Improved scheduler suspend functionality

- The calling process is now suspended while synchronizing
  scheduler suspends via erlang:system_flag(schedulers_online, _)
  and erlang:system_flag(multi_scheduling, _), instead of blocking
  the scheduler thread in the BIF call waiting for the operation
  to synchronize. Besides releasing the scheduler for other work
  (or immediate suspend) it also makes it possible to abort the
  operation by killing the process.
- erlang:system_flag(schedulers_online, _) now only wait for normal
  schedulers to complete before it returns. This since it may take
  a very long time before all dirty schedulers suspends.
- erlang:system_flag(multi_scheduling, block_normal|unblock_normal)
  which only operate on normal schedulers has been introduced. This
  since there are use cases where suspend of dirty schedulers are
  not of interest (hipe loader).
- erlang:system_flag(multi_scheduling, block) still blocks all
  dirty schedulers as well as all normal schedulers except one since
  it is hard to redefine what multi scheduling block means.
- The three operations:
  - changing amount of schedulers online
  - blocking/unblocking normal multi scheduling
  - blocking/unblocking full multi scheduling
  can now be done in parallel. This is important since otherwise
  a full multi scheduling block would potentially delay the other
  operations for a very long time.

1 files changed, 33 insertions, 33 deletions

diff --git a/erts/emulator/beam/bif.c b/erts/emulator/beam/bif.c
index 6ab75496a0..37bb28c6f8 100644
--- a/erts/emulator/beam/bif.c
+++ b/erts/emulator/beam/bif.c
@@ -4197,22 +4197,33 @@ BIF_RETTYPE system_flag_2(BIF_ALIST_2)
     Sint n;
 
     if (BIF_ARG_1 == am_multi_scheduling) {
-	if (BIF_ARG_2 == am_block || BIF_ARG_2 == am_unblock) {
+	if (BIF_ARG_2 == am_block || BIF_ARG_2 == am_unblock
+	    || BIF_ARG_2 == am_block_normal || BIF_ARG_2 == am_unblock_normal) {
 #ifndef ERTS_SMP
 	    BIF_RET(am_disabled);
 #else
+	    int block = (BIF_ARG_2 == am_block
+			 || BIF_ARG_2 == am_block_normal);
+	    int normal = (BIF_ARG_2 == am_block_normal
+			  || BIF_ARG_2 == am_unblock_normal);
 	    if (erts_no_schedulers == 1)
 		BIF_RET(am_disabled);
 	    else {
 		switch (erts_block_multi_scheduling(BIF_P,
 						    ERTS_PROC_LOCK_MAIN,
-						    BIF_ARG_2 == am_block,
+						    block,
+						    normal,
 						    0)) {
 		case ERTS_SCHDLR_SSPND_DONE_MSCHED_BLOCKED:
 		    BIF_RET(am_blocked);
+		case ERTS_SCHDLR_SSPND_DONE_NMSCHED_BLOCKED:
+		    BIF_RET(am_blocked_normal);
 		case ERTS_SCHDLR_SSPND_YIELD_DONE_MSCHED_BLOCKED:
 		    ERTS_BIF_YIELD_RETURN_X(BIF_P, am_blocked,
 					    am_multi_scheduling);
+		case ERTS_SCHDLR_SSPND_YIELD_DONE_NMSCHED_BLOCKED:
+		    ERTS_BIF_YIELD_RETURN_X(BIF_P, am_blocked_normal,
+					    am_multi_scheduling);
 		case ERTS_SCHDLR_SSPND_DONE:
 		    BIF_RET(am_enabled);
 		case ERTS_SCHDLR_SSPND_YIELD_RESTART:
@@ -4245,11 +4256,7 @@ BIF_RETTYPE system_flag_2(BIF_ALIST_2)
 	switch (erts_set_schedulers_online(BIF_P,
 					   ERTS_PROC_LOCK_MAIN,
 					   signed_val(BIF_ARG_2),
-					   &old_no
-#ifdef ERTS_DIRTY_SCHEDULERS
-					   , 0
-#endif
-					   )) {
+					   &old_no, 0)) {
 	case ERTS_SCHDLR_SSPND_DONE:
 	    BIF_RET(make_small(old_no));
 	case ERTS_SCHDLR_SSPND_YIELD_RESTART:
@@ -4619,29 +4626,27 @@ BIF_RETTYPE erts_internal_cmp_term_2(BIF_ALIST_2) {
 /*
  * Processes doing yield on return in a bif ends up in bif_return_trap().
  */
-static BIF_RETTYPE bif_return_trap(
-#ifdef DEBUG
-    BIF_ALIST_2
-#else
-    BIF_ALIST_1
-#endif
-    )
+static BIF_RETTYPE bif_return_trap(BIF_ALIST_2)
 {
-#ifdef DEBUG
+    Eterm res = BIF_ARG_1;
+
     switch (BIF_ARG_2) {
-    case am_multi_scheduling:
 #ifdef ERTS_SMP
-	erts_dbg_multi_scheduling_return_trap(BIF_P, BIF_ARG_1);
-#endif
-	break;
-    case am_schedulers_online:
+    case am_multi_scheduling: {
+	int msb = erts_is_multi_scheduling_blocked();
+	if (msb > 0)
+	    res = am_blocked;
+	else if (msb < 0)
+	    res = am_blocked_normal;
+	else
+	    ERTS_INTERNAL_ERROR("Unexpected multi scheduling block state");
 	break;
+    }
+#endif
     default:
 	break;
     }
-#endif
-
-    BIF_RET(BIF_ARG_1);
+    BIF_RET(res);
 }
 
 /*
@@ -4746,17 +4751,12 @@ void erts_init_bif(void)
     erts_smp_atomic_init_nob(&erts_dead_ports_ptr, (erts_aint_t) NULL);
 
     /*
-     * bif_return_trap/1 is a hidden BIF that bifs that need to
-     * yield the calling process traps to. The only thing it does:
-     * return the value passed as argument.
+     * bif_return_trap/2 is a hidden BIF that bifs that need to
+     * yield the calling process traps to.
      */
-    erts_init_trap_export(&bif_return_trap_export, am_erlang, am_bif_return_trap,
-#ifdef DEBUG
-		     2
-#else
-		     1
-#endif
-		     , &bif_return_trap);
+    erts_init_trap_export(&bif_return_trap_export,
+			  am_erlang, am_bif_return_trap, 2,
+			  &bif_return_trap);
 
     erts_await_result = erts_export_put(am_erts_internal,
 					am_await_result,