Date: Wed, 16 Mar 2005 15:55:26 -0800
From: Chris Wright <chrisw@osdl.org>
To: linux-kernel@vger.kernel.org, stable@kernel.org
Cc: hugh@veritas.com, roland@redhat.com, torvalds@osdl.org, akpm@osdl.org,
       alan@lxorguk.ukuu.org.uk, jmforbes@linuxtx.org, zwane@arm.linux.org.uk,
       cliffw@osdl.org, tytso@mit.edu, rddunlap@osdl.org
Subject: [6/9] tasklist left locked
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-stable review patch.  If anyone has any objections, please let us know.

----

From: Hugh Dickins <hugh@veritas.com>

On 4-way SMP, about one reboot in twenty hangs while killing processes:
exit needs exclusive tasklist_lock, but something still holds read_lock.
do_signal_stop race case misses unlock, and fixing it fixes the symptom.

Signed-off-by: Hugh Dickins <hugh@veritas.com>
Acked-by: Roland McGrath <roland@redhat.com>
Signed-off-by: Chris Wright <chrisw@osdl.org>

--- 2.6.11/kernel/signal.c	2005-03-02 07:38:56.000000000 +0000
+++ linux/kernel/signal.c	2005-03-16 18:10:17.000000000 +0000
@@ -1728,6 +1728,7 @@ do_signal_stop(int signr)
 			 * with another processor delivering a stop signal,
 			 * then the SIGCONT that wakes us up should clear it.
 			 */
+			read_unlock(&tasklist_lock);
 			return 0;
 		}
 
-
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