Functionality for disabling garbage collection

Being able to disable garbage collection over context
switches vastly simplifies implementation of yielding
native code that builds large or complex data structures
on the heap. This since the heap can be left in an
inconsistent state over the context switch.

9 files changed, 368 insertions, 28 deletions

diff --git a/erts/emulator/beam/beam_bif_load.c b/erts/emulator/beam/beam_bif_load.c
index 5239940a50..3f92c5b025 100644
--- a/erts/emulator/beam/beam_bif_load.c
+++ b/erts/emulator/beam/beam_bif_load.c
@@ -495,6 +495,8 @@ BIF_RETTYPE erts_internal_check_process_code_2(BIF_ALIST_2)
 
     res = erts_check_process_code(BIF_P, BIF_ARG_1, allow_gc, &reds);
 
+    ASSERT(is_value(res));
+
     BIF_RET2(res, reds);
 
 badarg:
@@ -784,6 +786,16 @@ check_process_code(Process* rp, Module* modp, int allow_gc, int *redsp)
 	}
     }
 
+    if (rp->flags & F_DISABLE_GC) {
+	/*
+	 * Cannot proceed. Process has disabled gc in order to
+	 * safely leave inconsistent data on the heap and/or
+	 * off heap lists. Need to wait for gc to be enabled
+	 * again.
+	 */ 
+	return THE_NON_VALUE;
+    }
+
     /*
      * See if there are funs that refer to the old version of the module.
      */
diff --git a/erts/emulator/beam/erl_bif_info.c b/erts/emulator/beam/erl_bif_info.c
index 673dfc658c..f5893f9291 100755
--- a/erts/emulator/beam/erl_bif_info.c
+++ b/erts/emulator/beam/erl_bif_info.c
@@ -3593,6 +3593,19 @@ BIF_RETTYPE erts_debug_set_internal_state_2(BIF_ALIST_2)
 		BIF_RET(am_true);
 	    }
 	}
+	else if (ERTS_IS_ATOM_STR("gc_state", BIF_ARG_1)) {
+	    /* Used by process_SUITE (emulator) */
+	    int res, enable;
+
+	    switch (BIF_ARG_2) {
+	    case am_true: enable = 1; break;
+	    case am_false: enable = 0; break;
+	    default: BIF_ERROR(BIF_P, BADARG); break;
+	    }
+ 
+	    res = erts_set_gc_state(BIF_P, enable);
+	    BIF_RET(res ? am_true : am_false);
+	}
 	else if (ERTS_IS_ATOM_STR("send_fake_exit_signal", BIF_ARG_1)) {
 	    /* Used by signal_SUITE (emulator) */
 
diff --git a/erts/emulator/beam/erl_debug.c b/erts/emulator/beam/erl_debug.c
index b90d00f236..dc79d45be7 100644
--- a/erts/emulator/beam/erl_debug.c
+++ b/erts/emulator/beam/erl_debug.c
@@ -299,6 +299,9 @@ void erts_check_for_holes(Process* p)
     ErlHeapFragment* hf;
     Eterm* start;
 
+    if (p->flags & F_DISABLE_GC)
+	return;
+
     start = p->last_htop ? p->last_htop : HEAP_START(p);
     check_memory(start, HEAP_TOP(p));
     p->last_htop = HEAP_TOP(p);
diff --git a/erts/emulator/beam/erl_gc.c b/erts/emulator/beam/erl_gc.c
index 8ba94d89e9..da254286c4 100644
--- a/erts/emulator/beam/erl_gc.c
+++ b/erts/emulator/beam/erl_gc.c
@@ -400,10 +400,16 @@ erts_garbage_collect(Process* p, int need, Eterm* objv, int nobj)
     Uint reclaimed_now = 0;
     int done = 0;
     Uint ms1, s1, us1;
-    ErtsSchedulerData *esdp = erts_get_scheduler_data();
+    ErtsSchedulerData *esdp;
 #ifdef USE_VM_PROBES
     DTRACE_CHARBUF(pidbuf, DTRACE_TERM_BUF_SIZE);
 #endif
+
+    if (p->flags & F_DISABLE_GC)
+	return 1;
+
+    esdp = erts_get_scheduler_data();
+
     if (IS_TRACED_FL(p, F_TRACE_GC)) {
         trace_gc(p, am_gc_start);
     }
@@ -532,6 +538,9 @@ erts_garbage_collect_hibernate(Process* p)
     Uint area_size;
     Sint offs;
 
