stdlib: Monitor proc_lib:start'ed processes to avoid waiting forever

Monitor the spawned process in proc_lib:start/[3|4|5], so
that a proper error is returned, if the spawned process crashes
before proclib:init_ack/1 is sent.

Previously the calling process would hang forever or until specified
timeout. Start link catches these errors but start did not.

start now behaves as start_link if process traps exit.

2 files changed, 60 insertions, 9 deletions

diff --git a/lib/stdlib/src/proc_lib.erl b/lib/stdlib/src/proc_lib.erl
index 02bcbb5a60..4bca4c1e6d 100644
--- a/lib/stdlib/src/proc_lib.erl
+++ b/lib/stdlib/src/proc_lib.erl
@@ -1,7 +1,7 @@
 %%
 %% %CopyrightBegin%
 %%
-%% Copyright Ericsson AB 1996-2011. All Rights Reserved.
+%% Copyright Ericsson AB 1996-2012. 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
@@ -184,6 +184,17 @@ check_for_monitor(SpawnOpts) ->
 	    false
     end.
 
+spawn_mon(M,F,A) ->
+    Parent = get_my_name(),
+    Ancestors = get_ancestors(),
+    erlang:spawn_monitor(?MODULE, init_p, [Parent,Ancestors,M,F,A]).
+
+spawn_opt_mon(M, F, A, Opts) when is_atom(M), is_atom(F), is_list(A) ->
+    Parent = get_my_name(),
+    Ancestors = get_ancestors(),
+    check_for_monitor(Opts),
+    erlang:spawn_opt(?MODULE, init_p, [Parent,Ancestors,M,F,A], [monitor|Opts]).
+
 -spec hibernate(Module, Function, Args) -> no_return() when
       Module :: module(),
       Function :: atom(),
@@ -270,8 +281,8 @@ start(M, F, A) when is_atom(M), is_atom(F), is_list(A) ->
       Ret :: term() | {error, Reason :: term()}.
 
 start(M, F, A, Timeout) when is_atom(M), is_atom(F), is_list(A) ->
-    Pid = ?MODULE:spawn(M, F, A),
-    sync_wait(Pid, Timeout).
+    PidRef = spawn_mon(M, F, A),
+    sync_wait_mon(PidRef, Timeout).
 
 -spec start(Module, Function, Args, Time, SpawnOpts) -> Ret when
       Module :: module(),
@@ -282,8 +293,8 @@ start(M, F, A, Timeout) when is_atom(M), is_atom(F), is_list(A) ->
       Ret :: term() | {error, Reason :: term()}.
 
 start(M, F, A, Timeout, SpawnOpts) when is_atom(M), is_atom(F), is_list(A) ->
-    Pid = ?MODULE:spawn_opt(M, F, A, SpawnOpts),
-    sync_wait(Pid, Timeout).
+    PidRef = spawn_opt_mon(M, F, A, SpawnOpts),
+    sync_wait_mon(PidRef, Timeout).
 
 -spec start_link(Module, Function, Args) -> Ret when
       Module :: module(),
@@ -330,6 +341,23 @@ sync_wait(Pid, Timeout) ->
 	    {error, timeout}
     end.
 
+sync_wait_mon({Pid, Ref}, Timeout) ->
+    receive
+	{ack, Pid, Return} ->
+	    erlang:demonitor(Ref, [flush]),
+	    Return;
+	{'DOWN', Ref, _Type, Pid, Reason} ->
+	    {error, Reason};
+	{'EXIT', Pid, Reason} -> %% link as spawn_opt?
+	    erlang:demonitor(Ref, [flush]),
+	    {error, Reason}
+    after Timeout ->
+	    erlang:demonitor(Ref, [flush]),
+	    exit(Pid, kill),
+	    flush(Pid),
+	    {error, timeout}
+    end.
+
 -spec flush(pid()) -> 'true'.
 
 flush(Pid) ->
diff --git a/lib/stdlib/test/proc_lib_SUITE.erl b/lib/stdlib/test/proc_lib_SUITE.erl
index c95089117c..8dca69bac4 100644
--- a/lib/stdlib/test/proc_lib_SUITE.erl
+++ b/lib/stdlib/test/proc_lib_SUITE.erl
@@ -1,7 +1,7 @@
 %%
 %% %CopyrightBegin%
 %% 
-%% Copyright Ericsson AB 1996-2011. All Rights Reserved.
+%% Copyright Ericsson AB 1996-2012. 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
@@ -28,7 +28,7 @@
 	 crash/1, sync_start_nolink/1, sync_start_link/1,
          spawn_opt/1, sp1/0, sp2/0, sp3/1, sp4/2, sp5/1,
 	 hibernate/1]).
--export([ otp_6345/1]).
+-export([ otp_6345/1, init_dont_hang/1]).
 
 -export([hib_loop/1, awaken/1]).
 
@@ -36,7 +36,7 @@
 	 handle_event/2, handle_call/2, handle_info/2,
 	 terminate/2]).
 
--export([otp_6345_init/1]).
+-export([otp_6345_init/1, init_dont_hang_init/1]).
 
 
 -ifdef(STANDALONE).
@@ -52,7 +52,7 @@ all() ->
      {group, tickets}].
 
 groups() -> 
-    [{tickets, [], [otp_6345]},
+    [{tickets, [], [otp_6345, init_dont_hang]},
      {sync_start, [], [sync_start_nolink, sync_start_link]}].
 
 init_per_suite(Config) ->
@@ -343,6 +343,29 @@ otp_6345_loop() ->
 	    otp_6345_loop()
     end.
 
+%% OTP-9803
+init_dont_hang(suite) ->
+    [];
+init_dont_hang(doc) ->
+    ["Check that proc_lib:start don't hang if spawned process crashes before proc_lib:init_ack/2"];
+init_dont_hang(Config) when is_list(Config) ->
+    %% Start should behave as start_link
+    process_flag(trap_exit, true),
+    StartLinkRes = proc_lib:start_link(?MODULE, init_dont_hang_init, [self()]),
+    try
+	StartLinkRes = proc_lib:start(?MODULE, init_dont_hang_init, [self()], 1000),
+	StartLinkRes = proc_lib:start(?MODULE, init_dont_hang_init, [self()], 1000, []),
+	ok
+    catch _:Error ->
+	    io:format("Error ~p /= ~p ~n",[erlang:get_stacktrace(), StartLinkRes]),
+	    exit(Error)
+    end.
+
+init_dont_hang_init(Parent) ->
+    1 = 2.
+
+
+
 %%-----------------------------------------------------------------
 %% The error_logger handler used.
 %%-----------------------------------------------------------------