
+#endif
+
+static void block_signals(void)
+{
+#if !CHLDWTHR
+   sys_sigblock(SIGCHLD);
+#endif
+#ifndef ERTS_SMP
+   sys_sigblock(SIGINT);
+#ifndef ETHR_UNUSABLE_SIGUSRX
+   sys_sigblock(SIGUSR1);
+#endif /* #ifndef ETHR_UNUSABLE_SIGUSRX */
+#endif /* #ifndef ERTS_SMP */
+
+#if defined(ERTS_SMP) && !defined(ETHR_UNUSABLE_SIGUSRX)
+   sys_sigblock(ERTS_SYS_SUSPEND_SIGNAL);
+#endif
+
+}
+
+static void unblock_signals(void)
+{
+    /* Update erl_child_setup.c if changed */
+#if !CHLDWTHR
+   sys_sigrelease(SIGCHLD);
+#endif
+#ifndef ERTS_SMP
+   sys_sigrelease(SIGINT);
+#ifndef ETHR_UNUSABLE_SIGUSRX
+   sys_sigrelease(SIGUSR1);
+#endif /* #ifndef ETHR_UNUSABLE_SIGUSRX */
+#endif /* #ifndef ERTS_SMP */
+
+#if defined(ERTS_SMP) && !defined(ETHR_UNUSABLE_SIGUSRX)
+   sys_sigrelease(ERTS_SYS_SUSPEND_SIGNAL);
+#endif
+
+}
+
+/************************** Port I/O *******************************/
+
+
+
+/* I. Common stuff */
+
+/*
+ * Decreasing the size of it below 16384 is not allowed.
+ */
+
+/* II. The spawn/fd/vanilla drivers */
+
+#define ERTS_SYS_READ_BUF_SZ (64*1024)
+
+/* Driver interfaces */
+static ErlDrvData spawn_start(ErlDrvPort, char*, SysDriverOpts*);
+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 ErlDrvData vanilla_start(ErlDrvPort, char*, SysDriverOpts*);
+static int spawn_init(void);
+static void fd_stop(ErlDrvData);
+static void fd_flush(ErlDrvData);
+static void stop(ErlDrvData);
+static void ready_input(ErlDrvData, ErlDrvEvent);
+static void ready_output(ErlDrvData, ErlDrvEvent);
+static void output(ErlDrvData, char*, ErlDrvSizeT);
+static void outputv(ErlDrvData, ErlIOVec*);
+static void stop_select(ErlDrvEvent, void*);
+
+struct erl_drv_entry spawn_driver_entry = {
+    spawn_init,
+    spawn_start,
+    stop,
+    output,
+    ready_input,
+    ready_output,
+    "spawn",
+    NULL,
+    NULL,
+    NULL,
+    NULL,
+    NULL,
+    NULL,
+    NULL,
+    NULL,
+    NULL,
+    ERL_DRV_EXTENDED_MARKER,
+    ERL_DRV_EXTENDED_MAJOR_VERSION,
+    ERL_DRV_EXTENDED_MINOR_VERSION,
+    ERL_DRV_FLAG_USE_PORT_LOCKING,
+    NULL, NULL,
+    stop_select
+};
+struct erl_drv_entry fd_driver_entry = {
+    NULL,
+    fd_start,
+    fd_stop,
+    output,
+    ready_input,
+    ready_output, 
+    "fd",
+    NULL,
+    NULL,
+    fd_control,
+    NULL,
+    outputv,
+#if FDBLOCK
+    fd_ready_async, /* ready_async */
+#else
+    NULL,
+#endif
+    fd_flush, /* flush */
+    NULL, /* call */
+    NULL, /* event */
+    ERL_DRV_EXTENDED_MARKER,
+    ERL_DRV_EXTENDED_MAJOR_VERSION,
+    ERL_DRV_EXTENDED_MINOR_VERSION,
+    0, /* ERL_DRV_FLAGs */
+    NULL, /* handle2 */
+    NULL, /* process_exit */
+    stop_select
+};
+struct erl_drv_entry vanilla_driver_entry = {
+    NULL,
+    vanilla_start,
+    stop,
+    output,
+    ready_input,
+    ready_output,
+    "vanilla",
+    NULL,
+    NULL,
+    NULL,
+    NULL,
+    NULL,
+    NULL,
+    NULL, /* flush */
+    NULL, /* call */
+    NULL, /* event */
+    ERL_DRV_EXTENDED_MARKER,
+    ERL_DRV_EXTENDED_MAJOR_VERSION,
+    ERL_DRV_EXTENDED_MINOR_VERSION,
+    0, /* ERL_DRV_FLAGs */
+    NULL, /* handle2 */
+    NULL, /* process_exit */
+    stop_select
+};
+
+/* Handle SIGCHLD signals. */
+#if (defined(SIG_SIGSET) || defined(SIG_SIGNAL))
+static RETSIGTYPE onchld(void)
+#else
+static RETSIGTYPE onchld(int signum)
+#endif
+{
+#if CHLDWTHR
+    ASSERT(0); /* We should *never* catch a SIGCHLD signal */
+#elif defined(ERTS_SMP)
+    smp_sig_notify('C');
+#else
+    children_died = 1;
+    ERTS_CHK_IO_AS_INTR(); /* Make sure we don't sleep in poll */
+#endif
+}
+
+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));
+
+    dd->blocking->pdl = driver_pdl_create(dd->port_num);
+    dd->blocking->res = 0;
+    dd->blocking->err = 0;
+    dd->blocking->pkey = driver_async_port_key(dd->port_num);
+
+    return 1;
+}
+
+static int set_driver_data(ErlDrvPort port_num,
+			   int ifd,
+			   int ofd,
+			   int packet_bytes,
+			   int read_write,
+			   int exit_status,
+			   int pid,
+                           int is_blocking)
+{
+    Port *prt;
+    ErtsSysReportExit *report_exit;
+
+    if (!exit_status)
+	report_exit = NULL;
+    else {
+	report_exit = erts_alloc(ERTS_ALC_T_PRT_REP_EXIT,
+				 sizeof(ErtsSysReportExit));
+	report_exit->next = report_exit_list;
+	report_exit->port = erts_drvport2id(port_num);
+	report_exit->pid = pid;
+	report_exit->ifd = read_write & DO_READ ? ifd : -1;
+	report_exit->ofd = read_write & DO_WRITE ? ofd : -1;
+#if CHLDWTHR && !defined(ERTS_SMP)
+	report_exit->status = 0;
+#endif
+	report_exit_list = report_exit;
+    }
+
+    prt = erts_drvport2port(port_num);
+    if (prt != ERTS_INVALID_ERL_DRV_PORT)
+	prt->os_pid = pid;
+
+    if (read_write & DO_READ) {
+	driver_data[ifd].packet_bytes = packet_bytes;
+	driver_data[ifd].port_num = port_num;
+	driver_data[ifd].report_exit = report_exit;
+	driver_data[ifd].pid = pid;
+	driver_data[ifd].alive = 1;
+	driver_data[ifd].status = 0;
+        driver_data[ifd].terminating = 0;
+        driver_data[ifd].blocking = NULL;
+	if (read_write & DO_WRITE) {
+	    driver_data[ifd].ofd = ofd;
+            if (is_blocking && FDBLOCK)
