12 files changed, 287 insertions, 137 deletions

diff --git a/erts/emulator/beam/bif.c b/erts/emulator/beam/bif.c
index 5ea441ad81..dc0dcbabd6 100644
--- a/erts/emulator/beam/bif.c
+++ b/erts/emulator/beam/bif.c
@@ -1908,7 +1908,7 @@ do_send(Process *p, Eterm to, Eterm msg, int suspend) {
         
 	/* We have waited for locks, trace schedule ports */
 	if (pt) {
-	    erts_aint32_t state;
+	    erts_aint32_t flags;
 	    if (IS_TRACED_FL(pt, F_TRACE_SCHED_PORTS)) {
 		trace_sched_ports_where(pt, am_in, am_command);
 	    }
@@ -1916,9 +1916,9 @@ do_send(Process *p, Eterm to, Eterm msg, int suspend) {
 		profile_runnable_port(pt, am_active);
 	    }
 	
-	    state = erts_atomic32_read_nob(&pt->state);
+	    flags = erts_atomic32_read_rb(&pt->sched.flags);
 	    /* XXX let port_command handle the busy stuff !!! */
-	    if (state & ERTS_PORT_SFLG_PORT_BUSY) {
+	    if (flags & ERTS_PTS_FLG_BUSY) {
 		if (suspend) {
 		    erts_suspend(p, ERTS_PROC_LOCK_MAIN, pt);
 		    if (erts_system_monitor_flags.busy_port) {
diff --git a/erts/emulator/beam/dist.c b/erts/emulator/beam/dist.c
index 432b842848..f28d9dff09 100644
--- a/erts/emulator/beam/dist.c
+++ b/erts/emulator/beam/dist.c
@@ -171,11 +171,10 @@ get_suspended_on_de(DistEntry *dep, Uint32 unset_qflgs)
 	return NULL;
     }
     else {
-	ErtsProcList *plp;
-	plp = dep->suspended.first;
-	dep->suspended.first = NULL;
-	dep->suspended.last = NULL;
-	return plp;
+	ErtsProcList *suspended = dep->suspended;
+	dep->suspended = NULL;
+	erts_proclist_fetch(&suspended, NULL);
+	return suspended;
     }
 }
 
@@ -1698,7 +1697,6 @@ dsig_send(ErtsDSigData *dsdp, Eterm ctl, Eterm msg, int force_busy)
 	    erts_smp_mtx_unlock(&dep->qlock);
 
 	    plp = erts_proclist_create(c_p);
-	    plp->next = NULL;
 	    erts_suspend(c_p, ERTS_PROC_LOCK_MAIN, NULL);
 	    suspended = 1;
 	    erts_smp_mtx_lock(&dep->qlock);
@@ -1731,11 +1729,7 @@ dsig_send(ErtsDSigData *dsdp, Eterm ctl, Eterm msg, int force_busy)
 	    else {
 		/* Enqueue suspended process on dist entry */
 		ASSERT(plp);
-		if (dep->suspended.last)
-		    dep->suspended.last->next = plp;
-		else
-		    dep->suspended.first = plp;
-		dep->suspended.last = plp;
+		erts_proclist_store_last(&dep->suspended, plp);
 	    }
 	}
 
@@ -1914,7 +1908,7 @@ erts_dist_command(Port *prt, int reds_limit)
     ErtsDistOutputQueue oq, foq;
     DistEntry *dep = prt->dist_entry;
     Uint (*send)(Port *prt, ErtsDistOutputBuf *obuf);
-    erts_aint32_t state;
+    erts_aint32_t sched_flags;
 
     ERTS_SMP_LC_ASSERT(erts_lc_is_port_locked(prt));
 
@@ -1957,12 +1951,12 @@ erts_dist_command(Port *prt, int reds_limit)
     dep->finalized_out_queue.first = NULL;
     dep->finalized_out_queue.last = NULL;
 
-    state = erts_atomic32_read_nob(&prt->state);
+    sched_flags = erts_smp_atomic32_read_nob(&prt->sched.flags);
 
     if (reds > reds_limit)
 	goto preempted;
 
-    if (!(state & ERTS_PORT_SFLG_PORT_BUSY) && foq.first) {
+    if (!(sched_flags & ERTS_PTS_FLG_BUSY) && foq.first) {
 	int preempt = 0;
 	do {
 	    Uint size;
@@ -1978,9 +1972,9 @@ erts_dist_command(Port *prt, int reds_limit)
 	    obufsize += size_obuf(fob);
 	    foq.first = foq.first->next;
 	    free_dist_obuf(fob);
-	    state = erts_atomic32_read_nob(&prt->state);
-	    preempt = reds > reds_limit || (state & ERTS_PORT_SFLGS_DEAD);
-	    if (state & ERTS_PORT_SFLG_PORT_BUSY)
+	    sched_flags = erts_smp_atomic32_read_nob(&prt->sched.flags);
+	    preempt = reds > reds_limit || (sched_flags & ERTS_PTS_FLG_EXIT);
+	    if (sched_flags & ERTS_PTS_FLG_BUSY)
 		break;
 	} while (foq.first && !preempt);
 	if (!foq.first)
@@ -1989,7 +1983,7 @@ erts_dist_command(Port *prt, int reds_limit)
 	    goto preempted;
     }
 