+    if (p->flags & F_DISABLE_GC)
+	ERTS_INTERNAL_ERROR("GC disabled");
+
     /*
      * Preliminaries.
      */
@@ -667,6 +676,8 @@ erts_garbage_collect_literals(Process* p, Eterm* literals,
     Uint n;
     struct erl_off_heap_header** prev;
 
+    if (p->flags & F_DISABLE_GC)
+	return;
     /*
      * Set GC state.
      */
diff --git a/erts/emulator/beam/erl_process.c b/erts/emulator/beam/erl_process.c
index ad806da660..13b18e9e0e 100644
--- a/erts/emulator/beam/erl_process.c
+++ b/erts/emulator/beam/erl_process.c
@@ -513,6 +513,11 @@ erts_pre_init_process(void)
      erts_psd_required_locks[ERTS_PSD_CALL_TIME_BP].set_locks
 	 = ERTS_PSD_CALL_TIME_BP_SET_LOCKS;
 
+     erts_psd_required_locks[ERTS_PSD_DELAYED_GC_TASK_QS].get_locks
+	 = ERTS_PSD_DELAYED_GC_TASK_QS_GET_LOCKS;
+     erts_psd_required_locks[ERTS_PSD_DELAYED_GC_TASK_QS].set_locks
+	 = ERTS_PSD_DELAYED_GC_TASK_QS_SET_LOCKS;
+
      /* Check that we have locks for all entries */
      for (ix = 0; ix < ERTS_PSD_SIZE; ix++) {
 	 ERTS_SMP_LC_ASSERT(erts_psd_required_locks[ix].get_locks);
@@ -7033,7 +7038,7 @@ erts_set_process_priority(Process *p, Eterm value)
 	    oprio = ERTS_PSFLGS_GET_USR_PRIO(a);
 	    n = e = a;
 
-	    if (!(a & ERTS_PSFLG_ACTIVE_SYS))
+	    if (!(a & (ERTS_PSFLG_ACTIVE_SYS|ERTS_PSFLG_DELAYED_SYS)))
 		aprio = nprio;
 	    else {
 		int max_qbit;
@@ -7043,7 +7048,15 @@ erts_set_process_priority(Process *p, Eterm value)
 		    slocked = 1;
 		}
 
-		max_qbit = p->sys_task_qs->qmask;
+		max_qbit = 0;
+		if (a & ERTS_PSFLG_ACTIVE_SYS)
+		    max_qbit |= p->sys_task_qs->qmask;
+		if (a & ERTS_PSFLG_DELAYED_SYS) {
+		    ErtsProcSysTaskQs *qs;
+		    qs = ERTS_PROC_GET_DELAYED_GC_TASK_QS(p);
+		    ASSERT(qs);
+		    max_qbit |= qs->qmask;
+		}
 		max_qbit &= -max_qbit;
 		switch (max_qbit) {
 		case MAX_BIT:
@@ -7731,12 +7744,14 @@ notify_sys_task_executed(Process *c_p, ErtsProcSysTask *st, Eterm st_result)
 }
 
 static ERTS_INLINE ErtsProcSysTask *
-fetch_sys_task(Process *c_p, erts_aint32_t state, int *qmaskp)
+fetch_sys_task(Process *c_p, erts_aint32_t state, int *qmaskp, int *priop)
 {
     ErtsProcSysTaskQs *unused_qs = NULL;
     int qbit, qmask;
     ErtsProcSysTask *st, **qp;
 
