Switch between scheduler types when multi-scheduling is blocked

5 files changed, 677 insertions, 352 deletions

diff --git a/erts/emulator/beam/bif.h b/erts/emulator/beam/bif.h
index ad55b19d0a..01cca90a7a 100644
--- a/erts/emulator/beam/bif.h
+++ b/erts/emulator/beam/bif.h
@@ -498,12 +498,6 @@ erts_bif_prep_await_proc_exit_apply_trap(Process *c_p,
 					 Eterm args[],
 					 int nargs);
 
-typedef enum {
-    ERTS_SCHED_NORMAL,
-    ERTS_SCHED_DIRTY_CPU,
-    ERTS_SCHED_DIRTY_IO
-} ErtsSchedType;
-
 #ifdef ERTS_DIRTY_SCHEDULERS
 int erts_call_dirty_bif(ErtsSchedulerData *esdp, Process *c_p,
 			BeamInstr *I, Eterm *reg);
diff --git a/erts/emulator/beam/erl_port_task.c b/erts/emulator/beam/erl_port_task.c
index 3102e44c11..4836b9e2d3 100644
--- a/erts/emulator/beam/erl_port_task.c
+++ b/erts/emulator/beam/erl_port_task.c
@@ -936,7 +936,7 @@ enqueue_port(ErtsRunQueue *runq, Port *pp)
     erts_smp_inc_runq_len(runq, &runq->ports.info, ERTS_PORT_PRIO_LEVEL);
 
 #ifdef ERTS_SMP
-    if (runq->halt_in_progress)
+    if (ERTS_RUNQ_FLGS_GET_NOB(runq) & ERTS_RUNQ_FLG_HALTING)
 	erts_non_empty_runq(runq);
 #endif
 }
diff --git a/erts/emulator/beam/erl_process.c b/erts/emulator/beam/erl_process.c
index da4b468d66..084ecb14ec 100644
--- a/erts/emulator/beam/erl_process.c
+++ b/erts/emulator/beam/erl_process.c
@@ -107,9 +107,31 @@
 #define LOW_BIT       (1 << PRIORITY_LOW)
 #define PORT_BIT      (1 << ERTS_PORT_PRIO_LEVEL)
 
-#define ERTS_EMPTY_RUNQ(RQ)					\
-    ((ERTS_RUNQ_FLGS_GET_NOB((RQ)) & ERTS_RUNQ_FLGS_QMASK) == 0	\
-     && (RQ)->misc.start == NULL)
+#define ERTS_IS_RUNQ_EMPTY_FLGS(FLGS) \
+    (!((FLGS) & (ERTS_RUNQ_FLGS_QMASK|ERTS_RUNQ_FLG_MISC_OP)))
+
+#define ERTS_IS_RUNQ_EMPTY_PORTS_FLGS(FLGS) \
+    (!((FLGS) & (PORT_BIT|ERTS_RUNQ_FLG_MISC_OP)))
+
+#define ERTS_EMPTY_RUNQ(RQ) \
+    ERTS_IS_RUNQ_EMPTY_FLGS(ERTS_RUNQ_FLGS_GET_NOB((RQ)))
+
+#define ERTS_EMPTY_RUNQ_PORTS(RQ) \
+    ERTS_IS_RUNQ_EMPTY_FLGS(ERTS_RUNQ_FLGS_GET_NOB((RQ)))
+
+static ERTS_INLINE int
+runq_got_work_to_execute_flags(Uint32 flags)
+{
+    if (flags & ERTS_RUNQ_FLG_HALTING)
+        return !ERTS_IS_RUNQ_EMPTY_PORTS_FLGS(flags);
+    return !ERTS_IS_RUNQ_EMPTY_FLGS(flags);
+}
+
+static ERTS_INLINE int
+runq_got_work_to_execute(ErtsRunQueue *rq)
+{
+    return runq_got_work_to_execute_flags(ERTS_RUNQ_FLGS_GET_NOB(rq));
+}
 
 #undef RUNQ_READ_RQ
 #undef RUNQ_SET_RQ
@@ -141,9 +163,6 @@ do { \
 #  define ERTS_DBG_VERIFY_VALID_RUNQP(RQP)
 #endif
 
-#define ERTS_EMPTY_RUNQ_PORTS(RQ) \
-    (RUNQ_READ_LEN(&(RQ)->ports.info.len) == 0 && (RQ)->misc.start == NULL)
-
 const Process erts_invalid_process = {{ERTS_INVALID_PID}};
 
 extern BeamInstr beam_apply[];
@@ -200,158 +219,139 @@ typedef struct {
     ErtsProcList *chngq;
 } ErtsMultiSchedulingBlock;
 
+typedef struct {
+    Uint32 normal;
+#ifdef ERTS_DIRTY_SCHEDULERS
+    Uint32 dirty_cpu;
+    Uint32 dirty_io;
+#endif
+} ErtsSchedTypeCounters;
+
 static struct {
     erts_smp_mtx_t mtx;
-    Uint32 online;
-    Uint32 curr_online;
-    Uint32 active;
+    ErtsSchedTypeCounters online;
+    ErtsSchedTypeCounters curr_online;
+    ErtsSchedTypeCounters active;
     erts_smp_atomic32_t changing;
     ErtsProcList *chngq;
     Eterm changer;
     ErtsMultiSchedulingBlock nmsb; /* Normal multi Scheduling Block */
     ErtsMultiSchedulingBlock msb; /* Multi Scheduling Block */
+#ifdef ERTS_DIRTY_SCHEDULERS
+    ErtsSchedType last_msb_dirty_type;
+#endif
 } schdlr_sspnd;
 
-#define ERTS_SCHDLR_SSPND_S_BITS	10
-#define ERTS_SCHDLR_SSPND_DCS_BITS	11
-#define ERTS_SCHDLR_SSPND_DIS_BITS	11
-
-#define ERTS_SCHDLR_SSPND_S_MASK	((1 << ERTS_SCHDLR_SSPND_S_BITS)-1)
-#define ERTS_SCHDLR_SSPND_DCS_MASK	((1 << ERTS_SCHDLR_SSPND_DCS_BITS)-1)
-#define ERTS_SCHDLR_SSPND_DIS_MASK	((1 << ERTS_SCHDLR_SSPND_DIS_BITS)-1)
-
-#define ERTS_SCHDLR_SSPND_S_SHIFT	0
-#define ERTS_SCHDLR_SSPND_DCS_SHIFT	(ERTS_SCHDLR_SSPND_S_SHIFT \
-					 + ERTS_SCHDLR_SSPND_S_BITS)
-#define ERTS_SCHDLR_SSPND_DIS_SHIFT	(ERTS_SCHDLR_SSPND_DCS_SHIFT \
-					 + ERTS_SCHDLR_SSPND_DCS_BITS)
-
-#if (ERTS_SCHDLR_SSPND_S_BITS		\
-     + ERTS_SCHDLR_SSPND_DCS_BITS	\
-     + ERTS_SCHDLR_SSPND_DIS_BITS) > 32
-#  error Wont fit in Uint32
-#endif
+static void init_scheduler_suspend(void);
 
-#if (ERTS_MAX_NO_OF_SCHEDULERS-1) > ERTS_SCHDLR_SSPND_S_MASK
-#  error Max no schedulers wont fit in its bit-field
-#endif
-#if ERTS_MAX_NO_OF_DIRTY_CPU_SCHEDULERS > ERTS_SCHDLR_SSPND_DCS_MASK
-#  error Max no dirty cpu schedulers wont fit in its bit-field
-#endif
-#if ERTS_MAX_NO_OF_DIRTY_IO_SCHEDULERS > ERTS_SCHDLR_SSPND_DIS_MASK
-#  error Max no dirty io schedulers wont fit in its bit-field
+static ERTS_INLINE Uint32
+schdlr_sspnd_eq_nscheds(ErtsSchedTypeCounters *val1p, ErtsSchedTypeCounters *val2p)
+{
+    int res = val1p->normal == val2p->normal;
+#ifdef ERTS_DIRTY_SCHEDULERS
+    res &= val1p->dirty_cpu == val2p->dirty_cpu;
+    res &= val1p->dirty_io == val2p->dirty_io;
 #endif
-
-#define ERTS_SCHDLR_SSPND_MAKE_NSCHEDS_VAL(S, DCS, DIS)			\
-    ((((Uint32) (((S) & ERTS_SCHDLR_SSPND_S_MASK))-1)			\
-      << ERTS_SCHDLR_SSPND_S_SHIFT)					\
-     | ((((Uint32) ((DCS) & ERTS_SCHDLR_SSPND_DCS_MASK))		\
-	 << ERTS_SCHDLR_SSPND_DCS_SHIFT))				\
-     | ((((Uint32) ((DIS) & ERTS_SCHDLR_SSPND_DIS_MASK))		\
-	 << ERTS_SCHDLR_SSPND_DIS_SHIFT)))
-
-static void init_scheduler_suspend(void);
+    return res;
+}
 
 static ERTS_INLINE Uint32
-schdlr_sspnd_get_nscheds(Uint32 *valp, ErtsSchedType type)
+schdlr_sspnd_get_nscheds(ErtsSchedTypeCounters *valp,
+                         ErtsSchedType type)
 {
-    Uint32 res = (Uint32) (*valp);
     switch (type) {
     case ERTS_SCHED_NORMAL:
-	res >>= ERTS_SCHDLR_SSPND_S_SHIFT;
-	res &= (Uint32) ERTS_SCHDLR_SSPND_S_MASK;
-	res++;
-	break;
+        return valp->normal;
+#ifdef ERTS_DIRTY_SCHEDULERS
     case ERTS_SCHED_DIRTY_CPU:
-	res >>= ERTS_SCHDLR_SSPND_DCS_SHIFT;
-	res &= (Uint32) ERTS_SCHDLR_SSPND_DCS_MASK;
-	break;
+        return valp->dirty_cpu;
     case ERTS_SCHED_DIRTY_IO:
-	res >>= ERTS_SCHDLR_SSPND_DIS_SHIFT;
-	res &= (Uint32) ERTS_SCHDLR_SSPND_DIS_MASK;
-	break;
+        return valp->dirty_io;
+#else
+    case ERTS_SCHED_DIRTY_CPU:
+    case ERTS_SCHED_DIRTY_IO:
+        return 0;
+#endif
     default:
 	ERTS_INTERNAL_ERROR("Invalid scheduler type");
 	return 0;
     }
+}
 
