Merge branch 'sverker/enif_select/OTP-13684'

* sverker/enif_select: (31 commits)
  Remove debug printout and comment
  Fix nif_SUITE:select for old linux
  Add docs for enif_compare_monitors and ErlNifMonitor
  Fix ErlNifMonitor handling
  Remove faulty debug ASSERT
  erts: Skip nif_SUITE:select on windows
  Fix enif_select for windows
  Fix whitebox monitor tests
  Fix erl_nif doc
  Expand nif_SUITE:monitor_frenzy to verify dtor calls
  Expand nif_SUITE:monitor_frenzy with binary_to_term
  erts: Avoid revival of dying resource by dec_term
  erts: Add enif_compare_monitors
  erts: Try fix enif_select for windows
  erts: Change return value for enif_select
  erts: Add pid argument to enif_select
  erts: Beautify enif_select
  erts: Fix bad_fd_in_pollset error case for enif_select
  erts: Add enif_monitor_process and enif_demonitor_process
  erts: Rename ErlNifResource as ErtsResource
  ...

21 files changed, 737 insertions, 206 deletions

diff --git a/erts/emulator/beam/bif.c b/erts/emulator/beam/bif.c
index 4c9b9887c1..614bedab12 100644
--- a/erts/emulator/beam/bif.c
+++ b/erts/emulator/beam/bif.c
@@ -361,7 +361,7 @@ remote_demonitor(Process *c_p, DistEntry *dep, Eterm ref, Eterm to)
 					    c_p->common.id, 
 					    (mon->name != NIL
 					     ? mon->name
-					     : mon->pid), 
+					     : mon->u.pid), 
 					    ref,
 					    0);
             res = (code == ERTS_DSIG_SEND_YIELD ? am_yield : am_true);
@@ -498,7 +498,7 @@ BIF_RETTYPE demonitor(Process *c_p, Eterm ref, Eterm *multip)
        res = am_true;
        break;
    case MON_ORIGIN:
-       to = mon->pid;
+       to = mon->u.pid;
        *multip = am_false;
        if (is_atom(to)) {
            /* Monitoring a name at node to */
diff --git a/erts/emulator/beam/break.c b/erts/emulator/beam/break.c
index b9c272d6d5..4dad5736c5 100644
--- a/erts/emulator/beam/break.c
+++ b/erts/emulator/beam/break.c
@@ -178,19 +178,28 @@ static void doit_print_monitor(ErtsMonitor *mon, void *vpcontext)
 	prefix = "";
     }
 
-    if (mon->type == MON_ORIGIN) {
-	if (is_atom(mon->pid)) { /* dist by name */
-	    ASSERT(is_node_name_atom(mon->pid));
+    switch (mon->type) {
+    case MON_ORIGIN:
+	if (is_atom(mon->u.pid)) { /* dist by name */
+	    ASSERT(is_node_name_atom(mon->u.pid));
 	    erts_print(to, to_arg, "%s{to,{%T,%T},%T}", prefix, mon->name,
-		       mon->pid, mon->ref);
+		       mon->u.pid, mon->ref);
 	} else if (is_atom(mon->name)){ /* local by name */
 	    erts_print(to, to_arg, "%s{to,{%T,%T},%T}", prefix, mon->name,
 		       erts_this_dist_entry->sysname, mon->ref);
 	} else { /* local and distributed by pid */
-	    erts_print(to, to_arg, "%s{to,%T,%T}", prefix, mon->pid, mon->ref);
+	    erts_print(to, to_arg, "%s{to,%T,%T}", prefix, mon->u.pid, mon->ref);
 	}
-    } else { /* MON_TARGET */
-	erts_print(to, to_arg, "%s{from,%T,%T}", prefix, mon->pid, mon->ref);
+	break;
+    case MON_TARGET:
+	erts_print(to, to_arg, "%s{from,%T,%T}", prefix, mon->u.pid, mon->ref);
+	break;
+    case MON_NIF_TARGET: {
+        ErtsResource* rsrc = mon->u.resource;
+        erts_print(to, to_arg, "%s{from,{%T,%T},%T}", prefix, rsrc->type->module,
+                   rsrc->type->name, mon->ref);
+	break;
+    }
     }
 }
 			       
diff --git a/erts/emulator/beam/dist.c b/erts/emulator/beam/dist.c
index e659ac071c..d1c2da9074 100644
--- a/erts/emulator/beam/dist.c
+++ b/erts/emulator/beam/dist.c
@@ -259,7 +259,7 @@ static void doit_monitor_net_exits(ErtsMonitor *mon, void *vnecp)
     DistEntry *dep = ((NetExitsContext *) vnecp)->dep;
     ErtsProcLocks rp_locks = ERTS_PROC_LOCK_LINK;
 
-    rp = erts_pid2proc(NULL, 0, mon->pid, rp_locks);
+    rp = erts_pid2proc(NULL, 0, mon->u.pid, rp_locks);
     if (!rp)
 	goto done;
 
@@ -278,10 +278,11 @@ static void doit_monitor_net_exits(ErtsMonitor *mon, void *vnecp)
 	rmon = erts_remove_monitor(&ERTS_P_MONITORS(rp), mon->ref);
 	/* ASSERT(rmon != NULL); can happen during process exit */
 	if (rmon != NULL) {
+            ASSERT(rmon->type == MON_ORIGIN);
 	    ASSERT(is_atom(rmon->name) || is_nil(rmon->name));
 	    watched = (is_atom(rmon->name)
 		       ? TUPLE2(lhp, rmon->name, dep->sysname)
-		       : rmon->pid);
+		       : rmon->u.pid);
 #ifdef ERTS_SMP
 	    rp_locks |= ERTS_PROC_LOCKS_MSG_SEND;
 	    erts_smp_proc_lock(rp, ERTS_PROC_LOCKS_MSG_SEND);
@@ -1391,7 +1392,7 @@ int erts_net_message(Port *prt,
 	if (mon == NULL) {
 	    break;
 	}
-	watched = mon->pid;
+	watched = mon->u.pid;
 	erts_destroy_monitor(mon);
 	rp = erts_pid2proc_opt(NULL, 0,
 			       watched, ERTS_PROC_LOCK_LINK,
@@ -1549,7 +1550,7 @@ int erts_net_message(Port *prt,
 	if (mon == NULL) {
 	    break;
 	}
-	rp = erts_pid2proc(NULL, 0, mon->pid, rp_locks);
+	rp = erts_pid2proc(NULL, 0, mon->u.pid, rp_locks);
 
 	erts_destroy_monitor(mon);
 	if (rp == NULL) {
@@ -1566,7 +1567,7 @@ int erts_net_message(Port *prt,
 	
 	watched = (is_not_nil(mon->name)
 		   ? TUPLE2(&lhp[0], mon->name, sysname)
-		   : mon->pid);
+		   : mon->u.pid);
 	
 	erts_queue_monitor_message(rp, &rp_locks,
 				   ref, am_process, watched, reason);
@@ -2415,21 +2416,21 @@ static void doit_print_monitor_info(ErtsMonitor *mon, void *vptdp)
     void *arg = ((struct print_to_data *) vptdp)->arg;
     Process *rp;
     ErtsMonitor *rmon;
-    rp = erts_proc_lookup(mon->pid);
+    rp = erts_proc_lookup(mon->u.pid);
     if (!rp || (rmon = erts_lookup_monitor(ERTS_P_MONITORS(rp), mon->ref)) == NULL) {
-	erts_print(to, arg, "Warning, stray monitor for: %T\n", mon->pid);
+	erts_print(to, arg, "Warning, stray monitor for: %T\n", mon->u.pid);
     } else if (mon->type == MON_ORIGIN) {
 	/* Local pid is being monitored */
 	erts_print(to, arg, "Remotely monitored by: %T %T\n",
-		   mon->pid, rmon->pid);
+		   mon->u.pid, rmon->u.pid);
     } else {
-	erts_print(to, arg, "Remote monitoring: %T ", mon->pid);
-	if (is_not_atom(rmon->pid))
-	    erts_print(to, arg, "%T\n", rmon->pid);
+	erts_print(to, arg, "Remote monitoring: %T ", mon->u.pid);
+	if (is_not_atom(rmon->u.pid))
+	    erts_print(to, arg, "%T\n", rmon->u.pid);
 	else
 	    erts_print(to, arg, "{%T, %T}\n",
 		       rmon->name,
-		       rmon->pid); /* which in this case is the 
+		       rmon->u.pid); /* which in this case is the 
 				      remote system name... */
     }
 }    
diff --git a/erts/emulator/beam/erl_alloc.c b/erts/emulator/beam/erl_alloc.c
index 6708d96d56..a374593c5d 100644
--- a/erts/emulator/beam/erl_alloc.c
+++ b/erts/emulator/beam/erl_alloc.c
@@ -664,6 +664,8 @@ erts_alloc_init(int *argc, char **argv, ErtsAllocInitOpts *eaiop)
 	= sizeof(ErtsDrvEventDataState);
     fix_type_sizes[ERTS_ALC_FIX_TYPE_IX(ERTS_ALC_T_DRV_SEL_D_STATE)]
 	= sizeof(ErtsDrvSelectDataState);
+    fix_type_sizes[ERTS_ALC_FIX_TYPE_IX(ERTS_ALC_T_NIF_SEL_D_STATE)]
+        = sizeof(ErtsNifSelectDataState);
     fix_type_sizes[ERTS_ALC_FIX_TYPE_IX(ERTS_ALC_T_MSG_REF)]
 	= sizeof(ErtsMessageRef);
 #ifdef ERTS_SMP
diff --git a/erts/emulator/beam/erl_alloc.types b/erts/emulator/beam/erl_alloc.types
index 295db2fe9b..3d5de72ee7 100644
--- a/erts/emulator/beam/erl_alloc.types
+++ b/erts/emulator/beam/erl_alloc.types
@@ -402,6 +402,7 @@ type	DRV_TAB		LONG_LIVED	SYSTEM		drv_tab
 type	DRV_EV_STATE	LONG_LIVED	SYSTEM		driver_event_state
 type	DRV_EV_D_STATE	FIXED_SIZE	SYSTEM		driver_event_data_state
 type	DRV_SEL_D_STATE	FIXED_SIZE	SYSTEM		driver_select_data_state
+type	NIF_SEL_D_STATE	FIXED_SIZE	SYSTEM		enif_select_data_state
 type	FD_LIST		SHORT_LIVED	SYSTEM		fd_list
 type	ACTIVE_FD_ARR	SHORT_LIVED	SYSTEM		active_fd_array
 type	POLLSET		LONG_LIVED	SYSTEM		pollset
diff --git a/erts/emulator/beam/erl_bif_info.c b/erts/emulator/beam/erl_bif_info.c
index 5a8776076e..06a73ffea5 100644
--- a/erts/emulator/beam/erl_bif_info.c
+++ b/erts/emulator/beam/erl_bif_info.c
@@ -228,8 +228,10 @@ bld_magic_ref_bin_list(Uint **hpp, Uint *szp, ErlOffHeap* oh)
 static void do_calc_mon_size(ErtsMonitor *mon, void *vpsz)
 {
     Uint *psz = vpsz;
-    *psz += IS_CONST(mon->ref) ? 0 : NC_HEAP_SIZE(mon->ref);
-    *psz += IS_CONST(mon->pid) ? 0 : NC_HEAP_SIZE(mon->pid);
+    *psz += NC_HEAP_SIZE(mon->ref);
+    *psz += (mon->type == MON_NIF_TARGET ?
+	     erts_resource_ref_size(mon->u.resource) :
+	     (is_immed(mon->u.pid) ? 0 : NC_HEAP_SIZE(mon->u.pid)));
     *psz += 8; /* CONS + 5-tuple */ 
 }
 