+    *priop = -1; /* Shut up annoying erroneous warning */
+
     erts_smp_proc_lock(c_p, ERTS_PROC_LOCK_STATUS);
 
     if (!c_p->sys_task_qs) {
@@ -7770,20 +7785,24 @@ fetch_sys_task(Process *c_p, erts_aint32_t state, int *qmaskp)
     switch (qbit) {
     case MAX_BIT:
 	qp = &c_p->sys_task_qs->q[PRIORITY_MAX];
+	*priop = PRIORITY_MAX;
 	break;
     case HIGH_BIT:
 	qp = &c_p->sys_task_qs->q[PRIORITY_HIGH];
+	*priop = PRIORITY_HIGH;
 	break;
     case NORMAL_BIT:
 	if (!(qmask & PRIORITY_LOW)
 	    || ++c_p->sys_task_qs->ncount <= RESCHEDULE_LOW) {
 	    qp = &c_p->sys_task_qs->q[PRIORITY_NORMAL];
+	    *priop = PRIORITY_NORMAL;
 	    break;
 	}
 	c_p->sys_task_qs->ncount = 0;
 	/* Fall through */
     case LOW_BIT:
 	qp = &c_p->sys_task_qs->q[PRIORITY_LOW];
+	*priop = PRIORITY_LOW;
 	break;
     default:
 	ERTS_INTERNAL_ERROR("Invalid qmask");
@@ -7807,6 +7826,12 @@ fetch_sys_task(Process *c_p, erts_aint32_t state, int *qmaskp)
 
 	qmask2 = qmask;
 
+	if (state & ERTS_PSFLG_DELAYED_SYS) {
+	    ErtsProcSysTaskQs *qs = ERTS_PROC_GET_DELAYED_GC_TASK_QS(c_p);
+	    ASSERT(qs);
+	    qmask2 |= qs->qmask;
+	}
+
 	switch (qmask2 & -qmask2) {
 	case MAX_BIT:
 	    st_prio = PRIORITY_MAX;
@@ -7818,17 +7843,18 @@ fetch_sys_task(Process *c_p, erts_aint32_t state, int *qmaskp)
 	    st_prio = PRIORITY_NORMAL;
 	    break;
 	case LOW_BIT:
-	    st_prio = PRIORITY_LOW;
-	    break;
 	case 0:
 	    st_prio = PRIORITY_LOW;
-	    unused_qs = c_p->sys_task_qs;
-	    c_p->sys_task_qs = NULL;
 	    break;
 	default:
 	    ERTS_INTERNAL_ERROR("Invalid qmask");
 	}
 
+	if (!qmask) {
+	    unused_qs = c_p->sys_task_qs;
+	    c_p->sys_task_qs = NULL;
+	}
+
 	a = state;
 	do {
 	    erts_aint32_t prio = ERTS_PSFLGS_GET_USR_PRIO(a);
@@ -7862,6 +7888,8 @@ done:
     return st;
 }
 
+static void save_gc_task(Process *c_p, ErtsProcSysTask *st, int prio);
+
 static int
 execute_sys_tasks(Process *c_p, erts_aint32_t *statep, int in_reds)
 {
@@ -7875,6 +7903,7 @@ execute_sys_tasks(Process *c_p, erts_aint32_t *statep, int in_reds)
 
     do {
 	ErtsProcSysTask *st;
+	int st_prio;
 	Eterm st_res;
 
 	if (state & (ERTS_PSFLG_EXITING|ERTS_PSFLG_PENDING_EXIT)) {
@@ -7886,24 +7915,39 @@ execute_sys_tasks(Process *c_p, erts_aint32_t *statep, int in_reds)
 	    break;
 	}
 
