Merge branch 'lukas/erts/fix-off-heap-change-gc/OTP-18075' into maint-22

* lukas/erts/fix-off-heap-change-gc/OTP-18075:
  erts: Fix gc to fetch sig queue at mqd change

2 files changed, 39 insertions, 8 deletions

diff --git a/erts/emulator/beam/erl_gc.c b/erts/emulator/beam/erl_gc.c
index 7456686f12..544f2b9330 100644
--- a/erts/emulator/beam/erl_gc.c
+++ b/erts/emulator/beam/erl_gc.c
@@ -431,7 +431,7 @@ erts_gc_after_bif_call_lhf(Process* p, ErlHeapFragment *live_hf_end,
 	return result;
     }
 
-    if (p->sig_qs.flags & FS_ON_HEAP_MSGQ) {
+    if (p->sig_qs.flags & (FS_ON_HEAP_MSGQ|FS_OFF_HEAP_MSGQ_CHNG)) {
         erts_proc_lock(p, ERTS_PROC_LOCK_MSGQ);
         erts_proc_sig_fetch(p);
 	erts_proc_unlock(p, ERTS_PROC_LOCK_MSGQ);
@@ -890,7 +890,7 @@ int
 erts_garbage_collect_nobump(Process* p, int need, Eterm* objv, int nobj, int fcalls)
 {
     int reds, reds_left;
-    if (p->sig_qs.flags & FS_ON_HEAP_MSGQ) {
+    if (p->sig_qs.flags & (FS_ON_HEAP_MSGQ|FS_OFF_HEAP_MSGQ_CHNG)) {
         erts_proc_lock(p, ERTS_PROC_LOCK_MSGQ);
         erts_proc_sig_fetch(p);
 	erts_proc_unlock(p, ERTS_PROC_LOCK_MSGQ);
@@ -907,7 +907,7 @@ void
 erts_garbage_collect(Process* p, int need, Eterm* objv, int nobj)
 {
     int reds;
-    if (p->sig_qs.flags & FS_ON_HEAP_MSGQ) {
+    if (p->sig_qs.flags & (FS_ON_HEAP_MSGQ|FS_OFF_HEAP_MSGQ_CHNG)) {
         erts_proc_lock(p, ERTS_PROC_LOCK_MSGQ);
         erts_proc_sig_fetch(p);
 	erts_proc_unlock(p, ERTS_PROC_LOCK_MSGQ);
@@ -1185,7 +1185,7 @@ erts_garbage_collect_literals(Process* p, Eterm* literals,
 
     p->flags |= F_NEED_FULLSWEEP;
 
-    if (p->sig_qs.flags & FS_ON_HEAP_MSGQ) {
+    if (p->sig_qs.flags & (FS_ON_HEAP_MSGQ|FS_OFF_HEAP_MSGQ_CHNG)) {
         erts_proc_lock(p, ERTS_PROC_LOCK_MSGQ);
         erts_proc_sig_fetch(p);
 	erts_proc_unlock(p, ERTS_PROC_LOCK_MSGQ);
@@ -2637,7 +2637,7 @@ setup_rootset(Process *p, Eterm *objv, int nobj, Rootset *rootset)
 	 */
 
 #ifdef DEBUG
-        if (p->sig_qs.flags & FS_ON_HEAP_MSGQ) {
+        if (p->sig_qs.flags & (FS_ON_HEAP_MSGQ|FS_OFF_HEAP_MSGQ_CHNG)) {
             ErtsMessage *mp;
             erts_proc_lock(p, ERTS_PROC_LOCK_MSGQ);
             /*
diff --git a/erts/emulator/test/message_queue_data_SUITE.erl b/erts/emulator/test/message_queue_data_SUITE.erl
index 7f0cbdd885..e162cd9cb3 100644
--- a/erts/emulator/test/message_queue_data_SUITE.erl
+++ b/erts/emulator/test/message_queue_data_SUITE.erl
@@ -21,9 +21,10 @@
 -module(message_queue_data_SUITE).
 
 -export([all/0, suite/0]).
--export([basic/1, process_info_messages/1, total_heap_size/1]).
+-export([basic/1, process_info_messages/1, total_heap_size/1,
+         change_to_off_heap_gc/1]).
 
--export([basic_test/1]).
+-export([basic_test/1, id/1]).
 
 -include_lib("common_test/include/ct.hrl").
 
@@ -32,7 +33,8 @@ suite() ->
      {timetrap, {minutes, 2}}].
 
 all() -> 
-    [basic, process_info_messages, total_heap_size].
+    [basic, process_info_messages, total_heap_size,
+     change_to_off_heap_gc].
 
 %%
 %%
@@ -186,12 +188,41 @@ total_heap_size(_Config) ->
     ct:log("OffSize = ~p, OffSizeAfter = ~p",[OffSize, OffSizeAfter]),
     true = OffSize == OffSizeAfter.
 
+%% Test that setting message queue to off_heap works if a GC is triggered
+%% as the message queue if moved off heap. See GH-5933 for more details.
+%% This testcase will most likely only fail in debug build.
+change_to_off_heap_gc(_Config) ->
+    Msg = {ok, lists:duplicate(20,20)},
+
+    %% We test that this process can receive a message and when it is still
+    %% in its external message queue we change the message queue data to
+    %% off_heap and then GC.
+    {Pid, Ref} = spawn_monitor(
+            fun() ->
+                    spinner(1, 10000),
+                    process_flag(message_queue_data, off_heap),
+                    garbage_collect(),
+                    receive {ok, _M} -> ok end
+            end),
+    Pid ! Msg,
+    receive
+        {'DOWN',Ref,_,_,_} ->
+            ok
+    end.
+
 %%
 %%
 %% helpers
 %%
 %%
 
+%% This spinner needs to make sure that it does not allocate any memory
+%% as a GC in here will break the test
+spinner(_N, 0) -> ok;
+spinner(N, M) -> spinner(?MODULE:id(N) div 1, M - 1).
+
+id(N) -> N.
+
 start_node(Config, Opts) when is_list(Config), is_list(Opts) ->
     Pa = filename:dirname(code:which(?MODULE)),
     Name = list_to_atom(atom_to_list(?MODULE)