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, 168 insertions, 8 deletions

diff --git a/erts/emulator/test/scheduler_SUITE.erl b/erts/emulator/test/scheduler_SUITE.erl
index 1f284228db..f998e7d4d2 100644
--- a/erts/emulator/test/scheduler_SUITE.erl
+++ b/erts/emulator/test/scheduler_SUITE.erl
@@ -54,6 +54,7 @@
 	 sct_cmd/1,
 	 sbt_cmd/1,
 	 scheduler_threads/1,
+	 scheduler_suspend_basic/1,
 	 scheduler_suspend/1,
 	 dirty_scheduler_threads/1,
 	 dirty_scheduler_exit/1,
@@ -69,8 +70,10 @@ all() ->
     [equal, few_low, many_low, equal_with_part_time_high,
      equal_with_part_time_max,
      equal_and_high_with_part_time_max, equal_with_high,
-     equal_with_high_max, bound_process,
-     {group, scheduler_bind}, scheduler_threads, scheduler_suspend,
+     equal_with_high_max,
+     bound_process,
+     {group, scheduler_bind}, scheduler_threads,
+     scheduler_suspend_basic, scheduler_suspend,
      dirty_scheduler_threads, dirty_scheduler_exit,
      reader_groups].
 
@@ -1131,6 +1134,7 @@ dirty_schedulers_online_test(true) ->
     dirty_schedulers_online_smp_test(erlang:system_info(schedulers_online)).
 dirty_schedulers_online_smp_test(SchedOnln) when SchedOnln < 4 -> ok;
 dirty_schedulers_online_smp_test(SchedOnln) ->
+    receive after 500 -> ok end,
     DirtyCPUSchedOnln = erlang:system_info(dirty_cpu_schedulers_online),
     SchedOnln = DirtyCPUSchedOnln,
     HalfSchedOnln = SchedOnln div 2,
@@ -1139,9 +1143,11 @@ dirty_schedulers_online_smp_test(SchedOnln) ->
     HalfDirtyCPUSchedOnln = erlang:system_flag(schedulers_online, SchedOnln),
     DirtyCPUSchedOnln = erlang:system_flag(dirty_cpu_schedulers_online,
 					   HalfDirtyCPUSchedOnln),
+    receive after 500 -> ok end,
     HalfDirtyCPUSchedOnln = erlang:system_info(dirty_cpu_schedulers_online),
     QrtrDirtyCPUSchedOnln = HalfDirtyCPUSchedOnln div 2,
     SchedOnln = erlang:system_flag(schedulers_online, HalfSchedOnln),
+    receive after 500 -> ok end,
     QrtrDirtyCPUSchedOnln = erlang:system_info(dirty_cpu_schedulers_online),
     ok.
 
@@ -1214,6 +1220,113 @@ wait_dse([Pid|Pids]) ->
 dirty_sleeper() ->
     erlang:nif_error({error,?MODULE}).
 