-	st = fetch_sys_task(c_p, state, &qmask);
+	st = fetch_sys_task(c_p, state, &qmask, &st_prio);
 	if (!st)
 	    break;
 
 	switch (st->type) {
 	case ERTS_PSTT_GC:
-	    if (!garbage_collected) {
-		FLAGS(c_p) |= F_NEED_FULLSWEEP;
-		reds += erts_garbage_collect(c_p, 0, c_p->arg_reg, c_p->arity);
-		garbage_collected = 1;
+	    if (c_p->flags & F_DISABLE_GC) {
+		save_gc_task(c_p, st, st_prio);
+		st = NULL;
+		reds++;
+	    }
+	    else {
+		if (!garbage_collected) {
+		    FLAGS(c_p) |= F_NEED_FULLSWEEP;
+		    reds += erts_garbage_collect(c_p,
+						 0,
+						 c_p->arg_reg,
+						 c_p->arity);
+		    garbage_collected = 1;
+		}
+		st_res = am_true;
 	    }
-	    st_res = am_true;
 	    break;
 	case ERTS_PSTT_CPC:
 	    st_res = erts_check_process_code(c_p,
 					     st->arg[0],
 					     st->arg[1] == am_true,
 					     &reds);
+	    if (is_non_value(st_res)) {
+		/* Needed gc, but gc was disabled */
+		save_gc_task(c_p, st, st_prio);
+		st = NULL;
+	    }
 	    break;
 	default:
 	    ERTS_INTERNAL_ERROR("Invalid process sys task type");
@@ -7934,8 +7978,9 @@ cleanup_sys_tasks(Process *c_p, erts_aint32_t in_state, int in_reds)
     do {
 	ErtsProcSysTask *st;
 	Eterm st_res;
+	int st_prio;
 
-	st = fetch_sys_task(c_p, state, &qmask);
+	st = fetch_sys_task(c_p, state, &qmask, &st_prio);
 	if (!st)
 	    break;
 