+static ERTS_INLINE Uint32
+schdlr_sspnd_get_nscheds_tot(ErtsSchedTypeCounters *valp)
+{
+    Uint32 res = valp->normal;
+#ifdef ERTS_DIRTY_SCHEDULERS
+    res += valp->dirty_cpu;
+    res += valp->dirty_io;
+#endif
     return res;
 }
 
 static ERTS_INLINE void
-schdlr_sspnd_dec_nscheds(Uint32 *valp, ErtsSchedType type)
+schdlr_sspnd_dec_nscheds(ErtsSchedTypeCounters *valp,
+                         ErtsSchedType type)
 {
     ASSERT(schdlr_sspnd_get_nscheds(valp, type) > 0);
 
     switch (type) {
     case ERTS_SCHED_NORMAL:
-	*valp -= ((Uint32) 1) << ERTS_SCHDLR_SSPND_S_SHIFT;
+        valp->normal--;
 	break;
+#ifdef ERTS_DIRTY_SCHEDULERS
     case ERTS_SCHED_DIRTY_CPU:
-	*valp -= ((Uint32) 1) << ERTS_SCHDLR_SSPND_DCS_SHIFT;
+        valp->dirty_cpu--;
 	break;
     case ERTS_SCHED_DIRTY_IO:
-	*valp -= ((Uint32) 1) << ERTS_SCHDLR_SSPND_DIS_SHIFT;
+        valp->dirty_io--;
 	break;
+#endif
     default:
 	ERTS_INTERNAL_ERROR("Invalid scheduler type");
     }
 }
 
 static ERTS_INLINE void
-schdlr_sspnd_inc_nscheds(Uint32 *valp, ErtsSchedType type)
+schdlr_sspnd_inc_nscheds(ErtsSchedTypeCounters *valp,
+                         ErtsSchedType type)
 {
     switch (type) {
     case ERTS_SCHED_NORMAL:
-	ASSERT(schdlr_sspnd_get_nscheds(valp, type)
-	       < ERTS_MAX_NO_OF_SCHEDULERS-1);
-	*valp += ((Uint32) 1) << ERTS_SCHDLR_SSPND_S_SHIFT;
+        valp->normal++;
 	break;
+#ifdef ERTS_DIRTY_SCHEDULERS
     case ERTS_SCHED_DIRTY_CPU:
-	ASSERT(schdlr_sspnd_get_nscheds(valp, type)
-	       < ERTS_MAX_NO_OF_DIRTY_CPU_SCHEDULERS);
-	*valp += ((Uint32) 1) << ERTS_SCHDLR_SSPND_DCS_SHIFT;
+        valp->dirty_cpu++;
 	break;
     case ERTS_SCHED_DIRTY_IO:
-	ASSERT(schdlr_sspnd_get_nscheds(valp, type)
-	       < ERTS_MAX_NO_OF_DIRTY_IO_SCHEDULERS);
-	*valp += ((Uint32) 1) << ERTS_SCHDLR_SSPND_DIS_SHIFT;
+        valp->dirty_io++;
 	break;
+#endif
     default:
 	ERTS_INTERNAL_ERROR("Invalid scheduler type");
     }
 }
 
 static ERTS_INLINE void
-schdlr_sspnd_set_nscheds(Uint32 *valp, ErtsSchedType type, Uint32 no)
+schdlr_sspnd_set_nscheds(ErtsSchedTypeCounters *valp,
+                         ErtsSchedType type, Uint32 no)
 {
-    Uint32 val = *valp;
-
     switch (type) {
     case ERTS_SCHED_NORMAL:
-	ASSERT(no > 0);
-	val &= ~(((Uint32) ERTS_SCHDLR_SSPND_S_MASK)
-		 << ERTS_SCHDLR_SSPND_S_SHIFT);
-	val |= (((no-1) & ((Uint32) ERTS_SCHDLR_SSPND_S_MASK))
-		<< ERTS_SCHDLR_SSPND_S_SHIFT);
+        valp->normal = no;
 	break;
+#ifdef ERTS_DIRTY_SCHEDULERS
     case ERTS_SCHED_DIRTY_CPU:
-	val &= ~(((Uint32) ERTS_SCHDLR_SSPND_DCS_MASK)
-		 << ERTS_SCHDLR_SSPND_DCS_SHIFT);
-	val |= ((no & ((Uint32) ERTS_SCHDLR_SSPND_DCS_MASK))
-		 << ERTS_SCHDLR_SSPND_DCS_SHIFT);
+        valp->dirty_cpu = no;
 	break;
     case ERTS_SCHED_DIRTY_IO:
-	val &= ~(((Uint32) ERTS_SCHDLR_SSPND_DIS_MASK)
-		 << ERTS_SCHDLR_SSPND_DIS_SHIFT);
-	val |= ((no & ((Uint32) ERTS_SCHDLR_SSPND_DIS_MASK))
-		<< ERTS_SCHDLR_SSPND_DIS_SHIFT);
+        valp->dirty_io = no;
 	break;
+#endif
     default:
 	ERTS_INTERNAL_ERROR("Invalid scheduler type");
     }
-
-    *valp = val;
 }
 
 static struct {
@@ -2293,7 +2293,8 @@ static ERTS_INLINE erts_aint32_t
 handle_reap_ports(ErtsAuxWorkData *awdp, erts_aint32_t aux_work, int waiting)
 {
     unset_aux_work_flags(awdp->ssi, ERTS_SSI_AUX_WORK_REAP_PORTS);
-    awdp->esdp->run_queue->halt_in_progress = 1;
+    ERTS_RUNQ_FLGS_SET(awdp->esdp->run_queue, ERTS_RUNQ_FLG_HALTING);
+
     if (erts_smp_atomic32_dec_read_acqb(&erts_halt_progress) == 0) {
 	int i, max = erts_ptab_max(&erts_port);
 	erts_smp_atomic32_set_nob(&erts_halt_progress, 1);
@@ -2833,11 +2834,12 @@ static erts_aint32_t
 sched_prep_spin_wait(ErtsSchedulerSleepInfo *ssi)
 {
     erts_aint32_t oflgs;
-    erts_aint32_t nflgs = (ERTS_SSI_FLG_SLEEPING
-			   | ERTS_SSI_FLG_WAITING);
+    erts_aint32_t nflgs;
     erts_aint32_t xflgs = 0;
 
     do {
+        nflgs = (xflgs & ERTS_SSI_FLG_MSB_EXEC);
+        nflgs |= ERTS_SSI_FLG_SLEEPING|ERTS_SSI_FLG_WAITING;
 	oflgs = erts_smp_atomic32_cmpxchg_acqb(&ssi->flags, nflgs, xflgs);
 	if (oflgs == xflgs)
 	    return nflgs;
@@ -2859,7 +2861,7 @@ sched_prep_cont_spin_wait(ErtsSchedulerSleepInfo *ssi)
 	if (oflgs == xflgs)
 	    return nflgs;
 	xflgs = oflgs;
-	nflgs |= oflgs & ERTS_SSI_FLG_SUSPENDED;
+	nflgs |= oflgs & (ERTS_SSI_FLG_SUSPENDED|ERTS_SSI_FLG_MSB_EXEC);
     } while (oflgs & ERTS_SSI_FLG_WAITING);
     return oflgs;
 }
@@ -2909,7 +2911,7 @@ sched_set_sleeptype(ErtsSchedulerSleepInfo *ssi, erts_aint32_t sleep_type)
 	    return oflgs;
 	}
 	xflgs = oflgs;
-	nflgs |= oflgs & ERTS_SSI_FLG_SUSPENDED;
+	nflgs |= oflgs & (ERTS_SSI_FLG_SUSPENDED|ERTS_SSI_FLG_MSB_EXEC);
     }
 }
 
@@ -3044,6 +3046,8 @@ aux_thread(void *unused)
     return NULL;
 }
 
+static void suspend_scheduler(ErtsSchedulerData *esdp);
+
 #endif /* ERTS_SMP */
 
 static void
@@ -3209,8 +3213,10 @@ scheduler_wait(int *fcalls, ErtsSchedulerData *esdp, ErtsRunQueue *rq)
 
 	}
 
-	if (flgs & ~ERTS_SSI_FLG_SUSPENDED)
-	    erts_smp_atomic32_read_band_nob(&ssi->flags, ERTS_SSI_FLG_SUSPENDED);
+	if (flgs & ~(ERTS_SSI_FLG_SUSPENDED|ERTS_SSI_FLG_MSB_EXEC))
+	    erts_smp_atomic32_read_band_nob(&ssi->flags,
+                                            (ERTS_SSI_FLG_SUSPENDED
+                                             | ERTS_SSI_FLG_MSB_EXEC));
 
 	if (!ERTS_SCHEDULER_IS_DIRTY(esdp) && !thr_prgr_active) {
 	    erts_thr_progress_active(esdp, thr_prgr_active = 1);
@@ -3409,8 +3415,10 @@ scheduler_wait(int *fcalls, ErtsSchedulerData *esdp, ErtsRunQueue *rq)
 	    erts_smp_runq_lock(rq);
 	}
 	clear_sys_scheduling();
-	if (flgs & ~ERTS_SSI_FLG_SUSPENDED)
-	    erts_smp_atomic32_read_band_nob(&ssi->flags, ERTS_SSI_FLG_SUSPENDED);
+	if (flgs & ~(ERTS_SSI_FLG_SUSPENDED|ERTS_SSI_FLG_MSB_EXEC))
+	    erts_smp_atomic32_read_band_nob(&ssi->flags,
+                                            (ERTS_SSI_FLG_SUSPENDED
+                                             | ERTS_SSI_FLG_MSB_EXEC));
 #endif
 	if (!working)
 	    sched_wall_time_change(esdp, working = 1);
@@ -3433,17 +3441,54 @@ ssi_flags_set_wake(ErtsSchedulerSleepInfo *ssi)
 	oflgs = erts_smp_atomic32_cmpxchg_relb(&ssi->flags, nflgs, xflgs);
 	if (oflgs == xflgs)
 	    return oflgs;
-	nflgs = oflgs & ERTS_SSI_FLG_SUSPENDED;
+	nflgs = oflgs & (ERTS_SSI_FLG_SUSPENDED|ERTS_SSI_FLG_MSB_EXEC);
 	xflgs = oflgs;
     }
 }
 
