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-rw-r--r--lib/kernel/doc/src/notes.xml16
-rw-r--r--lib/kernel/src/os.erl59
-rw-r--r--lib/kernel/test/os_SUITE.erl46
3 files changed, 104 insertions, 17 deletions
diff --git a/lib/kernel/doc/src/notes.xml b/lib/kernel/doc/src/notes.xml
index 7bb6aea40e..9c3f6524ae 100644
--- a/lib/kernel/doc/src/notes.xml
+++ b/lib/kernel/doc/src/notes.xml
@@ -30,6 +30,22 @@
</header>
<p>This document describes the changes made to the Kernel application.</p>
+<section><title>Kernel 2.13.5.1</title>
+
+ <section><title>Fixed Bugs and Malfunctions</title>
+ <list>
+ <item>
+ <p>
+ A race condition in <c>os:cmd/1</c> could cause the
+ caller to get stuck in <c>os:cmd/1</c> forever.</p>
+ <p>
+ Own Id: OTP-8502</p>
+ </item>
+ </list>
+ </section>
+
+</section>
+
<section><title>Kernel 2.13.5</title>
<section><title>Fixed Bugs and Malfunctions</title>
diff --git a/lib/kernel/src/os.erl b/lib/kernel/src/os.erl
index 196e6cdeb2..d0b498edc9 100644
--- a/lib/kernel/src/os.erl
+++ b/lib/kernel/src/os.erl
@@ -1,19 +1,19 @@
%%
%% %CopyrightBegin%
-%%
-%% Copyright Ericsson AB 1997-2009. All Rights Reserved.
-%%
+%%
+%% Copyright Ericsson AB 1997-2010. 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%
%%
-module(os).
@@ -169,6 +169,7 @@ unix_cmd(Cmd) ->
%% $1 parameter for easy identification of the resident shell.
%%
-define(SHELL, "/bin/sh -s unix:cmd 2>&1").
+-define(PORT_CREATOR_NAME, os_cmd_port_creator).
%%
%% Serializing open_port through a process to avoid smp lock contention
@@ -176,18 +177,37 @@ unix_cmd(Cmd) ->
%%
-spec start_port() -> port().
start_port() ->
- {Ref,Client} = {make_ref(),self()},
- try (os_cmd_port_creator ! {Ref,Client})
- catch
- error:_ -> spawn(fun() -> start_port_srv({Ref,Client}) end)
- end,
+ Ref = make_ref(),
+ Request = {Ref,self()},
+ {Pid, Mon} = case whereis(?PORT_CREATOR_NAME) of
+ undefined ->
+ spawn_monitor(fun() ->
+ start_port_srv(Request)
+ end);
+ P ->
+ P ! Request,
+ M = erlang:monitor(process, P),
+ {P, M}
+ end,
receive
- {Ref,Port} when is_port(Port) -> Port;
- {Ref,Error} -> exit(Error)
+ {Ref, Port} when is_port(Port) ->
+ erlang:demonitor(Mon, [flush]),
+ Port;
+ {Ref, Error} ->
+ erlang:demonitor(Mon, [flush]),
+ exit(Error);
+ {'DOWN', Mon, process, Pid, _Reason} ->
+ start_port()
end.
start_port_srv(Request) ->
- StayAlive = try register(os_cmd_port_creator, self())
+ %% We don't want a group leader of some random application. Use
+ %% kernel_sup's group leader.
+ {group_leader, GL} = process_info(whereis(kernel_sup),
+ group_leader),
+ true = group_leader(GL, self()),
+ process_flag(trap_exit, true),
+ StayAlive = try register(?PORT_CREATOR_NAME, self())
catch
error:_ -> false
end,
@@ -196,7 +216,7 @@ start_port_srv(Request) ->
start_port_srv_loop({Ref,Client}, StayAlive) ->
Reply = try open_port({spawn, ?SHELL},[stream]) of
Port when is_port(Port) ->
- port_connect(Port, Client),
+ (catch port_connect(Port, Client)),
unlink(Port),
Port
catch
@@ -205,10 +225,19 @@ start_port_srv_loop({Ref,Client}, StayAlive) ->
end,
Client ! {Ref,Reply},
case StayAlive of
- true -> start_port_srv_loop(receive Msg -> Msg end, true);
+ true -> start_port_srv_loop(get_open_port_request(), true);
false -> exiting
end.