+scheduler_suspend_basic(Config) when is_list(Config) ->
+    case erlang:system_info(multi_scheduling) of
+	disabled ->
+	    {skip, "Nothing to test"};
+	_ ->
+	    Onln = erlang:system_info(schedulers_online),
+	    try
+		scheduler_suspend_basic_test()
+	    after
+		erlang:system_flag(schedulers_online, Onln)
+	    end
+    end.
+
+scheduler_suspend_basic_test() ->
+    %% The receives after setting scheduler states are there
+    %% since the operation is not fully synchronous. For example,
+    %% we do not wait for dirty cpu schedulers online to complete
+    %% before returning from erlang:system_flag(schedulers_online, _).
+
+    erlang:system_flag(schedulers_online,
+		       erlang:system_info(schedulers)),
+    try
+	erlang:system_flag(dirty_cpu_schedulers_online,
+			   erlang:system_info(dirty_cpu_schedulers)),
+	receive after 500 -> ok end
+    catch
+	_ : _ ->
+	    ok
+    end,
+
+    S0 = sched_state(),
+    io:format("~p~n", [S0]),
+    {{normal,NTot0,NOnln0,NAct0},
+     {dirty_cpu,DCTot0,DCOnln0,DCAct0},
+     {dirty_io,DITot0,DIOnln0,DIAct0}} = S0,
+    enabled = erlang:system_info(multi_scheduling),
+
+    DCOne = case DCTot0 of
+		0 -> 0;
+		_ -> 1
+	    end,
+
+    blocked_normal = erlang:system_flag(multi_scheduling, block_normal),
+    blocked_normal = erlang:system_info(multi_scheduling),
+    {{normal,NTot0,NOnln0,1},
+     {dirty_cpu,DCTot0,DCOnln0,DCAct0},
+     {dirty_io,DITot0,DIOnln0,DIAct0}} = sched_state(),
+
+    NOnln0 = erlang:system_flag(schedulers_online, 1),
+    receive after 500 -> ok end,
+    {{normal,NTot0,1,1},
+     {dirty_cpu,DCTot0,DCOne,DCOne},
+     {dirty_io,DITot0,DIOnln0,DIAct0}} = sched_state(),
+
+    1 = erlang:system_flag(schedulers_online, NOnln0),
+    receive after 500 -> ok end,
+    {{normal,NTot0,NOnln0,1},
+     {dirty_cpu,DCTot0,DCOnln0,DCAct0},
+     {dirty_io,DITot0,DIOnln0,DIAct0}} = sched_state(),
+
+    blocked = erlang:system_flag(multi_scheduling, block),
+    blocked = erlang:system_info(multi_scheduling),
+    receive after 500 -> ok end,
+    {{normal,NTot0,NOnln0,1},
+     {dirty_cpu,DCTot0,DCOnln0,0},
+     {dirty_io,DITot0,DIOnln0,0}} = sched_state(),
+
+    NOnln0 = erlang:system_flag(schedulers_online, 1),
+    receive after 500 -> ok end,
+    {{normal,NTot0,1,1},
+     {dirty_cpu,DCTot0,DCOne,0},
+     {dirty_io,DITot0,DIOnln0,0}} = sched_state(),
+
+    1 = erlang:system_flag(schedulers_online, NOnln0),
+    receive after 500 -> ok end,
+    {{normal,NTot0,NOnln0,1},
+     {dirty_cpu,DCTot0,DCOnln0,0},
+     {dirty_io,DITot0,DIOnln0,0}} = sched_state(),
+
+    blocked = erlang:system_flag(multi_scheduling, unblock_normal),
+    blocked = erlang:system_info(multi_scheduling),
+    {{normal,NTot0,NOnln0,1},
+     {dirty_cpu,DCTot0,DCOnln0,0},
+     {dirty_io,DITot0,DIOnln0,0}} = sched_state(),
+
+    enabled = erlang:system_flag(multi_scheduling, unblock),
+    enabled = erlang:system_info(multi_scheduling),
+    receive after 500 -> ok end,
+    {{normal,NTot0,NOnln0,NAct0},
+     {dirty_cpu,DCTot0,DCOnln0,DCAct0},
+     {dirty_io,DITot0,DIOnln0,DIAct0}} = sched_state(),
+
+    NOnln0 = erlang:system_flag(schedulers_online, 1),
+    receive after 500 -> ok end,
+    {{normal,NTot0,1,1},
+     {dirty_cpu,DCTot0,DCOne,DCOne},
+     {dirty_io,DITot0,DIOnln0,DIAct0}} = sched_state(),
+
+    1 = erlang:system_flag(schedulers_online, NOnln0),
+    receive after 500 -> ok end,
+    {{normal,NTot0,NOnln0,NAct0},
+     {dirty_cpu,DCTot0,DCOnln0,DCAct0},
+     {dirty_io,DITot0,DIOnln0,DIAct0}} = sched_state(),
+
+    ok.
+    
+
 scheduler_suspend(Config) when is_list(Config) ->
     ?line Dog = ?t:timetrap(?t:minutes(5)),
     ?line lists:foreach(fun (S) -> scheduler_suspend_test(Config, S) end,
@@ -1238,12 +1351,17 @@ scheduler_suspend_test(Config, Schedulers) ->
     ?line [ok] = mcall(Node, [fun () -> sst0_loop(300) end]),
     ?line [ok] = mcall(Node, [fun () -> sst1_loop(300) end]),
     ?line [ok] = mcall(Node, [fun () -> sst2_loop(300) end]),
-    ?line [ok, ok, ok, ok, ok] = mcall(Node,
-				       [fun () -> sst0_loop(200) end,
-					fun () -> sst1_loop(200) end,
-					fun () -> sst2_loop(200) end,
-					fun () -> sst2_loop(200) end,
-					fun () -> sst3_loop(Sched, 200) end]),
+    ?line [ok] = mcall(Node, [fun () -> sst4_loop(300) end]),
+    ?line [ok] = mcall(Node, [fun () -> sst5_loop(300) end]),
+    ?line [ok, ok, ok, ok,
+	   ok, ok, ok] = mcall(Node,
+			       [fun () -> sst0_loop(200) end,
+				fun () -> sst1_loop(200) end,
+				fun () -> sst2_loop(200) end,
+				fun () -> sst2_loop(200) end,
+				fun () -> sst3_loop(Sched, 200) end,
+				fun () -> sst4_loop(200) end,
+				fun () -> sst5_loop(200) end]),
     ?line [SState] = mcall(Node, [fun () ->
 					  case Sched == SchedOnln of
 					      false ->
@@ -1320,6 +1438,20 @@ sst3_loop_with_dirty_schedulers(S, DS, N) ->
     erlang:system_flag(dirty_cpu_schedulers_online, DS),
     sst3_loop_with_dirty_schedulers(S, DS, N-1).
 