+static ERTS_INLINE void
+ssi_wake(ErtsSchedulerSleepInfo *ssi)
+{
+    erts_sched_finish_poke(ssi, ssi_flags_set_wake(ssi));
+}
+
+#ifdef ERTS_DIRTY_SCHEDULERS
+
 static void
-wake_scheduler(ErtsRunQueue *rq)
+dcpu_sched_ix_suspend_wake(Uint ix)
 {
-    ErtsSchedulerSleepInfo *ssi;
-    erts_aint32_t flgs;
+    ErtsSchedulerSleepInfo* ssi = ERTS_DIRTY_CPU_SCHED_SLEEP_INFO_IX(ix);
+    erts_smp_atomic32_read_bor_nob(&ssi->flags, ERTS_SSI_FLG_SUSPENDED);
+    ssi_wake(ssi);
+}
+
+static void
+dio_sched_ix_suspend_wake(Uint ix)
+{
+    ErtsSchedulerSleepInfo* ssi = ERTS_DIRTY_IO_SCHED_SLEEP_INFO_IX(ix);
+    erts_smp_atomic32_read_bor_nob(&ssi->flags, ERTS_SSI_FLG_SUSPENDED);
+    ssi_wake(ssi);
+}
+
+static void
+dcpu_sched_ix_wake(Uint ix)
+{
+    ssi_wake(ERTS_DIRTY_CPU_SCHED_SLEEP_INFO_IX(ix));
+}
+
+#if 0
+static void
+dio_sched_ix_wake(Uint ix)
+{
+    ssi_wake(ERTS_DIRTY_IO_SCHED_SLEEP_INFO_IX(ix));
+}
+#endif
 
+#endif
+
+static void
+wake_scheduler(ErtsRunQueue *rq)
+{
     /*
      * The unlocked run queue is not strictly necessary
      * from a thread safety or deadlock prevention
@@ -3455,10 +3500,7 @@ wake_scheduler(ErtsRunQueue *rq)
     ERTS_SMP_LC_ASSERT(!erts_smp_lc_runq_is_locked(rq)
 		       || ERTS_RUNQ_IX_IS_DIRTY(rq->ix));
 
-    ssi = rq->scheduler->ssi;
-
-    flgs = ssi_flags_set_wake(ssi);
-    erts_sched_finish_poke(ssi, flgs);
+    ssi_wake(rq->scheduler->ssi);
 }
 
 #ifdef ERTS_DIRTY_SCHEDULERS
@@ -3505,6 +3547,13 @@ wake_dirty_schedulers(ErtsRunQueue *rq, int one)
 	} while (ssi);
     }
 }
+
+static void
+wake_dirty_scheduler(ErtsRunQueue *rq)
+{
+    wake_dirty_schedulers(rq, 1);
+}
+
 #endif
 
 #define ERTS_NO_USED_RUNQS_SHIFT 16
@@ -3645,7 +3694,7 @@ smp_notify_inc_runq(ErtsRunQueue *runq)
     if (runq) {
 #ifdef ERTS_DIRTY_SCHEDULERS
 	if (ERTS_RUNQ_IX_IS_DIRTY(runq->ix))
-	    wake_dirty_schedulers(runq, 1);
+	    wake_dirty_scheduler(runq);
 	else
 #endif
 	    wake_scheduler(runq);
@@ -3949,8 +3998,7 @@ suspend_run_queue(ErtsRunQueue *rq)
     wake_scheduler(rq);
 }
 
-static void scheduler_ix_resume_wake(Uint ix);
-static void scheduler_ssi_resume_wake(ErtsSchedulerSleepInfo *ssi);
+static void nrml_sched_ix_resume_wake(Uint ix);
 
 static ERTS_INLINE void
 resume_run_queue(ErtsRunQueue *rq)
@@ -3958,16 +4006,19 @@ resume_run_queue(ErtsRunQueue *rq)
     int pix;
     Uint32 oflgs;
 
+    ASSERT(!ERTS_RUNQ_IX_IS_DIRTY(rq->ix));
+
     erts_smp_runq_lock(rq);
 
     oflgs = ERTS_RUNQ_FLGS_READ_BSET(rq,
 				     (ERTS_RUNQ_FLG_OUT_OF_WORK
 				      | ERTS_RUNQ_FLG_HALFTIME_OUT_OF_WORK
-				      | ERTS_RUNQ_FLG_SUSPENDED),
+				      | ERTS_RUNQ_FLG_SUSPENDED
+                                      | ERTS_RUNQ_FLG_MSB_EXEC),
 				     (ERTS_RUNQ_FLG_OUT_OF_WORK
 				      | ERTS_RUNQ_FLG_HALFTIME_OUT_OF_WORK));
 
-    if (oflgs & ERTS_RUNQ_FLG_SUSPENDED) {
+    if (oflgs & (ERTS_RUNQ_FLG_SUSPENDED|ERTS_RUNQ_FLG_MSB_EXEC)) {
 	erts_aint32_t len;
 
 	rq->check_balance_reds = ERTS_RUNQ_CALL_CHECK_BALANCE_REDS;
@@ -3986,10 +4037,7 @@ resume_run_queue(ErtsRunQueue *rq)
 
     erts_smp_runq_unlock(rq);
 
-#ifdef ERTS_DIRTY_SCHEDULERS
-    if (!ERTS_RUNQ_IX_IS_DIRTY(rq->ix))
-#endif
-	scheduler_ix_resume_wake(rq->ix);
+    nrml_sched_ix_resume_wake(rq->ix);
 }
 
 typedef struct {
@@ -4047,28 +4095,22 @@ evacuate_run_queue(ErtsRunQueue *rq,
     int prio_q;
     ErtsRunQueue *to_rq;
     ErtsMigrationPaths *mps;
-    ErtsMigrationPath *mp = NULL;
+    ErtsMigrationPath *mp;
 
     ERTS_SMP_LC_ASSERT(erts_smp_lc_runq_is_locked(rq));
 
     (void) ERTS_RUNQ_FLGS_UNSET(rq, ERTS_RUNQ_FLG_PROTECTED);
 
-#ifdef ERTS_DIRTY_SCHEDULERS
-    if (!ERTS_RUNQ_IX_IS_DIRTY(rq->ix))
-#endif
-    {
-	mps = erts_get_migration_paths_managed();
-	mp = &mps->mpath[rq->ix];
-    }
+    ASSERT(!ERTS_RUNQ_IX_IS_DIRTY(rq->ix));
+
+    mps = erts_get_migration_paths_managed();
+    mp = &mps->mpath[rq->ix];
 
     /* Evacuate scheduled misc ops */
 
     if (rq->misc.start) {
 	ErtsMiscOpList *start, *end;
 
-#ifdef ERTS_DIRTY_SCHEDULERS
-	ASSERT(!ERTS_RUNQ_IX_IS_DIRTY(rq->ix));
-#endif
 	to_rq = mp->misc_evac_runq;
 	if (!to_rq)
 	    return;
@@ -4077,6 +4119,7 @@ evacuate_run_queue(ErtsRunQueue *rq,
 	end = rq->misc.end;
 	rq->misc.start = NULL;
 	rq->misc.end = NULL;
+        ERTS_RUNQ_FLGS_UNSET_NOB(rq, ERTS_RUNQ_FLG_MISC_OP);
 	erts_smp_runq_unlock(rq);
 
 	erts_smp_runq_lock(to_rq);
@@ -4097,9 +4140,6 @@ evacuate_run_queue(ErtsRunQueue *rq,
     if (rq->ports.start) {
 	Port *prt;
 
-#ifdef ERTS_DIRTY_SCHEDULERS
-	ASSERT(!ERTS_RUNQ_IX_IS_DIRTY(rq->ix));
-#endif
 	to_rq = mp->prio[ERTS_PORT_PRIO_LEVEL].runq;
 	if (!to_rq)
 	    return;
@@ -4137,15 +4177,10 @@ evacuate_run_queue(ErtsRunQueue *rq,
 	int notify = 0;
 	to_rq = NULL;
 
-#ifdef ERTS_DIRTY_SCHEDULERS
-	if (!ERTS_RUNQ_IX_IS_DIRTY(rq->ix))
-#endif
-	{
-	    if (!mp->prio[prio_q].runq)
-		return;
-	    if (prio_q == PRIORITY_NORMAL && !mp->prio[PRIORITY_LOW].runq)
-		return;
-	}
+        if (!mp->prio[prio_q].runq)
+            return;
+        if (prio_q == PRIORITY_NORMAL && !mp->prio[PRIORITY_LOW].runq)
+            return;
 
 	proc = dequeue_process(rq, prio_q, &state);
 	while (proc) {
@@ -4201,11 +4236,6 @@ evacuate_run_queue(ErtsRunQueue *rq,
 		goto handle_next_proc;
 	    }
 
-#ifdef ERTS_DIRTY_SCHEDULERS
-	    if (ERTS_RUNQ_IX_IS_DIRTY(rq->ix))
-		clear_proc_dirty_queue_bit(real_proc, rq, qbit);
-#endif
-
 	    if (ERTS_PSFLG_BOUND & real_state) {
 		/* Bound processes get stuck here... */
 		proc->next = NULL;
@@ -4219,16 +4249,7 @@ evacuate_run_queue(ErtsRunQueue *rq,
 		int prio = (int) ERTS_PSFLGS_GET_PRQ_PRIO(state);
 		erts_smp_runq_unlock(rq);
 
-#ifdef ERTS_DIRTY_SCHEDULERS
-		if (ERTS_RUNQ_IX_IS_DIRTY(rq->ix))
-		    /*
-		     * dirty run queues evacuate only to run
-		     * queue 0 during multi-scheduling blocking
-		     */
-		    to_rq = ERTS_RUNQ_IX(0);
-		else
-#endif
-		    to_rq = mp->prio[prio].runq;
+                to_rq = mp->prio[prio].runq;
 		RUNQ_SET_RQ(&proc->run_queue, to_rq);
 
 		erts_smp_runq_lock(to_rq);
@@ -4263,7 +4284,7 @@ try_steal_task_from_victim(ErtsRunQueue *rq, int *rq_lockedp, ErtsRunQueue *vrq,
 
     erts_smp_runq_lock(vrq);
 
-    if (rq->halt_in_progress)
+    if (ERTS_RUNQ_FLGS_GET_NOB(rq) & ERTS_RUNQ_FLG_HALTING)
 	goto no_procs;
 