@@ -244,12 +246,11 @@ static void do_make_one_mon_element(ErtsMonitor *mon, void * vpmlc)
 {
     MonListContext *pmlc = vpmlc;
     Eterm tup;
-    Eterm r = (IS_CONST(mon->ref)
-	       ? mon->ref
-	       : STORE_NC(&(pmlc->hp), &MSO(pmlc->p), mon->ref));
-    Eterm p = (IS_CONST(mon->pid)
-	       ? mon->pid
-	       : STORE_NC(&(pmlc->hp), &MSO(pmlc->p), mon->pid));
+    Eterm r = STORE_NC(&(pmlc->hp), &MSO(pmlc->p), mon->ref);
+    Eterm p = (mon->type == MON_NIF_TARGET ?
+	       erts_bld_resource_ref(&(pmlc->hp), &MSO(pmlc->p), mon->u.resource)
+	       : (is_immed(mon->u.pid) ? mon->u.pid
+		  : STORE_NC(&(pmlc->hp), &MSO(pmlc->p), mon->u.pid)));
     tup = TUPLE5(pmlc->hp, pmlc->tag, make_small(mon->type), r, p, mon->name);
     pmlc->hp += 6;
     pmlc->res = CONS(pmlc->hp, tup, pmlc->res);
@@ -288,7 +289,7 @@ make_monitor_list(Process *p, ErtsMonitor *root)
 static void do_calc_lnk_size(ErtsLink *lnk, void *vpsz)
 {
     Uint *psz = vpsz;
-    *psz += IS_CONST(lnk->pid) ? 0 : NC_HEAP_SIZE(lnk->pid);
+    *psz += is_immed(lnk->pid) ? 0 : NC_HEAP_SIZE(lnk->pid);
     if (lnk->type != LINK_NODE && ERTS_LINK_ROOT(lnk) != NULL) { 
 	/* Node links use this pointer as ref counter... */
 	erts_doforall_links(ERTS_LINK_ROOT(lnk),&do_calc_lnk_size,vpsz);
@@ -308,7 +309,7 @@ static void do_make_one_lnk_element(ErtsLink *lnk, void * vpllc)
     LnkListContext *pllc = vpllc;
     Eterm tup;
     Eterm old_res, targets = NIL;
-    Eterm p = (IS_CONST(lnk->pid)
+    Eterm p = (is_immed(lnk->pid)
 	       ? lnk->pid
 	       : STORE_NC(&(pllc->hp), &MSO(pllc->p), lnk->pid));
     if (lnk->type == LINK_NODE) {
@@ -392,8 +393,12 @@ erts_print_system_version(fmtfn_t to, void *arg, Process *c_p)
 typedef struct {
     /* {Entity,Node} = {monitor.Name,monitor.Pid} for external by name
      * {Entity,Node} = {monitor.Pid,NIL} for external/external by pid
-     * {Entity,Node} = {monitor.Name,erlang:node()} for internal by name */
-    Eterm entity;
+     * {Entity,Node} = {monitor.Name,erlang:node()} for internal by name 
+     * {Entity,Node} = {monitor.resource,MON_NIF_TARGET}*/
+    union {
+	Eterm term;
+	ErtsResource* resource;
+    }entity;
     Eterm node;
     /* pid is actual target being monitored, no matter pid/port or name */
     Eterm pid;
@@ -439,7 +444,7 @@ static void collect_one_link(ErtsLink *lnk, void *vmicp)
     if (!(lnk->type == LINK_PID)) {
 	return;
     }
-    micp->mi[micp->mi_i].entity = lnk->pid;
+    micp->mi[micp->mi_i].entity.term = lnk->pid;
     micp->sz += 2 + NC_HEAP_SIZE(lnk->pid);
     micp->mi_i++;
 } 
@@ -452,20 +457,20 @@ static void collect_one_origin_monitor(ErtsMonitor *mon, void *vmicp)
 	return;
     }
     EXTEND_MONITOR_INFOS(micp);
-    if (is_atom(mon->pid)) { /* external by name */
-	micp->mi[micp->mi_i].entity = mon->name;
-        micp->mi[micp->mi_i].node = mon->pid;
+    if (is_atom(mon->u.pid)) { /* external by name */
+	micp->mi[micp->mi_i].entity.term = mon->name;
+        micp->mi[micp->mi_i].node = mon->u.pid;
         micp->sz += 3; /* need one 2-tuple */
-    } else if (is_external_pid(mon->pid)) { /* external by pid */
-	micp->mi[micp->mi_i].entity = mon->pid;
+    } else if (is_external_pid(mon->u.pid)) { /* external by pid */
+	micp->mi[micp->mi_i].entity.term = mon->u.pid;
         micp->mi[micp->mi_i].node = NIL;
-        micp->sz += NC_HEAP_SIZE(mon->pid);
+        micp->sz += NC_HEAP_SIZE(mon->u.pid);
     } else if (!is_nil(mon->name)) { /* internal by name */
-	micp->mi[micp->mi_i].entity = mon->name;
+	micp->mi[micp->mi_i].entity.term = mon->name;
         micp->mi[micp->mi_i].node = erts_this_dist_entry->sysname;
         micp->sz += 3; /* need one 2-tuple */
     } else { /* internal by pid */
-	micp->mi[micp->mi_i].entity = mon->pid;
+	micp->mi[micp->mi_i].entity.term = mon->u.pid;
         micp->mi[micp->mi_i].node = NIL;
 	/* no additional heap space needed */
     }
@@ -473,7 +478,7 @@ static void collect_one_origin_monitor(ErtsMonitor *mon, void *vmicp)
     /* have always pid at hand, to assist with figuring out if its a port or
      * a process, when we monitored by name and process_info is requested.
      * See: erl_bif_info.c:process_info_aux section for am_monitors */
-    micp->mi[micp->mi_i].pid = mon->pid;
+    micp->mi[micp->mi_i].pid = mon->u.pid;
 
     micp->mi_i++;
     micp->sz += 2 + 3; /* For a cons cell and a 2-tuple */
@@ -483,15 +488,24 @@ static void collect_one_target_monitor(ErtsMonitor *mon, void *vmicp)
 {
     MonitorInfoCollection *micp = vmicp;
  
-    if (mon->type != MON_TARGET) {
-	return;
+    if (mon->type != MON_TARGET && mon->type != MON_NIF_TARGET) {
+        return;
     }
 
     EXTEND_MONITOR_INFOS(micp);
   
-    micp->mi[micp->mi_i].node = NIL;
-    micp->mi[micp->mi_i].entity = mon->pid;
-    micp->sz += (NC_HEAP_SIZE(mon->pid) + 2 /* cons */);
+
+    if (mon->type == MON_NIF_TARGET) {
+	micp->mi[micp->mi_i].entity.resource = mon->u.resource;
+        micp->mi[micp->mi_i].node = make_small(MON_NIF_TARGET);
+        micp->sz += erts_resource_ref_size(mon->u.resource);
+    }
+    else {
+	micp->mi[micp->mi_i].entity.term = mon->u.pid;
+        micp->mi[micp->mi_i].node = NIL;
+        micp->sz += NC_HEAP_SIZE(mon->u.pid);
+    }
+    micp->sz += 2; /* cons */;
     micp->mi_i++;
 }
 
@@ -1222,7 +1236,7 @@ process_info_aux(Process *BIF_P,
 	hp = HAlloc(BIF_P, 3 + mic.sz);
 	res = NIL;
 	for (i = 0; i < mic.mi_i; i++) {
-	    item = STORE_NC(&hp, &MSO(BIF_P), mic.mi[i].entity); 
+	    item = STORE_NC(&hp, &MSO(BIF_P), mic.mi[i].entity.term); 
 	    res = CONS(hp, item, res);
 	    hp += 2;
 	}
@@ -1240,7 +1254,7 @@ process_info_aux(Process *BIF_P,
         hp = HAlloc(BIF_P, 3 + mic.sz);
 	res = NIL;
 	for (i = 0; i < mic.mi_i; i++) {
-	    if (is_atom(mic.mi[i].entity)) {
+	    if (is_atom(mic.mi[i].entity.term)) {
 		/* Monitor by name. 
                  * Build {process|port, {Name, Node}} and cons it.
 		 */
@@ -1252,7 +1266,7 @@ process_info_aux(Process *BIF_P,
                     || is_port(mic.mi[i].pid)
                     || is_atom(mic.mi[i].pid));
 
-		t1 = TUPLE2(hp, mic.mi[i].entity, mic.mi[i].node);
+		t1 = TUPLE2(hp, mic.mi[i].entity.term, mic.mi[i].node);
 		hp += 3;
                 t2 = TUPLE2(hp, m_type, t1);
 		hp += 3;
@@ -1262,7 +1276,7 @@ process_info_aux(Process *BIF_P,
 	    else {
                 /* Monitor by pid. Build {process|port, Pid} and cons it. */
 		Eterm t;
-		Eterm pid = STORE_NC(&hp, &MSO(BIF_P), mic.mi[i].entity);
+		Eterm pid = STORE_NC(&hp, &MSO(BIF_P), mic.mi[i].entity.term);
 
                 Eterm m_type = is_port(mic.mi[i].pid) ? am_port : am_process;
                 ASSERT(is_pid(mic.mi[i].pid)
@@ -1289,7 +1303,12 @@ process_info_aux(Process *BIF_P,
 
 	res = NIL;
 	for (i = 0; i < mic.mi_i; ++i) {
-	    item = STORE_NC(&hp, &MSO(BIF_P), mic.mi[i].entity); 
+            if (mic.mi[i].node == make_small(MON_NIF_TARGET)) {
+                item = erts_bld_resource_ref(&hp, &MSO(BIF_P), mic.mi[i].entity.resource);
+            }
+            else {
+                item = STORE_NC(&hp, &MSO(BIF_P), mic.mi[i].entity.term);
+            }
 	    res = CONS(hp, item, res);
 	    hp += 2;
 	}
@@ -2986,7 +3005,7 @@ erts_bld_port_info(Eterm **hpp, ErlOffHeap *ohp, Uint *szp, Port *prt,
 	if (hpp) {
 	    res = NIL;
 	    for (i = 0; i < mic.mi_i; i++) {
-		item = STORE_NC(hpp, ohp, mic.mi[i].entity);
+		item = STORE_NC(hpp, ohp, mic.mi[i].entity.term);
 		res = CONS(*hpp, item, res);
 		*hpp += 2;
 	    }
@@ -3017,7 +3036,7 @@ erts_bld_port_info(Eterm **hpp, ErlOffHeap *ohp, Uint *szp, Port *prt,
 		Eterm t;
                 Eterm m_type;
 
