From 2dd9d721ed6820a584654c82f4ae1d6331f78a9e Mon Sep 17 00:00:00 2001
From: kosaki <kosaki@b2dd03c8-39d4-4d8f-98ff-823fe69b080e>
Date: Tue, 30 Aug 2011 00:59:52 +0000
Subject: [PATCH] * lib/thread.rb (Queue#pop): fix a race against
 Thread.wakeup.   Patch by Masaki Matsushita <glass.saga at gmail dot com>  
 [Bug #5195] [ruby-dev:44400]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@33121 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
---
 ChangeLog     | 6 ++++++
 lib/thread.rb | 4 +++-
 2 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/ChangeLog b/ChangeLog
index 6cf7e473d5..30d35c1309 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+Tue Aug 30 09:57:50 2011  KOSAKI Motohiro  <kosaki.motohiro@gmail.com>
+
+	* lib/thread.rb (Queue#pop): fix a race against Thread.wakeup.
+	  Patch by Masaki Matsushita <glass.saga at gmail dot com>
+	  [Bug #5195] [ruby-dev:44400]
+
 Tue Aug 30 09:48:07 2011  KOSAKI Motohiro  <kosaki.motohiro@gmail.com>
 
 	* cont.c (fiber_entry): fix stack allocation failure on Debian
diff --git a/lib/thread.rb b/lib/thread.rb
index 58c4f6b9e6..09f2d58ecc 100644
--- a/lib/thread.rb
+++ b/lib/thread.rb
@@ -185,7 +185,9 @@ class Queue
       while true
         if @que.empty?
           raise ThreadError, "queue empty" if non_block
-          @waiting.push Thread.current
+          # @waiting.include? check is necessary for avoiding a race against
+          # Thread.wakeup [Bug 5195]
+          @waiting.push Thread.current unless @waiting.include?(Thread.current)
           @mutex.sleep
         else
           return @que.shift