@@ -8168,6 +8213,183 @@ badarg:
     BIF_ERROR(BIF_P, BADARG);
 }
 
+static void
+save_gc_task(Process *c_p, ErtsProcSysTask *st, int prio)
+{
+    erts_aint32_t state;
+    ErtsProcSysTaskQs *qs;
+
+    ERTS_SMP_LC_ASSERT(ERTS_PROC_LOCK_MAIN == erts_proc_lc_my_proc_locks(c_p));
+
+    qs = ERTS_PROC_GET_DELAYED_GC_TASK_QS(c_p);
+    if (!qs) {
+	st->next = st->prev = st;
+	qs = proc_sys_task_queues_alloc();
+	qs->qmask = 1 << prio;
+	qs->ncount = 0;
+	qs->q[PRIORITY_MAX] = NULL;
+	qs->q[PRIORITY_HIGH] = NULL;
+	qs->q[PRIORITY_NORMAL] = NULL;
+	qs->q[PRIORITY_LOW] = NULL;
+	qs->q[prio] = st;
+	(void) ERTS_PROC_SET_DELAYED_GC_TASK_QS(c_p, ERTS_PROC_LOCK_MAIN, qs);
+    }
+    else {
+	if (!qs->q[prio]) {
+	    st->next = st->prev = st;
+	    qs->q[prio] = st;
+	    qs->qmask |= 1 << prio;
+	}
+	else {
+	    st->next = qs->q[prio];
+	    st->prev = qs->q[prio]->prev;
+	    st->next->prev = st;
+	    st->prev->next = st;
+	    ASSERT(qs->qmask & (1 << prio));
+	}
+    }
+
+    state = erts_smp_atomic32_read_nob(&c_p->state);
+    ASSERT((ERTS_PSFLG_RUNNING|ERTS_PSFLG_RUNNING_SYS) & state);
+
+    while (!(state & ERTS_PSFLG_DELAYED_SYS)
+	   || prio < ERTS_PSFLGS_GET_ACT_PRIO(state)) {
+	erts_aint32_t n, e;
+
+	n = e = state;
+	n |= ERTS_PSFLG_DELAYED_SYS;
+	if (prio < ERTS_PSFLGS_GET_ACT_PRIO(state)) {
+	    n &= ~ERTS_PSFLGS_ACT_PRIO_MASK;
+	    n |= prio << ERTS_PSFLGS_ACT_PRIO_OFFSET;
+	}
+	state = erts_smp_atomic32_cmpxchg_relb(&c_p->state, n, e);
+	if (state == e)
+	    break;
+    }
+}
+
+int
+erts_set_gc_state(Process *c_p, int enable)
+{
+    int res;
+    ErtsProcSysTaskQs *dgc_tsk_qs;
+    ASSERT(c_p == erts_get_current_process());
+    ASSERT((ERTS_PSFLG_RUNNING|ERTS_PSFLG_RUNNING_SYS)
+	   & erts_smp_atomic32_read_nob(&c_p->state));
+    ERTS_SMP_LC_ASSERT(ERTS_PROC_LOCK_MAIN == erts_proc_lc_my_proc_locks(c_p));
+
+    res = !(c_p->flags & F_DISABLE_GC);
+
+    if (!enable) {
+	c_p->flags |= F_DISABLE_GC;
+	return res;
+    }
+
+    c_p->flags &= ~F_DISABLE_GC;
+
+    dgc_tsk_qs = ERTS_PROC_GET_DELAYED_GC_TASK_QS(c_p);
+    if (!dgc_tsk_qs)
+	return res;
+
+    /* Move delayed gc tasks into sys tasks queues. */
+
+    erts_smp_proc_lock(c_p, ERTS_PROC_LOCK_STATUS);
+
+    if (!c_p->sys_task_qs) {
+	c_p->sys_task_qs = dgc_tsk_qs;
+	dgc_tsk_qs = NULL;
+    }
+    else {
+	ErtsProcSysTaskQs *stsk_qs;
+	int prio;
+
+	/*
+	 * We push delayed tasks to the front of the queue
+	 * since they have already made it to the front
+	 * once and then been delayed after that.
+	 */
+
+	stsk_qs = c_p->sys_task_qs;
+
+	while (dgc_tsk_qs->qmask) {
+	    int qbit = dgc_tsk_qs->qmask & -dgc_tsk_qs->qmask;
+	    dgc_tsk_qs->qmask &= ~qbit;
+	    switch (qbit) {
+	    case MAX_BIT:
+		prio = PRIORITY_MAX;
+		break;
+	    case HIGH_BIT:
+		prio = PRIORITY_HIGH;
+		break;
+	    case NORMAL_BIT:
+		prio = PRIORITY_NORMAL;
+		break;
+	    case LOW_BIT:
+		prio = PRIORITY_LOW;
+		break;
+	    default:
+		ERTS_INTERNAL_ERROR("Invalid qmask");
+		prio = -1;
+		break;
+	    }
+
+	    ASSERT(dgc_tsk_qs->q[prio]);
+
+	    if (!stsk_qs->q[prio]) {
+		stsk_qs->q[prio] = dgc_tsk_qs->q[prio];
+		stsk_qs->qmask |= 1 << prio;
+	    }
+	    else {
+		ErtsProcSysTask *first1, *last1, *first2, *last2;
+
+		ASSERT(stsk_qs->qmask & (1 << prio));
+		first1 = dgc_tsk_qs->q[prio];
+		last1 = first1->prev;
+		first2 = stsk_qs->q[prio];
+		last2 = first1->prev;
+
+		last1->next = first2;
+		first2->prev = last1;
+
+		first1->prev = last2;
+		last2->next = first1;
+
+		stsk_qs->q[prio] = first1;
+	    }
+
+	}
+    }
+
+#ifdef DEBUG
+    {
+	int qmask;
+	erts_aint32_t aprio, state =
+#endif
+
+	    erts_smp_atomic32_read_bset_nob(&c_p->state,
+					    (ERTS_PSFLG_DELAYED_SYS
+					     | ERTS_PSFLG_ACTIVE_SYS),
+					    ERTS_PSFLG_ACTIVE_SYS);
+
+#ifdef DEBUG
+	ASSERT(state & ERTS_PSFLG_DELAYED_SYS);
+	qmask = c_p->sys_task_qs->qmask;
+	aprio = ERTS_PSFLGS_GET_ACT_PRIO(state);
+	ASSERT(ERTS_PSFLGS_GET_USR_PRIO(state) >= aprio);
+	ASSERT((qmask & -qmask) >= (1 << aprio));
+    }
+#endif
+
+    erts_smp_proc_unlock(c_p, ERTS_PROC_LOCK_STATUS);
+
+    (void) ERTS_PROC_SET_DELAYED_GC_TASK_QS(c_p, ERTS_PROC_LOCK_MAIN, NULL);
+
+    if (dgc_tsk_qs)
+	proc_sys_task_queues_free(dgc_tsk_qs);
+
+    return res;
+}
+
 void
 erts_sched_stat_modify(int what)
 {
@@ -9839,6 +10061,7 @@ erts_continue_exit_process(Process *p)
 	p->flags &= ~F_USING_DB;
     }
 