-    if (state & ERTS_PORT_SFLG_PORT_BUSY) {
+    if (sched_flags & ERTS_PTS_FLG_BUSY) {
 	if (oq.first) {
 	    ErtsDistOutputBuf *ob;
 	    int preempt;
@@ -2060,9 +2054,9 @@ erts_dist_command(Port *prt, int reds_limit)
 	    obufsize += size_obuf(fob);
 	    oq.first = oq.first->next;
 	    free_dist_obuf(fob);
-	    state = erts_atomic32_read_nob(&prt->state);
-	    preempt = reds > reds_limit || (state & ERTS_PORT_SFLGS_DEAD);
-	    if ((state & ERTS_PORT_SFLG_PORT_BUSY) && oq.first && !preempt)
+	    sched_flags = erts_smp_atomic32_read_nob(&prt->sched.flags);
+	    preempt = reds > reds_limit || (sched_flags & ERTS_PTS_FLG_EXIT);
+	    if ((sched_flags & ERTS_PTS_FLG_BUSY) && oq.first && !preempt)
 		goto finalize_only;
 	}
 
@@ -2091,7 +2085,7 @@ erts_dist_command(Port *prt, int reds_limit)
 	ASSERT(dep->qsize >= obufsize);
 	dep->qsize -= obufsize;
 	obufsize = 0;
-	if (!(state & ERTS_PORT_SFLG_PORT_BUSY)
+	if (!(sched_flags & ERTS_PTS_FLG_BUSY)
 	    && (dep->qflgs & ERTS_DE_QFLG_BUSY)
 	    && dep->qsize < erts_dist_buf_busy_limit) {
 	    ErtsProcList *suspendees;
@@ -2145,7 +2139,7 @@ erts_dist_command(Port *prt, int reds_limit)
     ASSERT(oq.first || !oq.last);
     ASSERT(!oq.first || oq.last);
 
-    if (state & ERTS_PORT_SFLGS_DEAD) {
+    if (sched_flags & ERTS_PTS_FLG_EXIT) {
 	/*
 	 * Port died during port command; clean up 'oq'
 	 * and 'foq'. Things buffered in dist entry after
@@ -2602,11 +2596,7 @@ BIF_RETTYPE setnode_3(BIF_ALIST_3)
 	plp->next = NULL;
 	erts_suspend(BIF_P, ERTS_PROC_LOCK_MAIN, NULL);
 	erts_smp_mtx_lock(&dep->qlock);
-	if (dep->suspended.last)
-	    dep->suspended.last->next = plp;
-	else
-	    dep->suspended.first = plp;
-	dep->suspended.last = plp;
+	erts_proclist_store_last(&dep->suspended, plp);
 	erts_smp_mtx_unlock(&dep->qlock);
 	goto yield;
     }
diff --git a/erts/emulator/beam/erl_bif_port.c b/erts/emulator/beam/erl_bif_port.c
index 31151dc9f5..477671f11f 100644
--- a/erts/emulator/beam/erl_bif_port.c
+++ b/erts/emulator/beam/erl_bif_port.c
@@ -168,7 +168,8 @@ do_port_command(Process *BIF_P, Eterm arg1, Eterm arg2, Eterm arg3,
 	ERTS_BIF_PREP_ERROR(res, BIF_P, EXC_NOTSUP);
     }
     else if (!(flags & ERTS_PORT_COMMAND_FLAG_FORCE)
-	     && (erts_atomic32_read_nob(&p->state) & ERTS_PORT_SFLG_PORT_BUSY)) {
+	     && (erts_smp_atomic32_read_nob(&p->sched.flags)
+		 & ERTS_PTS_FLG_BUSY)) {
 	if (flags & ERTS_PORT_COMMAND_FLAG_NOSUSPEND) {
 	    ERTS_BIF_PREP_RET(res, am_false);
 	}
diff --git a/erts/emulator/beam/erl_node_tables.c b/erts/emulator/beam/erl_node_tables.c
index 67f413ef28..6bda07e9b0 100644
--- a/erts/emulator/beam/erl_node_tables.c
+++ b/erts/emulator/beam/erl_node_tables.c
@@ -116,8 +116,7 @@ dist_table_alloc(void *dep_tmpl)
     dep->qsize				= 0;
     dep->out_queue.first		= NULL;
     dep->out_queue.last			= NULL;
-    dep->suspended.first		= NULL;
-    dep->suspended.last			= NULL;
+    dep->suspended			= NULL;
 