+                if (!set_blocking_data(driver_data+ifd))
+                    return -1;
+	    if (ifd != ofd)
+		driver_data[ofd] = driver_data[ifd];  /* structure copy */
+	} else {		/* DO_READ only */
+	    driver_data[ifd].ofd = -1;
+	}
+	(void) driver_select(port_num, ifd, (ERL_DRV_READ|ERL_DRV_USE), 1);
+	return(ifd);
+    } else {			/* DO_WRITE only */
+	driver_data[ofd].packet_bytes = packet_bytes;
+	driver_data[ofd].port_num = port_num;
+	driver_data[ofd].report_exit = report_exit;
+	driver_data[ofd].ofd = ofd;
+	driver_data[ofd].pid = pid;
+	driver_data[ofd].alive = 1;
+	driver_data[ofd].status = 0;
+        driver_data[ofd].terminating = 0;
+        driver_data[ofd].blocking = NULL;
+        if (is_blocking && FDBLOCK)
+            if (!set_blocking_data(driver_data+ofd))
+                return -1;
+	return(ofd);
+    }
+}
+
+static int spawn_init()
+{
+   int i;
+#if CHLDWTHR
+   erts_thr_opts_t thr_opts = ERTS_THR_OPTS_DEFAULT_INITER;
+#endif
+   int res;
+   char bindir[MAXPATHLEN];
+   size_t bindirsz = sizeof(bindir);
+   Uint csp_path_sz;
+
+#if CHLDWTHR
+   thr_opts.detached = 0;
+   thr_opts.suggested_stack_size = 0; /* Smallest possible */
+   thr_opts.name = "child_waiter";
+#endif
+
+#if !DISABLE_VFORK
+   res = erts_sys_getenv_raw("BINDIR", bindir, &bindirsz);
+   if (res != 0) {
+    if (res < 0)
+        erl_exit(-1,
+        "Environment variable BINDIR is not set\n");
+    if (res > 0)
+        erl_exit(-1,
+        "Value of environment variable BINDIR is too large\n");
+   }
+   if (bindir[0] != DIR_SEPARATOR_CHAR)
+       erl_exit(-1,
+                "Environment variable BINDIR does not contain an"
+                " absolute path\n");
+   csp_path_sz = (strlen(bindir)
+                  + 1 /* DIR_SEPARATOR_CHAR */
+                  + sizeof(CHILD_SETUP_PROG_NAME)
+                  + 1);
+   child_setup_prog = erts_alloc(ERTS_ALC_T_CS_PROG_PATH, csp_path_sz);
+   erts_smp_atomic_add_nob(&sys_misc_mem_sz, csp_path_sz);
+   erts_snprintf(child_setup_prog, csp_path_sz,
+                 "%s%c%s",
+                 bindir,
+                 DIR_SEPARATOR_CHAR,
+                 CHILD_SETUP_PROG_NAME);
+#endif
+
+   report_exit_list = NULL;
+
+#ifdef USE_THREADS
+
+#if CHLDWTHR || defined(ERTS_SMP)
+    erts_mtx_init(&chld_stat_mtx, "child_status");
+#endif
+#if CHLDWTHR
+#ifndef ERTS_SMP
+    report_exit_transit_list = NULL;
+#endif
+    erts_cnd_init(&chld_stat_cnd);
+    children_alive = 0;
+#endif
+
+#if !CHLDWTHR && !defined(ERTS_SMP)
+    children_died = 0;
+#endif
+
+#endif /* USE_THREADS */
+
+   sys_signal(SIGPIPE, SIG_IGN); /* Ignore - we'll handle the write failure */
+   driver_data = (ErtsSysDriverData *)
+       erts_alloc(ERTS_ALC_T_DRV_TAB, sys_max_files() * sizeof(ErtsSysDriverData));
+   erts_smp_atomic_add_nob(&sys_misc_mem_sz,
+			   sys_max_files() * sizeof(ErtsSysDriverData));
+
+   for (i = 0; i < sys_max_files(); i++)
+      driver_data[i].pid = -1;
+
+   fd_data = (ErtsSysFdData *)
+       erts_alloc(ERTS_ALC_T_FD_TAB, sys_max_files() * sizeof(ErtsSysFdData));
+   erts_smp_atomic_add_nob(&sys_misc_mem_sz,
+        sys_max_files() * sizeof(ErtsSysFdData));
+
+#if CHLDWTHR
+   sys_sigblock(SIGCHLD);
+#endif
+
+   sys_signal(SIGCHLD, onchld); /* Reap children */
+
+#if CHLDWTHR
+   erts_thr_create(&child_waiter_tid, child_waiter, NULL, &thr_opts);
+#endif
+
+   return 1;
+}
+
+static void close_pipes(int ifd[2], int ofd[2], int read_write)
+{
+    if (read_write & DO_READ) {
+	(void) close(ifd[0]);
+	(void) close(ifd[1]);
+    }
+    if (read_write & DO_WRITE) {
+	(void) close(ofd[0]);
+	(void) close(ofd[1]);
+    }
+}
+
+static void init_fd_data(int fd, ErlDrvPort port_num)
+{
+    fd_data[fd].buf = NULL;
+    fd_data[fd].cpos = NULL;
+    fd_data[fd].remain = 0;
+    fd_data[fd].sz = 0;
+    fd_data[fd].psz = 0;
+}
+
+static char **build_unix_environment(char *block)
+{
+    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;
+    }
+
+    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;
+
+	    s = cpp[j];
+	    t = old;
+	    while (*s == *t && *s != '=') {
+		s++, t++;
+	    }
+	    if (*s == '=' && *t == '=') {
+		break;
+	    }
+	}
+
+	if (j == len) {		/* New version not found */
+	    cpp[len++] = old;
+	}
+    }
+
+    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++;
+	}
+    }
+
+    cpp[len] = NULL;
+    return cpp;
+}
+
+/*
+  [arndt] In most Unix systems, including Solaris 2.5, 'fork' allocates memory
+  in swap space for the child of a 'fork', whereas 'vfork' does not do this.
+  The natural call to use here is therefore 'vfork'. Due to a bug in
+  'vfork' in Solaris 2.5 (apparently fixed in 2.6), using 'vfork'
+  can be dangerous in what seems to be these circumstances:
+      If the child code under a vfork sets the signal action to SIG_DFL
+      (or SIG_IGN)
+      for any signal which was previously set to a signal handler, the
+      state of the parent is clobbered, so that the later arrival of
+      such a signal yields a sigsegv in the parent. If the signal was
+      not set to a signal handler, but ignored, all seems to work.
+  If you change the forking code below, beware of this.