-                item = STORE_NC(hpp, ohp, mic.mi[i].entity);
+                item = STORE_NC(hpp, ohp, mic.mi[i].entity.term);
                 m_type = is_port(item) ? am_port : am_process;
                 t = TUPLE2(*hpp, m_type, item);
 		*hpp += 3;
@@ -3046,7 +3065,8 @@ erts_bld_port_info(Eterm **hpp, ErlOffHeap *ohp, Uint *szp, Port *prt,
         if (hpp) {
             res = NIL;
             for (i = 0; i < mic.mi_i; ++i) {
-                item = STORE_NC(hpp, ohp, mic.mi[i].entity);
+                ASSERT(mic.mi[i].node == NIL);
+                item = STORE_NC(hpp, ohp, mic.mi[i].entity.term);
                 res = CONS(*hpp, item, res);
                 *hpp += 2;
             }
diff --git a/erts/emulator/beam/erl_binary.h b/erts/emulator/beam/erl_binary.h
index db259be2a7..946d3cfe03 100644
--- a/erts/emulator/beam/erl_binary.h
+++ b/erts/emulator/beam/erl_binary.h
@@ -79,11 +79,9 @@ struct magic_binary {
     } u;
 };
 
-#ifdef ARCH_32
-#define ERTS_MAGIC_BIN_BYTES_TO_ALIGN 4
-#else
-#define ERTS_MAGIC_BIN_BYTES_TO_ALIGN 0
-#endif
+#define ERTS_MAGIC_BIN_BYTES_TO_ALIGN \
+    (offsetof(ErtsMagicBinary,u.aligned.data) - \
+     offsetof(ErtsMagicBinary,u.unaligned.data))
 
 typedef union {
     Binary binary;
diff --git a/erts/emulator/beam/erl_bits.c b/erts/emulator/beam/erl_bits.c
index 6bf52fb303..885e955332 100644
--- a/erts/emulator/beam/erl_bits.c
+++ b/erts/emulator/beam/erl_bits.c
@@ -110,9 +110,6 @@ erts_init_bits(void)
 {
     ERTS_CT_ASSERT(offsetof(Binary,orig_bytes) % 8 == 0);
     ERTS_CT_ASSERT(offsetof(ErtsMagicBinary,u.aligned.data) % 8 == 0);
-    ERTS_CT_ASSERT(ERTS_MAGIC_BIN_BYTES_TO_ALIGN ==
-                   (offsetof(ErtsMagicBinary,u.aligned.data)
-                    - offsetof(ErtsMagicBinary,u.unaligned.data)));
     ERTS_CT_ASSERT(offsetof(ErtsBinary,driver.binary.orig_bytes)
                 == offsetof(Binary,orig_bytes));
 
diff --git a/erts/emulator/beam/erl_driver.h b/erts/emulator/beam/erl_driver.h
index 97a69140c3..b386b68cff 100644
--- a/erts/emulator/beam/erl_driver.h
+++ b/erts/emulator/beam/erl_driver.h
@@ -76,11 +76,10 @@ typedef struct {
 #  endif
 #endif
 
-/* Values for mode arg to driver_select() */
-#define ERL_DRV_READ  (1 << 0)
-#define ERL_DRV_WRITE (1 << 1)
-#define ERL_DRV_USE   (1 << 2)
-#define ERL_DRV_USE_NO_CALLBACK (ERL_DRV_USE | (1 << 3))
+#define ERL_DRV_READ  ((int)ERL_NIF_SELECT_READ)
+#define ERL_DRV_WRITE ((int)ERL_NIF_SELECT_WRITE)
+#define ERL_DRV_USE   ((int)ERL_NIF_SELECT_STOP)
+#define ERL_DRV_USE_NO_CALLBACK (ERL_DRV_USE | (ERL_DRV_USE  << 1))
 
 /* Old deprecated */
 #define DO_READ  ERL_DRV_READ
@@ -176,13 +175,6 @@ struct erl_drv_event_data {
 #endif
 typedef struct erl_drv_event_data *ErlDrvEventData; /* Event data */
 
-/*
- * A driver monitor
- */
-typedef struct {
-    unsigned char data[sizeof(void *)*4];
-} ErlDrvMonitor;
-
 typedef struct {
     unsigned long megasecs;
     unsigned long secs;
diff --git a/erts/emulator/beam/erl_drv_nif.h b/erts/emulator/beam/erl_drv_nif.h
index 2489099b5c..2d21dac87a 100644
--- a/erts/emulator/beam/erl_drv_nif.h
+++ b/erts/emulator/beam/erl_drv_nif.h
@@ -49,6 +49,21 @@ typedef enum {
     ERL_DIRTY_JOB_IO_BOUND  = 2
 } ErlDirtyJobFlags;
 
+/* Values for enif_select AND mode arg for driver_select() */
+enum ErlNifSelectFlags {
+    ERL_NIF_SELECT_READ      = (1 << 0),
+    ERL_NIF_SELECT_WRITE     = (1 << 1),
+    ERL_NIF_SELECT_STOP      = (1 << 2)
+};
+
+/*
+ * A driver monitor
+ */
+typedef struct {
+    unsigned char data[sizeof(void *)*4];
+} ErlDrvMonitor;
+
+
 #ifdef SIZEOF_CHAR
 #  define SIZEOF_CHAR_SAVED__ SIZEOF_CHAR
 #  undef SIZEOF_CHAR
diff --git a/erts/emulator/beam/erl_lock_check.c b/erts/emulator/beam/erl_lock_check.c
index c98581a45e..6ff9aea5ab 100644
--- a/erts/emulator/beam/erl_lock_check.c
+++ b/erts/emulator/beam/erl_lock_check.c
@@ -89,6 +89,9 @@ static erts_lc_lock_order_t erts_lock_order[] = {
     {	"hipe_mfait_lock",			NULL			},
 #endif
     {	"nodes_monitors",			NULL			},
+#ifdef ERTS_SMP
+    {	"resource_monitors",			"address"	        },
+#endif
     {   "driver_list",                          NULL                    },
     {	"proc_link",				"pid"			},
     {	"proc_msgq",				"pid"			},
diff --git a/erts/emulator/beam/erl_monitors.c b/erts/emulator/beam/erl_monitors.c
index f813f19dbc..6dee1d5ef3 100644
--- a/erts/emulator/beam/erl_monitors.c
+++ b/erts/emulator/beam/erl_monitors.c
@@ -109,7 +109,7 @@ static ERTS_INLINE int cmp_mon_ref(Eterm ref1, Eterm ref2)
 	    
 #define CP_LINK_VAL(To, Hp, From)				\
 do {								\
-    if (IS_CONST(From))						\
+    if (is_immed(From))						\
 	(To) = (From);						\
     else {							\
 	Uint i__;						\
@@ -128,15 +128,15 @@ do {								\
     }								\
 } while (0)
 
-static ErtsMonitor *create_monitor(Uint type, Eterm ref, Eterm pid, Eterm name)
+static ErtsMonitor *create_monitor(Uint type, Eterm ref, UWord entity, Eterm name)
 {
      Uint mon_size = ERTS_MONITOR_SIZE;
      ErtsMonitor *n;
      Eterm *hp;
 
      mon_size += NC_HEAP_SIZE(ref);
-     if (!IS_CONST(pid)) {
-	 mon_size += NC_HEAP_SIZE(pid);
+     if (type != MON_NIF_TARGET && is_not_immed(entity)) {
+	 mon_size += NC_HEAP_SIZE(entity);
      }
 
      if (mon_size <= ERTS_MONITOR_SH_SIZE) {
@@ -155,7 +155,10 @@ static ErtsMonitor *create_monitor(Uint type, Eterm ref, Eterm pid, Eterm name)
      n->balance = 0;            /* Always the same initial value */
      n->name = name; /* atom() or [] */
      CP_LINK_VAL(n->ref, hp, ref); /*XXX Unnecessary check, never immediate*/
-     CP_LINK_VAL(n->pid, hp, pid);
+     if (type == MON_NIF_TARGET)
+         n->u.resource = (ErtsResource*)entity;
+     else
+         CP_LINK_VAL(n->u.pid, hp, (Eterm)entity);
 
      return n;
 }
@@ -166,7 +169,7 @@ static ErtsLink *create_link(Uint type, Eterm pid)
      ErtsLink *n;
      Eterm *hp;
 
-     if (!IS_CONST(pid)) {
+     if (is_not_immed(pid)) {
 	 lnk_size += NC_HEAP_SIZE(pid);
      }
 
@@ -225,16 +228,16 @@ void erts_destroy_monitor(ErtsMonitor *mon)
     Uint mon_size = ERTS_MONITOR_SIZE;
     ErlNode *node;
 
-    ASSERT(!IS_CONST(mon->ref));
+    ASSERT(is_not_immed(mon->ref));
     mon_size +=  NC_HEAP_SIZE(mon->ref);
     if (is_external(mon->ref)) {
 	node = external_thing_ptr(mon->ref)->node;
 	erts_deref_node_entry(node);
     }
-    if (!IS_CONST(mon->pid)) {
-	mon_size += NC_HEAP_SIZE(mon->pid);
-	if (is_external(mon->pid)) {
-	    node = external_thing_ptr(mon->pid)->node;
+    if (mon->type != MON_NIF_TARGET && is_not_immed(mon->u.pid)) {
+	mon_size += NC_HEAP_SIZE(mon->u.pid);
+	if (is_external(mon->u.pid)) {
+	    node = external_thing_ptr(mon->u.pid)->node;
 	    erts_deref_node_entry(node);
 	}
     }
@@ -253,7 +256,7 @@ void erts_destroy_link(ErtsLink *lnk)
 
     ASSERT(lnk->type == LINK_NODE || ERTS_LINK_ROOT(lnk) == NULL);
 
-    if (!IS_CONST(lnk->pid)) {
+    if (is_not_immed(lnk->pid)) {
 	lnk_size += NC_HEAP_SIZE(lnk->pid);
 	if (is_external(lnk->pid)) {
 	    node = external_thing_ptr(lnk->pid)->node;
@@ -348,7 +351,7 @@ static void insertion_rotation(int dstack[], int dpos,
     }
 }
 
-void erts_add_monitor(ErtsMonitor **root, Uint type, Eterm ref, Eterm pid, 
+void erts_add_monitor(ErtsMonitor **root, Uint type, Eterm ref, UWord entity, 
 		      Eterm name)
 {
     void *tstack[STACK_NEED];
@@ -365,7 +368,7 @@ void erts_add_monitor(ErtsMonitor **root, Uint type, Eterm ref, Eterm pid,
     for (;;) {
 	if (!*this) { /* Found our place */
 	    state = 1;
-	    *this = create_monitor(type,ref,pid,name);
+	    *this = create_monitor(type,ref,entity,name);
 	    break;
 	} else if ((c = CMP_MON_REF(ref,(*this)->ref)) < 0) { 
 	    /* go left */
@@ -935,8 +938,12 @@ static void erts_dump_monitors(ErtsMonitor *root, int indent)
     if (root == NULL)
 	return;
     erts_dump_monitors(root->right,indent+2);
-    erts_printf("%*s[%b16d:%b16u:%T:%T:%T]\n", indent, "", root->balance,
-		root->type, root->ref, root->pid, root->name);
+    erts_printf("%*s[%b16d:%b16u:%T:%T", indent, "", root->balance,
+		root->type, root->ref, root->name);
+    if (root->type == MON_NIF_TARGET)
+	erts_printf(":%p]\n", root->u.resource);
+    else
+	erts_printf(":%T]\n", root->u.pid);
     erts_dump_monitors(root->left,indent+2);
 }
 