     /*
@@ -4362,8 +4383,7 @@ check_possible_steal_victim(ErtsRunQueue *rq, int *rq_lockedp, int vix)
 {
     ErtsRunQueue *vrq = ERTS_RUNQ_IX(vix);
     Uint32 flags = ERTS_RUNQ_FLGS_GET(vrq);
-    if ((flags & (ERTS_RUNQ_FLG_NONEMPTY
-		  | ERTS_RUNQ_FLG_PROTECTED)) == ERTS_RUNQ_FLG_NONEMPTY)
+    if (runq_got_work_to_execute_flags(flags) & (!(flags & ERTS_RUNQ_FLG_PROTECTED)))
 	return try_steal_task_from_victim(rq, rq_lockedp, vrq, flags);
     else
 	return 0;
@@ -4431,11 +4451,9 @@ try_steal_task(ErtsRunQueue *rq)
     if (!rq_locked)
 	erts_smp_runq_lock(rq);
 
-    if (!res)
-	res = rq->halt_in_progress ?
-	    !ERTS_EMPTY_RUNQ_PORTS(rq) : !ERTS_EMPTY_RUNQ(rq);
-
-    return res;
+    if (res)
+        return res;
+    return runq_got_work_to_execute(rq);
 }
 
 /* Run queue balancing */
@@ -5347,7 +5365,7 @@ wakeup_other_check(ErtsRunQueue *rq, Uint32 flags)
 #ifdef ERTS_DIRTY_SCHEDULERS
 		if (ERTS_RUNQ_IX_IS_DIRTY(rq->ix)) {
 		    if (rq->waiting) {
-			wake_dirty_schedulers(rq, 1);
+			wake_dirty_scheduler(rq);
 		    }
 		} else
 #endif
@@ -5710,13 +5728,29 @@ init_scheduler_data(ErtsSchedulerData* esdp, int num,
 	erts_alloc_permanent_cache_aligned(ERTS_ALC_T_BEAM_REGISTER,
 					   MAX_REG * sizeof(FloatDef));
 #ifdef ERTS_DIRTY_SCHEDULERS
+    esdp->run_queue = runq;
     if (ERTS_RUNQ_IX_IS_DIRTY(runq->ix)) {
 	esdp->no = 0;
+        if (runq == ERTS_DIRTY_CPU_RUNQ)
+            esdp->type = ERTS_SCHED_DIRTY_CPU;
+        else {
+            ASSERT(runq == ERTS_DIRTY_IO_RUNQ);
+            esdp->type = ERTS_SCHED_DIRTY_IO;
+        }
 	ERTS_DIRTY_SCHEDULER_NO(esdp) = (Uint) num;
+        if (num == 1) {
+            /*
+             * Multi-scheduling block functionality depends
+             * on finding dirty scheduler number 1 here...
+             */
+            runq->scheduler = esdp;
+        }
     }
     else {
+        esdp->type = ERTS_SCHED_NORMAL;
 	esdp->no = (Uint) num;
 	ERTS_DIRTY_SCHEDULER_NO(esdp) = 0;
+        runq->scheduler = esdp;
     }
     esdp->dirty_shadow_process = shadow_proc;
     if (shadow_proc) {
@@ -5728,6 +5762,8 @@ init_scheduler_data(ErtsSchedulerData* esdp, int num,
 	shadow_proc->static_flags = ERTS_STC_FLG_SHADOW_PROC;
     }
 #else
+    runq->scheduler = esdp;
+    esdp->run_queue = runq;
     esdp->no = (Uint) num;
 #endif
 
@@ -5740,9 +5776,6 @@ init_scheduler_data(ErtsSchedulerData* esdp, int num,
 
     erts_init_atom_cache_map(&esdp->atom_cache_map);
 
-    esdp->run_queue = runq;
-    esdp->run_queue->scheduler = esdp;
-
     esdp->last_monotonic_time = 0;
     esdp->check_time_reds = 0;
 
@@ -5858,7 +5891,6 @@ erts_init_scheduling(int no_schedulers, int no_schedulers_online
 	erts_smp_atomic32_set_nob(&rq->len, 0);
 	rq->wakeup_other = 0;
 	rq->wakeup_other_reds = 0;
-	rq->halt_in_progress = 0;
 
 	rq->procs.pending_exiters = NULL;
 	rq->procs.context_switches = 0;
@@ -6974,15 +7006,8 @@ resume_process(Process *p, ErtsProcLocks locks)
 
 #ifdef ERTS_SMP
 
-static void
-scheduler_ix_resume_wake(Uint ix)
-{
-    ErtsSchedulerSleepInfo *ssi = ERTS_SCHED_SLEEP_INFO_IX(ix);
-    scheduler_ssi_resume_wake(ssi);
-}
-
-static void
-scheduler_ssi_resume_wake(ErtsSchedulerSleepInfo *ssi)
+static ERTS_INLINE void
+sched_resume_wake__(ErtsSchedulerSleepInfo *ssi)
 {
     erts_aint32_t xflgs = (ERTS_SSI_FLG_SLEEPING
 			   | ERTS_SSI_FLG_TSE_SLEEPING
@@ -6996,9 +7021,31 @@ scheduler_ssi_resume_wake(ErtsSchedulerSleepInfo *ssi)
 	    break;
 	}
 	xflgs = oflgs;
-    } while (oflgs & ERTS_SSI_FLG_SUSPENDED);
+    } while (oflgs & (ERTS_SSI_FLG_MSB_EXEC|ERTS_SSI_FLG_SUSPENDED));
+}
+
+static void
+nrml_sched_ix_resume_wake(Uint ix)
+{
+    sched_resume_wake__(ERTS_SCHED_SLEEP_INFO_IX(ix));
 }
 
+#ifdef ERTS_DIRTY_SCHEDULERS
+
+static void
+dcpu_sched_ix_resume_wake(Uint ix)
+{
+    sched_resume_wake__(ERTS_DIRTY_CPU_SCHED_SLEEP_INFO_IX(ix));
+}
+
+static void
+dio_sched_ix_resume_wake(Uint ix)
+{
+    sched_resume_wake__(ERTS_DIRTY_IO_SCHED_SLEEP_INFO_IX(ix));
+}
+
+#endif
+
 static erts_aint32_t
 sched_prep_spin_suspended(ErtsSchedulerSleepInfo *ssi, erts_aint32_t xpct)
 {
@@ -7078,9 +7125,18 @@ static void
 init_scheduler_suspend(void)
 {
     erts_smp_mtx_init(&schdlr_sspnd.mtx, "schdlr_sspnd");
-    schdlr_sspnd.online = ERTS_SCHDLR_SSPND_MAKE_NSCHEDS_VAL(1, 0, 0);
-    schdlr_sspnd.curr_online = ERTS_SCHDLR_SSPND_MAKE_NSCHEDS_VAL(1, 0, 0);
-    schdlr_sspnd.active = ERTS_SCHDLR_SSPND_MAKE_NSCHEDS_VAL(1, 0, 0);
+    schdlr_sspnd.online.normal = 1;
+    schdlr_sspnd.curr_online.normal = 1;
+    schdlr_sspnd.active.normal = 1;
+#ifdef ERTS_DIRTY_SCHEDULERS
+    schdlr_sspnd.online.dirty_cpu = 0;
+    schdlr_sspnd.curr_online.dirty_cpu = 0;
+    schdlr_sspnd.active.dirty_cpu = 0;
+    schdlr_sspnd.online.dirty_io = 0;
+    schdlr_sspnd.curr_online.dirty_io = 0;
+    schdlr_sspnd.active.dirty_io = 0;
+    schdlr_sspnd.last_msb_dirty_type = ERTS_SCHED_DIRTY_IO;
+#endif
     erts_smp_atomic32_init_nob(&schdlr_sspnd.changing, 0);
     schdlr_sspnd.chngq = NULL;
     schdlr_sspnd.changer = am_false;
@@ -7141,6 +7197,252 @@ schdlr_sspnd_resume_procs(ErtsSchedType sched_type,
     }
 }
 