+ */
+
+static ErlDrvData spawn_start(ErlDrvPort port_num, char* name, SysDriverOpts* opts)
+{
+#define CMD_LINE_PREFIX_STR "exec "
+#define CMD_LINE_PREFIX_STR_SZ (sizeof(CMD_LINE_PREFIX_STR) - 1)
+
+    int ifd[2], ofd[2], len, pid, i;
+    char **volatile new_environ; /* volatile since a vfork() then cannot
+				    cause 'new_environ' to be clobbered
+				    in the parent process. */
+    int saved_errno;
+    long res;
+    char *cmd_line;
+#ifndef QNX
+    int unbind;
+#endif
+#if !DISABLE_VFORK
+    int no_vfork;
+    size_t no_vfork_sz = sizeof(no_vfork);
+
+    no_vfork = (erts_sys_getenv_raw("ERL_NO_VFORK",
+				    (char *) &no_vfork,
+				    &no_vfork_sz) >= 0);
+#endif
+
+    switch (opts->read_write) {
+    case DO_READ:
+	if (pipe(ifd) < 0)
+	    return ERL_DRV_ERROR_ERRNO;
+	if (ifd[0] >= sys_max_files()) {
+	    close_pipes(ifd, ofd, opts->read_write);
+	    errno = EMFILE;
+	    return ERL_DRV_ERROR_ERRNO;
+	}
+	ofd[1] = -1;		/* keep purify happy */
+	break;
+    case DO_WRITE:
+	if (pipe(ofd) < 0) return ERL_DRV_ERROR_ERRNO;
+	if (ofd[1] >= sys_max_files()) {
+	    close_pipes(ifd, ofd, opts->read_write);
+	    errno = EMFILE;
+	    return ERL_DRV_ERROR_ERRNO;
+	}
+	ifd[0] = -1;		/* keep purify happy */
+	break;
+    case DO_READ|DO_WRITE:
+	if (pipe(ifd) < 0) return ERL_DRV_ERROR_ERRNO;
+	errno = EMFILE;		/* default for next two conditions */
+	if (ifd[0] >= sys_max_files() || pipe(ofd) < 0) {
+	    close_pipes(ifd, ofd, DO_READ);
+	    return ERL_DRV_ERROR_ERRNO;
+	}
+	if (ofd[1] >= sys_max_files()) {
+	    close_pipes(ifd, ofd, opts->read_write);
+	    errno = EMFILE;
+	    return ERL_DRV_ERROR_ERRNO;
+	}
+	break;
+    default:
+	ASSERT(0);
+	return ERL_DRV_ERROR_GENERAL;
+    }
+
+    if (opts->spawn_type == ERTS_SPAWN_EXECUTABLE) {
+	/* started with spawn_executable, not with spawn */
+	len = strlen(name);
+	cmd_line = (char *) erts_alloc_fnf(ERTS_ALC_T_TMP, len + 1);
+	if (!cmd_line) {
+	    close_pipes(ifd, ofd, opts->read_write);
+	    errno = ENOMEM;
+	    return ERL_DRV_ERROR_ERRNO;
+	}
+	memcpy((void *) cmd_line,(void *) name, len);
+	cmd_line[len] = '\0';
+	if (access(cmd_line,X_OK) != 0) {
+	    int save_errno = errno;
+	    erts_free(ERTS_ALC_T_TMP, cmd_line);
+	    errno = save_errno;
+	    return ERL_DRV_ERROR_ERRNO;
+	}
+    } else {
+	/* make the string suitable for giving to "sh" */
+	len = strlen(name);
+	cmd_line = (char *) erts_alloc_fnf(ERTS_ALC_T_TMP,
+					   CMD_LINE_PREFIX_STR_SZ + len + 1);
+	if (!cmd_line) {
+	    close_pipes(ifd, ofd, opts->read_write);
+	    errno = ENOMEM;
+	    return ERL_DRV_ERROR_ERRNO;
+	}
+	memcpy((void *) cmd_line,
+	       (void *) CMD_LINE_PREFIX_STR,
+	       CMD_LINE_PREFIX_STR_SZ);
+	memcpy((void *) (cmd_line + CMD_LINE_PREFIX_STR_SZ), (void *) name, len);
+	cmd_line[CMD_LINE_PREFIX_STR_SZ + len] = '\0';
+    }
+
+    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);
+	erts_free(ERTS_ALC_T_TMP, (void *) cmd_line);
+	errno = ENOMEM;
+	return ERL_DRV_ERROR_ERRNO;
+    } 
+
+#ifndef QNX
+    /* Block child from SIGINT and SIGUSR1. Must be before fork()
+       to be safe. */
+    block_signals();
+
+    CHLD_STAT_LOCK;
+
+    unbind = erts_sched_bind_atfork_prepare();
+
+#if !DISABLE_VFORK
+    /* See fork/vfork discussion before this function. */
+    if (no_vfork) {
+#endif
+
+	DEBUGF(("Using fork\n"));
+	pid = fork();
+
+	if (pid == 0) {
+	    /* The child! Setup child... */
+
+	    if (erts_sched_bind_atfork_child(unbind) != 0)
+		goto child_error;
+
+	    /* OBSERVE!
+	     * Keep child setup after vfork() (implemented below and in
+	     * erl_child_setup.c) up to date if changes are made here.
+	     */
+
+	    if (opts->use_stdio) {
+		if (opts->read_write & DO_READ) {
+		    /* stdout for process */
+		    if (dup2(ifd[1], 1) < 0)
+			goto child_error;
+		    if(opts->redir_stderr)
+			/* stderr for process */
+			if (dup2(ifd[1], 2) < 0)
+			    goto child_error;
+		}
+		if (opts->read_write & DO_WRITE)
+		    /* stdin for process */
+		    if (dup2(ofd[0], 0) < 0)
+			goto child_error;
+	    }
+	    else {	/* XXX will fail if ofd[0] == 4 (unlikely..) */
+		if (opts->read_write & DO_READ)
+		    if (dup2(ifd[1], 4) < 0)
+			goto child_error;
+		if (opts->read_write & DO_WRITE)
+		    if (dup2(ofd[0], 3) < 0)
+			goto child_error;
+	    }
+
+#if defined(HAVE_CLOSEFROM)
+	    closefrom(opts->use_stdio ? 3 : 5);
+#else
+	    for (i = opts->use_stdio ? 3 : 5; i < sys_max_files(); i++)
+		(void) close(i);
+#endif
+
+	    if (opts->wd && chdir(opts->wd) < 0)
+		goto child_error;
+
+#if defined(USE_SETPGRP_NOARGS)		/* SysV */
+	    (void) setpgrp();
+#elif defined(USE_SETPGRP)		/* BSD */
+	    (void) setpgrp(0, getpid());
+#else					/* POSIX */
+	    (void) setsid();
+#endif
+	    
+	    unblock_signals();
+
+	    if (opts->spawn_type == ERTS_SPAWN_EXECUTABLE) {
+		if (opts->argv == NULL) {
+		    execle(cmd_line,cmd_line,(char *) NULL, new_environ);
+		} else {
+		    if (opts->argv[0] == erts_default_arg0) {
+			opts->argv[0] = cmd_line;
+		    }
+		    execve(cmd_line, opts->argv, new_environ);
+		    if (opts->argv[0] == cmd_line) {
+			opts->argv[0] = erts_default_arg0;
+		    }
+		}
+	    } else {
+		execle(SHELL, "sh", "-c", cmd_line, (char *) NULL, new_environ);
+	    }
+	child_error:
+	    _exit(1);
+	}
+#if !DISABLE_VFORK
+    }
+#define ENOUGH_BYTES (44)
+    else { /* Use vfork() */
+	char **cs_argv= erts_alloc(ERTS_ALC_T_TMP,(CS_ARGV_NO_OF_ARGS + 1)*
+				   sizeof(char *));
+	char fd_close_range[ENOUGH_BYTES];                  /* 44 bytes are enough to  */
+	char dup2_op[CS_ARGV_NO_OF_DUP2_OPS][ENOUGH_BYTES]; /* hold any "%d:%d" string */
+                                                            /* on a 64-bit machine.    */
+
+	/* Setup argv[] for the child setup program (implemented in
+	   erl_child_setup.c) */
+	i = 0;
+	if (opts->use_stdio) {
+	    if (opts->read_write & DO_READ){
+		/* stdout for process */
+		erts_snprintf(&dup2_op[i++][0], ENOUGH_BYTES, "%d:%d", ifd[1], 1);
+		if(opts->redir_stderr)
+		    /* stderr for process */
+		    erts_snprintf(&dup2_op[i++][0], ENOUGH_BYTES, "%d:%d", ifd[1], 2);
+	    }
+	    if (opts->read_write & DO_WRITE)
+		/* stdin for process */
+		erts_snprintf(&dup2_op[i++][0], ENOUGH_BYTES, "%d:%d", ofd[0], 0);
+	} else {	/* XXX will fail if ofd[0] == 4 (unlikely..) */
+	    if (opts->read_write & DO_READ)
+		erts_snprintf(&dup2_op[i++][0], ENOUGH_BYTES, "%d:%d", ifd[1], 4);
+	    if (opts->read_write & DO_WRITE)
+		erts_snprintf(&dup2_op[i++][0], ENOUGH_BYTES, "%d:%d", ofd[0], 3);
+	}
+	for (; i < CS_ARGV_NO_OF_DUP2_OPS; i++)
+	    strcpy(&dup2_op[i][0], "-");
+	erts_snprintf(fd_close_range, ENOUGH_BYTES, "%d:%d", opts->use_stdio ? 3 : 5, sys_max_files()-1);
+
+	cs_argv[CS_ARGV_PROGNAME_IX] = child_setup_prog;
+	cs_argv[CS_ARGV_WD_IX] = opts->wd ? opts->wd : ".";
+	cs_argv[CS_ARGV_UNBIND_IX] = erts_sched_bind_atvfork_child(unbind);
+	cs_argv[CS_ARGV_FD_CR_IX] = fd_close_range;
+	for (i = 0; i < CS_ARGV_NO_OF_DUP2_OPS; i++)
+	    cs_argv[CS_ARGV_DUP2_OP_IX(i)] = &dup2_op[i][0];
+
+	if (opts->spawn_type == ERTS_SPAWN_EXECUTABLE) {
+	    int num = 0;
+	    int j = 0;
+	    if (opts->argv != NULL) {
+		for(; opts->argv[num] != NULL; ++num)
+		    ;
+	    }
+	    cs_argv = erts_realloc(ERTS_ALC_T_TMP,cs_argv, (CS_ARGV_NO_OF_ARGS + 1 + num + 1) * sizeof(char *));
+	    cs_argv[CS_ARGV_CMD_IX] = "-";
+	    cs_argv[CS_ARGV_NO_OF_ARGS] = cmd_line;
+	    if (opts->argv != NULL) {
+		for (;opts->argv[j] != NULL; ++j) {
+		    if (opts->argv[j] == erts_default_arg0) {
+			cs_argv[CS_ARGV_NO_OF_ARGS + 1 + j] = cmd_line;
+		    } else {
+			cs_argv[CS_ARGV_NO_OF_ARGS + 1 + j] = opts->argv[j];
+		    }
+		}
+	    }
+	    cs_argv[CS_ARGV_NO_OF_ARGS + 1 + j] = NULL;
+	} else {
+	    cs_argv[CS_ARGV_CMD_IX] = cmd_line; /* Command */
+	    cs_argv[CS_ARGV_NO_OF_ARGS] = NULL;
+	}
+	DEBUGF(("Using vfork\n"));
+	pid = vfork();
+
+	if (pid == 0) {
+	    /* The child! */
+
+	    /* Observe!