@@ -1051,7 +1058,7 @@ void erts_one_link_size(ErtsLink *lnk, void *vpu)
 {
     Uint *pu = vpu;
     *pu += ERTS_LINK_SIZE*sizeof(Uint);
-    if(!IS_CONST(lnk->pid))
+    if(is_not_immed(lnk->pid))
 	*pu += NC_HEAP_SIZE(lnk->pid)*sizeof(Uint);
     if (lnk->type != LINK_NODE && ERTS_LINK_ROOT(lnk) != NULL) {
 	erts_doforall_links(ERTS_LINK_ROOT(lnk),&erts_one_link_size,vpu);
@@ -1061,8 +1068,8 @@ void erts_one_mon_size(ErtsMonitor *mon, void *vpu)
 {
     Uint *pu = vpu;
     *pu += ERTS_MONITOR_SIZE*sizeof(Uint);
-    if(!IS_CONST(mon->pid))
-	*pu += NC_HEAP_SIZE(mon->pid)*sizeof(Uint);
-    if(!IS_CONST(mon->ref))
+    if(mon->type != MON_NIF_TARGET && is_not_immed(mon->u.pid))
+	*pu += NC_HEAP_SIZE(mon->u.pid)*sizeof(Uint);
+    if(is_not_immed(mon->ref))
 	*pu += NC_HEAP_SIZE(mon->ref)*sizeof(Uint);
 }
diff --git a/erts/emulator/beam/erl_monitors.h b/erts/emulator/beam/erl_monitors.h
index bb493bf336..f659829e6c 100644
--- a/erts/emulator/beam/erl_monitors.h
+++ b/erts/emulator/beam/erl_monitors.h
@@ -82,8 +82,9 @@
 
 /* Type tags for monitors */
 #define MON_ORIGIN 1
-#define MON_TARGET 3
-#define MON_TIME_OFFSET 7
+#define MON_TARGET 2
+#define MON_NIF_TARGET 3
+#define MON_TIME_OFFSET 4
 
 /* Type tags for links */
 #define LINK_PID 1   /* ...Or port */
@@ -105,11 +106,15 @@ typedef struct erts_monitor_or_link {
 typedef struct erts_monitor {
     struct erts_monitor *left, *right; 
     Sint16 balance;
-    Uint16 type;  /* MON_ORIGIN | MON_TARGET | MON_TIME_OFFSET */
+    Uint16 type;  /* MON_ORIGIN | MON_TARGET | MON_NIF_TARGET | MON_TIME_OFFSET */
     Eterm ref;
-    Eterm pid;    /* In case of distributed named monitor, this is the
-		     nodename atom in MON_ORIGIN process, otherwise a pid or
-		     , in case of a MON_TARGET, a port */
+    union {
+        Eterm pid;  /* In case of distributed named monitor, this is the
+		     * nodename atom in MON_ORIGIN process, otherwise a pid or,
+		     * in case of a MON_TARGET, a port
+                     */
+        struct ErtsResource_* resource; /* MON_NIF_TARGET */
+    }u;
     Eterm name;   /* When monitoring a named process: atom() else [] */
     Uint heap[1]; /* Larger in reality */
 } ErtsMonitor;
@@ -144,7 +149,7 @@ Uint erts_tot_link_lh_size(void);
 
 /* Prototypes */
 void erts_destroy_monitor(ErtsMonitor *mon);
-void erts_add_monitor(ErtsMonitor **root, Uint type, Eterm ref, Eterm pid,
+void erts_add_monitor(ErtsMonitor **root, Uint type, Eterm ref, UWord entity,
 		      Eterm name);
 ErtsMonitor *erts_remove_monitor(ErtsMonitor **root, Eterm ref);
 ErtsMonitor *erts_lookup_monitor(ErtsMonitor *root, Eterm ref);
diff --git a/erts/emulator/beam/erl_nif.c b/erts/emulator/beam/erl_nif.c
index 7fe7b8bd93..e6da4c1a76 100644
--- a/erts/emulator/beam/erl_nif.c
+++ b/erts/emulator/beam/erl_nif.c
@@ -1942,37 +1942,9 @@ int enif_snprintf(char *buffer, size_t size, const char* format, ...)
  **       Memory managed (GC'ed) "resource" objects       **
  ***********************************************************/
 
-
-struct enif_resource_type_t
-{
-    struct enif_resource_type_t* next;   /* list of all resource types */
-    struct enif_resource_type_t* prev;    
-    struct erl_module_nif* owner;  /* that created this type and thus implements the destructor*/
-    ErlNifResourceDtor* dtor;      /* user destructor function */
-    erts_refc_t refc;  /* num of resources of this type (HOTSPOT warning)
-                          +1 for active erl_module_nif */
-    Eterm module;
-    Eterm name;
-};
-
 /* dummy node in circular list */
 struct enif_resource_type_t resource_type_list; 
 
-typedef struct enif_resource_t
-{
-    struct enif_resource_type_t* type;
-#ifdef DEBUG
-    erts_refc_t nif_refc;
-# ifdef ARCH_32
-    byte align__[4];
-# endif
-#endif
-    char data[1];
-}ErlNifResource;
-
-#define SIZEOF_ErlNifResource(SIZE) (offsetof(ErlNifResource,data) + (SIZE))
-#define DATA_TO_RESOURCE(PTR) ((ErlNifResource*)((char*)(PTR) - offsetof(ErlNifResource,data)))
-
 static ErlNifResourceType* find_resource_type(Eterm module, Eterm name)
 {
     ErlNifResourceType* type;
@@ -2034,24 +2006,23 @@ struct opened_resource_type
 
     ErlNifResourceFlags op;
     ErlNifResourceType* type;
-    ErlNifResourceDtor* new_dtor;
+    ErlNifResourceTypeInit new_callbacks;
 };
 static struct opened_resource_type* opened_rt_list = NULL;
 
-ErlNifResourceType*
-enif_open_resource_type(ErlNifEnv* env,
-			const char* module_str, 
-			const char* name_str, 
-			ErlNifResourceDtor* dtor,
-			ErlNifResourceFlags flags,
-			ErlNifResourceFlags* tried)
+static
+ErlNifResourceType* open_resource_type(ErlNifEnv* env,
+                                       const char* name_str,
+                                       const ErlNifResourceTypeInit* init,
+                                       ErlNifResourceFlags flags,
+                                       ErlNifResourceFlags* tried,
+                                       size_t sizeof_init)
 {
     ErlNifResourceType* type = NULL;
     ErlNifResourceFlags op = flags;
     Eterm module_am, name_am;
 
     ASSERT(erts_smp_thr_progress_is_blocking());
-    ASSERT(module_str == NULL); /* for now... */
     module_am = make_atom(env->mod_nif->mod->module);
     name_am = enif_make_atom(env, name_str);
 
@@ -2085,7 +2056,9 @@ enif_open_resource_type(ErlNifEnv* env,
 						sizeof(struct opened_resource_type));
 	ort->op = op;
 	ort->type = type;
-	ort->new_dtor = dtor;
+        sys_memzero(&ort->new_callbacks, sizeof(ErlNifResourceTypeInit));
+        ASSERT(sizeof_init > 0 && sizeof_init <= sizeof(ErlNifResourceTypeInit));
+        sys_memcpy(&ort->new_callbacks, init, sizeof_init);
 	ort->next = opened_rt_list;
 	opened_rt_list = ort;
     }
@@ -2095,6 +2068,31 @@ enif_open_resource_type(ErlNifEnv* env,
     return type;
 }
 
+ErlNifResourceType*
+enif_open_resource_type(ErlNifEnv* env,
+                        const char* module_str,
+                        const char* name_str,
+			ErlNifResourceDtor* dtor,
+			ErlNifResourceFlags flags,
+			ErlNifResourceFlags* tried)
+{
+    ErlNifResourceTypeInit init =  {dtor, NULL};
+    ASSERT(module_str == NULL); /* for now... */
+    return open_resource_type(env, name_str, &init, flags, tried,
+                              sizeof(init));
+}
+
+ErlNifResourceType*
+enif_open_resource_type_x(ErlNifEnv* env,
+                          const char* name_str,
+                          const ErlNifResourceTypeInit* init,
+                          ErlNifResourceFlags flags,
+                          ErlNifResourceFlags* tried)
+{
+    return open_resource_type(env, name_str, init, flags, tried,
+                              env->mod_nif->entry.sizeof_ErlNifResourceTypeInit);
+}
+
 static void commit_opened_resource_types(struct erl_module_nif* lib)
 {
     while (opened_rt_list) {
@@ -2113,7 +2111,9 @@ static void commit_opened_resource_types(struct erl_module_nif* lib)
 	}
 
 	type->owner = lib;
-	type->dtor = ort->new_dtor;
+	type->dtor = ort->new_callbacks.dtor;
+        type->stop = ort->new_callbacks.stop;
+        type->down = ort->new_callbacks.down;
 
 	if (type->dtor != NULL) {
 	    erts_refc_inc(&lib->rt_dtor_cnt, 1);
@@ -2139,12 +2139,145 @@ static void rollback_opened_resource_types(void)
     }
 }
 
+struct destroy_monitor_ctx
+{
+    ErtsResource* resource;
+    int exiting_procs;
+    int scheduler;
+};
+
+static void destroy_one_monitor(ErtsMonitor* mon, void* context)
+{
+    struct destroy_monitor_ctx* ctx = (struct destroy_monitor_ctx*) context;
+    Process* rp;
+    ErtsMonitor *rmon = NULL;
+    int is_exiting;
+
+    ASSERT(mon->type == MON_ORIGIN);
+    ASSERT(is_internal_pid(mon->u.pid));
+    ASSERT(is_internal_ref(mon->ref));
+
+    if (ctx->scheduler > 0) { /* Normal scheduler */
+        rp = erts_proc_lookup(mon->u.pid);
+    }
+    else {
+#ifdef ERTS_SMP
+        rp = erts_proc_lookup_inc_refc(mon->u.pid);
+#else
+        ASSERT(!"nif monitor destruction in non-scheduler thread");
+        rp = NULL;
+#endif
+    }
+
+    if (!rp) {
+        is_exiting = 1;
+    }
+    if (rp) {
+        erts_smp_proc_lock(rp, ERTS_PROC_LOCK_LINK);
+        if (ERTS_PROC_IS_EXITING(rp)) {
+            is_exiting = 1;
+        } else {
+            rmon = erts_remove_monitor(&ERTS_P_MONITORS(rp), mon->ref);
+            ASSERT(rmon);
+            is_exiting = 0;
+        }
+        erts_smp_proc_unlock(rp, ERTS_PROC_LOCK_LINK);
+#ifdef ERTS_SMP
+        if (ctx->scheduler <= 0)
+            erts_proc_dec_refc(rp);
+#endif
+    }
+    if (is_exiting) {
+        ctx->resource->monitors->pending_failed_fire++;
+    }
+
+    /* ToDo: Delay destruction after monitor_locks */
+    if (rmon) {
+        ASSERT(rmon->type == MON_NIF_TARGET);
+        ASSERT(rmon->u.resource == ctx->resource);
+        erts_destroy_monitor(rmon);
+    }
+    erts_destroy_monitor(mon);
+}
+
+static void destroy_all_monitors(ErtsMonitor* monitors, ErtsResource* resource)
+{
+    struct destroy_monitor_ctx ctx;
+
+    execution_state(NULL, NULL, &ctx.scheduler);
+
+    ctx.resource = resource;
+    erts_sweep_monitors(monitors, &destroy_one_monitor, &ctx);
+}
+
+
+#ifdef ERTS_SMP
+#  define NIF_RESOURCE_DTOR &nif_resource_dtor
+#else
+#  define NIF_RESOURCE_DTOR &nosmp_nif_resource_dtor_prologue
+
+/*
+ * NO-SMP: Always run resource destructor on scheduler thread 
+ *         as we may have to remove process monitors.
+ */
+static int nif_resource_dtor(Binary*);
+
+static void nosmp_nif_resource_dtor_scheduled(void* vbin)
+{
+    erts_bin_free((Binary*)vbin);
+}
+
+static int nosmp_nif_resource_dtor_prologue(Binary* bin)
+{
+    if (is_scheduler()) {
+        return nif_resource_dtor(bin);
+    }
+    else {
+        erts_schedule_misc_aux_work(1, nosmp_nif_resource_dtor_scheduled, bin);
+        return 0; /* do not free */
+    }
+}
+
+#endif /* !ERTS_SMP */
 
