OTP-8502 os:cmd hang

A race condition in os:cmd/1 could cause the caller to get stuck in
os:cmd/1 forever.

1 files changed, 44 insertions, 2 deletions

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