+	     * OTP-4389: The child setup program (implemented in
+	     * erl_child_setup.c) will perform the necessary setup of the
+	     * child before it execs to the user program. This because
+	     * vfork() only allow an *immediate* execve() or _exit() in the
+	     * child.
+	     */
+	    execve(child_setup_prog, cs_argv, new_environ);
+	    _exit(1);
+	}
+	erts_free(ERTS_ALC_T_TMP,cs_argv);
+    }
+#undef ENOUGH_BYTES
+#endif
+
+    erts_sched_bind_atfork_parent(unbind);
+
+    if (pid == -1) {
+        saved_errno = errno;
+	CHLD_STAT_UNLOCK;
+	erts_smp_rwmtx_runlock(&environ_rwmtx);
+	erts_free(ERTS_ALC_T_TMP, (void *) cmd_line);
+        unblock_signals();
+        close_pipes(ifd, ofd, opts->read_write);
+	errno = saved_errno;
+	return ERL_DRV_ERROR_ERRNO;
+    }
+#else /* QNX */
+    if (opts->use_stdio) {
+	if (opts->read_write & DO_READ)
+	    qnx_spawn_options.iov[1] = ifd[1];  /* stdout for process */
+	if (opts->read_write & DO_WRITE)
+	    qnx_spawn_options.iov[0] = ofd[0];  /* stdin for process */
+	} 
+    else {
+	if (opts->read_write & DO_READ)
+	    qnx_spawn_options.iov[4] = ifd[1];
+	if (opts->read_write & DO_WRITE)
+	    qnx_spawn_options.iov[3] = ofd[0];
+    }
+    /* Close fds on exec */
+    for (i = 3; i < sys_max_files(); i++)
+	fcntl(i, F_SETFD, 1);
+
+    qnx_spawn_options.flags = _SPAWN_SETSID;
+    if ((pid = spawnl(P_NOWAIT, SHELL, SHELL, "-c", cmd_line, 
+                      (char *) 0)) < 0) {
+	erts_free(ERTS_ALC_T_TMP, (void *) cmd_line);
+        reset_qnx_spawn();
+	erts_smp_rwmtx_runlock(&environ_rwmtx);
+	close_pipes(ifd, ofd, opts->read_write);
+	return ERL_DRV_ERROR_GENERAL;
+    }
+    reset_qnx_spawn();
+#endif /* QNX */
+
+    erts_free(ERTS_ALC_T_TMP, (void *) cmd_line);
+
+    if (new_environ != environ)
+	erts_free(ERTS_ALC_T_ENVIRONMENT, (void *) new_environ);
+
+    if (opts->read_write & DO_READ) 
+	(void) close(ifd[1]);
+    if (opts->read_write & DO_WRITE)
+	(void) close(ofd[0]);
+	
+    if (opts->read_write & DO_READ) {
+	SET_NONBLOCKING(ifd[0]);
+	init_fd_data(ifd[0], port_num);
+    }
+    if (opts->read_write & DO_WRITE) {
+	SET_NONBLOCKING(ofd[1]);
+        init_fd_data(ofd[1], port_num);
+    }
+
+    res = set_driver_data(port_num, ifd[0], ofd[1], opts->packet_bytes,
+			  opts->read_write, opts->exit_status, pid, 0);
+    /* Don't unblock SIGCHLD until now, since the call above must
+       first complete putting away the info about our new subprocess. */
+    unblock_signals();
+
+#if CHLDWTHR
+    ASSERT(children_alive >= 0);
+
+    if (!(children_alive++))
+	CHLD_STAT_SIGNAL; /* Wake up child waiter thread if no children
+			     was alive before we fork()ed ... */
+#endif
+    /* Don't unlock chld_stat_mtx until now of the same reason as above */
+    CHLD_STAT_UNLOCK;
+
+    erts_smp_rwmtx_runlock(&environ_rwmtx);
+
+    return (ErlDrvData)res;
+#undef CMD_LINE_PREFIX_STR
+#undef CMD_LINE_PREFIX_STR_SZ
+}
+
+#ifdef QNX
+static reset_qnx_spawn()
+{
+    int i;
+
+    /* Reset qnx_spawn_options */
+    qnx_spawn_options.flags = 0; 
+    qnx_spawn_options.iov[0] = 0xff;
+    qnx_spawn_options.iov[1] = 0xff;
+    qnx_spawn_options.iov[2] = 0xff;
+    qnx_spawn_options.iov[3] = 0xff;
+}
+#endif
+
+#define FD_DEF_HEIGHT 24
+#define FD_DEF_WIDTH 80
+/* Control op */
+#define FD_CTRL_OP_GET_WINSIZE 100
+
+static int fd_get_window_size(int fd, Uint32 *width, Uint32 *height)
+{
+#ifdef TIOCGWINSZ 
+    struct winsize ws;
+    if (ioctl(fd,TIOCGWINSZ,&ws) == 0) {
+	*width = (Uint32) ws.ws_col;
+	*height = (Uint32) ws.ws_row;
+	return 0;
+    }
+#endif
+    return -1;
+}
+
+static ErlDrvSSizeT fd_control(ErlDrvData drv_data,
+			       unsigned int command,
+			       char *buf, ErlDrvSizeT len,
+			       char **rbuf, ErlDrvSizeT rlen)
+{
+    int fd = (int)(long)drv_data;
+    char resbuff[2*sizeof(Uint32)];
+    switch (command) {
+    case FD_CTRL_OP_GET_WINSIZE:
+	{
+	    Uint32 w,h;
+	    if (fd_get_window_size(fd,&w,&h)) 
+		return 0;
+	    memcpy(resbuff,&w,sizeof(Uint32));
+	    memcpy(resbuff+sizeof(Uint32),&h,sizeof(Uint32));
+	}
+	break;
+    default:
+	return 0;
+    }
+    if (rlen < 2*sizeof(Uint32)) {
+	*rbuf = driver_alloc(2*sizeof(Uint32));
+    }
+    memcpy(*rbuf,resbuff,2*sizeof(Uint32));
+    return 2*sizeof(Uint32);
+}
+
+static ErlDrvData fd_start(ErlDrvPort port_num, char* name,
+			   SysDriverOpts* opts)
+{
+    ErlDrvData res;
+    int non_blocking = 0;
+
+    if (((opts->read_write & DO_READ) && opts->ifd >= sys_max_files()) ||
+	((opts->read_write & DO_WRITE) && opts->ofd >= sys_max_files()))
+	return ERL_DRV_ERROR_GENERAL;
+
+    /*
+     * Historical:
+     *
+     * "Note about nonblocking I/O.
+     *
+     * At least on Solaris, setting the write end of a TTY to nonblocking,
+     * will set the input end to nonblocking as well (and vice-versa).
+     * If erl is run in a pipeline like this:  cat | erl
+     * the input end of the TTY will be the standard input of cat.