+#ifdef ERTS_DIRTY_SCHEDULERS
+
+static ERTS_INLINE int
+have_dirty_work(void)
+{
+    return !(ERTS_EMPTY_RUNQ(ERTS_DIRTY_CPU_RUNQ)
+             | ERTS_EMPTY_RUNQ(ERTS_DIRTY_IO_RUNQ));
+}
+
+#define ERTS_MSB_NONE_PRIO_BIT PORT_BIT
+
+static ERTS_INLINE Uint32
+msb_runq_prio_bit(Uint32 flgs)
+{
+    int pbit;
+
+    pbit = (int) (flgs & ERTS_RUNQ_FLGS_PROCS_QMASK);
+    if (flgs & PORT_BIT) {
+        /* rate ports as proc prio high */
+        pbit |= HIGH_BIT;
+    }
+    if (flgs & ERTS_RUNQ_FLG_MISC_OP) {
+        /* rate misc ops as proc prio normal */
+        pbit |= NORMAL_BIT;
+    }
+    if (flgs & LOW_BIT) {
+        /* rate low prio as normal (avoid starvation) */
+        pbit |= NORMAL_BIT;
+    }
+    if (!pbit)
+        pbit = (int) ERTS_MSB_NONE_PRIO_BIT;
+    else
+        pbit &= -pbit; /* least significant bit set... */
+    ASSERT(pbit);
+
+    /* High prio low value; low prio high value... */
+    return (Uint32) pbit;
+}
+
+static ERTS_INLINE void
+msb_runq_prio_bits(Uint32 *nrmlp, Uint32 *dcpup, Uint32 *diop)
+{
+    Uint32 flgs = ERTS_RUNQ_FLGS_GET(ERTS_RUNQ_IX(0));
+    if (flgs & ERTS_RUNQ_FLG_HALTING) {
+        /*
+         * Emulator is halting; only execute port jobs
+         * on normal scheduler. Ensure that we switch
+         * to the normal scheduler.
+         */
+        *nrmlp = HIGH_BIT;
+        *dcpup = ERTS_MSB_NONE_PRIO_BIT;
+        *diop = ERTS_MSB_NONE_PRIO_BIT;
+    }
+    else {
+        *nrmlp = msb_runq_prio_bit(flgs);
+
+        flgs = ERTS_RUNQ_FLGS_GET(ERTS_DIRTY_CPU_RUNQ);
+        *dcpup = msb_runq_prio_bit(flgs);
+
+        flgs = ERTS_RUNQ_FLGS_GET(ERTS_DIRTY_IO_RUNQ);
+        *diop = msb_runq_prio_bit(flgs);
+    }
+}
+
+static int
+msb_scheduler_type_switch(ErtsSchedType sched_type,
+                          ErtsSchedulerData *esdp,
+                          long no)
+{
+    Uint32 nrml_prio, dcpu_prio, dio_prio;
+    ErtsSchedType exec_type;
+    ErtsRunQueue *exec_rq;
+#ifdef DEBUG
+    erts_aint32_t dbg_val;
+#endif
+
+    ASSERT(schdlr_sspnd.msb.ongoing);
+
+    /*
+     * This function determines how to switch
+     * between scheduler types when multi-scheduling
+     * is blocked.
+     *
+     * If no dirty work exist, we always select
+     * execution of normal scheduler. If nothing
+     * executes, normal scheduler 1 should be waiting
+     * in sys_schedule(), otherwise we cannot react
+     * on I/O events.
+     *
+     * We unconditionally switch back to normal
+     * scheduler after executing dirty in order to
+     * make sure we check for I/O...
+     */
+
+    msb_runq_prio_bits(&nrml_prio, &dcpu_prio, &dio_prio);
+
+    exec_type = ERTS_SCHED_NORMAL;
+    if (sched_type == ERTS_SCHED_NORMAL) {
+
+        /*
+         * Check priorities of work in the
+         * different run-queues and determine
+         * run-queue with highest prio job...
+         */
+
+        if ((dcpu_prio == ERTS_MSB_NONE_PRIO_BIT)
+            & (dio_prio == ERTS_MSB_NONE_PRIO_BIT)) {
+            /*
+             * No dirty work exist; continue on normal
+             * scheduler...
+             */
+            return 0;
+        }
+
+        if (dcpu_prio < nrml_prio) {
+            exec_type = ERTS_SCHED_DIRTY_CPU;
+            if (dio_prio < dcpu_prio)
+                exec_type = ERTS_SCHED_DIRTY_IO;
+        }
+        else {
+            if (dio_prio < nrml_prio)
+                exec_type = ERTS_SCHED_DIRTY_IO;
+        }
+
+        /*
+         * Make sure to alternate between dirty types
+         * inbetween normal execution if highest 
+         * priorities are equal.
+         */
+
+        if (exec_type == ERTS_SCHED_NORMAL) {
+            if (dcpu_prio == nrml_prio)
+                exec_type = ERTS_SCHED_DIRTY_CPU;
+            else if (dio_prio == nrml_prio)
+                exec_type = ERTS_SCHED_DIRTY_IO;
+            else {
+                /*
+                 * Normal work has higher prio than
+                 * dirty work; continue on normal
+                 * scheduler...
+                 */
+                return 0;
+            }
+        }
+
+        ASSERT(exec_type != ERTS_SCHED_NORMAL);
+        if (dio_prio == dcpu_prio) {
+            /* Alter between dirty types... */
+            if (schdlr_sspnd.last_msb_dirty_type == ERTS_SCHED_DIRTY_IO)
+                exec_type = ERTS_SCHED_DIRTY_CPU;
+            else
+                exec_type = ERTS_SCHED_DIRTY_IO;
+        }
+    }
+
+    ASSERT(sched_type != exec_type);
+
+    if (exec_type != ERTS_SCHED_NORMAL)
+        schdlr_sspnd.last_msb_dirty_type = exec_type;
+    else {
+        erts_aint32_t calls;
+        /*
+         * Going back to normal scheduler after
+         * dirty execution; make sure it will check
+         * for I/O...
+         */
+        if (ERTS_USE_MODIFIED_TIMING())
+            calls = ERTS_MODIFIED_TIMING_INPUT_REDS + 1;
+        else
+            calls = INPUT_REDUCTIONS + 1;
+        erts_smp_atomic32_set_nob(&function_calls, calls);
+
+        if ((nrml_prio == ERTS_MSB_NONE_PRIO_BIT)
+            & ((dcpu_prio != ERTS_MSB_NONE_PRIO_BIT)
+               | (dio_prio != ERTS_MSB_NONE_PRIO_BIT))) {
+            /*
+             * We have dirty work, but an empty
+             * normal run-queue.
+             *
+             * Since the normal run-queue is
+             * empty, the normal scheduler will
+             * go to sleep when selected for
+             * execution. We have dirty work to
+             * do, so we only want it to check
+             * I/O, and then come back here and
+             * switch to dirty execution.
+             *
+             * To prevent the scheduler from going
+             * to sleep we trick it into believing
+             * it has work to do...
+             */
+            ERTS_RUNQ_FLGS_SET_NOB(ERTS_RUNQ_IX(0),
+                                   ERTS_RUNQ_FLG_MISC_OP);
+        }
+    }
+
+    /*
+     * Suspend this scheduler and wake up scheduler
+     * number one of another type...
+     */
+#ifdef DEBUG
+    dbg_val =
+#else
+    (void)
+#endif
+        erts_smp_atomic32_read_bset_mb(&esdp->ssi->flags,
+                                       (ERTS_SSI_FLG_SUSPENDED
+                                        | ERTS_SSI_FLG_MSB_EXEC),
+                                       ERTS_SSI_FLG_SUSPENDED);
+    ASSERT(dbg_val & ERTS_SSI_FLG_MSB_EXEC);
+
+    switch (exec_type) {
+    case ERTS_SCHED_NORMAL:
+        exec_rq = ERTS_RUNQ_IX(0);
+        break;
+    case ERTS_SCHED_DIRTY_CPU:
+        exec_rq = ERTS_DIRTY_CPU_RUNQ;
+        break;
+    case ERTS_SCHED_DIRTY_IO:
+        exec_rq = ERTS_DIRTY_IO_RUNQ;
+        break;
+    default:
+        ERTS_INTERNAL_ERROR("Invalid scheduler type");
+        exec_rq = NULL;
+        break;
+    }
+
+#ifdef DEBUG
+    dbg_val =
+#else
+    (void)
+#endif
+        erts_smp_atomic32_read_bset_mb(&exec_rq->scheduler->ssi->flags,
+                                       (ERTS_SSI_FLG_SUSPENDED
+                                        | ERTS_SSI_FLG_MSB_EXEC),
+                                       ERTS_SSI_FLG_MSB_EXEC);
+    ASSERT(dbg_val & ERTS_SSI_FLG_SUSPENDED);
+
+    wake_scheduler(exec_rq);
+
+    return 1; /* suspend this scheduler... */
+
+}
+
+#endif
+
 static void
 suspend_scheduler(ErtsSchedulerData *esdp)
 {
@@ -7166,32 +7468,49 @@ suspend_scheduler(ErtsSchedulerData *esdp)
      * Regardless of why a scheduler is suspended, it ends up here.
      */
 
-#ifdef ERTS_DIRTY_SCHEDULERS
-    if (ERTS_SCHEDULER_IS_DIRTY(esdp)) {
+
+#if !defined(ERTS_DIRTY_SCHEDULERS)
+
+    sched_type = ERTS_SCHED_NORMAL;
+    online_flag = ERTS_SCHDLR_SSPND_CHNG_ONLN;
+    no = esdp->no;
+    ASSERT(no != 1);
+
+#else
+
+    sched_type = esdp->type;
+    switch (sched_type) {
+    case ERTS_SCHED_NORMAL:
+        online_flag = ERTS_SCHDLR_SSPND_CHNG_ONLN;
+        no = esdp->no;
+        break;
+    case ERTS_SCHED_DIRTY_CPU:
+        online_flag = ERTS_SCHDLR_SSPND_CHNG_DCPU_ONLN;
+        no = ERTS_DIRTY_SCHEDULER_NO(esdp);
+        break;
+    case ERTS_SCHED_DIRTY_IO:
+        online_flag = 0;
 	no = ERTS_DIRTY_SCHEDULER_NO(esdp);
-	if (ERTS_RUNQ_IS_DIRTY_CPU_RUNQ(esdp->run_queue)) {
-	    online_flag = ERTS_SCHDLR_SSPND_CHNG_DCPU_ONLN;
-	    sched_type = ERTS_SCHED_DIRTY_CPU;
-	}
-	else {
-	    online_flag = 0;
-	    sched_type = ERTS_SCHED_DIRTY_IO;
-	}
+        break;
+    default:
+        ERTS_INTERNAL_ERROR("Invalid scheduler type");
+        return;
     }
-    else
-#endif
-    {
-	online_flag = ERTS_SCHDLR_SSPND_CHNG_ONLN;
-	no = esdp->no;
-	sched_type = ERTS_SCHED_NORMAL;
+
+    if (erts_smp_atomic32_read_nob(&ssi->flags) & ERTS_SSI_FLG_MSB_EXEC) {
+        ASSERT(no == 1);
+        if (!msb_scheduler_type_switch(sched_type, esdp, no))
+            return;
+        /* Suspend and let scheduler 1 of another type execute... */
     }
 
-    ASSERT(sched_type != ERTS_SCHED_NORMAL || no != 1);
+#endif
 
     if (sched_type != ERTS_SCHED_NORMAL)
 	erts_smp_runq_unlock(esdp->run_queue);
     else {
-	evacuate_run_queue(esdp->run_queue, &sbp);
+        if (no != 1)
+            evacuate_run_queue(esdp->run_queue, &sbp);
 
 	erts_smp_runq_unlock(esdp->run_queue);
 
@@ -7200,8 +7519,6 @@ suspend_scheduler(ErtsSchedulerData *esdp)
 	if (erts_system_profile_flags.scheduler)
 	    profile_scheduler(make_small(esdp->no), am_inactive);
 
-	sched_wall_time_change(esdp, 0);
-
     }
     erts_smp_mtx_lock(&schdlr_sspnd.mtx);
 
@@ -7210,9 +7527,6 @@ suspend_scheduler(ErtsSchedulerData *esdp)
 
 	schdlr_sspnd_dec_nscheds(&schdlr_sspnd.active, sched_type);
 