 static int nif_resource_dtor(Binary* bin)
 {
-    ErlNifResource* resource = (ErlNifResource*) ERTS_MAGIC_BIN_UNALIGNED_DATA(bin);
+    ErtsResource* resource = (ErtsResource*) ERTS_MAGIC_BIN_UNALIGNED_DATA(bin);
     ErlNifResourceType* type = resource->type;
-    ASSERT(ERTS_MAGIC_BIN_DESTRUCTOR(bin) == &nif_resource_dtor);
+    ASSERT(ERTS_MAGIC_BIN_DESTRUCTOR(bin) == NIF_RESOURCE_DTOR);
+
+    if (resource->monitors) {
+        ErtsResourceMonitors* rm = resource->monitors;
+
+        ASSERT(type->down);
+        erts_smp_mtx_lock(&rm->lock);
+        ASSERT(erts_refc_read(&bin->refc, 0) == 0);
+        if (rm->root) {
+            ASSERT(!rm->is_dying);
+            destroy_all_monitors(rm->root, resource);
+            rm->root = NULL;
+        }
+        if (rm->pending_failed_fire) {
+            /*
+             * Resource death struggle prolonged to serve exiting process(es).
+             * Destructor will be called again when last exiting process
+             * tries to fire its MON_NIF_TARGET monitor (and fails).
+             *
+             * This resource is doomed. It has no "real" references and
+             * should get not get called upon to do anything except the
+             * final destructor call.
+             *
+             * We keep refc at 0 and use a separate counter for exiting
+             * processes to avoid resource getting revived by "dec_term".
+             */
+            ASSERT(!rm->is_dying);
+            rm->is_dying = 1;
+            erts_smp_mtx_unlock(&rm->lock);
+            return 0;
+        }
+        erts_smp_mtx_unlock(&rm->lock);
+        erts_smp_mtx_destroy(&rm->lock);
+    }
 
     if (type->dtor != NULL) {
         struct enif_msg_environment_t msg_env;
@@ -2162,13 +2295,89 @@ static int nif_resource_dtor(Binary* bin)
     return 1;
 }
 
-void* enif_alloc_resource(ErlNifResourceType* type, size_t size)
+void erts_resource_stop(ErtsResource* resource, ErlNifEvent e,
+                        int is_direct_call)
 {
-    Binary* bin = erts_create_magic_binary_x(SIZEOF_ErlNifResource(size),
-                                             &nif_resource_dtor,
-                                             ERTS_ALC_T_BINARY,
-                                             1); /* unaligned */
-    ErlNifResource* resource = ERTS_MAGIC_BIN_UNALIGNED_DATA(bin);
+    struct enif_msg_environment_t msg_env;
+    ASSERT(resource->type->stop);
+    pre_nif_noproc(&msg_env, resource->type->owner, NULL);
+    resource->type->stop(&msg_env.env, resource->data, e, is_direct_call);
+    post_nif_noproc(&msg_env);
+}
+
+void erts_fire_nif_monitor(ErtsResource* resource, Eterm pid, Eterm ref)
+{
+    ErtsMonitor* rmon;
+    ErtsBinary* bin = ERTS_MAGIC_BIN_FROM_UNALIGNED_DATA(resource);
+    struct enif_msg_environment_t msg_env;
+    ErlNifPid nif_pid;
+    ErlNifMonitor nif_monitor;
+    ErtsResourceMonitors* rmp = resource->monitors;
+
+    ASSERT(rmp);
+    ASSERT(resource->type->down);
+
+    erts_smp_mtx_lock(&rmp->lock);
+    rmon = erts_remove_monitor(&rmp->root, ref);
+    if (!rmon) {
+        int free_me = (--rmp->pending_failed_fire == 0) && rmp->is_dying;
+        ASSERT(rmp->pending_failed_fire >= 0);
+        erts_smp_mtx_unlock(&rmp->lock);
+
+        if (free_me) {
+            ASSERT(erts_refc_read(&bin->binary.refc, 0) == 0);
+            erts_bin_free(&bin->binary);
+        }
+        return;
+    }
+    ASSERT(!rmp->is_dying);
+    if (erts_refc_inc_unless(&bin->binary.refc, 0, 0) == 0) {
+        /*
+         * Racing resource destruction. 
+         * To avoid a more complex refc-dance with destructing thread
+         * we avoid calling 'down' and just silently remove the monitor.
+         * This can happen even for non smp as destructor calls may be scheduled.
+         */
+        erts_smp_mtx_unlock(&rmp->lock);
+    }
+    else {
+        erts_smp_mtx_unlock(&rmp->lock);
+
+        ASSERT(rmon->u.pid == pid);
+        erts_ref_to_driver_monitor(ref, &nif_monitor);
+        nif_pid.pid = pid;
+        pre_nif_noproc(&msg_env, resource->type->owner, NULL);
+        resource->type->down(&msg_env.env, resource->data, &nif_pid, &nif_monitor);
+        post_nif_noproc(&msg_env);
+
+        if (erts_refc_dectest(&bin->binary.refc, 0) == 0) {
+            erts_bin_free(&bin->binary);
+        }
+    }
+    erts_destroy_monitor(rmon);
+}
+
+void* enif_alloc_resource(ErlNifResourceType* type, size_t data_sz)
+{
+    size_t magic_sz = offsetof(ErtsResource,data);
+    Binary* bin;
+    ErtsResource* resource;
+    size_t monitors_offs;
+
+    if (type->down) {
+        /* Put ErtsResourceMonitors after user data and properly aligned */
+        monitors_offs = ((data_sz + ERTS_ALLOC_ALIGN_BYTES - 1)
+                         & ~((size_t)ERTS_ALLOC_ALIGN_BYTES - 1));
+        magic_sz += monitors_offs + sizeof(ErtsResourceMonitors);
+    }
+    else {
+        ERTS_UNDEF(monitors_offs, 0);
+        magic_sz += data_sz;
+    }
+    bin = erts_create_magic_binary_x(magic_sz, NIF_RESOURCE_DTOR,
+                                     ERTS_ALC_T_BINARY,
+                                     1); /* unaligned */
+    resource = ERTS_MAGIC_BIN_UNALIGNED_DATA(bin);
 
     ASSERT(type->owner && type->next && type->prev); /* not allowed in load/upgrade */
     resource->type = type;
@@ -2177,15 +2386,27 @@ void* enif_alloc_resource(ErlNifResourceType* type, size_t size)
     erts_refc_init(&resource->nif_refc, 1);
 #endif
     erts_refc_inc(&resource->type->refc, 2);
+    if (type->down) {
+        resource->monitors = (ErtsResourceMonitors*) (resource->data + monitors_offs);
+        erts_smp_mtx_init(&resource->monitors->lock, "resource_monitors");
+        resource->monitors->root = NULL;
+        resource->monitors->pending_failed_fire = 0;
+        resource->monitors->is_dying = 0;
+        resource->monitors->user_data_sz = data_sz;
+    }
+    else {
+        resource->monitors = NULL;
+    }
     return resource->data;
 }
 
 void enif_release_resource(void* obj)
 {
-    ErlNifResource* resource = DATA_TO_RESOURCE(obj);
+    ErtsResource* resource = DATA_TO_RESOURCE(obj);
     ErtsBinary* bin = ERTS_MAGIC_BIN_FROM_UNALIGNED_DATA(resource);
 
-    ASSERT(ERTS_MAGIC_BIN_DESTRUCTOR(bin) == &nif_resource_dtor);
+    ASSERT(ERTS_MAGIC_BIN_DESTRUCTOR(bin) == NIF_RESOURCE_DTOR);
+    ASSERT(!(resource->monitors && resource->monitors->is_dying));
 #ifdef DEBUG
     erts_refc_dec(&resource->nif_refc, 0);
 #endif
@@ -2196,28 +2417,37 @@ void enif_release_resource(void* obj)
 
 void enif_keep_resource(void* obj)
 {
-    ErlNifResource* resource = DATA_TO_RESOURCE(obj);
+    ErtsResource* resource = DATA_TO_RESOURCE(obj);
     ErtsBinary* bin = ERTS_MAGIC_BIN_FROM_UNALIGNED_DATA(resource);
 
-    ASSERT(ERTS_MAGIC_BIN_DESTRUCTOR(bin) == &nif_resource_dtor);
+    ASSERT(ERTS_MAGIC_BIN_DESTRUCTOR(bin) == NIF_RESOURCE_DTOR);
+    ASSERT(!(resource->monitors && resource->monitors->is_dying));
 #ifdef DEBUG
     erts_refc_inc(&resource->nif_refc, 1);
 #endif
     erts_refc_inc(&bin->binary.refc, 2);
 }
 
+Eterm erts_bld_resource_ref(Eterm** hpp, ErlOffHeap* oh, ErtsResource* resource)
+{
+    ErtsBinary* bin = ERTS_MAGIC_BIN_FROM_UNALIGNED_DATA(resource);
+    ASSERT(!(resource->monitors && resource->monitors->is_dying));
+    return erts_mk_magic_ref(hpp, oh, &bin->binary);
+}
+
 ERL_NIF_TERM enif_make_resource(ErlNifEnv* env, void* obj)
 {
-    ErlNifResource* resource = DATA_TO_RESOURCE(obj);
+    ErtsResource* resource = DATA_TO_RESOURCE(obj);
     ErtsBinary* bin = ERTS_MAGIC_BIN_FROM_UNALIGNED_DATA(resource);
     Eterm* hp = alloc_heap(env, ERTS_MAGIC_REF_THING_SIZE);
+    ASSERT(!(resource->monitors && resource->monitors->is_dying));
     return erts_mk_magic_ref(&hp, &MSO(env->proc), &bin->binary);
 }
 