     dep->finalized_out_queue.first	= NULL;
     dep->finalized_out_queue.last	= NULL;
@@ -769,8 +768,7 @@ void erts_init_node_tables(void)
     erts_this_dist_entry->qsize				= 0;
     erts_this_dist_entry->out_queue.first		= NULL;
     erts_this_dist_entry->out_queue.last		= NULL;
-    erts_this_dist_entry->suspended.first		= NULL;
-    erts_this_dist_entry->suspended.last		= NULL;
+    erts_this_dist_entry->suspended			= NULL;
 
     erts_this_dist_entry->finalized_out_queue.first	= NULL;
     erts_this_dist_entry->finalized_out_queue.last	= NULL;
diff --git a/erts/emulator/beam/erl_node_tables.h b/erts/emulator/beam/erl_node_tables.h
index 3a74888522..af60071ea5 100644
--- a/erts/emulator/beam/erl_node_tables.h
+++ b/erts/emulator/beam/erl_node_tables.h
@@ -84,10 +84,6 @@ typedef struct {
 } ErtsDistOutputQueue;
 
 struct ErtsProcList_;
-typedef struct {
-    struct ErtsProcList_ *first;
-    struct ErtsProcList_ *last;
-} ErtsDistSuspended;
 
 /*
  * Lock order:
@@ -134,7 +130,7 @@ typedef struct dist_entry_ {
     Uint32 qflgs;
     Sint qsize;
     ErtsDistOutputQueue out_queue;
-    ErtsDistSuspended suspended;
+    struct ErtsProcList_ *suspended;
 
     ErtsDistOutputQueue finalized_out_queue;
     erts_smp_atomic_t dist_cmd_scheduled;
diff --git a/erts/emulator/beam/erl_port.h b/erts/emulator/beam/erl_port.h
index ce8d809245..00394f279e 100644
--- a/erts/emulator/beam/erl_port.h
+++ b/erts/emulator/beam/erl_port.h
@@ -214,22 +214,20 @@ extern erts_smp_atomic_t erts_bytes_in;		/* no bytes sent into the system */
 #define ERTS_PORT_SFLG_BINARY_IO	((Uint32) (1 <<  3))
 #define ERTS_PORT_SFLG_SOFT_EOF		((Uint32) (1 <<  4))
 /* Flow control */
-#define ERTS_PORT_SFLG_PORT_BUSY	((Uint32) (1 <<  5))
 /* Port is closing (no i/o accepted) */
-#define ERTS_PORT_SFLG_CLOSING		((Uint32) (1 <<  6))
+#define ERTS_PORT_SFLG_CLOSING		((Uint32) (1 <<  5))
 /* Send a closed message when terminating */
-#define ERTS_PORT_SFLG_SEND_CLOSED	((Uint32) (1 <<  7))
+#define ERTS_PORT_SFLG_SEND_CLOSED	((Uint32) (1 <<  6))
 /* Line orinted io on port */  
-#define ERTS_PORT_SFLG_LINEBUF_IO	((Uint32) (1 <<  8))
+#define ERTS_PORT_SFLG_LINEBUF_IO	((Uint32) (1 <<  7))
 /* Immortal port (only certain system ports) */
-#define ERTS_PORT_SFLG_IMMORTAL		((Uint32) (1 <<  9))
-#define ERTS_PORT_SFLG_FREE		((Uint32) (1 << 10))
-#define ERTS_PORT_SFLG_INITIALIZING	((Uint32) (1 << 11))
+#define ERTS_PORT_SFLG_FREE		((Uint32) (1 <<  8))
+#define ERTS_PORT_SFLG_INITIALIZING	((Uint32) (1 <<  9))
 /* Port uses port specific locking (opposed to driver specific locking) */
-#define ERTS_PORT_SFLG_PORT_SPECIFIC_LOCK ((Uint32) (1 << 12))
-#define ERTS_PORT_SFLG_INVALID		((Uint32) (1 << 13))
+#define ERTS_PORT_SFLG_PORT_SPECIFIC_LOCK ((Uint32) (1 << 10))
+#define ERTS_PORT_SFLG_INVALID		((Uint32) (1 << 11))
 /* Last port to terminate halts the emulator */
-#define ERTS_PORT_SFLG_HALT		((Uint32) (1 << 14))
+#define ERTS_PORT_SFLG_HALT		((Uint32) (1 << 12))
 #ifdef DEBUG
 /* Only debug: make sure all flags aren't cleared unintentionally */
 #define ERTS_PORT_SFLG_PORT_DEBUG	((Uint32) (1 << 31))
@@ -237,8 +235,7 @@ extern erts_smp_atomic_t erts_bytes_in;		/* no bytes sent into the system */
 