-	ASSERT(schdlr_sspnd_get_nscheds(&schdlr_sspnd.active,
-					ERTS_SCHED_NORMAL) >= 1);
-
 	changing = erts_smp_atomic32_read_nob(&schdlr_sspnd.changing);
 
 	while (1) {
@@ -7234,9 +7548,13 @@ suspend_scheduler(ErtsSchedulerData *esdp)
 						    ERTS_SCHED_NORMAL) == 1) {
 			clr_flg = ERTS_SCHDLR_SSPND_CHNG_NMSB;
 		    }
-		    else if (schdlr_sspnd.active
-			     == ERTS_SCHDLR_SSPND_MAKE_NSCHEDS_VAL(1, 0, 0)) {
-			clr_flg = ERTS_SCHDLR_SSPND_CHNG_MSB;
+		    else if (schdlr_sspnd_get_nscheds(&schdlr_sspnd.active,
+                                                      ERTS_SCHED_NORMAL) == 1
+                             && schdlr_sspnd_get_nscheds(&schdlr_sspnd.active,
+                                                         ERTS_SCHED_DIRTY_CPU) == 0
+                             && schdlr_sspnd_get_nscheds(&schdlr_sspnd.active,
+                                                         ERTS_SCHED_DIRTY_IO) == 0) {
+                        clr_flg = ERTS_SCHDLR_SSPND_CHNG_MSB;
 		    }
 
 		    if (clr_flg) {
@@ -7308,10 +7626,7 @@ suspend_scheduler(ErtsSchedulerData *esdp)
 		}
 	    }
 
-	    if (curr_online
-		&& (sched_type == ERTS_SCHED_NORMAL
-		    ? !(schdlr_sspnd.msb.ongoing|schdlr_sspnd.nmsb.ongoing)
-		    : !schdlr_sspnd.msb.ongoing)) {
+	    if (curr_online) {
 		flgs = erts_smp_atomic32_read_acqb(&ssi->flags);
 		if (!(flgs & ERTS_SSI_FLG_SUSPENDED))
 		    break;
@@ -7327,13 +7642,11 @@ suspend_scheduler(ErtsSchedulerData *esdp)
 		if (sched_type != ERTS_SCHED_NORMAL)
 		    aux_work = 0;
 		else {
-		    erts_aint32_t qmask;
-		    qmask = (ERTS_RUNQ_FLGS_GET(esdp->run_queue)
-			     & ERTS_RUNQ_FLGS_QMASK);
+                    int evacuate = no == 1 ? 0 : !ERTS_EMPTY_RUNQ(esdp->run_queue);
 
 		    aux_work = erts_atomic32_read_acqb(&ssi->aux_work);
 
-		    if (aux_work|qmask) {
+		    if (aux_work|evacuate) {
 			if (!thr_prgr_active) {
 			    erts_thr_progress_active(esdp, thr_prgr_active = 1);
 			    sched_wall_time_change(esdp, 1);
@@ -7345,7 +7658,7 @@ suspend_scheduler(ErtsSchedulerData *esdp)
 
 			if (aux_work && erts_thr_progress_update(esdp))
 			    erts_thr_progress_leader_update(esdp);
-			if (qmask) {
+			if (evacuate) {
 			    erts_smp_runq_lock(esdp->run_queue);
 			    evacuate_run_queue(esdp->run_queue, &sbp);
 			    erts_smp_runq_unlock(esdp->run_queue);
@@ -7460,7 +7773,8 @@ suspend_scheduler(ErtsSchedulerData *esdp)
         if (changing) {
             if ((changing & ERTS_SCHDLR_SSPND_CHNG_MSB)
                 && !schdlr_sspnd.msb.ongoing
-                && schdlr_sspnd.online == schdlr_sspnd.active) {
+                && schdlr_sspnd_eq_nscheds(&schdlr_sspnd.online,
+                                           &schdlr_sspnd.active)) {
                 erts_smp_atomic32_read_band_nob(&schdlr_sspnd.changing,
                                                 ~ERTS_SCHDLR_SSPND_CHNG_MSB);
             }
@@ -7475,19 +7789,16 @@ suspend_scheduler(ErtsSchedulerData *esdp)
             }
         }
 	ASSERT(no <= schdlr_sspnd_get_nscheds(&schdlr_sspnd.online, sched_type));
-	ASSERT((sched_type == ERTS_SCHED_NORMAL
-		? !(schdlr_sspnd.msb.ongoing|schdlr_sspnd.nmsb.ongoing)
-		: !schdlr_sspnd.msb.ongoing));
     }
 
     erts_smp_mtx_unlock(&schdlr_sspnd.mtx);
 
-    ASSERT(!resume.msb.chngrs);
     schdlr_sspnd_resume_procs(sched_type, &resume);
 
     ASSERT(curr_online);
 
-    if (!ERTS_SCHEDULER_IS_DIRTY(esdp)) {
+    if (sched_type == ERTS_SCHED_NORMAL) {
+	(void) erts_get_monotonic_time(esdp);
 	if (erts_system_profile_flags.scheduler)
 	    profile_scheduler(make_small(esdp->no), am_active);
 
@@ -7497,8 +7808,6 @@ suspend_scheduler(ErtsSchedulerData *esdp)
 	}
     }
 
-    if (sched_type == ERTS_SCHED_NORMAL)
-	(void) erts_get_monotonic_time(esdp);
     erts_smp_runq_lock(esdp->run_queue);
     non_empty_runq(esdp->run_queue);
 
@@ -7768,10 +8077,8 @@ erts_set_schedulers_online(Process *p,
 		    erts_sched_poke(ssi);
 		}
 	    } else {
-		for (ix = dirty_online; ix < dirty_no; ix++) {
-		    ssi = ERTS_DIRTY_CPU_SCHED_SLEEP_INFO_IX(ix);
-		    scheduler_ssi_resume_wake(ssi);
-		}
+		for (ix = dirty_online; ix < dirty_no; ix++)
+		    dcpu_sched_ix_resume_wake(ix);
 	    }
 	}
 	if (!dirty_only)
@@ -7799,19 +8106,19 @@ erts_set_schedulers_online(Process *p,
     else /* if decrease */ {
 #ifdef ERTS_DIRTY_SCHEDULERS
 	if (change_dirty) {
-	    ErtsSchedulerSleepInfo* ssi;
 	    if (schdlr_sspnd.msb.ongoing) {
-		for (ix = dirty_no; ix < dirty_online; ix++) {
-		    ssi = ERTS_DIRTY_CPU_SCHED_SLEEP_INFO_IX(ix);
-		    erts_sched_poke(ssi);
-		}
-	    } else {
-		for (ix = dirty_no; ix < dirty_online; ix++) {
-		    ssi = ERTS_DIRTY_CPU_SCHED_SLEEP_INFO_IX(ix);
-		    erts_smp_atomic32_read_bor_nob(&ssi->flags,
-						   ERTS_SSI_FLG_SUSPENDED);
-		}
-		wake_dirty_schedulers(ERTS_DIRTY_CPU_RUNQ, 0);
+		for (ix = dirty_no; ix < dirty_online; ix++)
+		    erts_sched_poke(ERTS_DIRTY_CPU_SCHED_SLEEP_INFO_IX(ix));
+	    }
+            else {
+		for (ix = dirty_no; ix < dirty_online; ix++)
+                    dcpu_sched_ix_suspend_wake(ix);
+                /*
+                 * Newly suspended scheduler may have just been
+                 * about to handle a task. Make sure someone takes
+                 * care of such a task...
+                 */
+                dcpu_sched_ix_wake(0);
 	    }
 	}
 	if (!dirty_only)
@@ -7874,9 +8181,6 @@ erts_block_multi_scheduling(Process *p, ErtsProcLocks plocks, int on, int normal
 {
     int resume_proc, ix, res, have_unlocked_plocks = 0;
     ErtsProcList *plp;
-#ifdef ERTS_DIRTY_SCHEDULERS
-    ErtsSchedulerSleepInfo* ssi;
-#endif
     ErtsMultiSchedulingBlock *msbp;
     erts_aint32_t chng_flg;
     int have_blckd_flg;
@@ -7923,8 +8227,9 @@ erts_block_multi_scheduling(Process *p, ErtsProcLocks plocks, int on, int normal
 	    erts_proclist_store_last(&msbp->blckrs, plp);
 	    p->flags |= have_blckd_flg;
 	    ASSERT(normal
-		   ? 1 == schdlr_sspnd_get_nscheds(&schdlr_sspnd.active, ERTS_SCHED_NORMAL)
-		   : schdlr_sspnd.active == ERTS_SCHDLR_SSPND_MAKE_NSCHEDS_VAL(1, 0, 0));
+                   ? 1 == schdlr_sspnd_get_nscheds(&schdlr_sspnd.active,
+                                                   ERTS_SCHED_NORMAL)
+                   : schdlr_sspnd_get_nscheds_tot(&schdlr_sspnd.active) == 1);
 	    ASSERT(erts_proc_sched_data(p)->no == 1);
 	    if (schdlr_sspnd.msb.ongoing)
 		res = ERTS_SCHDLR_SSPND_DONE_MSCHED_BLOCKED;
@@ -7942,59 +8247,41 @@ erts_block_multi_scheduling(Process *p, ErtsProcLocks plocks, int on, int normal
 	    }
 	    ASSERT(!msbp->ongoing);
 	    msbp->ongoing = 1;
-	    if (schdlr_sspnd.active == ERTS_SCHDLR_SSPND_MAKE_NSCHEDS_VAL(1, 0, 0)
-		|| (normal && schdlr_sspnd_get_nscheds(&schdlr_sspnd.active,
-						       ERTS_SCHED_NORMAL) == 1)) {
-		ASSERT(erts_proc_sched_data(p)->no == 1);
-		plp = proclist_create(p);
-		erts_proclist_store_last(&msbp->blckrs, plp);
-		if (schdlr_sspnd.msb.ongoing)
-		    res = ERTS_SCHDLR_SSPND_DONE_MSCHED_BLOCKED;
-		else
-		    res = ERTS_SCHDLR_SSPND_DONE_NMSCHED_BLOCKED;
-	    }
-	    else {
-		erts_smp_atomic32_read_bor_nob(&schdlr_sspnd.changing,
-					       chng_flg);
-		change_no_used_runqs(1);
-		for (ix = 1; ix < erts_no_run_queues; ix++)
-		    suspend_run_queue(ERTS_RUNQ_IX(ix));
 
-		for (ix = 1; ix < online; ix++) {
-		    ErtsRunQueue *rq = ERTS_RUNQ_IX(ix);
-		    wake_scheduler(rq);
-		}
+            erts_smp_atomic32_read_bor_nob(&schdlr_sspnd.changing,
+                                           chng_flg);
+            change_no_used_runqs(1);
+            for (ix = 1; ix < erts_no_run_queues; ix++)
+                suspend_run_queue(ERTS_RUNQ_IX(ix));
 