+    erts_set_gc_state(p, 1);
     state = erts_smp_atomic32_read_acqb(&p->state);
     if (state & ERTS_PSFLG_ACTIVE_SYS) {
 	if (cleanup_sys_tasks(p, state, CONTEXT_REDS) >= CONTEXT_REDS/2)
diff --git a/erts/emulator/beam/erl_process.h b/erts/emulator/beam/erl_process.h
index 814e3d34df..0b8d2976ed 100644
--- a/erts/emulator/beam/erl_process.h
+++ b/erts/emulator/beam/erl_process.h
@@ -631,8 +631,9 @@ erts_smp_reset_max_len(ErtsRunQueue *rq, ErtsRunQueueInfo *rqi)
 #define ERTS_PSD_SCHED_ID			2
 #define ERTS_PSD_DIST_ENTRY			3
 #define ERTS_PSD_CALL_TIME_BP			4
+#define ERTS_PSD_DELAYED_GC_TASK_QS		5
 
-#define ERTS_PSD_SIZE				5
+#define ERTS_PSD_SIZE				6
 
 typedef struct {
     void *data[ERTS_PSD_SIZE];
@@ -656,6 +657,9 @@ typedef struct {
 #define ERTS_PSD_CALL_TIME_BP_GET_LOCKS ERTS_PROC_LOCK_MAIN
 #define ERTS_PSD_CALL_TIME_BP_SET_LOCKS ERTS_PROC_LOCK_MAIN
 
+#define ERTS_PSD_DELAYED_GC_TASK_QS_GET_LOCKS ERTS_PROC_LOCK_MAIN
+#define ERTS_PSD_DELAYED_GC_TASK_QS_SET_LOCKS ERTS_PROC_LOCK_MAIN
+
 typedef struct {
     ErtsProcLocks get_locks;
     ErtsProcLocks set_locks;
@@ -859,6 +863,7 @@ struct process {
     Uint64 bin_old_vheap;	/* Virtual old heap size for binaries */
 
     ErtsProcSysTaskQs *sys_task_qs;
+
     erts_smp_atomic32_t state;  /* Process state flags (see ERTS_PSFLG_*) */
 
 #ifdef ERTS_SMP
@@ -976,6 +981,7 @@ void erts_check_for_holes(Process* p);
 #define ERTS_PSFLG_ACTIVE_SYS		ERTS_PSFLG_BIT(14)
 #define ERTS_PSFLG_RUNNING_SYS		ERTS_PSFLG_BIT(15)
 #define ERTS_PSFLG_PROXY		ERTS_PSFLG_BIT(16)
+#define ERTS_PSFLG_DELAYED_SYS		ERTS_PSFLG_BIT(17)
 