+sst4_loop(0) ->
+    ok;
+sst4_loop(N) ->
+    erlang:system_flag(multi_scheduling, block_normal),
+    erlang:system_flag(multi_scheduling, unblock_normal),
+    sst4_loop(N-1).
+
+sst5_loop(0) ->
+    ok;
+sst5_loop(N) ->
+    erlang:system_flag(multi_scheduling, block_normal),
+    erlang:system_flag(multi_scheduling, unblock_normal),
+    sst5_loop(N-1).
+
 reader_groups(Config) when is_list(Config) ->
     %% White box testing. These results are correct, but other results
     %% could be too...
@@ -1598,6 +1730,34 @@ reader_groups_map(CPUT, Groups) ->
 %% Utils
 %%
 
+sched_state() ->
+    sched_state(erlang:system_info(all_schedulers_state),
+		undefined,
+		{dirty_cpu,0,0,0},
+		{dirty_io,0,0,0}).
+
+	    
+sched_state([], N, DC, DI) ->
+    try
+	chk_basic(N),
+	chk_basic(DC),
+	chk_basic(DI),
+	{N, DC, DI}
+    catch
+	_ : _ ->
+	    ?t:fail({inconsisten_scheduler_state, {N, DC, DI}})
+    end;
+sched_state([{normal, _, _, _} = S | Rest], _S, DC, DI) ->
+    sched_state(Rest, S, DC, DI);
+sched_state([{dirty_cpu, _, _, _} = DC | Rest], S, _DC, DI) ->
+    sched_state(Rest, S, DC, DI);
+sched_state([{dirty_io, _, _, _} = DI | Rest], S, DC, _DI) ->
+    sched_state(Rest, S, DC, DI).
+
+chk_basic({_Type, Tot, Onln, Act}) ->
+    true = Tot >= Onln,
+    true = Onln >= Act.
+
 l(Id) ->
     {logical, Id}.