 ERL_NIF_TERM enif_make_resource_binary(ErlNifEnv* env, void* obj,
 				       const void* data, size_t size)
 {
-    ErlNifResource* resource = DATA_TO_RESOURCE(obj);
+    ErtsResource* resource = DATA_TO_RESOURCE(obj);
     ErtsBinary* bin = ERTS_MAGIC_BIN_FROM_UNALIGNED_DATA(resource);
     ErlOffHeap *ohp = &MSO(env->proc);
     Eterm* hp = alloc_heap(env,PROC_BIN_SIZE);
@@ -2241,7 +2471,7 @@ int enif_get_resource(ErlNifEnv* env, ERL_NIF_TERM term, ErlNifResourceType* typ
 		      void** objp)
 {
     Binary* mbin;
-    ErlNifResource* resource;
+    ErtsResource* resource;
     if (is_internal_magic_ref(term))
 	mbin = erts_magic_ref2bin(term);
     else {
@@ -2260,8 +2490,8 @@ int enif_get_resource(ErlNifEnv* env, ERL_NIF_TERM term, ErlNifResourceType* typ
         if (!(mbin->flags & BIN_FLAG_MAGIC))
             return 0;
     }
-    resource = (ErlNifResource*) ERTS_MAGIC_BIN_UNALIGNED_DATA(mbin);
-    if (ERTS_MAGIC_BIN_DESTRUCTOR(mbin) != &nif_resource_dtor
+    resource = (ErtsResource*) ERTS_MAGIC_BIN_UNALIGNED_DATA(mbin);
+    if (ERTS_MAGIC_BIN_DESTRUCTOR(mbin) != NIF_RESOURCE_DTOR
 	|| resource->type != type) {	
 	return 0;
     }
@@ -2271,9 +2501,14 @@ int enif_get_resource(ErlNifEnv* env, ERL_NIF_TERM term, ErlNifResourceType* typ
 
 size_t enif_sizeof_resource(void* obj)
 {
-    ErlNifResource* resource = DATA_TO_RESOURCE(obj);
-    Binary* bin = &ERTS_MAGIC_BIN_FROM_UNALIGNED_DATA(resource)->binary;
-    return ERTS_MAGIC_BIN_UNALIGNED_DATA_SIZE(bin) - offsetof(ErlNifResource,data);
+    ErtsResource* resource = DATA_TO_RESOURCE(obj);
+    if (resource->monitors) {
+        return resource->monitors->user_data_sz;
+    }
+    else {
+        Binary* bin = &ERTS_MAGIC_BIN_FROM_UNALIGNED_DATA(resource)->binary;
+        return ERTS_MAGIC_BIN_UNALIGNED_DATA_SIZE(bin) - offsetof(ErtsResource,data);
+    }
 }
 
 
@@ -2885,6 +3120,157 @@ int enif_map_iterator_get_pair(ErlNifEnv *env,
     return 0;
 }
 
+int enif_monitor_process(ErlNifEnv* env, void* obj, const ErlNifPid* target_pid,
+                         ErlNifMonitor* monitor)
+{
+    int scheduler;
+    ErtsResource* rsrc = DATA_TO_RESOURCE(obj);
+    Process *rp;
+    Eterm tmp[ERTS_REF_THING_SIZE];
+    Eterm ref;
+    int retval;
+
+    ASSERT(ERTS_MAGIC_BIN_FROM_UNALIGNED_DATA(rsrc)->magic_binary.destructor
+           == NIF_RESOURCE_DTOR);
+    ASSERT(!(rsrc->monitors && rsrc->monitors->is_dying));
+    ASSERT(!rsrc->monitors == !rsrc->type->down);
+
+
+    if (!rsrc->monitors) {
+        ASSERT(!rsrc->type->down);
+        return -1;
+    }
+    ASSERT(rsrc->type->down);
+
+    execution_state(env, NULL, &scheduler);
+
+#ifdef ERTS_SMP
+    if (scheduler > 0) /* Normal scheduler */
+        rp = erts_proc_lookup_raw(target_pid->pid);
+    else
+        rp = erts_proc_lookup_raw_inc_refc(target_pid->pid);
+#else
+    if (scheduler <= 0) {
+        erts_exit(ERTS_ABORT_EXIT, "enif_monitor_process: called from "
+                  "non-scheduler thread on non-SMP VM");
+    }
+    rp = erts_proc_lookup(target_pid->pid);
+#endif
+
+    if (!rp)
+        return 1;
+
+    ref = erts_make_ref_in_buffer(tmp);
+
+    erts_smp_mtx_lock(&rsrc->monitors->lock);
+    erts_smp_proc_lock(rp, ERTS_PROC_LOCK_LINK);
+    if (ERTS_PSFLG_FREE & erts_smp_atomic32_read_nob(&rp->state)) {
+        retval = 1;
+    }
+    else {
+        erts_add_monitor(&rsrc->monitors->root, MON_ORIGIN, ref, rp->common.id, NIL);
+        erts_add_monitor(&ERTS_P_MONITORS(rp), MON_NIF_TARGET, ref, (UWord)rsrc, NIL);
+        retval = 0;
+    }
+    erts_smp_proc_unlock(rp, ERTS_PROC_LOCK_LINK);
+    erts_smp_mtx_unlock(&rsrc->monitors->lock);
+
+#ifdef ERTS_SMP
+    if (scheduler <= 0)
+        erts_proc_dec_refc(rp);
+#endif
+    if (monitor)
+        erts_ref_to_driver_monitor(ref,monitor);
+
+    return retval;
+}
+
+int enif_demonitor_process(ErlNifEnv* env, void* obj, const ErlNifMonitor* monitor)
+{
+    int scheduler;
+    ErtsResource* rsrc = DATA_TO_RESOURCE(obj);
+#ifdef DEBUG
+    ErtsBinary* bin = ERTS_MAGIC_BIN_FROM_UNALIGNED_DATA(rsrc);
+#endif
+    Process *rp;
+    ErtsMonitor *mon;
+    ErtsMonitor *rmon = NULL;
+    Eterm ref_heap[ERTS_REF_THING_SIZE];
+    Eterm ref;
+    int is_exiting;
+
+    ASSERT(bin->magic_binary.destructor == NIF_RESOURCE_DTOR);
+    ASSERT(!(rsrc->monitors && rsrc->monitors->is_dying));
+
+    execution_state(env, NULL, &scheduler);
+
+    ref = erts_driver_monitor_to_ref(ref_heap, monitor);
+
+    erts_smp_mtx_lock(&rsrc->monitors->lock);
+    mon = erts_remove_monitor(&rsrc->monitors->root, ref);
+
+    if (mon == NULL) {
+        erts_smp_mtx_unlock(&rsrc->monitors->lock);
+        return 1;
+    }
+
+    ASSERT(mon->type == MON_ORIGIN);
+    ASSERT(is_internal_pid(mon->u.pid));
+
+#ifdef ERTS_SMP
+    if (scheduler > 0) /* Normal scheduler */
+        rp = erts_proc_lookup(mon->u.pid);
+    else
+        rp = erts_proc_lookup_inc_refc(mon->u.pid);
+#else
+    if (scheduler <= 0) {
+        erts_exit(ERTS_ABORT_EXIT, "enif_demonitor_process: called from "
+                  "non-scheduler thread on non-SMP VM");
+    }
+    rp = erts_proc_lookup(mon->u.pid);
+#endif
+
+    if (!rp) {
+        is_exiting = 1;
+    }
+    else {
+        erts_smp_proc_lock(rp, ERTS_PROC_LOCK_LINK);
+        if (ERTS_PROC_IS_EXITING(rp)) {
+            is_exiting = 1;
+        } else {
+            rmon = erts_remove_monitor(&ERTS_P_MONITORS(rp), ref);
+            ASSERT(rmon);
+            is_exiting = 0;
+        }
+        erts_smp_proc_unlock(rp, ERTS_PROC_LOCK_LINK);
+
+#ifdef ERTS_SMP
+        if (scheduler <= 0)
+            erts_proc_dec_refc(rp);
+#endif
+    }
+    if (is_exiting) {
+        rsrc->monitors->pending_failed_fire++;
+    }
+    erts_smp_mtx_unlock(&rsrc->monitors->lock);
+
+    if (rmon) {
+        ASSERT(rmon->type == MON_NIF_TARGET);
+        ASSERT(rmon->u.resource == rsrc);
+        erts_destroy_monitor(rmon);
+    }
+    erts_destroy_monitor(mon);
+
+    return 0;
+}
+
+int enif_compare_monitors(const ErlNifMonitor *monitor1,
+                          const ErlNifMonitor *monitor2)
+{
+    return sys_memcmp((void *) monitor1, (void *) monitor2,
+                      ERTS_REF_THING_SIZE*sizeof(Eterm));
+}
+
 /***************************************************************************
  **                              load_nif/2                               **
  ***************************************************************************/
@@ -3035,6 +3421,11 @@ static struct erl_module_nif* create_lib(const ErlNifEntry* src)
         dst->funcs = lib->_funcs_copy_;
         dst->options = 0;
     }
+    if (AT_LEAST_VERSION(src, 2, 12)) {
+        dst->sizeof_ErlNifResourceTypeInit = src->sizeof_ErlNifResourceTypeInit;
+    } else {
+        dst->sizeof_ErlNifResourceTypeInit = 0;
+    }
     return lib;
 };
 
@@ -3353,7 +3744,8 @@ erts_unload_nif(struct erl_module_nif* lib)
 
 void erl_nif_init()
 {
-    ERTS_CT_ASSERT((offsetof(ErlNifResource,data) % 8) == ERTS_MAGIC_BIN_BYTES_TO_ALIGN);
+    ERTS_CT_ASSERT((offsetof(ErtsResource,data) % 8)
+                   == ERTS_MAGIC_BIN_BYTES_TO_ALIGN);
 
     resource_type_list.next = &resource_type_list;
     resource_type_list.prev = &resource_type_list;
diff --git a/erts/emulator/beam/erl_nif.h b/erts/emulator/beam/erl_nif.h
index 413b4f7343..ac45f3ac81 100644
--- a/erts/emulator/beam/erl_nif.h
+++ b/erts/emulator/beam/erl_nif.h
@@ -52,7 +52,7 @@
 ** 2.11: 19.0 enif_snprintf 
 */
 #define ERL_NIF_MAJOR_VERSION 2
-#define ERL_NIF_MINOR_VERSION 11
+#define ERL_NIF_MINOR_VERSION 12
 
 /*
  * The emulator will refuse to load a nif-lib with a major version
@@ -122,6 +122,9 @@ typedef struct enif_entry_t
 
     /* Added in 2.7 */
     unsigned options;   /* Unused. Can be set to 0 or 1 (dirty sched config) */
+
+    /* Added in 2.12 */
+    size_t sizeof_ErlNifResourceTypeInit;
 }ErlNifEntry;
 
 
@@ -135,8 +138,18 @@ typedef struct
     void* ref_bin;
 }ErlNifBinary;
 
-typedef struct enif_resource_type_t ErlNifResourceType;
-typedef void ErlNifResourceDtor(ErlNifEnv*, void*);
+#if (defined(__WIN32__) || defined(_WIN32) || defined(_WIN32_))
+typedef void* ErlNifEvent; /* FIXME: Use 'HANDLE' somehow without breaking existing source */
+#else
+typedef int ErlNifEvent;
+#endif
+
+/* Return bits from enif_select: */
+#define ERL_NIF_SELECT_STOP_CALLED    (1 << 0)
+#define ERL_NIF_SELECT_STOP_SCHEDULED (1 << 1)
+#define ERL_NIF_SELECT_INVALID_EVENT  (1 << 2)
+#define ERL_NIF_SELECT_FAILED         (1 << 3)
+
 typedef enum
 {
     ERL_NIF_RT_CREATE = 1,
@@ -158,6 +171,19 @@ typedef struct
     ERL_NIF_TERM port_id;  /* internal, may change */
 }ErlNifPort;
 
