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Date: Sat, 21 Jul 2007 19:02:06 +0400
From: Oleg Nesterov <oleg@tv-sign.ru>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>, Ingo Molnar <mingo@elte.hu>,
       linux-kernel@vger.kernel.org
Subject: [PATCH] fix theoretical ccids_{read,write}_lock() race
Message-ID: <20070721150206.GA1083@tv-sign.ru>
References: <20070721115712.GA871@tv-sign.ru> <20070721123159.GB1769@elte.hu> <20070721141814.GA1013@tv-sign.ru>
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Make sure that spin_unlock_wait() is properly ordered wrt atomic_inc().

Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>

--- t/net/dccp/ccid.c~ccid	2006-12-18 18:17:31.000000000 +0300
+++ t/net/dccp/ccid.c	2007-07-21 18:29:21.000000000 +0400
@@ -40,6 +40,7 @@ static inline void ccids_write_unlock(vo
 static inline void ccids_read_lock(void)
 {
 	atomic_inc(&ccids_lockct);
+	smp_mb__after_atomic_inc();
 	spin_unlock_wait(&ccids_lock);
 }