-#ifdef ERTS_DIRTY_SCHEDULERS
-		if (!normal) {
-		    for (ix = 0; ix < erts_no_dirty_cpu_schedulers; ix++) {
-			ssi = ERTS_DIRTY_CPU_SCHED_SLEEP_INFO_IX(ix);
-			erts_smp_atomic32_read_bor_nob(&ssi->flags,
-						       ERTS_SSI_FLG_SUSPENDED);
-		    }
-		    wake_dirty_schedulers(ERTS_DIRTY_CPU_RUNQ, 0);
+            for (ix = 1; ix < online; ix++) {
+                ErtsRunQueue *rq = ERTS_RUNQ_IX(ix);
+                wake_scheduler(rq);
+            }
 
-		    for (ix = 0; ix < erts_no_dirty_io_schedulers; ix++) {
-			ssi = ERTS_DIRTY_IO_SCHED_SLEEP_INFO_IX(ix);
-			erts_smp_atomic32_read_bor_nob(&ssi->flags,
-						       ERTS_SSI_FLG_SUSPENDED);
-		    }
-		    wake_dirty_schedulers(ERTS_DIRTY_IO_RUNQ, 0);
-		}
+#ifdef ERTS_DIRTY_SCHEDULERS
+            if (!normal) {
+                ERTS_RUNQ_FLGS_SET_NOB(ERTS_RUNQ_IX(0), ERTS_RUNQ_FLG_MSB_EXEC);
+                erts_smp_atomic32_read_bor_nob(&ERTS_RUNQ_IX(0)->scheduler->ssi->flags,
+                                               ERTS_SSI_FLG_MSB_EXEC);
+                for (ix = 0; ix < erts_no_dirty_cpu_schedulers; ix++)
+                    dcpu_sched_ix_suspend_wake(ix);
+                for (ix = 0; ix < erts_no_dirty_io_schedulers; ix++)
+                    dio_sched_ix_suspend_wake(ix);
+            }
 #endif
 
-	    wait_until_msb:
+        wait_until_msb:
 
-		ASSERT(chng_flg & erts_smp_atomic32_read_nob(&schdlr_sspnd.changing));
+            ASSERT(chng_flg & erts_smp_atomic32_read_nob(&schdlr_sspnd.changing));
 
-		plp = proclist_create(p);
-		erts_proclist_store_last(&msbp->chngq, plp);
-		resume_proc = 0;
-		if (schdlr_sspnd.msb.ongoing)
-		    res = ERTS_SCHDLR_SSPND_YIELD_DONE_MSCHED_BLOCKED;
-		else
-		    res = ERTS_SCHDLR_SSPND_YIELD_DONE_NMSCHED_BLOCKED;
-	    }
+            plp = proclist_create(p);
+            erts_proclist_store_last(&msbp->chngq, plp);
+            resume_proc = 0;
+            if (schdlr_sspnd.msb.ongoing)
+                res = ERTS_SCHDLR_SSPND_YIELD_DONE_MSCHED_BLOCKED;
+            else
+                res = ERTS_SCHDLR_SSPND_YIELD_DONE_NMSCHED_BLOCKED;
 	    ASSERT(erts_proc_sched_data(p));
 	}
     }
@@ -8026,27 +8313,19 @@ erts_block_multi_scheduling(Process *p, ErtsProcLocks plocks, int on, int normal
 	    }
 	}
 	if (!msbp->blckrs && !msbp->chngq) {
-	    int online = (int) schdlr_sspnd_get_nscheds(&schdlr_sspnd.online,
-							ERTS_SCHED_NORMAL);
+	    int online;
 	    erts_smp_atomic32_read_bor_nob(&schdlr_sspnd.changing,
 					   chng_flg);
 	    p->flags &= ~have_blckd_flg;
 	    msbp->ongoing = 0;
-	    if (online == 1) {
-		/* No normal schedulers to resume */
-		ASSERT(schdlr_sspnd_get_nscheds(&schdlr_sspnd.active,
-						ERTS_SCHED_NORMAL) == 1);
-#ifndef ERTS_DIRTY_SCHEDULERS
-		erts_smp_atomic32_read_band_nob(&schdlr_sspnd.changing,
-						~chng_flg);
-#endif
-	    }
-	    else if (!(schdlr_sspnd.msb.ongoing|schdlr_sspnd.nmsb.ongoing)) {
-		if (plocks) {
+            if (!(schdlr_sspnd.msb.ongoing|schdlr_sspnd.nmsb.ongoing)) {
+                if (plocks) {
 		    have_unlocked_plocks = 1;
 		    erts_smp_proc_unlock(p, plocks);
 		}
 
+                online = (int) schdlr_sspnd_get_nscheds(&schdlr_sspnd.online,
+							ERTS_SCHED_NORMAL);
 		change_no_used_runqs(online);
 
 		/* Resume all online run queues */
@@ -8057,19 +8336,15 @@ erts_block_multi_scheduling(Process *p, ErtsProcLocks plocks, int on, int normal
 		    suspend_run_queue(ERTS_RUNQ_IX(ix));
 	    }
 #ifdef ERTS_DIRTY_SCHEDULERS
-	    if (!normal) {
-		ASSERT(!schdlr_sspnd.msb.ongoing);
+            if (!schdlr_sspnd.msb.ongoing) {
+                /* Get rid of msb-exec flag in run-queue of scheduler 1 */
+                resume_run_queue(ERTS_RUNQ_IX(0));
 		online = (int) schdlr_sspnd_get_nscheds(&schdlr_sspnd.online,
 							ERTS_SCHED_DIRTY_CPU);
-		for (ix = 0; ix < online; ix++) {
-		    ssi = ERTS_DIRTY_CPU_SCHED_SLEEP_INFO_IX(ix);
-		    scheduler_ssi_resume_wake(ssi);
-		}
-
-		for (ix = 0; ix < erts_no_dirty_io_schedulers; ix++) {
-		    ssi = ERTS_DIRTY_IO_SCHED_SLEEP_INFO_IX(ix);
-		    scheduler_ssi_resume_wake(ssi);
-		}
+		for (ix = 0; ix < online; ix++)
+		    dcpu_sched_ix_resume_wake(ix);
+		for (ix = 0; ix < erts_no_dirty_io_schedulers; ix++)
+		    dio_sched_ix_resume_wake(ix);
 	    }
 #endif
 	}
@@ -9734,7 +10009,7 @@ Process *erts_schedule(ErtsSchedulerData *esdp, Process *p, int calls)
 
 	if (!is_normal_sched) {
 	    if (erts_smp_atomic32_read_acqb(&esdp->ssi->flags)
-		& ERTS_SSI_FLG_SUSPENDED) {
+		& (ERTS_SSI_FLG_SUSPENDED|ERTS_SSI_FLG_MSB_EXEC)) {
 		suspend_scheduler(esdp);
 	    }
 	}
@@ -9744,8 +10019,10 @@ Process *erts_schedule(ErtsSchedulerData *esdp, Process *p, int calls)
 
 	    ASSERT(is_normal_sched);
 
-	    if (flags & (ERTS_RUNQ_FLG_CHK_CPU_BIND|ERTS_RUNQ_FLG_SUSPENDED)) {
-		if (flags & ERTS_RUNQ_FLG_SUSPENDED) {
+	    if (flags & (ERTS_RUNQ_FLG_CHK_CPU_BIND
+                         | ERTS_RUNQ_FLG_SUSPENDED
+                         | ERTS_RUNQ_FLG_MSB_EXEC)) {
+		if (flags & (ERTS_RUNQ_FLG_SUSPENDED|ERTS_RUNQ_FLG_MSB_EXEC)) {
 		    (void) ERTS_RUNQ_FLGS_UNSET_NOB(rq, ERTS_RUNQ_FLG_EXEC);
 		    suspend_scheduler(esdp);
 		    flags = ERTS_RUNQ_FLGS_SET_NOB(rq, ERTS_RUNQ_FLG_EXEC);
@@ -9784,13 +10061,12 @@ Process *erts_schedule(ErtsSchedulerData *esdp, Process *p, int calls)
 
 	flags = ERTS_RUNQ_FLGS_GET_NOB(rq);
 
-	if (!is_normal_sched && rq->halt_in_progress) {
+	if (!is_normal_sched & !!(flags & ERTS_RUNQ_FLG_HALTING)) {
 	    /* Wait for emulator to terminate... */
 	    while (1)
 		erts_milli_sleep(1000*1000);
 	}
-	else if ((!(flags & ERTS_RUNQ_FLGS_QMASK) && !rq->misc.start)
-		 || (rq->halt_in_progress && ERTS_EMPTY_RUNQ_PORTS(rq))) {
+	else if (!runq_got_work_to_execute_flags(flags)) {
 	    /* Prepare for scheduler wait */
 #ifdef ERTS_SMP
 	    ERTS_SMP_LC_ASSERT(erts_smp_lc_runq_is_locked(rq));
@@ -9804,21 +10080,44 @@ Process *erts_schedule(ErtsSchedulerData *esdp, Process *p, int calls)
 	    if (flags & ERTS_RUNQ_FLG_INACTIVE)
 		empty_runq(rq);
 	    else {
-		if (is_normal_sched && try_steal_task(rq))
-		    goto continue_check_activities_to_run;
-
-		empty_runq(rq);
-
-		/*
-		 * Check for ERTS_RUNQ_FLG_SUSPENDED has to be done
-		 * after trying to steal a task.
-		 */
-		flags = ERTS_RUNQ_FLGS_GET_NOB(rq);
-		if (flags & ERTS_RUNQ_FLG_SUSPENDED) {
-		    non_empty_runq(rq);
-		    flags |= ERTS_RUNQ_FLG_NONEMPTY;
-		    goto continue_check_activities_to_run_known_flags;
+                ASSERT(!runq_got_work_to_execute(rq));
+		if (!is_normal_sched) {
+                    /* Dirty scheduler */
+                    if (erts_smp_atomic32_read_acqb(&esdp->ssi->flags)
+                        & (ERTS_SSI_FLG_SUSPENDED|ERTS_SSI_FLG_MSB_EXEC)) {
+                        /* Go suspend... */
+                        goto continue_check_activities_to_run_known_flags;
+                    }
+                }
+                else {
+                    /* Normal scheduler */
+                    if (try_steal_task(rq))
+                        goto continue_check_activities_to_run;
+                    /*
+                     * Check for suspend has to be done after trying
+                     * to steal a task...
+                     */
+                    flags = ERTS_RUNQ_FLGS_GET_NOB(rq);
+                    if ((flags & ERTS_RUNQ_FLG_SUSPENDED)
+#ifdef ERTS_DIRTY_SCHEDULERS
+                        /* If multi scheduling block and we have
+                         * dirty work, suspend and let dirty
+                         * scheduler handle work... */
+                        || ((((flags & (ERTS_RUNQ_FLG_HALTING
+                                       | ERTS_RUNQ_FLG_MSB_EXEC))
+                              == ERTS_RUNQ_FLG_MSB_EXEC))
+                            && have_dirty_work())
+#endif
+                        ) {
+                        non_empty_runq(rq);
+                        flags |= ERTS_RUNQ_FLG_NONEMPTY;
+                        /*
+                         * Go suspend...
+                         */
+                        goto continue_check_activities_to_run_known_flags;
+                    }
 		}
+		empty_runq(rq);
 	    }
 #endif
 
