From 630d7e7df458490ae4d5c263e096851e14349537 Mon Sep 17 00:00:00 2001
From: Rickard Green <rickard@erlang.org>
Date: Wed, 25 Apr 2018 13:00:36 +0200
Subject: Restore merge of signal queues in queue_messages() if main lock is
 held

---
 erts/emulator/beam/erl_gc.c      | 34 ++++------------------------------
 erts/emulator/beam/erl_message.c |  6 ++++++
 2 files changed, 10 insertions(+), 30 deletions(-)

diff --git a/erts/emulator/beam/erl_gc.c b/erts/emulator/beam/erl_gc.c
index ea87cd7f50..dbdfdc6e86 100644
--- a/erts/emulator/beam/erl_gc.c
+++ b/erts/emulator/beam/erl_gc.c
@@ -61,7 +61,7 @@
 #  define ERTS_GC_ASSERT(B) ((void) 1)
 #endif
 
-#if defined(DEBUG) && 1
+#if defined(DEBUG) && 0
 #  define HARDDEBUG 1
 #endif
 
@@ -223,23 +223,6 @@ ERTS_SCHED_PREF_QUICK_ALLOC_IMPL(gcireq,
                                  5,
                                  ERTS_ALC_T_GC_INFO_REQ)
 
-static ERTS_INLINE void
-ensure_sigq_roots_available(Process *p)
-{
-    ERTS_LC_ASSERT(ERTS_PROC_LOCK_MAIN == erts_proc_lc_my_proc_locks(p));
-    switch (p->flags & (F_OFF_HEAP_MSGQ|F_OFF_HEAP_MSGQ_CHNG)) {
-    case F_OFF_HEAP_MSGQ_CHNG:
-    case 0:
-        erts_proc_lock(p, ERTS_PROC_LOCK_MSGQ);
-        erts_proc_sig_fetch(p);
-        erts_proc_unlock(p, ERTS_PROC_LOCK_MSGQ);
-        break;
-    default:
-        break;
-    }
-}
-
-
 /*
  * Initialize GC global data.
  */
@@ -443,8 +426,6 @@ erts_gc_after_bif_call_lhf(Process* p, ErlHeapFragment *live_hf_end,
 	live_hf_end = ERTS_INVALID_HFRAG_PTR;
     }
 
-    ensure_sigq_roots_available(p);
-
     if (is_non_value(result)) {
 	if (p->freason == TRAP) {
 #ifdef HIPE
@@ -888,11 +869,8 @@ do_major_collection:
 int
 erts_garbage_collect_nobump(Process* p, int need, Eterm* objv, int nobj, int fcalls)
 {
-    int reds; 
-    int reds_left;
-    ensure_sigq_roots_available(p);
-    reds = garbage_collect(p, ERTS_INVALID_HFRAG_PTR, need, objv, nobj, fcalls, 0);
-    reds_left = ERTS_REDS_LEFT(p, fcalls);
+    int reds = garbage_collect(p, ERTS_INVALID_HFRAG_PTR, need, objv, nobj, fcalls, 0);
+    int reds_left = ERTS_REDS_LEFT(p, fcalls);
     if (reds > reds_left)
 	reds = reds_left;
     ASSERT(CONTEXT_REDS - (reds_left - reds) >= erts_proc_sched_data(p)->virtual_reds);
@@ -902,9 +880,7 @@ erts_garbage_collect_nobump(Process* p, int need, Eterm* objv, int nobj, int fca
 void
 erts_garbage_collect(Process* p, int need, Eterm* objv, int nobj)
 {
-    int reds;
-    ensure_sigq_roots_available(p);
-    reds = garbage_collect(p, ERTS_INVALID_HFRAG_PTR, need, objv, nobj, p->fcalls, 0);
+    int reds = garbage_collect(p, ERTS_INVALID_HFRAG_PTR, need, objv, nobj, p->fcalls, 0);
     BUMP_REDS(p, reds);
     ASSERT(CONTEXT_REDS - ERTS_BIF_REDS_LEFT(p)
 	   >= erts_proc_sched_data(p)->virtual_reds);
@@ -1130,8 +1106,6 @@ erts_garbage_collect_literals(Process* p, Eterm* literals,
      * First an ordinary major collection...
      */
 
-    ensure_sigq_roots_available(p);
-
     p->flags |= F_NEED_FULLSWEEP;
 
     if (ERTS_SCHEDULER_IS_DIRTY(erts_proc_sched_data(p)))
diff --git a/erts/emulator/beam/erl_message.c b/erts/emulator/beam/erl_message.c
index 541d2e8ad1..deca426543 100644
--- a/erts/emulator/beam/erl_message.c
+++ b/erts/emulator/beam/erl_message.c
@@ -311,6 +311,9 @@ erts_queue_dist_message(Process *rcvr,
 
 	LINK_MESSAGE(rcvr, mp, &mp->next, 1);
 
+        if (rcvr_locks & ERTS_PROC_LOCK_MAIN)
+            erts_proc_sig_fetch(rcvr);
+
 	if (!(rcvr_locks & ERTS_PROC_LOCK_MSGQ))
 	    erts_proc_unlock(rcvr, ERTS_PROC_LOCK_MSGQ);
 
@@ -376,6 +379,9 @@ queue_messages(Process* receiver,
 
     LINK_MESSAGE(receiver, first, last, len);
 
+    if (receiver_locks & ERTS_PROC_LOCK_MAIN)
+        erts_proc_sig_fetch(receiver);
+
     if (locked_msgq) {
 	erts_proc_unlock(receiver, ERTS_PROC_LOCK_MSGQ);
     }
-- 
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