[6/9] tasklist left locked

[Chris Wright]

-stable review patch.  If anyone has any objections, please let us know.

----

From: Hugh Dickins <hugh@xxxxxxxxxxx>

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@xxxxxxxxxxx>
Acked-by: Roland McGrath <roland@xxxxxxxxxx>
Signed-off-by: Chris Wright <chrisw@xxxxxxxx>

--- 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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