+     * And cat is not prepared to handle nonblocking I/O."
+     *
+     * Actually, the reason for this is not that the tty itself gets set
+     * in non-blocking mode, but that the "input end" (cat's stdin) and
+     * the "output end" (erlang's stdout) are typically the "same" file
+     * descriptor, dup()'ed from a single fd by one of this process'
+     * ancestors.
+     *
+     * The workaround for this problem used to be a rather bad kludge,
+     * interposing an extra process ("internal cat") between erlang's
+     * stdout and the original stdout, allowing erlang to set its stdout
+     * in non-blocking mode without affecting the stdin of the preceding
+     * process in the pipeline - and being a kludge, it caused all kinds
+     * of weird problems.
+     *
+     * So, this is the current logic:
+     *
+     * The only reason to set non-blocking mode on the output fd at all is
+     * if it's something that can cause a write() to block, of course,
+     * i.e. primarily if it points to a tty, socket, pipe, or fifo. 
+     *
+     * If we don't set non-blocking mode when we "should" have, and output
+     * becomes blocked, the entire runtime system will be suspended - this
+     * is normally bad of course, and can happen fairly "easily" - e.g. user
+     * hits ^S on tty - but doesn't necessarily happen.
+     * 
+     * If we do set non-blocking mode when we "shouldn't" have, the runtime
+     * system will end up seeing EOF on the input fd (due to the preceding
+     * process dying), which typically will cause the entire runtime system
+     * to terminate immediately (due to whatever erlang process is seeing
+     * the EOF taking it as a signal to halt the system). This is *very* bad.
+     * 
+     * I.e. we should take a conservative approach, and only set non-
+     * blocking mode when we a) need to, and b) are reasonably certain
+     * that it won't be a problem. And as in the example above, the problem
+     * occurs when input fd and output fd point to different "things".
+     *
+     * However, determining that they are not just the same "type" of
+     * "thing", but actually the same instance of that type of thing, is
+     * unreasonably complex in many/most cases.
+     *
+     * Also, with pipes, sockets, and fifos it's far from obvious that the
+     * user *wants* non-blocking output: If you're running erlang inside
+     * some complex pipeline, you're probably not running a real-time system
+     * that must never stop, but rather *want* it to suspend if the output
+     * channel is "full".
+     *
+     * So, the bottom line: We will only set the output fd non-blocking if
+     * it points to a tty, and either a) the input fd also points to a tty,
+     * or b) we can make sure that setting the output fd non-blocking
+     * doesn't interfere with someone else's input, via a somewhat milder
+     * kludge than the above.
+     *
+     * Also keep in mind that while this code is almost exclusively run as
+     * a result of an erlang open_port({fd,0,1}, ...), that isn't the only
+     * case - it can be called with any old pre-existing file descriptors,
+     * the relations between which (if they're even two) we can only guess
+     * at - still, we try our best...
+     *
+     * Added note OTP 18: Some systems seem to use stdout/stderr to log data
+     * using unix pipes, so we cannot allow the system to block on a write.
+     * Therefore we use an async thread to write the data to fd's that could
+     * not be set to non-blocking. When no async threads are available we
+     * fall back on the old behaviour.
+     *
+     * Also the guarantee about what is delivered to the OS has changed.
+     * Pre 18 the fd driver did no flushing of data before terminating.
+     * Now it does. This is because we want to be able to guarantee that things
+     * such as escripts and friends really have outputted all data before
+     * terminating. This could potentially block the termination of the system
+     * for a very long time, but if the user wants to terminate fast she should
+     * use erlang:halt with flush=false.
+     */
+
+    if (opts->read_write & DO_READ) {
+	init_fd_data(opts->ifd, port_num);
+    }
+    if (opts->read_write & DO_WRITE) {
+	init_fd_data(opts->ofd, port_num);
+
+	/* If we don't have a read end, all bets are off - no non-blocking. */
+	if (opts->read_write & DO_READ) {
+
+	    if (isatty(opts->ofd)) { /* output fd is a tty:-) */
+
+		if (isatty(opts->ifd)) { /* input fd is also a tty */
+
+		    /* To really do this "right", we should also check that
+		       input and output fd point to the *same* tty - but
+		       this seems like overkill; ttyname() isn't for free,
+		       and this is a very common case - and it's hard to
+		       imagine a scenario where setting non-blocking mode
+		       here would cause problems - go ahead and do it. */
+
+                    non_blocking = 1;
+		    SET_NONBLOCKING(opts->ofd);
+
+		} else {	/* output fd is a tty, input fd isn't */
+
+		    /* This is a "problem case", but also common (see the
+		       example above) - i.e. it makes sense to try a bit
+		       harder before giving up on non-blocking mode: Try to
+		       re-open the tty that the output fd points to, and if
+		       successful replace the original one with the "new" fd
+		       obtained this way, and set *that* one in non-blocking
+		       mode. (Yes, this is a kludge.)
+
+		       However, re-opening the tty may fail in a couple of
+		       (unusual) cases:
+
+		       1) The name of the tty (or an equivalent one, i.e.
+			  same major/minor number) can't be found, because
+			  it actually lives somewhere other than /dev (or
+			  wherever ttyname() looks for it), and isn't
+			  equivalent to any of those that do live in the
+			  "standard" place - this should be *very* unusual.
+
+		       2) Permissions on the tty don't allow us to open it -
+			  it's perfectly possible to have an fd open to an
+			  object whose permissions wouldn't allow us to open
+			  it. This is not as unusual as it sounds, one case
+			  is if the user has su'ed to someone else (not
+			  root) - we have a read/write fd open to the tty
+			  (because it has been inherited all the way down
+			  here), but we have neither read nor write
+			  permission for the tty.
+
+		       In these cases, we finally give up, and don't set the
+		       output fd in non-blocking mode. */
+
+		    char *tty;
+		    int nfd;
+
+		    if ((tty = ttyname(opts->ofd)) != NULL &&
+			(nfd = open(tty, O_WRONLY)) != -1) {
+			dup2(nfd, opts->ofd);
+			close(nfd);
+                        non_blocking = 1;
+			SET_NONBLOCKING(opts->ofd);
+		    }
+		}
+	    }
+	}
+    }
+    CHLD_STAT_LOCK;
+    res = (ErlDrvData)(long)set_driver_data(port_num, opts->ifd, opts->ofd,
+                                            opts->packet_bytes,
+                                            opts->read_write, 0, -1,
+                                            !non_blocking);
+    CHLD_STAT_UNLOCK;
+    return res;
+}
+
+static void clear_fd_data(int fd) 
+{
+    if (fd_data[fd].sz > 0) {
+	erts_free(ERTS_ALC_T_FD_ENTRY_BUF, (void *) fd_data[fd].buf);
+	ASSERT(erts_smp_atomic_read_nob(&sys_misc_mem_sz) >= fd_data[fd].sz);
+	erts_smp_atomic_add_nob(&sys_misc_mem_sz, -1*fd_data[fd].sz);