 /* Combinations of port status flags */ 
 #define ERTS_PORT_SFLGS_DEAD						\
-  (ERTS_PORT_SFLG_FREE							\
-   | ERTS_PORT_SFLG_INITIALIZING)
+  (ERTS_PORT_SFLG_FREE | ERTS_PORT_SFLG_INITIALIZING)
 #define ERTS_PORT_SFLGS_INVALID_DRIVER_LOOKUP				\
   (ERTS_PORT_SFLGS_DEAD | ERTS_PORT_SFLG_INVALID)
 #define ERTS_PORT_SFLGS_INVALID_LOOKUP					\
@@ -246,7 +243,6 @@ extern erts_smp_atomic_t erts_bytes_in;		/* no bytes sent into the system */
    | ERTS_PORT_SFLG_CLOSING)
 #define ERTS_PORT_SFLGS_INVALID_TRACER_LOOKUP				\
   (ERTS_PORT_SFLGS_INVALID_LOOKUP					\
-   | ERTS_PORT_SFLG_PORT_BUSY						\
    | ERTS_PORT_SFLG_DISTRIBUTION)
 
 void print_port_info(Port *, int, void *);
diff --git a/erts/emulator/beam/erl_port_task.c b/erts/emulator/beam/erl_port_task.c
index edcd3112da..dceecda973 100644
--- a/erts/emulator/beam/erl_port_task.c
+++ b/erts/emulator/beam/erl_port_task.c
@@ -530,6 +530,7 @@ fail:
 void
 erts_port_task_free_port(Port *pp)
 {
+    ErtsProcList *suspended;
     erts_aint32_t flags;
     ErtsRunQueue *runq;
 
@@ -542,6 +543,8 @@ erts_port_task_free_port(Port *pp)
     erts_port_task_sched_lock(&pp->sched);
     flags = erts_smp_atomic32_read_bor_relb(&pp->sched.flags,
 					    ERTS_PTS_FLG_EXIT);
+    suspended = pp->suspended;
+    pp->suspended = NULL;
     erts_port_task_sched_unlock(&pp->sched);
     erts_atomic32_read_bset_relb(&pp->state,
 				 (ERTS_PORT_SFLG_CLOSING
@@ -550,6 +553,9 @@ erts_port_task_free_port(Port *pp)
 
     erts_smp_runq_unlock(runq);
 
+    if (erts_proclist_fetch(&suspended, NULL))
+	erts_resume_processes(suspended);
+
     if (!(flags & (ERTS_PTS_FLG_IN_RUNQ|ERTS_PTS_FLG_EXEC)))
 	begin_port_cleanup(pp, NULL);
 }
diff --git a/erts/emulator/beam/erl_port_task.h b/erts/emulator/beam/erl_port_task.h
index 3e87d5b778..71b1cc6e25 100644
--- a/erts/emulator/beam/erl_port_task.h
+++ b/erts/emulator/beam/erl_port_task.h
@@ -60,6 +60,8 @@ extern erts_smp_atomic_t erts_port_task_outstanding_io_tasks;
 #define ERTS_PTS_FLG_EXEC		(((erts_aint32_t) 1) << 1)
 #define ERTS_PTS_FLG_HAVE_TASKS		(((erts_aint32_t) 1) << 2)
 #define ERTS_PTS_FLG_EXIT		(((erts_aint32_t) 1) << 3)
+#define ERTS_PTS_FLG_BUSY		(((erts_aint32_t) 1) << 4)
+
 
 typedef struct ErtsPortTask_ ErtsPortTask;
 
diff --git a/erts/emulator/beam/erl_process.c b/erts/emulator/beam/erl_process.c
index 07b1ecdbb4..6cf267b01e 100644
--- a/erts/emulator/beam/erl_process.c
+++ b/erts/emulator/beam/erl_process.c
@@ -770,14 +770,6 @@ proclist_destroy(ErtsProcList *plp)
     proclist_free(plp);
 }
 
-static ERTS_INLINE int
-proclist_same(ErtsProcList *plp, Process *p)
-{
-    return (plp->pid == p->common.id
-	    && (plp->started_interval
-		== p->common.u.alive.started_interval));
-}
-
 ErtsProcList *
 erts_proclist_create(Process *p)
 {
@@ -790,12 +782,6 @@ erts_proclist_destroy(ErtsProcList *plp)
     proclist_destroy(plp);
 }
 
-int
-erts_proclist_same(ErtsProcList *plp, Process *p)
-{
-    return proclist_same(plp, p);
-}
-
 void *
 erts_psd_set_init(Process *p, ErtsProcLocks plocks, int ix, void *data)
 {
@@ -4980,8 +4966,7 @@ erts_block_multi_scheduling(Process *p, ErtsProcLocks plocks, int on, int all)
     else if (on) { /* ------ BLOCK ------ */
 	if (schdlr_sspnd.msb.procs) {
 	    plp = proclist_create(p);
-	    plp->next = schdlr_sspnd.msb.procs;
-	    schdlr_sspnd.msb.procs = plp;
+	    erts_proclist_store_last(&schdlr_sspnd.msb.procs, plp);
 	    p->flags |= F_HAVE_BLCKD_MSCHED;
 	    ASSERT(erts_smp_atomic32_read_nob(&schdlr_sspnd.active) == 1);
 	    ASSERT(p->scheduler_data->no == 1);
@@ -5066,8 +5051,7 @@ erts_block_multi_scheduling(Process *p, ErtsProcLocks plocks, int on, int all)
 						~ERTS_SCHDLR_SSPND_CHNG_WAITER);
 	    }
 	    plp = proclist_create(p);
-	    plp->next = schdlr_sspnd.msb.procs;
-	    schdlr_sspnd.msb.procs = plp;
+	    erts_proclist_store_last(&schdlr_sspnd.msb.procs, plp);
 	    ASSERT(p->scheduler_data);
 	}
     }
@@ -5078,20 +5062,16 @@ erts_block_multi_scheduling(Process *p, ErtsProcLocks plocks, int on, int all)
     }
     else {  /* ------ UNBLOCK ------ */
 	if (p->flags & F_HAVE_BLCKD_MSCHED) {
-	    ErtsProcList **plpp = &schdlr_sspnd.msb.procs;
-	    plp = schdlr_sspnd.msb.procs;
+	    ErtsProcList *plp = erts_proclist_peek_first(schdlr_sspnd.msb.procs);
 