+typedef ErlDrvMonitor ErlNifMonitor;
+
+typedef struct enif_resource_type_t ErlNifResourceType;
+typedef void ErlNifResourceDtor(ErlNifEnv*, void*);
+typedef void ErlNifResourceStop(ErlNifEnv*, void*, ErlNifEvent, int is_direct_call);
+typedef void ErlNifResourceDown(ErlNifEnv*, void*, ErlNifPid*, ErlNifMonitor*);
+
+typedef struct {
+    ErlNifResourceDtor* dtor;
+    ErlNifResourceStop* stop;  /* at ERL_NIF_SELECT_STOP event */
+    ErlNifResourceDown* down;  /* enif_monitor_process */
+} ErlNifResourceTypeInit;
+
 typedef ErlDrvSysInfo ErlNifSysInfo;
 
 typedef struct ErlDrvTid_ *ErlNifTid;
@@ -292,7 +318,8 @@ ERL_NIF_INIT_DECL(NAME)			\
 	FUNCS,				\
 	LOAD, RELOAD, UPGRADE, UNLOAD,	\
 	ERL_NIF_VM_VARIANT,		\
-	1		                \
+        1,                              \
+        sizeof(ErlNifResourceTypeInit)  \
     };                                  \
     ERL_NIF_INIT_BODY;                  \
     return &entry;			\
diff --git a/erts/emulator/beam/erl_nif_api_funcs.h b/erts/emulator/beam/erl_nif_api_funcs.h
index 9a8f216773..01d9e386ed 100644
--- a/erts/emulator/beam/erl_nif_api_funcs.h
+++ b/erts/emulator/beam/erl_nif_api_funcs.h
@@ -175,6 +175,11 @@ ERL_NIF_API_FUNC_DECL(size_t, enif_binary_to_term, (ErlNifEnv *env, const unsign
 ERL_NIF_API_FUNC_DECL(int, enif_port_command, (ErlNifEnv *env, const ErlNifPort* to_port, ErlNifEnv *msg_env, ERL_NIF_TERM msg));
 ERL_NIF_API_FUNC_DECL(int,enif_thread_type,(void));
 ERL_NIF_API_FUNC_DECL(int,enif_snprintf,(char * buffer, size_t size, const char *format, ...));
+ERL_NIF_API_FUNC_DECL(int,enif_select,(ErlNifEnv* env, ErlNifEvent e, enum ErlNifSelectFlags flags, void* obj, const ErlNifPid* pid, ERL_NIF_TERM ref));
+ERL_NIF_API_FUNC_DECL(ErlNifResourceType*,enif_open_resource_type_x,(ErlNifEnv*, const char* name_str, const ErlNifResourceTypeInit*, ErlNifResourceFlags flags, ErlNifResourceFlags* tried));
+ERL_NIF_API_FUNC_DECL(int, enif_monitor_process,(ErlNifEnv*,void* obj,const ErlNifPid*,ErlDrvMonitor *monitor));
+ERL_NIF_API_FUNC_DECL(int, enif_demonitor_process,(ErlNifEnv*,void* obj,const ErlDrvMonitor *monitor));
+ERL_NIF_API_FUNC_DECL(int, enif_compare_monitors,(const ErlNifMonitor*,const ErlNifMonitor*));
 
 /*
 ** ADD NEW ENTRIES HERE (before this comment) !!!
@@ -332,6 +337,11 @@ ERL_NIF_API_FUNC_DECL(int,enif_snprintf,(char * buffer, size_t size, const char
 #  define enif_port_command ERL_NIF_API_FUNC_MACRO(enif_port_command)
 #  define enif_thread_type ERL_NIF_API_FUNC_MACRO(enif_thread_type)
 #  define enif_snprintf ERL_NIF_API_FUNC_MACRO(enif_snprintf)
+#  define enif_select ERL_NIF_API_FUNC_MACRO(enif_select)
+#  define enif_open_resource_type_x ERL_NIF_API_FUNC_MACRO(enif_open_resource_type_x)
+#  define enif_monitor_process ERL_NIF_API_FUNC_MACRO(enif_monitor_process)
+#  define enif_demonitor_process ERL_NIF_API_FUNC_MACRO(enif_demonitor_process)
+#  define enif_compare_monitors ERL_NIF_API_FUNC_MACRO(enif_compare_monitors)
 
 /*
 ** ADD NEW ENTRIES HERE (before this comment)
diff --git a/erts/emulator/beam/erl_node_tables.c b/erts/emulator/beam/erl_node_tables.c
index 5e54e5aef2..e2072fe30f 100644
--- a/erts/emulator/beam/erl_node_tables.c
+++ b/erts/emulator/beam/erl_node_tables.c
@@ -1166,8 +1166,8 @@ insert_offheap(ErlOffHeap *oh, int type, Eterm id)
 static void doit_insert_monitor(ErtsMonitor *monitor, void *p)
 {
     Eterm *idp = p;
-    if(is_external(monitor->pid))
-	insert_node(external_thing_ptr(monitor->pid)->node, MONITOR_REF, *idp);
+    if(monitor->type != MON_NIF_TARGET && is_external(monitor->u.pid))
+	insert_node(external_thing_ptr(monitor->u.pid)->node, MONITOR_REF, *idp);
     if(is_external(monitor->ref))
 	insert_node(external_thing_ptr(monitor->ref)->node, MONITOR_REF, *idp);
 }
diff --git a/erts/emulator/beam/erl_process.c b/erts/emulator/beam/erl_process.c
index c5a7b67764..52d9f9ddf7 100644
--- a/erts/emulator/beam/erl_process.c
+++ b/erts/emulator/beam/erl_process.c
@@ -13323,9 +13323,9 @@ static void doit_exit_monitor(ErtsMonitor *mon, void *vpcontext)
     switch (mon->type) {
     case MON_ORIGIN:
 	/* We are monitoring someone else, we need to demonitor that one.. */
-	if (is_atom(mon->pid)) { /* remote by name */
-	    ASSERT(is_node_name_atom(mon->pid));
-	    dep = erts_sysname_to_connected_dist_entry(mon->pid);
+	if (is_atom(mon->u.pid)) { /* remote by name */
+	    ASSERT(is_node_name_atom(mon->u.pid));
+	    dep = erts_sysname_to_connected_dist_entry(mon->u.pid);
 	    if (dep) {
 		erts_smp_de_links_lock(dep);
 		rmon = erts_remove_monitor(&(dep->monitors), mon->ref);
@@ -13336,7 +13336,7 @@ static void doit_exit_monitor(ErtsMonitor *mon, void *vpcontext)
 						 ERTS_DSP_NO_LOCK, 0);
 		    if (code == ERTS_DSIG_PREP_CONNECTED) {
 			code = erts_dsig_send_demonitor(&dsd,
-							rmon->pid,
+							rmon->u.pid,
 							mon->name,
 							mon->ref,
 							1);
@@ -13347,10 +13347,10 @@ static void doit_exit_monitor(ErtsMonitor *mon, void *vpcontext)
 		erts_deref_dist_entry(dep);
 	    }
 	} else {
-            ASSERT(is_pid(mon->pid) || is_port(mon->pid));
+            ASSERT(is_pid(mon->u.pid) || is_port(mon->u.pid));
             /* if is local by pid or name */
-            if (is_internal_pid(mon->pid)) {
-                Process *rp = erts_pid2proc(NULL, 0, mon->pid, ERTS_PROC_LOCK_LINK);
+            if (is_internal_pid(mon->u.pid)) {
+                Process *rp = erts_pid2proc(NULL, 0, mon->u.pid, ERTS_PROC_LOCK_LINK);
 		if (!rp) {
 		    goto done;
 		}
@@ -13360,9 +13360,9 @@ static void doit_exit_monitor(ErtsMonitor *mon, void *vpcontext)
 		    goto done;
 		}
 		erts_destroy_monitor(rmon);
-            } else if (is_internal_port(mon->pid)) {
+            } else if (is_internal_port(mon->u.pid)) {
                 /* Is a local port */
-                Port *prt = erts_port_lookup_raw(mon->pid);
+                Port *prt = erts_port_lookup_raw(mon->u.pid);
                 if (!prt) {
                     goto done;
                 }
@@ -13370,8 +13370,8 @@ static void doit_exit_monitor(ErtsMonitor *mon, void *vpcontext)
                                     ERTS_PORT_DEMONITOR_ORIGIN_ON_DEATHBED,
                                     prt, mon->ref, NULL);
             } else { /* remote by pid */
-		ASSERT(is_external_pid(mon->pid));
-		dep = external_pid_dist_entry(mon->pid);
+		ASSERT(is_external_pid(mon->u.pid));
+		dep = external_pid_dist_entry(mon->u.pid);
 		ASSERT(dep != NULL);
 		if (dep) {
 		    erts_smp_de_links_lock(dep);
@@ -13383,8 +13383,8 @@ static void doit_exit_monitor(ErtsMonitor *mon, void *vpcontext)
 						     ERTS_DSP_NO_LOCK, 0);
 			if (code == ERTS_DSIG_PREP_CONNECTED) {
 			    code = erts_dsig_send_demonitor(&dsd,
-							    rmon->pid,
-							    mon->pid,
+							    rmon->u.pid,
+							    mon->u.pid,
 							    mon->ref,
 							    1);
 			    ASSERT(code == ERTS_DSIG_SEND_OK);
@@ -13396,22 +13396,21 @@ static void doit_exit_monitor(ErtsMonitor *mon, void *vpcontext)
 	}
 	break;
     case MON_TARGET:
-	ASSERT(mon->type == MON_TARGET);
-	ASSERT(is_pid(mon->pid) || is_internal_port(mon->pid));
-	if (is_internal_port(mon->pid)) {
-	    Port *prt = erts_id2port(mon->pid);
+	ASSERT(is_pid(mon->u.pid) || is_internal_port(mon->u.pid));
+	if (is_internal_port(mon->u.pid)) {
+	    Port *prt = erts_id2port(mon->u.pid);
 	    if (prt == NULL) {
 		goto done;
 	    }
 	    erts_fire_port_monitor(prt, mon->ref);
 	    erts_port_release(prt); 
-	} else if (is_internal_pid(mon->pid)) {/* local by name or pid */
+	} else if (is_internal_pid(mon->u.pid)) {/* local by name or pid */
 	    Eterm watched;
             Process *rp;
 	    DeclareTmpHeapNoproc(lhp,3);
 	    ErtsProcLocks rp_locks = (ERTS_PROC_LOCK_LINK
 				      | ERTS_PROC_LOCKS_MSG_SEND);
-	    rp = erts_pid2proc(NULL, 0, mon->pid, rp_locks);
+	    rp = erts_pid2proc(NULL, 0, mon->u.pid, rp_locks);
 	    if (rp == NULL) {
 		goto done;
 	    }
@@ -13430,8 +13429,8 @@ static void doit_exit_monitor(ErtsMonitor *mon, void *vpcontext)
 	    /* else: demonitor while we exited, i.e. do nothing... */
 	    erts_smp_proc_unlock(rp, rp_locks);
 	} else { /* external by pid or name */
-	    ASSERT(is_external_pid(mon->pid));    
-	    dep = external_pid_dist_entry(mon->pid);
+	    ASSERT(is_external_pid(mon->u.pid));    
+	    dep = external_pid_dist_entry(mon->u.pid);
 	    ASSERT(dep != NULL);
 	    if (dep) {
 		erts_smp_de_links_lock(dep);
@@ -13443,10 +13442,10 @@ static void doit_exit_monitor(ErtsMonitor *mon, void *vpcontext)
 						 ERTS_DSP_NO_LOCK, 0);
 		    if (code == ERTS_DSIG_PREP_CONNECTED) {
 			code = erts_dsig_send_m_exit(&dsd,
-						     mon->pid,
+						     mon->u.pid,
 						     (rmon->name != NIL
 						      ? rmon->name
-						      : rmon->pid),
+						      : rmon->u.pid),
 						     mon->ref,
 						     pcontext->reason);
 			ASSERT(code == ERTS_DSIG_SEND_OK);
@@ -13456,6 +13455,11 @@ static void doit_exit_monitor(ErtsMonitor *mon, void *vpcontext)
 	    }
 	}
 	break;
+    case MON_NIF_TARGET:
+        erts_fire_nif_monitor(mon->u.resource,
+                              pcontext->p->common.id,
+                              mon->ref);
+        break;
     case MON_TIME_OFFSET:
 	erts_demonitor_time_offset(mon->ref);
 	break;
diff --git a/erts/emulator/beam/erl_time_sup.c b/erts/emulator/beam/erl_time_sup.c
index ed40539b78..cf9d3adc86 100644
--- a/erts/emulator/beam/erl_time_sup.c
+++ b/erts/emulator/beam/erl_time_sup.c
@@ -1869,7 +1869,7 @@ save_time_offset_monitor(ErtsMonitor *mon, void *vcntxt)
 
