Explicitly kill dynamic children in supervisors

According to the supervisor's documentation:
  "Important note on simple-one-for-one supervisors: The dynamically
   created child processes of a simple-one-for-one supervisor are not
   explicitly killed, regardless of shutdown strategy, but are expected
   to terminate when the supervisor does (that is, when an exit signal
   from the parent process is received)."

All is fine as long as we stop simple_one_for_one supervisor manually.
Dynamic children catch the exit signal from the supervisor and leave.
But, if this happens when we stop an application, after the top
supervisor has stopped, the application master kills all remaining
processes associated to this application. So, dynamic children that trap
exit signals can be killed during their cleanup (here we mean inside
terminate/2). This is unpredictable and highly time-dependent.

In this commit, supervisor module is patched to explicitly terminate
dynamic children accordingly to the shutdown strategy.

NOTE: Order in which dynamic children are stopped is not defined. In
fact, this is "almost" done at the same time.

1 files changed, 42 insertions, 0 deletions

diff --git a/lib/stdlib/test/supervisor_2.erl b/lib/stdlib/test/supervisor_2.erl
new file mode 100644
index 0000000000..67aacf5a9c
--- /dev/null
+++ b/lib/stdlib/test/supervisor_2.erl
@@ -0,0 +1,42 @@
+%%
+%% %CopyrightBegin%
+%%
+%% Copyright Ericsson AB 1996-2010. All Rights Reserved.
+%%
+%% The contents of this file are subject to the Erlang Public License,
+%% Version 1.1, (the "License"); you may not use this file except in
+%% compliance with the License. You should have received a copy of the
+%% Erlang Public License along with this software. If not, it can be
+%% retrieved online at http://www.erlang.org/.
+%%
+%% Software distributed under the License is distributed on an "AS IS"
+%% basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See
+%% the License for the specific language governing rights and limitations
+%% under the License.
+%%
+%% %CopyrightEnd%
+%%
+%% Description: Simulates the behaviour that a child process may have.
+%% Is used by the supervisor_SUITE test suite.
+-module(supervisor_2).
+
+-export([start_child/1, init/1]).
+
+-export([handle_call/3, handle_info/2, terminate/2]).
+
+start_child(Time) when is_integer(Time), Time > 0 ->
+    gen_server:start_link(?MODULE, Time, []).
+
+init(Time) ->
+    process_flag(trap_exit, true),
+    {ok, Time}.
+
+handle_call(Req, _From, State) ->
+    {reply, Req, State}.
+
+handle_info(_, State) ->
+    {noreply, State}.
+
+terminate(_Reason, Time) ->
+    timer:sleep(Time),
+    ok.