 	    while (plp) {
-		if (!proclist_same(plp, p)){
-		    plpp = &plp->next;
-		    plp = plp->next;
-		}
-		else {
-		    *plpp = plp->next;
-		    proclist_destroy(plp);
+		ErtsProcList *tmp_plp = plp;
+		plp = erts_proclist_peek_next(schdlr_sspnd.msb.procs, plp);
+		if (erts_proclist_same(tmp_plp, p)) {
+		    erts_proclist_remove(&schdlr_sspnd.msb.procs, tmp_plp);
+		    proclist_destroy(tmp_plp);
 		    if (!all)
 			break;
-		    plp = *plpp;
 		}
 	    }
 	}
@@ -5160,23 +5140,25 @@ erts_multi_scheduling_blockers(Process *p)
     Eterm res = NIL;
 
     erts_smp_mtx_lock(&schdlr_sspnd.mtx);
-    if (schdlr_sspnd.msb.procs) {
+    if (!erts_proclist_is_empty(schdlr_sspnd.msb.procs)) {
 	Eterm *hp, *hp_end;
 	ErtsProcList *plp1, *plp2;
-	Uint max_size;
-	ASSERT(schdlr_sspnd.msb.procs);
-	for (max_size = 0, plp1 = schdlr_sspnd.msb.procs;
+	Uint max_size = 0;
+
+	for (plp1 = erts_proclist_peek_first(schdlr_sspnd.msb.procs);
 	     plp1;
-	     plp1 = plp1->next) {
+	     plp1 = erts_proclist_peek_next(schdlr_sspnd.msb.procs, plp1)) {
 	    max_size += 2;
 	}
 	ASSERT(max_size);
 	hp = HAlloc(p, max_size);
 	hp_end = hp + max_size;
-	for (plp1 = schdlr_sspnd.msb.procs; plp1; plp1 = plp1->next) {
-	    for (plp2 = schdlr_sspnd.msb.procs;
+	for (plp1 = erts_proclist_peek_first(schdlr_sspnd.msb.procs);
+	     plp1;
+	     plp1 = erts_proclist_peek_next(schdlr_sspnd.msb.procs, plp1)) {
+	    for (plp2 = erts_proclist_peek_first(schdlr_sspnd.msb.procs);
 		 plp2->pid != plp1->pid;
-		 plp2 = plp2->next);
+		 plp2 = erts_proclist_peek_next(schdlr_sspnd.msb.procs, plp2));
 	    if (plp2 == plp1) {
 		res = CONS(hp, plp1->pid, res);
 		hp += 2;
@@ -6081,23 +6063,25 @@ erts_process_status(Process *c_p, ErtsProcLocks c_p_locks,
 void
 erts_suspend(Process* c_p, ErtsProcLocks c_p_locks, Port *busy_port)
 {
-#ifdef DEBUG
-    int res;
-#endif
+    int suspend;
+
     ASSERT(c_p == erts_get_current_process());
     ERTS_SMP_LC_ASSERT(c_p_locks == erts_proc_lc_my_proc_locks(c_p));
     if (!(c_p_locks & ERTS_PROC_LOCK_STATUS))
 	erts_smp_proc_lock(c_p, ERTS_PROC_LOCK_STATUS);
 
+    if (busy_port)
+	suspend = erts_save_suspend_process_on_port(busy_port, c_p);
+    else
+	suspend = 1;
+
+    if (suspend) {
 #ifdef DEBUG
-    res =
+	int res =
 #endif
-	suspend_process(c_p, c_p);
-
-    ASSERT(res);
-
-    if (busy_port)
-	erts_wake_process_later(busy_port, c_p);
+	    suspend_process(c_p, c_p);
+	ASSERT(res);
+    }
 
     if (!(c_p_locks & ERTS_PROC_LOCK_STATUS))
 	erts_smp_proc_unlock(c_p, ERTS_PROC_LOCK_STATUS);
@@ -6116,16 +6100,19 @@ erts_resume(Process* process, ErtsProcLocks process_locks)
 }
 