     cntxt = (ErtsTimeOffsetMonitorContext *) vcntxt;
     mix = (cntxt->ix)++;
-    cntxt->to_mon_info[mix].pid = mon->pid;
+    cntxt->to_mon_info[mix].pid = mon->u.pid;
     to_hp = &cntxt->to_mon_info[mix].heap[0];
 
     ASSERT(is_internal_ordinary_ref(mon->ref));
diff --git a/erts/emulator/beam/global.h b/erts/emulator/beam/global.h
index fff22fe9c1..c4c848f49f 100644
--- a/erts/emulator/beam/global.h
+++ b/erts/emulator/beam/global.h
@@ -42,6 +42,7 @@
 #include "erl_utils.h"
 #include "erl_port.h"
 #include "erl_gc.h"
+#include "erl_nif.h"
 #define ERTS_BINARY_TYPES_ONLY__
 #include "erl_binary.h"
 #undef ERTS_BINARY_TYPES_ONLY__
@@ -68,9 +69,54 @@ struct enif_environment_t /* ErlNifEnv */
     int dbg_disable_assert_in_env;
 #endif
 };
+struct enif_resource_type_t
+{
+    struct enif_resource_type_t* next;   /* list of all resource types */
+    struct enif_resource_type_t* prev;
+    struct erl_module_nif* owner;  /* that created this type and thus implements the destructor*/
+    ErlNifResourceDtor* dtor;      /* user destructor function */
+    ErlNifResourceStop* stop;
+    ErlNifResourceDown* down;
+    erts_refc_t refc;  /* num of resources of this type (HOTSPOT warning)
+                          +1 for active erl_module_nif */
+    Eterm module;
+    Eterm name;
+};
+
+typedef struct
+{
+    erts_smp_mtx_t lock;
+    ErtsMonitor* root;
+    int pending_failed_fire;
+    int is_dying;
+
+    size_t user_data_sz;
+} ErtsResourceMonitors;
+
+typedef struct ErtsResource_
+{
+    struct enif_resource_type_t* type;
+    ErtsResourceMonitors* monitors;
+#ifdef DEBUG
+    erts_refc_t nif_refc;
+#else
+# ifdef ARCH_32
+    byte align__[4];
+# endif
+#endif
+    char data[1];
+}ErtsResource;
+
+#define DATA_TO_RESOURCE(PTR) ErtsContainerStruct(PTR, ErtsResource, data)
+#define erts_resource_ref_size(P) ERTS_MAGIC_REF_THING_SIZE
+
+extern Eterm erts_bld_resource_ref(Eterm** hp, ErlOffHeap*, ErtsResource*);
+
 extern void erts_pre_nif(struct enif_environment_t*, Process*,
 			 struct erl_module_nif*, Process* tracee);
 extern void erts_post_nif(struct enif_environment_t* env);
+extern void erts_resource_stop(ErtsResource*, ErlNifEvent, int is_direct_call);
+void erts_fire_nif_monitor(ErtsResource*, Eterm pid, Eterm ref);
 extern Eterm erts_nif_taints(Process* p);
 extern void erts_print_nif_taints(fmtfn_t to, void* to_arg);
 void erts_unload_nif(struct erl_module_nif* nif);
@@ -1129,6 +1175,8 @@ void erts_stale_drv_select(Eterm, ErlDrvPort, ErlDrvEvent, int, int);
 
 Port *erts_get_heart_port(void);
 void erts_emergency_close_ports(void);
+void erts_ref_to_driver_monitor(Eterm ref, ErlDrvMonitor *mon);
+Eterm erts_driver_monitor_to_ref(Eterm* hp, const ErlDrvMonitor *mon);
 
 #if defined(ERTS_SMP) && defined(ERTS_ENABLE_LOCK_COUNT)
 void erts_lcnt_enable_io_lock_count(int enable);
diff --git a/erts/emulator/beam/io.c b/erts/emulator/beam/io.c
index f24528635b..ebff564421 100644
--- a/erts/emulator/beam/io.c
+++ b/erts/emulator/beam/io.c
@@ -4192,8 +4192,8 @@ static void sweep_one_monitor(ErtsMonitor *mon, void *vpsc)
         ErtsMonitor *rmon;
         Process *rp;
 
-        ASSERT(is_internal_pid(mon->pid));
-        rp = erts_pid2proc(NULL, 0, mon->pid, ERTS_PROC_LOCK_LINK);
+        ASSERT(is_internal_pid(mon->u.pid));
+        rp = erts_pid2proc(NULL, 0, mon->u.pid, ERTS_PROC_LOCK_LINK);
         if (!rp) {
             goto done;
         }
@@ -4294,7 +4294,7 @@ port_fire_one_monitor(ErtsMonitor *mon, void *ctx0)
     Process      *origin;
     ErtsProcLocks origin_locks;
 
-    if (mon->type != MON_TARGET || ! is_pid(mon->pid)) {
+    if (mon->type != MON_TARGET || ! is_pid(mon->u.pid)) {
         return;
     }
     /*
@@ -4303,7 +4303,7 @@ port_fire_one_monitor(ErtsMonitor *mon, void *ctx0)
      */
     origin_locks = ERTS_PROC_LOCKS_MSG_SEND | ERTS_PROC_LOCK_LINK;
 
-    origin = erts_pid2proc(NULL, 0, mon->pid, origin_locks);
+    origin = erts_pid2proc(NULL, 0, mon->u.pid, origin_locks);
     if (origin) {
         DeclareTmpHeapNoproc(lhp,3);
         SweepContext    *ctx = (SweepContext *)ctx0;
@@ -5491,7 +5491,7 @@ typedef struct {
 static void prt_one_monitor(ErtsMonitor *mon, void *vprtd)
 {
     prt_one_lnk_data *prtd = (prt_one_lnk_data *) vprtd;
-    erts_print(prtd->to, prtd->arg, "(%T,%T)", mon->pid,mon->ref);
+    erts_print(prtd->to, prtd->arg, "(%T,%T)", mon->u.pid, mon->ref);
 }
 
 static void prt_one_lnk(ErtsLink *lnk, void *vprtd)
@@ -7613,7 +7613,7 @@ erl_drv_convert_time_unit(ErlDrvTime val,
 						    (int) to);
 }
 
-static void ref_to_driver_monitor(Eterm ref, ErlDrvMonitor *mon)
+void erts_ref_to_driver_monitor(Eterm ref, ErlDrvMonitor *mon)
 {
     ERTS_CT_ASSERT(ERTS_REF_THING_SIZE*sizeof(Uint) <= sizeof(ErlDrvMonitor));
     ASSERT(is_internal_ordinary_ref(ref));
@@ -7621,7 +7621,7 @@ static void ref_to_driver_monitor(Eterm ref, ErlDrvMonitor *mon)
                ERTS_REF_THING_SIZE*sizeof(Uint));
 }
 
-static Eterm driver_monitor_to_ref(Eterm *hp, const ErlDrvMonitor *mon)
+Eterm erts_driver_monitor_to_ref(Eterm *hp, const ErlDrvMonitor *mon)
 {
     Eterm ref;
     ERTS_CT_ASSERT(ERTS_REF_THING_SIZE*sizeof(Uint) <= sizeof(ErlDrvMonitor));
@@ -7654,7 +7654,7 @@ static int do_driver_monitor_process(Port *prt,
     erts_add_monitor(&ERTS_P_MONITORS(rp), MON_TARGET, ref, prt->common.id, NIL);
 
     erts_smp_proc_unlock(rp, ERTS_PROC_LOCK_LINK);
-    ref_to_driver_monitor(ref,monitor);
+    erts_ref_to_driver_monitor(ref,monitor);
     return 0;
 }
 
@@ -7691,14 +7691,14 @@ static int do_driver_demonitor_process(Port *prt, const ErlDrvMonitor *monitor)
     ErtsMonitor *mon;
     Eterm to;
 
-    ref = driver_monitor_to_ref(heap, monitor);
+    ref = erts_driver_monitor_to_ref(heap, monitor);
 
     mon = erts_lookup_monitor(ERTS_P_MONITORS(prt), ref);
     if (mon == NULL) {
 	return 1;
     }
     ASSERT(mon->type == MON_ORIGIN);
-    to = mon->pid;
+    to = mon->u.pid;
     ASSERT(is_internal_pid(to));
     rp = erts_pid2proc_opt(NULL,
 			   0,
@@ -7748,14 +7748,14 @@ static ErlDrvTermData do_driver_get_monitored_process(Port *prt,const ErlDrvMoni
     Eterm to;
     Eterm heap[ERTS_REF_THING_SIZE];
 
-    ref = driver_monitor_to_ref(heap, monitor);
+    ref = erts_driver_monitor_to_ref(heap, monitor);
 
     mon = erts_lookup_monitor(ERTS_P_MONITORS(prt), ref);
     if (mon == NULL) {
 	return driver_term_nil;
     }
     ASSERT(mon->type == MON_ORIGIN);
-    to = mon->pid;
+    to = mon->u.pid;
     ASSERT(is_internal_pid(to));
     return (ErlDrvTermData) to;
 }
@@ -7806,7 +7806,7 @@ void erts_fire_port_monitor(Port *prt, Eterm ref)
     }
     callback = prt->drv_ptr->process_exit;
     ASSERT(callback != NULL);
-    ref_to_driver_monitor(ref,&drv_monitor);
+    erts_ref_to_driver_monitor(ref,&drv_monitor);
     ERTS_MSACC_SET_STATE_CACHED_M(ERTS_MSACC_STATE_PORT);
     DRV_MONITOR_UNLOCK_PDL(prt);
 #ifdef USE_VM_PROBES