+get_open_port_request() ->
+ receive
+ {Ref, Client} = Request when is_reference(Ref),
+ is_pid(Client) ->
+ Request;
+ _Junk ->
+ get_open_port_request()
+ end.
+
%%
%% unix_get_data(Port) -> Result
%%
diff --git a/lib/kernel/test/os_SUITE.erl b/lib/kernel/test/os_SUITE.erl
index 1673b33010..6a3534b094 100644
--- a/lib/kernel/test/os_SUITE.erl
+++ b/lib/kernel/test/os_SUITE.erl
@@ -20,13 +20,13 @@
-export([all/1]).
-export([space_in_cwd/1, quoting/1, space_in_name/1, bad_command/1,
- find_executable/1, unix_comment_in_command/1]).
+ find_executable/1, unix_comment_in_command/1, evil/1]).
-include("test_server.hrl").
all(suite) ->
[space_in_cwd, quoting, space_in_name, bad_command, find_executable,
- unix_comment_in_command].
+ unix_comment_in_command, evil].
space_in_cwd(doc) ->
"Test that executing a command in a current working directory "
@@ -186,6 +186,48 @@ unix_comment_in_command(Config) when is_list(Config) ->
?line test_server:timetrap_cancel(Dog),
ok.
+-define(EVIL_PROCS, 100).
+-define(EVIL_LOOPS, 100).
+-define(PORT_CREATOR, os_cmd_port_creator).
+evil(Config) when is_list(Config) ->
+ Dog = test_server:timetrap(test_server:minutes(5)),
+ Parent = self(),
+ Ps = lists:map(fun (N) ->
+ spawn_link(fun () ->
+ evil_loop(Parent, ?EVIL_LOOPS,N)
+ end)
+ end, lists:seq(1, ?EVIL_PROCS)),
+ Devil = spawn(fun () -> devil(hd(Ps), hd(lists:reverse(Ps))) end),
+ lists:foreach(fun (P) -> receive {P, done} -> ok end end, Ps),
+ exit(Devil, kill),
+ test_server:timetrap_cancel(Dog),
+ ok.
+
+devil(P1, P2) ->
+ erlang:display({?PORT_CREATOR, whereis(?PORT_CREATOR)}),
+ (catch ?PORT_CREATOR ! lists:seq(1,1000000)),
+ (catch ?PORT_CREATOR ! lists:seq(1,666)),
+ (catch ?PORT_CREATOR ! grrrrrrrrrrrrrrrr),
+ (catch ?PORT_CREATOR ! {'EXIT', P1, buhuuu}),
+ (catch ?PORT_CREATOR ! {'EXIT', hd(erlang:ports()), buhuuu}),
+ (catch ?PORT_CREATOR ! {'EXIT', P2, arggggggg}),
+ receive after 500 -> ok end,
+ (catch exit(whereis(?PORT_CREATOR), kill)),
+ (catch ?PORT_CREATOR ! ">8|"),
+ receive after 500 -> ok end,
+ (catch exit(whereis(?PORT_CREATOR), diiiiiiiiiiiiiiiiiiiie)),
+ receive after 100 -> ok end,
+ devil(P1, P2).
+
+evil_loop(Parent, Loops, N) ->
+ Res = integer_to_list(N),
+ evil_loop(Parent, Loops, Res, "echo " ++ Res).
+
+evil_loop(Parent, 0, _Res, _Cmd) ->
+ Parent ! {self(), done};
+evil_loop(Parent, Loops, Res, Cmd) ->
+ comp(Res, os:cmd(Cmd)),
+ evil_loop(Parent, Loops-1, Res, Cmd).
comp(Expected, Got) ->
case strip_nl(Got) of
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