 int
-erts_resume_processes(ErtsProcList *plp)
+erts_resume_processes(ErtsProcList *list)
 {
+    /* 'list' is expected to have been fetched (i.e. not a ring anymore) */
     int nresumed = 0;
+    ErtsProcList *plp = list;
+
     while (plp) {
 	Process *proc;
 	ErtsProcList *fplp;
 	ASSERT(is_internal_pid(plp->pid));
 	proc = erts_pid2proc(NULL, 0, plp->pid, ERTS_PROC_LOCK_STATUS);
 	if (proc) {
-	    if (proclist_same(plp, proc)) {
+	    if (erts_proclist_same(plp, proc)) {
 		resume_process(proc);
 		nresumed++;
 	    }
@@ -6354,9 +6341,8 @@ Process *schedule(Process *p, int calls)
 #ifdef ERTS_SMP
 	{
 	    ErtsProcList *pnd_xtrs = rq->procs.pending_exiters;
-	    rq->procs.pending_exiters = NULL;
-
-	    if (pnd_xtrs) {
+	    if (erts_proclist_fetch(&pnd_xtrs, NULL)) {
+		rq->procs.pending_exiters = NULL;
 		erts_smp_runq_unlock(rq);
 		handle_pending_exiters(pnd_xtrs);
 		erts_smp_runq_lock(rq);
@@ -7700,12 +7686,14 @@ erts_handle_pending_exit(Process *c_p, ErtsProcLocks locks)
 static void
 handle_pending_exiters(ErtsProcList *pnd_xtrs)
 {
+    /* 'list' is expected to have been fetched (i.e. not a ring anymore) */
     ErtsProcList *plp = pnd_xtrs;
-    ErtsProcList *free_plp;
+
     while (plp) {
+	ErtsProcList *free_plp;
 	Process *p = erts_pid2proc(NULL, 0, plp->pid, ERTS_PROC_LOCKS_ALL);
 	if (p) {
-	    if (proclist_same(plp, p)) {
+	    if (erts_proclist_same(plp, p)) {
 		erts_aint32_t state = erts_smp_atomic32_read_acqb(&p->state);
 		if (!(state & ERTS_PSFLG_RUNNING)) {
 		    ASSERT(state & ERTS_PSFLG_PENDING_EXIT);
@@ -7734,8 +7722,7 @@ save_pending_exiter(Process *p)
 
     erts_smp_runq_lock(rq);
 
-    plp->next = rq->procs.pending_exiters;
-    rq->procs.pending_exiters = plp;
+    erts_proclist_store_last(&rq->procs.pending_exiters, plp);
 
     erts_smp_runq_unlock(rq);
     wake_scheduler(rq, 1);
diff --git a/erts/emulator/beam/erl_process.h b/erts/emulator/beam/erl_process.h
index 1feb5b96db..d613321421 100644
--- a/erts/emulator/beam/erl_process.h
+++ b/erts/emulator/beam/erl_process.h
@@ -290,6 +290,7 @@ struct ErtsProcList_ {
     Eterm pid;
     Uint64 started_interval;
     ErtsProcList* next;
+    ErtsProcList* prev;
 };
 
 typedef struct ErtsMiscOpList_ ErtsMiscOpList;
@@ -1135,7 +1136,172 @@ Uint64 erts_step_proc_interval(void);
 