+    }
+    fd_data[fd].buf = NULL;
+    fd_data[fd].sz = 0;
+    fd_data[fd].remain = 0;
+    fd_data[fd].cpos = NULL;
+    fd_data[fd].psz = 0;
+}
+
+static void nbio_stop_fd(ErlDrvPort prt, int fd)
+{
+    driver_select(prt,fd,DO_READ|DO_WRITE,0);
+    clear_fd_data(fd);
+    SET_BLOCKING(fd);
+}
+
+static void fd_stop(ErlDrvData ev)  /* Does not close the fds */
+{
+    int ofd;
+    int fd = (int)(long)ev;
+    ErlDrvPort prt = driver_data[fd].port_num;
+    
+#if FDBLOCK
+    if (driver_data[fd].blocking) {
+        erts_free(ERTS_ALC_T_SYS_BLOCKING,driver_data[fd].blocking);
+        driver_data[fd].blocking = NULL;
+        erts_smp_atomic_add_nob(&sys_misc_mem_sz, -1*sizeof(ErtsSysBlocking));
+    }
+#endif
+
+    nbio_stop_fd(prt, fd);
+    ofd = driver_data[fd].ofd;
+    if (ofd != fd && ofd != -1)
+	nbio_stop_fd(prt, ofd);
+}
+
+static void fd_flush(ErlDrvData fd)
+{
+    if (!driver_data[(int)(long)fd].terminating)
+        driver_data[(int)(long)fd].terminating = 1;
+}
+
+static ErlDrvData vanilla_start(ErlDrvPort port_num, char* name,
+				SysDriverOpts* opts)
+{
+    int flags, fd;
+    ErlDrvData res;
+
+    flags = (opts->read_write == DO_READ ? O_RDONLY :
+	     opts->read_write == DO_WRITE ? O_WRONLY|O_CREAT|O_TRUNC :
+	     O_RDWR|O_CREAT);
+    if ((fd = open(name, flags, 0666)) < 0)
+	return ERL_DRV_ERROR_GENERAL;
+    if (fd >= sys_max_files()) {
+	close(fd);
+	return ERL_DRV_ERROR_GENERAL;
+    }
+    SET_NONBLOCKING(fd);
+    init_fd_data(fd, port_num);
+
+    CHLD_STAT_LOCK;
+    res = (ErlDrvData)(long)set_driver_data(port_num, fd, fd,
+                                            opts->packet_bytes,
+                                            opts->read_write, 0, -1, 0);
+    CHLD_STAT_UNLOCK;
+    return res;
+}
+
+/* Note that driver_data[fd].ifd == fd if the port was opened for reading, */
+/* otherwise (i.e. write only) driver_data[fd].ofd = fd.  */
+
+static void stop(ErlDrvData fd)
+{
+    ErlDrvPort prt;
+    int ofd;
+
+    prt = driver_data[(int)(long)fd].port_num;
+    nbio_stop_fd(prt, (int)(long)fd);
+
+    ofd = driver_data[(int)(long)fd].ofd;
+    if (ofd != (int)(long)fd && (int)(long)ofd != -1)
+	nbio_stop_fd(prt, ofd);
+    else
+	ofd = -1;
+
+    CHLD_STAT_LOCK;
+
+    /* Mark as unused. */
+    driver_data[(int)(long)fd].pid = -1;
+
+    CHLD_STAT_UNLOCK;
+
+    /* SMP note: Close has to be last thing done (open file descriptors work
+       as locks on driver_data[] entries) */
+    driver_select(prt, (int)(long)fd, ERL_DRV_USE, 0);  /* close(fd); */
+    if (ofd >= 0) {
+	driver_select(prt, (int)(long)ofd, ERL_DRV_USE, 0);  /* close(ofd); */
+    }
+}
+
+/* used by fd_driver */
+static void outputv(ErlDrvData e, ErlIOVec* ev)
+{
+    int fd = (int)(long)e;
+    ErlDrvPort ix = driver_data[fd].port_num;
+    int pb = driver_data[fd].packet_bytes;
+    int ofd = driver_data[fd].ofd;
+    ssize_t n;
+    ErlDrvSizeT sz;
+    char lb[4];
+    char* lbp;
+    ErlDrvSizeT len = ev->size;
+
+    /* (len > ((unsigned long)-1 >> (4-pb)*8)) */
+    /*    if (pb >= 0 && (len & (((ErlDrvSizeT)1 << (pb*8))) - 1) != len) {*/
+    if (((pb == 2) && (len > 0xffff)) || (pb == 1 && len > 0xff)) {
+	driver_failure_posix(ix, EINVAL);
+	return; /* -1; */
+    }
+    /* Handles 0 <= pb <= 4 only */
+    put_int32((Uint32) len, lb);
+    lbp = lb + (4-pb);
+
+    ev->iov[0].iov_base = lbp;
+    ev->iov[0].iov_len = pb;
+    ev->size += pb;
+
+    if (driver_data[fd].blocking && FDBLOCK)
+        driver_pdl_lock(driver_data[fd].blocking->pdl);
+
+    if ((sz = driver_sizeq(ix)) > 0) {
+	driver_enqv(ix, ev, 0);
+
+        if (driver_data[fd].blocking && FDBLOCK)
+            driver_pdl_unlock(driver_data[fd].blocking->pdl);
+
+	if (sz + ev->size >= (1 << 13))
+	    set_busy_port(ix, 1);
+    }
+    else if (!driver_data[fd].blocking || !FDBLOCK) {
+        /* We try to write directly if the fd in non-blocking */
+	int vsize = ev->vsize > MAX_VSIZE ? MAX_VSIZE : ev->vsize;
+
+	n = writev(ofd, (const void *) (ev->iov), vsize);
+	if (n == ev->size)
+	    return; /* 0;*/
+	if (n < 0) {
+	    if ((errno != EINTR) && (errno != ERRNO_BLOCK)) {
+		driver_failure_posix(ix, errno);
+		return; /* -1;*/
+	    }
+	    n = 0;
+	}
+	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);
+            driver_pdl_unlock(driver_data[fd].blocking->pdl);
+            driver_async(ix, &driver_data[fd].blocking->pkey,
+                         fd_async, driver_data+fd, NULL);
+        } else {
+            driver_pdl_unlock(driver_data[fd].blocking->pdl);
+        }
+    }
+#endif
+    /* return 0;*/
+}
+
+/* Used by spawn_driver and vanilla driver */
+static void output(ErlDrvData e, char* buf, ErlDrvSizeT len)
+{
+    int fd = (int)(long)e;
+    ErlDrvPort ix = driver_data[fd].port_num;
+    int pb = driver_data[fd].packet_bytes;
+    int ofd = driver_data[fd].ofd;
+    ssize_t n;
+    ErlDrvSizeT sz;
+    char lb[4];
+    char* lbp;
+    struct iovec iv[2];
+
+    /* (len > ((unsigned long)-1 >> (4-pb)*8)) */
+    if (((pb == 2) && (len > 0xffff)) || (pb == 1 && len > 0xff)) {
+	driver_failure_posix(ix, EINVAL);
+	return; /* -1; */
+    }
+    put_int32(len, lb);
+    lbp = lb + (4-pb);
+
+    if ((sz = driver_sizeq(ix)) > 0) {
+	driver_enq(ix, lbp, pb);
+	driver_enq(ix, buf, len);
+	if (sz + len + pb >= (1 << 13))
+	    set_busy_port(ix, 1);
+    }
+    else {
+	iv[0].iov_base = lbp;
+	iv[0].iov_len = pb;  /* should work for pb=0 */
+	iv[1].iov_base = buf;
+	iv[1].iov_len = len;
+	n = writev(ofd, iv, 2);
+	if (n == pb+len)
+	    return; /* 0; */
+	if (n < 0) {
+	    if ((errno != EINTR) && (errno != ERRNO_BLOCK)) {
+		driver_failure_posix(ix, errno);
+		return; /* -1; */
+	    }
+	    n = 0;
+	}
+	if (n < pb) {
+	    driver_enq(ix, lbp+n, pb-n);
+	    driver_enq(ix, buf, len);
+	}
+	else {
+	    n -= pb;
+	    driver_enq(ix, buf+n, len-n);
+	}
+	driver_select(ix, ofd, ERL_DRV_WRITE|ERL_DRV_USE, 1);
+    }
+    return; /* 0; */
+}
+
+static int port_inp_failure(ErlDrvPort port_num, int ready_fd, int res)
+				/* Result: 0 (eof) or -1 (error) */
+{
+    int err = errno;
+
+    ASSERT(res <= 0);
+    (void) driver_select(port_num, ready_fd, ERL_DRV_READ|ERL_DRV_WRITE, 0); 
+    clear_fd_data(ready_fd);
+
+    if (driver_data[ready_fd].blocking && FDBLOCK) {
+        driver_pdl_lock(driver_data[ready_fd].blocking->pdl);
+        if (driver_sizeq(driver_data[ready_fd].port_num) > 0) {
+            driver_pdl_unlock(driver_data[ready_fd].blocking->pdl);
+            /* We have stuff in the output queue, so we just
+               set the state to terminating and wait for fd_async_ready
+               to terminate the port */
+            if (res == 0)
+                driver_data[ready_fd].terminating = 2;
+            else
+                driver_data[ready_fd].terminating = -err;
+            return 0;
+        }
+        driver_pdl_unlock(driver_data[ready_fd].blocking->pdl);
+    }
+
+    if (res == 0) {
+	if (driver_data[ready_fd].report_exit) {
+	    CHLD_STAT_LOCK;
+
+	    if (driver_data[ready_fd].alive) {
+		/*
+		 * We have eof and want to report exit status, but the process
+		 * hasn't exited yet. When it does report_exit_status() will
+		 * driver_select() this fd which will make sure that we get
+		 * back here with driver_data[ready_fd].alive == 0 and
+		 * driver_data[ready_fd].status set.
