From f0c32433dc057a83f0cddb04f34146e458cf4b6a Mon Sep 17 00:00:00 2001
From: Evgeniy Khramtsov <ekhramtsov@process-one.net>
Date: Mon, 30 May 2011 16:51:55 +1000
Subject: [PATCH] Fix race condition (EJABS-1677)

---
 src/mod_ack.erl | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/src/mod_ack.erl b/src/mod_ack.erl
index 68606283f..7268b549e 100644
--- a/src/mod_ack.erl
+++ b/src/mod_ack.erl
@@ -233,8 +233,16 @@ handle_cast(_Msg, State) ->
 handle_info({timeout, _TRef, {ID, Pid}}, State) ->
     case lookup(Pid, ID, State#state.timers) of
 	{ok, _} ->
-	    catch ejabberd_c2s:stop(Pid),
-	    handle_cast({del, Pid}, State);
+            MRef = erlang:monitor(process, Pid),
+            catch ejabberd_c2s:stop(Pid),
+            receive
+                {'DOWN', MRef, process, Pid, _Reason}->
+                    ok
+            after 5 ->
+                    catch exit(Pid, kill)
+            end,
+            erlang:demonitor(MRef, [flush]),
+            handle_cast({del, Pid}, State);
 	error ->
 	    {noreply, State}
     end;