 ErtsProcList *erts_proclist_create(Process *);
 void erts_proclist_destroy(ErtsProcList *);
-int erts_proclist_same(ErtsProcList *, Process *);
+
+ERTS_GLB_INLINE int erts_proclist_same(ErtsProcList *, Process *);
+ERTS_GLB_INLINE void erts_proclist_store_first(ErtsProcList **, ErtsProcList *);
+ERTS_GLB_INLINE void erts_proclist_store_last(ErtsProcList **, ErtsProcList *);
+ERTS_GLB_INLINE ErtsProcList *erts_proclist_peek_first(ErtsProcList *);
+ERTS_GLB_INLINE ErtsProcList *erts_proclist_peek_last(ErtsProcList *);
+ERTS_GLB_INLINE ErtsProcList *erts_proclist_peek_next(ErtsProcList *, ErtsProcList *);
+ERTS_GLB_INLINE ErtsProcList *erts_proclist_peek_prev(ErtsProcList *, ErtsProcList *);
+ERTS_GLB_INLINE ErtsProcList *erts_proclist_fetch_first(ErtsProcList **);
+ERTS_GLB_INLINE ErtsProcList *erts_proclist_fetch_last(ErtsProcList **);
+ERTS_GLB_INLINE int erts_proclist_fetch(ErtsProcList **, ErtsProcList **);
+ERTS_GLB_INLINE void erts_proclist_remove(ErtsProcList **, ErtsProcList *);
+ERTS_GLB_INLINE int erts_proclist_is_empty(ErtsProcList *);
+ERTS_GLB_INLINE int erts_proclist_is_first(ErtsProcList *, ErtsProcList *);
+ERTS_GLB_INLINE int erts_proclist_is_last(ErtsProcList *, ErtsProcList *);
+
+#if ERTS_GLB_INLINE_INCL_FUNC_DEF
+
+ERTS_GLB_INLINE int
+erts_proclist_same(ErtsProcList *plp, Process *p)
+{
+    return (plp->pid == p->common.id
+	    && (plp->started_interval
+		== p->common.u.alive.started_interval));
+}
+
+ERTS_GLB_INLINE void erts_proclist_store_first(ErtsProcList **list,
+					       ErtsProcList *element)
+{
+    if (!*list)
+	element->next = element->prev = element;
+    else {
+	element->prev = (*list)->prev;
+	element->next = *list;
+	element->prev->next = element;
+	element->next->prev = element;
+    }
+    *list = element;
+}
+
+ERTS_GLB_INLINE void erts_proclist_store_last(ErtsProcList **list,
+					      ErtsProcList *element)
+{
+    if (!*list) {
+	element->next = element->prev = element;
+	*list = element;
+    }
+    else {
+	element->prev = (*list)->prev;
+	element->next = *list;
+	element->prev->next = element;
+	element->next->prev = element;
+    }
+}
+
+ERTS_GLB_INLINE ErtsProcList *erts_proclist_peek_first(ErtsProcList *list)
+{
+    return list;
+}
+
+ERTS_GLB_INLINE ErtsProcList *erts_proclist_peek_last(ErtsProcList *list)
+{
+    if (!list)
+	return NULL;
+    else
+	return list->prev;
+}
+
+ERTS_GLB_INLINE ErtsProcList *erts_proclist_peek_next(ErtsProcList *list,
+						      ErtsProcList *element)
+{
+    ErtsProcList *next;
+    ASSERT(list && element);
+    next = element->next;
+    return list == next ? NULL : next;
+}
+
+ERTS_GLB_INLINE ErtsProcList *erts_proclist_peek_prev(ErtsProcList *list,
+						      ErtsProcList *element)
+{
+    ErtsProcList *prev;
+    ASSERT(list && element);
+    prev = element->prev;
+    return list == element ? NULL : prev;
+}
+
+ERTS_GLB_INLINE ErtsProcList *erts_proclist_fetch_first(ErtsProcList **list)
+{
+    if (!*list)
+	return NULL;
+    else {
+	ErtsProcList *res = *list;
+	if (res == *list)
+	    *list = NULL;
+	else
+	    *list = res->next;
+	res->next->prev = res->prev;
+	res->prev->next = res->next;
+	return res;
+    }
+}
+
+ERTS_GLB_INLINE ErtsProcList *erts_proclist_fetch_last(ErtsProcList **list)
+{
+    if (!*list)
+	return NULL;
+    else {
+	ErtsProcList *res = (*list)->prev;
+	if (res == *list)
+	    *list = NULL;
+	res->next->prev = res->prev;
+	res->prev->next = res->next;
+	return res;
+    }
+}
+
+ERTS_GLB_INLINE int erts_proclist_fetch(ErtsProcList **list_first,
+					ErtsProcList **list_last)
+{
+    if (!*list_first) {
+	if (list_last)
+	    *list_last = NULL;
+	return 0;
+    }
+    else {
+	if (list_last)
+	    *list_last = (*list_first)->prev;
+	(*list_first)->prev->next = NULL;
+	(*list_first)->prev = NULL;
+	return !0;
+    }
+}
+
+ERTS_GLB_INLINE void erts_proclist_remove(ErtsProcList **list,
+					  ErtsProcList *element)
+{
+    ASSERT(list && *list);
+    if (*list == element) {
+	*list = element->next;
+	if (*list == element)
+	    *list = NULL;
+    }
+    element->next->prev = element->prev;
+    element->prev->next = element->next;
+}
+
+ERTS_GLB_INLINE int erts_proclist_is_empty(ErtsProcList *list)
+{
+    return list == NULL;
+}
+
+ERTS_GLB_INLINE int erts_proclist_is_first(ErtsProcList *list,
+					   ErtsProcList *element)
+{
+    ASSERT(list && element);
+    return list == element;
+}
+
+ERTS_GLB_INLINE int erts_proclist_is_last(ErtsProcList *list,
+					  ErtsProcList *element)
+{
+    ASSERT(list && element);
+    return list->prev == element;
+}
+
+#endif
 
 void erts_schedule_thr_prgr_later_op(void (*)(void *),
 				     void *,
diff --git a/erts/emulator/beam/global.h b/erts/emulator/beam/global.h
index bce4619645..6713481a04 100644
--- a/erts/emulator/beam/global.h
+++ b/erts/emulator/beam/global.h
@@ -895,7 +895,7 @@ typedef struct {
 
 int erts_add_driver_entry(ErlDrvEntry *drv, DE_Handle *handle, int driver_list_locked);
 void erts_destroy_driver(erts_driver_t *drv);
-void erts_wake_process_later(Port*, Process*);
+int erts_save_suspend_process_on_port(Port*, Process*);
 Port *erts_open_driver(erts_driver_t*, Eterm, char*, SysDriverOpts*, int *, int *);
 int erts_is_port_ioq_empty(Port *);
 void erts_terminate_port(Port *);
diff --git a/erts/emulator/beam/io.c b/erts/emulator/beam/io.c
index 9d38e5539e..96a89a3b4e 100644
--- a/erts/emulator/beam/io.c
+++ b/erts/emulator/beam/io.c
@@ -476,23 +476,19 @@ static void stopq(Port* prt)
     }
 }
 