+		 */
+		CHLD_STAT_UNLOCK;
+		return 0;
+	    }
+	    else {
+		int status = driver_data[ready_fd].status;
+		CHLD_STAT_UNLOCK;
+
+		/* We need not be prepared for stopped/continued processes. */
+		if (WIFSIGNALED(status))
+		    status = 128 + WTERMSIG(status);
+		else
+		    status = WEXITSTATUS(status);
+
+		driver_report_exit(driver_data[ready_fd].port_num, status);
+	    }
+       }
+       driver_failure_eof(port_num);
+    } else {
+	driver_failure_posix(port_num, err);
+    }
+    return 0;
+}
+
+/* fd is the drv_data that is returned from the */
+/* initial start routine                        */
+/* ready_fd is the descriptor that is ready to read */
+
+static void ready_input(ErlDrvData e, ErlDrvEvent ready_fd)
+{
+    int fd = (int)(long)e;
+    ErlDrvPort port_num;
+    int packet_bytes;
+    int res;
+    Uint h;
+
+    port_num = driver_data[fd].port_num;
+    packet_bytes = driver_data[fd].packet_bytes;
+
+
+    if (packet_bytes == 0) {
+	byte *read_buf = (byte *) erts_alloc(ERTS_ALC_T_SYS_READ_BUF,
+					     ERTS_SYS_READ_BUF_SZ);
+	res = read(ready_fd, read_buf, ERTS_SYS_READ_BUF_SZ);
+	if (res < 0) {
+	    if ((errno != EINTR) && (errno != ERRNO_BLOCK))
+		port_inp_failure(port_num, ready_fd, res);
+	}
+	else if (res == 0)
+	    port_inp_failure(port_num, ready_fd, res);
+	else 
+	    driver_output(port_num, (char*) read_buf, res);
+	erts_free(ERTS_ALC_T_SYS_READ_BUF, (void *) read_buf);
+    }
+    else if (fd_data[ready_fd].remain > 0) { /* We try to read the remainder */
+	/* space is allocated in buf */
+	res = read(ready_fd, fd_data[ready_fd].cpos, 
+		   fd_data[ready_fd].remain);
+	if (res < 0) {
+	    if ((errno != EINTR) && (errno != ERRNO_BLOCK))
+		port_inp_failure(port_num, ready_fd, res);
+	}
+	else if (res == 0) {
+	    port_inp_failure(port_num, ready_fd, res);
+	}
+	else if (res == fd_data[ready_fd].remain) { /* we're done  */
+	    driver_output(port_num, fd_data[ready_fd].buf, 
+			  fd_data[ready_fd].sz);
+	    clear_fd_data(ready_fd);
+	}
+	else { /*  if (res < fd_data[ready_fd].remain) */
+	    fd_data[ready_fd].cpos += res;
+	    fd_data[ready_fd].remain -= res;
+	}
+    }
+    else if (fd_data[ready_fd].remain == 0) { /* clean fd */
+	byte *read_buf = (byte *) erts_alloc(ERTS_ALC_T_SYS_READ_BUF,
+					     ERTS_SYS_READ_BUF_SZ);
+	/* We make one read attempt and see what happens */
+	res = read(ready_fd, read_buf, ERTS_SYS_READ_BUF_SZ);
+	if (res < 0) {  
+	    if ((errno != EINTR) && (errno != ERRNO_BLOCK))
+		port_inp_failure(port_num, ready_fd, res);
+	}
+	else if (res == 0) {     	/* eof */
+	    port_inp_failure(port_num, ready_fd, res);
+	} 
+	else if (res < packet_bytes - fd_data[ready_fd].psz) { 
+	    memcpy(fd_data[ready_fd].pbuf+fd_data[ready_fd].psz,
+		   read_buf, res);
+	    fd_data[ready_fd].psz += res;
+	}
+	else  { /* if (res >= packet_bytes) */
+	    unsigned char* cpos = read_buf;
+	    int bytes_left = res;
+
+	    while (1) {
+		int psz = fd_data[ready_fd].psz;
+		char* pbp = fd_data[ready_fd].pbuf + psz;
+
+		while(bytes_left && (psz < packet_bytes)) {
+		    *pbp++ = *cpos++;
+		    bytes_left--;
+		    psz++;
+		}
+		
+		if (psz < packet_bytes) {
+		    fd_data[ready_fd].psz = psz;
+		    break;
+		}
+		fd_data[ready_fd].psz = 0;
+
+		switch (packet_bytes) {
+		case 1: h = get_int8(fd_data[ready_fd].pbuf);  break;
+		case 2: h = get_int16(fd_data[ready_fd].pbuf); break;
+		case 4: h = get_int32(fd_data[ready_fd].pbuf); break;
+		default: ASSERT(0); return; /* -1; */
+		}
+
+		if (h <= (bytes_left)) {
+		    driver_output(port_num, (char*) cpos, h);
+		    cpos += h;
+		    bytes_left -= h;
+		    continue;
+		}
+		else {		/* The last message we got was split */
+		        char *buf = erts_alloc_fnf(ERTS_ALC_T_FD_ENTRY_BUF, h);
+		    if (!buf) {
+			errno = ENOMEM;
+			port_inp_failure(port_num, ready_fd, -1);
+		    }
+		    else {
+			erts_smp_atomic_add_nob(&sys_misc_mem_sz, h);
+			sys_memcpy(buf, cpos, bytes_left);
+			fd_data[ready_fd].buf = buf;
+			fd_data[ready_fd].sz = h;
+			fd_data[ready_fd].remain = h - bytes_left;
+			fd_data[ready_fd].cpos = buf + bytes_left;
+		    }
+		    break;
+		}
+	    }
+	}
+	erts_free(ERTS_ALC_T_SYS_READ_BUF, (void *) read_buf);
+    }
+}
+
+
+/* fd is the drv_data that is returned from the */
+/* initial start routine                        */
+/* ready_fd is the descriptor that is ready to read */
+
+static void ready_output(ErlDrvData e, ErlDrvEvent ready_fd)
+{
+    int fd = (int)(long)e;
+    ErlDrvPort ix = driver_data[fd].port_num;
+    int n;
+    struct iovec* iv;
+    int vsize;
+    
+
+    if ((iv = (struct iovec*) driver_peekq(ix, &vsize)) == NULL) {
+	driver_select(ix, ready_fd, ERL_DRV_WRITE, 0);
+        if (driver_data[fd].terminating)
+            driver_failure_atom(driver_data[fd].port_num,"normal");
+	return; /* 0; */
+    }
+    vsize = vsize > MAX_VSIZE ? MAX_VSIZE : vsize;
+    if ((n = writev(ready_fd, iv, vsize)) > 0) {
+	if (driver_deq(ix, n) == 0)
+	    set_busy_port(ix, 0);
+    }
+    else if (n < 0) {
+	if (errno == ERRNO_BLOCK || errno == EINTR)
+	    return; /* 0; */
+	else {
+	    int res = errno;
+	    driver_select(ix, ready_fd, ERL_DRV_WRITE, 0);
+	    driver_failure_posix(ix, res);
+	    return; /* -1; */
+	}
+    }
+    return; /* 0; */
+}
+
+static void stop_select(ErlDrvEvent fd, void* _)
+{
+    close((int)fd);
+}
+
+#if FDBLOCK
+
+static void
+fd_async(void *async_data)
+{
+    int res;
+    ErtsSysDriverData *dd = (ErtsSysDriverData*)async_data;
+    SysIOVec      *iov0;
+    SysIOVec      *iov;
+    int            iovlen;
+    int            err = 0;
+    /* much of this code is stolen from efile_drv:invoke_writev */
+    driver_pdl_lock(dd->blocking->pdl);
+    iov0 = driver_peekq(dd->port_num, &iovlen);
+    iovlen = iovlen < MAXIOV ? iovlen : MAXIOV;
+    iov = erts_alloc_fnf(ERTS_ALC_T_SYS_WRITE_BUF,
+                         sizeof(SysIOVec)*iovlen);