@@ -9870,7 +10169,7 @@ Process *erts_schedule(ErtsSchedulerData *esdp, Process *p, int calls)
 #endif
 	}
 
-	if (rq->misc.start)
+        if (flags & ERTS_RUNQ_FLG_MISC_OP)
 	    exec_misc_ops(rq);
 
 #ifdef ERTS_SMP
@@ -9881,13 +10180,15 @@ Process *erts_schedule(ErtsSchedulerData *esdp, Process *p, int calls)
 	 * Find a new port to run.
 	 */
 
-	if (RUNQ_READ_LEN(&rq->ports.info.len)) {
+        flags = ERTS_RUNQ_FLGS_GET_NOB(rq);
+
+	if (flags & PORT_BIT) {
 	    int have_outstanding_io;
 	    have_outstanding_io = erts_port_task_execute(rq, &esdp->current_port);
 	    if ((!erts_eager_check_io
 		 && have_outstanding_io
 		 && fcalls > 2*input_reductions)
-		|| rq->halt_in_progress) {
+		|| (flags & ERTS_RUNQ_FLG_HALTING)) {
 		/*
 		 * If we have performed more than 2*INPUT_REDUCTIONS since
 		 * last call to erl_sys_schedule() and we still haven't
@@ -11419,6 +11720,8 @@ erts_schedule_misc_op(void (*func)(void *), void *arg)
     non_empty_runq(rq);
 #endif
 
+    ERTS_RUNQ_FLGS_SET_NOB(rq, ERTS_RUNQ_FLG_MISC_OP);
+
     erts_smp_runq_unlock(rq);
 
     smp_notify_inc_runq(rq);
@@ -11449,6 +11752,9 @@ exec_misc_ops(ErtsRunQueue *rq)
 	    rq->misc.end = NULL;
     }
 
+    if (!rq->misc.start)
+        ERTS_RUNQ_FLGS_UNSET_NOB(rq, ERTS_RUNQ_FLG_MISC_OP);
+
     erts_smp_runq_unlock(rq);
 
     while (molp) {
@@ -13576,6 +13882,8 @@ erts_print_scheduler_info(fmtfn_t to, void *to_arg, ErtsSchedulerData *esdp) {
                 erts_print(to, to_arg, "WAITING"); break;
             case ERTS_SSI_FLG_SUSPENDED:
                 erts_print(to, to_arg, "SUSPENDED"); break;
+            case ERTS_SSI_FLG_MSB_EXEC:
+                erts_print(to, to_arg, "MSB_EXEC"); break;
             default:
                 erts_print(to, to_arg, "UNKNOWN(%d)", flg); break;
             }
@@ -13685,6 +13993,12 @@ erts_print_scheduler_info(fmtfn_t to, void *to_arg, ErtsSchedulerData *esdp) {
                 erts_print(to, to_arg, "NONEMPTY"); break;
             case ERTS_RUNQ_FLG_PROTECTED:
                 erts_print(to, to_arg, "PROTECTED"); break;
+            case ERTS_RUNQ_FLG_EXEC:
+                erts_print(to, to_arg, "EXEC"); break;
+            case ERTS_RUNQ_FLG_MSB_EXEC:
+                erts_print(to, to_arg, "MSB_EXEC"); break;
+            case ERTS_RUNQ_FLG_MISC_OP:
+                erts_print(to, to_arg, "MISC_OP"); break;
             default:
                 erts_print(to, to_arg, "UNKNOWN(%d)", flg); break;
             }
@@ -13734,11 +14048,11 @@ erts_print_scheduler_info(fmtfn_t to, void *to_arg, ErtsSchedulerData *esdp) {
  * A nice system halt closing all open port goes as follows:
  * 1) This function schedules the aux work ERTS_SSI_AUX_WORK_REAP_PORTS
  *    on all schedulers, then schedules itself out.
- * 2) All shedulers detect this and set the flag halt_in_progress
+ * 2) All shedulers detect this and set the flag ERTS_RUNQ_FLG_HALTING
  *    on their run queue. The last scheduler sets all non-closed ports
  *    ERTS_PORT_SFLG_HALT. Global atomic erts_halt_progress is used
  *    as refcount to determine which is last.
- * 3) While the run ques has flag halt_in_progress no processes
+ * 3) While the run queues has flag ERTS_RUNQ_FLG_HALTING no processes
  *    will be scheduled, only ports.
  * 4) When the last port closes that scheduler calls erlang:halt/1.
  *    The same global atomic is used as refcount.
@@ -13753,8 +14067,8 @@ void erts_halt(int code)
 					     erts_no_schedulers,
 					     -1)) {
 #ifdef ERTS_DIRTY_SCHEDULERS
-	ERTS_DIRTY_CPU_RUNQ->halt_in_progress = 1;
-	ERTS_DIRTY_IO_RUNQ->halt_in_progress = 1;
+        ERTS_RUNQ_FLGS_SET(ERTS_DIRTY_CPU_RUNQ, ERTS_RUNQ_FLG_HALTING);
+        ERTS_RUNQ_FLGS_SET(ERTS_DIRTY_IO_RUNQ, ERTS_RUNQ_FLG_HALTING);
 #endif
 	erts_halt_code = code;
 	notify_reap_ports_relb();
diff --git a/erts/emulator/beam/erl_process.h b/erts/emulator/beam/erl_process.h
index 3938c4c913..fc2055332b 100644
--- a/erts/emulator/beam/erl_process.h
+++ b/erts/emulator/beam/erl_process.h
@@ -170,8 +170,14 @@ extern int erts_sched_thread_suggested_stack_size;
   (((Uint32) 1) << (ERTS_RUNQ_FLG_BASE2 + 6))
 #define ERTS_RUNQ_FLG_EXEC \
   (((Uint32) 1) << (ERTS_RUNQ_FLG_BASE2 + 7))
+#define ERTS_RUNQ_FLG_MSB_EXEC \
+  (((Uint32) 1) << (ERTS_RUNQ_FLG_BASE2 + 8))
+#define ERTS_RUNQ_FLG_MISC_OP \
+  (((Uint32) 1) << (ERTS_RUNQ_FLG_BASE2 + 9))
+#define ERTS_RUNQ_FLG_HALTING \
+  (((Uint32) 1) << (ERTS_RUNQ_FLG_BASE2 + 10))
 
-#define ERTS_RUNQ_FLG_MAX (ERTS_RUNQ_FLG_BASE2 + 8)
+#define ERTS_RUNQ_FLG_MAX (ERTS_RUNQ_FLG_BASE2 + 11)
 
 #define ERTS_RUNQ_FLGS_MIGRATION_QMASKS	\
   (ERTS_RUNQ_FLGS_EMIGRATE_QMASK	\
@@ -262,8 +268,9 @@ typedef enum {
 #define ERTS_SSI_FLG_TSE_SLEEPING 	(((erts_aint32_t) 1) << 2)
 #define ERTS_SSI_FLG_WAITING		(((erts_aint32_t) 1) << 3)
 #define ERTS_SSI_FLG_SUSPENDED	 	(((erts_aint32_t) 1) << 4)
+#define ERTS_SSI_FLG_MSB_EXEC	 	(((erts_aint32_t) 1) << 5)
 
-#define ERTS_SSI_FLGS_MAX                                       5
+#define ERTS_SSI_FLGS_MAX                                       6
 
 #define ERTS_SSI_FLGS_SLEEP_TYPE			\
  (ERTS_SSI_FLG_TSE_SLEEPING|ERTS_SSI_FLG_POLL_SLEEPING)
@@ -274,7 +281,8 @@ typedef enum {
 #define ERTS_SSI_FLGS_ALL				\
  (ERTS_SSI_FLGS_SLEEP					\
   | ERTS_SSI_FLG_WAITING				\
-  | ERTS_SSI_FLG_SUSPENDED)
+  | ERTS_SSI_FLG_SUSPENDED                              \
+  | ERTS_SSI_FLG_MSB_EXEC)
 
 /*
  * Keep ERTS_SSI_AUX_WORK flags ordered in expected frequency
@@ -393,6 +401,12 @@ typedef struct {
     Process* last;
 } ErtsRunPrioQueue;
 
+typedef enum {
+    ERTS_SCHED_NORMAL,
+    ERTS_SCHED_DIRTY_CPU,
+    ERTS_SCHED_DIRTY_IO
+} ErtsSchedType;
+
 typedef struct ErtsSchedulerData_ ErtsSchedulerData;
 
 typedef struct ErtsRunQueue_ ErtsRunQueue;
@@ -478,7 +492,6 @@ struct ErtsRunQueue_ {
     erts_smp_atomic32_t len;
     int wakeup_other;
     int wakeup_other_reds;
-    int halt_in_progress;
 
     struct {
 	ErtsProcList *pending_exiters;
@@ -642,6 +655,7 @@ struct ErtsSchedulerData_ {
 #endif
     ErtsSchedulerSleepInfo *ssi;
     Process *current_process;
+    ErtsSchedType type;
     Uint no;			/* Scheduler number for normal schedulers */
 #ifdef ERTS_DIRTY_SCHEDULERS
     ErtsDirtySchedId dirty_no;  /* Scheduler number for dirty schedulers */
diff --git a/erts/etc/unix/etp-commands.in b/erts/etc/unix/etp-commands.in
index 0990fcf8a7..f00f3d83aa 100644
--- a/erts/etc/unix/etp-commands.in
+++ b/erts/etc/unix/etp-commands.in
@@ -2389,6 +2389,9 @@ define etp-ssi-flags
   if ($arg0 & 0x10)
     printf " suspended"
   end
+  if ($arg0 & 0x20)
+    printf " msb_exec"
+  end
   printf "\n"
 end