-void
-erts_wake_process_later(Port *prt, Process *process)
+int
+erts_save_suspend_process_on_port(Port *prt, Process *process)
 {
-    ErtsProcList** p;
-    ErtsProcList* new_p;
-
-    ERTS_SMP_LC_ASSERT(erts_lc_is_port_locked(prt));
-
-    if (erts_atomic32_read_nob(&prt->state) & ERTS_PORT_SFLGS_DEAD)
-	return;
-
-    for (p = &(prt->suspended); *p != NULL; p = &((*p)->next))
-	/* Empty loop body */;
-
-    new_p = erts_proclist_create(process);
-    new_p->next = NULL;
-    *p = new_p;
+    int saved;
+    erts_aint32_t flags;
+    erts_port_task_sched_lock(&prt->sched);
+    flags = erts_smp_atomic32_read_nob(&prt->sched.flags);
+    saved = ((flags & (ERTS_PTS_FLG_BUSY
+		       | ERTS_PTS_FLG_EXIT)) == ERTS_PTS_FLG_BUSY);
+    if (saved)
+	erts_proclist_store_last(&prt->suspended, erts_proclist_create(process));
+    erts_port_task_sched_unlock(&prt->sched);
+    return saved;
 }
 
 /*
@@ -2094,9 +2090,7 @@ erts_do_exit_port(Port *p, Eterm from, Eterm reason)
 #endif
 
    state = erts_atomic32_read_nob(&p->state);
-   if ((state & (ERTS_PORT_SFLGS_DEAD
-		 | ERTS_PORT_SFLG_EXITING
-		 | ERTS_PORT_SFLG_IMMORTAL))
+   if ((state & (ERTS_PORT_SFLGS_DEAD|ERTS_PORT_SFLG_EXITING))
        || ((reason == am_normal) &&
 	   ((from != p->connected) && (from != p->common.id)))) {
       return;
@@ -2468,6 +2462,8 @@ void
 set_busy_port(ErlDrvPort port_num, int on)
 {
     Port *prt;
+    erts_aint32_t flags;
+
 #ifdef USE_VM_PROBES
     DTRACE_CHARBUF(port_str, 16);
 #endif
@@ -2479,8 +2475,10 @@ set_busy_port(ErlDrvPort port_num, int on)
 	return;
 
     if (on) {
-	erts_atomic32_read_bor_relb(&prt->state,
-				    ERTS_PORT_SFLG_PORT_BUSY);
+	flags = erts_smp_atomic32_read_bor_nob(&prt->sched.flags,
+					       ERTS_PTS_FLG_BUSY);
+	if (flags & ERTS_PTS_FLG_BUSY)
+	    return; /* Already busy */
 #ifdef USE_VM_PROBES
         if (DTRACE_ENABLED(port_busy)) {
             erts_snprintf(port_str, sizeof(port_str),
@@ -2489,10 +2487,12 @@ set_busy_port(ErlDrvPort port_num, int on)
         }
 #endif
     } else {
-        ErtsProcList* plp = prt->suspended;
-	erts_atomic32_read_band_relb(&prt->state,
-				     ~ERTS_PORT_SFLG_PORT_BUSY);
-        prt->suspended = NULL;
+        ErtsProcList *plp;
+
+	flags = erts_smp_atomic32_read_band_nob(&prt->sched.flags,
+						~ERTS_PTS_FLG_BUSY);
+	if (!(flags & ERTS_PTS_FLG_BUSY))
+	    return; /* Already non-busy */
 
 #ifdef USE_VM_PROBES
         if (DTRACE_ENABLED(port_not_busy)) {
@@ -2517,7 +2517,13 @@ set_busy_port(ErlDrvPort port_num, int on)
 	 * the first process.
 	 */
 
-        if (plp) {
+	erts_port_task_sched_lock(&prt->sched);
+	plp = prt->suspended;
+	prt->suspended = NULL;
+	erts_port_task_sched_unlock(&prt->sched);
+
+        if (erts_proclist_fetch(&plp, NULL)) {
+
 #ifdef USE_VM_PROBES
             /*
              * Hrm, for blocked dist ports, plp always seems to be NULL.
@@ -2540,8 +2546,10 @@ set_busy_port(ErlDrvPort port_num, int on)
                 }
             }
 #endif
+
             /* First proc should be resumed last */
 	    if (plp->next) {
+		plp->next->prev = NULL;
 		erts_resume_processes(plp->next);
 		plp->next = NULL;
 	    }