 #define ERTS_PSFLGS_IN_PRQ_MASK 	(ERTS_PSFLG_IN_PRQ_MAX		\
 					 | ERTS_PSFLG_IN_PRQ_HIGH	\
@@ -1102,6 +1108,7 @@ extern struct erts_system_profile_flags_t erts_system_profile_flags;
 #define F_HAVE_BLCKD_MSCHED  (1 <<  8) /* Process has blocked multi-scheduling */
 #define F_P2PNR_RESCHED      (1 <<  9) /* Process has been rescheduled via erts_pid2proc_not_running() */
 #define F_FORCE_GC           (1 << 10) /* Force gc at process in-scheduling */
+#define F_DISABLE_GC         (1 << 11) /* Disable GC */
 
 /* process trace_flags */
 #define F_SENSITIVE          (1 << 0)
@@ -1192,6 +1199,7 @@ void erts_late_init_process(void);
 void erts_early_init_scheduling(int);
 void erts_init_scheduling(int, int);
 
+int erts_set_gc_state(Process *c_p, int enable);
 Eterm erts_sched_wall_time_request(Process *c_p, int set, int enable);
 Eterm erts_gc_info_request(Process *c_p);
 Uint64 erts_get_proc_interval(void);
@@ -1637,6 +1645,11 @@ erts_psd_set(Process *p, ErtsProcLocks plocks, int ix, void *data)
 #define ERTS_PROC_SET_CALL_TIME(P, L, PBT) \
   ((process_breakpoint_time_t *) erts_psd_set((P), (L), ERTS_PSD_CALL_TIME_BP, (void *) (PBT)))
 
+#define ERTS_PROC_GET_DELAYED_GC_TASK_QS(P) \
+    ((ErtsProcSysTaskQs *) erts_psd_get((P), ERTS_PSD_DELAYED_GC_TASK_QS))
+#define ERTS_PROC_SET_DELAYED_GC_TASK_QS(P, L, PBT) \
+    ((ErtsProcSysTaskQs *) erts_psd_set((P), (L), ERTS_PSD_DELAYED_GC_TASK_QS, (void *) (PBT)))
+
 
 ERTS_GLB_INLINE Eterm erts_proc_get_error_handler(Process *p);
 ERTS_GLB_INLINE Eterm erts_proc_set_error_handler(Process *p,
diff --git a/erts/emulator/beam/global.h b/erts/emulator/beam/global.h
index 885f092aca..6b720b53d8 100755
--- a/erts/emulator/beam/global.h
+++ b/erts/emulator/beam/global.h
@@ -1114,7 +1114,12 @@ erts_alloc_message_heap_state(Uint size,
 	if (statep)
 	    *statep = state;
 	if ((state & (ERTS_PSFLG_EXITING|ERTS_PSFLG_PENDING_EXIT))
+	    || (receiver->flags & F_DISABLE_GC)
 	    || HEAP_LIMIT(receiver) - HEAP_TOP(receiver) <= size) {
+	    /*
+	     * The heap is either potentially in an inconsistent
+	     * state, or not large enough.
+	     */
 #ifdef ERTS_SMP
 	    if (locked_main) {
 		*receiver_locks &= ~ERTS_PROC_LOCK_MAIN;
diff --git a/erts/emulator/test/process_SUITE.erl b/erts/emulator/test/process_SUITE.erl
index e66c6f09b6..bf31655066 100644
--- a/erts/emulator/test/process_SUITE.erl
+++ b/erts/emulator/test/process_SUITE.erl
@@ -55,7 +55,9 @@
 	 no_priority_inversion/1,
 	 no_priority_inversion2/1,
 	 system_task_blast/1,
-	 system_task_on_suspended/1]).
+	 system_task_on_suspended/1,
+	 gc_request_when_gc_disabled/1,
+	 gc_request_blast_when_gc_disabled/1]).
 -export([prio_server/2, prio_client/2]).
 
 -export([init_per_testcase/2, end_per_testcase/2]).
@@ -95,7 +97,8 @@ groups() ->
        otp_7738_resume]},
      {system_task, [],
       [no_priority_inversion, no_priority_inversion2,
-       system_task_blast, system_task_on_suspended]}].
+       system_task_blast, system_task_on_suspended,
+       gc_request_when_gc_disabled, gc_request_blast_when_gc_disabled]}].
 
 init_per_suite(Config) ->
     A0 = case application:start(sasl) of
@@ -2361,15 +2364,69 @@ system_task_on_suspended(Config) when is_list(Config) ->
 	    ok
     end.
 