+    if (!iov) {
+        res = -1;
+        err = ENOMEM;
+        driver_pdl_unlock(dd->blocking->pdl);
+    } else {
+        memcpy(iov,iov0,iovlen*sizeof(SysIOVec));
+        driver_pdl_unlock(dd->blocking->pdl);
+
+        do {
+            res = writev(dd->ofd, iov, iovlen);
+        } while (res < 0 && errno == EINTR);
+        if (res < 0)
+            err = errno;
+        err = errno;
+
+        erts_free(ERTS_ALC_T_SYS_WRITE_BUF, iov);
+    }
+    dd->blocking->res = res;
+    dd->blocking->err = err;
+}
+
+void fd_ready_async(ErlDrvData drv_data,
+                    ErlDrvThreadData thread_data) {
+    ErtsSysDriverData *dd = (ErtsSysDriverData *)thread_data;
+    ErlDrvPort port_num = dd->port_num;
+
+    ASSERT(dd->blocking);
+    ASSERT(dd == (driver_data + (int)(long)drv_data));
+
+    if (dd->blocking->res > 0) {
+        driver_pdl_lock(dd->blocking->pdl);
+        if (driver_deq(port_num, dd->blocking->res) == 0) {
+            driver_pdl_unlock(dd->blocking->pdl);
+            set_busy_port(port_num, 0);
+            if (dd->terminating) {
+                /* The port is has been ordered to terminate
+                   from either fd_flush or port_inp_failure */
+                if (dd->terminating == 1)
+                    driver_failure_atom(port_num, "normal");
+                else if (dd->terminating == 2)
+                    driver_failure_eof(port_num);
+                else if (dd->terminating < 0)
+                    driver_failure_posix(port_num, -dd->terminating);
+                return; /* -1; */
+            }
+        } else {
+            driver_pdl_unlock(dd->blocking->pdl);
+            /* still data left to write in queue */
+            driver_async(port_num, &dd->blocking->pkey, fd_async, dd, NULL);
+            return /* 0; */;
+        }
+    } else if (dd->blocking->res < 0) {
+        if (dd->blocking->err == ERRNO_BLOCK) {
+            set_busy_port(port_num, 1);
+            /* still data left to write in queue */
+            driver_async(port_num, &dd->blocking->pkey, fd_async, dd, NULL);
+        } else
+            driver_failure_posix(port_num, dd->blocking->err);
+        return; /* -1; */
+    }
+    return; /* 0; */
+}
+
+#endif
+
+static ERTS_INLINE void
+report_exit_status(ErtsSysReportExit *rep, int status)
+{
+    Port *pp;
+#ifdef ERTS_SMP
+    CHLD_STAT_UNLOCK;
+    pp = erts_thr_id2port_sflgs(rep->port,
+				ERTS_PORT_SFLGS_INVALID_DRIVER_LOOKUP);
+    CHLD_STAT_LOCK;
+#else
+    pp = erts_id2port_sflgs(rep->port,
+			    NULL,
+			    0,
+			    ERTS_PORT_SFLGS_INVALID_DRIVER_LOOKUP);
+#endif
+    if (pp) {
+	if (rep->ifd >= 0) {
+	    driver_data[rep->ifd].alive = 0;
+	    driver_data[rep->ifd].status = status;
+	    (void) driver_select(ERTS_Port2ErlDrvPort(pp),
+				 rep->ifd,
+				 (ERL_DRV_READ|ERL_DRV_USE),
+				 1);
+	}
+	if (rep->ofd >= 0) {
+	    driver_data[rep->ofd].alive = 0;
+	    driver_data[rep->ofd].status = status;
+	    (void) driver_select(ERTS_Port2ErlDrvPort(pp),
+				 rep->ofd,
+				 (ERL_DRV_WRITE|ERL_DRV_USE),
+				 1);
+	}
+#ifdef ERTS_SMP
+	erts_thr_port_release(pp);
+#else
+	erts_port_release(pp);
+#endif
+    }
+    erts_free(ERTS_ALC_T_PRT_REP_EXIT, rep);
+}
+
+#if !CHLDWTHR  /* ---------------------------------------------------------- */
+
+#define ERTS_REPORT_EXIT_STATUS report_exit_status
+
+int check_children(void)
+{
+    int res = 0;
+    int pid;
+    int status;
+
+#ifndef ERTS_SMP
+    if (children_died)
+#endif
+    {
+	sys_sigblock(SIGCHLD);
+	CHLD_STAT_LOCK;
+	while ((pid = waitpid(-1, &status, WNOHANG)) > 0)
+	    note_child_death(pid, status);
+#ifndef ERTS_SMP
+	children_died = 0;
+#endif
+	CHLD_STAT_UNLOCK;
+	sys_sigrelease(SIGCHLD);
+	res = 1;
+    }
+    return res;
+}
+
+#ifdef ERTS_SMP
+
+void
+erts_check_children(void)
+{
+    (void) check_children();
+}
+
+#endif
+
+#elif CHLDWTHR && defined(ERTS_SMP) /* ------------------------------------- */
+
+#define ERTS_REPORT_EXIT_STATUS report_exit_status
+
+int check_children(void)
+{
+    return 0;
+}
+
+#else /* CHLDWTHR && !defined(ERTS_SMP) ------------------------------------ */
+
+#define ERTS_REPORT_EXIT_STATUS initiate_report_exit_status
+
+static ERTS_INLINE void
+initiate_report_exit_status(ErtsSysReportExit *rep, int status)
+{
+    rep->next = report_exit_transit_list;
+    rep->status = status;
+    report_exit_transit_list = rep;
+    erts_sys_schedule_interrupt(1);
+}
+
+int check_children(void)
+{
+    int res;
+    ErtsSysReportExit *rep;
+    CHLD_STAT_LOCK;
+    rep = report_exit_transit_list;
+    res = rep != NULL;
+    while (rep) {
+	ErtsSysReportExit *curr_rep = rep;
+	rep = rep->next;
+	report_exit_status(curr_rep, curr_rep->status);
+    }
+    report_exit_transit_list = NULL;
+    CHLD_STAT_UNLOCK;
+    return res;
+}
+
+#endif /* ------------------------------------------------------------------ */
+
+static void note_child_death(int pid, int status)
+{
+    ErtsSysReportExit **repp = &report_exit_list;
+    ErtsSysReportExit *rep = report_exit_list;
+
+    while (rep) {
+	if (pid == rep->pid) {
+	    *repp = rep->next;
+	    ERTS_REPORT_EXIT_STATUS(rep, status);
+	    break;
+	}
+	repp = &rep->next;
+	rep = rep->next;
+    }
+}
+
+#if CHLDWTHR
+
+static void *
+child_waiter(void *unused)
+{
+  int pid;
+  int status;
+
+#ifdef ERTS_ENABLE_LOCK_CHECK
+  erts_lc_set_thread_name("child waiter");
+#endif
+
+  while(1) {
+#ifdef DEBUG
+      int waitpid_errno;
+#endif
+      pid = waitpid(-1, &status, 0);
+#ifdef DEBUG
+      waitpid_errno = errno;
+#endif
+      CHLD_STAT_LOCK;
+      if (pid < 0) {
+	  ASSERT(waitpid_errno == ECHILD);
+      }
+      else {
+	  children_alive--;
+	  ASSERT(children_alive >= 0);
+	  note_child_death(pid, status);
+      }
+      while (!children_alive)
+	  CHLD_STAT_WAIT; /* Wait for children to wait on... :) */
+      CHLD_STAT_UNLOCK;
+  }
+
+  return NULL;
+}
+
+#endif