-gc_req(_Pid, 0) ->
-    [];
-gc_req(Pid, N) ->
-    R0 = erts_internal:request_system_task(Pid, low, garbage_collect),
-    R1 = erts_internal:request_system_task(Pid, normal, garbage_collect),
-    R2 = erts_internal:request_system_task(Pid, high, garbage_collect),
-    R3 = erts_internal:request_system_task(Pid, max, garbage_collect),
-    [R0, R1, R2, R3 | gc_req(Pid, N-1)].
-		  
+gc_request_when_gc_disabled(Config) when is_list(Config) ->
+    Master = self(),
+    AIS = erts_debug:set_internal_state(available_internal_state, true),
+    {P, M} = spawn_opt(fun () ->
+			       true = erts_debug:set_internal_state(gc_state,
+								    false),
+			       Master ! {self(), gc_state, false},
+			       receive after 1000 -> ok end,
+			       Master ! {self(), gc_state, true},
+			       false = erts_debug:set_internal_state(gc_state,
+								     true),
+			       receive after 100 -> ok end
+		       end, [monitor, link]),
+    receive {P, gc_state, false} -> ok end,
+    ReqId = make_ref(),
+    async = garbage_collect(P, [{async, ReqId}]),
+    receive
+	{garbage_collect, ReqId, Result} ->
+	    ?t:fail({unexpected_gc, Result});
+	{P, gc_state, true} ->
+	    ok
+    end,
+    receive {garbage_collect, ReqId, true} -> ok end,
+    erts_debug:set_internal_state(available_internal_state, AIS),
+    receive {'DOWN', M, process, P, _Reason} -> ok end,
+    ok.
+
+gc_request_blast_when_gc_disabled(Config) when is_list(Config) ->
+    Master = self(),
+    AIS = erts_debug:set_internal_state(available_internal_state, true),
+    {P, M} = spawn_opt(fun () ->
+			       true = erts_debug:set_internal_state(gc_state,
+								    false),
+			       Master ! {self(), gc_state, false},
+			       receive after 1000 -> ok end,
+			       false = erts_debug:set_internal_state(gc_state,
+								     true),
+			       receive after 100 -> ok end
+		       end, [monitor, link]),
+    receive {P, gc_state, false} -> ok end,
+    PMs = lists:map(fun (N) ->
+			    Prio = case N rem 4 of
+				       0 -> max;
+				       1 -> high;
+				       2 -> normal;
+				       3 -> low
+				   end,
+			    spawn_opt(fun () ->
+					      erlang:garbage_collect(P)
+				      end, [monitor, link, {priority, Prio}])
+		    end, lists:seq(1, 10000)),
+    lists:foreach(fun ({Proc, Mon}) ->
+			  receive
+			      {'DOWN', Mon, process, Proc, normal} ->
+				  ok
+			  end
+		  end,
+		  PMs),
+    erts_debug:set_internal_state(available_internal_state, AIS),
+    receive {'DOWN', M, process, P, _Reason} -> ok end,
+    ok.
+
+
 %% Internal functions
 
 wait_until(Fun) ->
diff --git a/erts/etc/unix/etp-commands.in b/erts/etc/unix/etp-commands.in
index 6e3466b8c0..73887931cc 100644
--- a/erts/etc/unix/etp-commands.in
+++ b/erts/etc/unix/etp-commands.in
@@ -1316,9 +1316,12 @@ end
 define etp-proc-state-int
 # Args: int
 #
-  if ($arg0 & 0xff800000)
+  if ($arg0 & 0xff000000)
     printf "GARBAGE | "
   end
+  if ($arg0 & 0x800000)
+    printf "delayed-sys | "
+  end
   if ($arg0 & 0x400000)
     printf "proxy | "
     set $proxy_process = 1