[PATCH] Race condition in del_timer_sync (2.5)

[Tejun Huh <tejun@aratech.co.kr>]

 Hello,

 This patch fixes a race between del_timer_sync and recursive timers.
Current implementation allows the value of timer->base that is used
for timer_pending test to be fetched before finishing running_timer
test, so it's possible for a recursive time to be pending after
del_timer_sync.  Adding smp_rmb before timer_pending removes the race.

 The patch is against the latest 2.5 bk tree.  Please point out if I
got something wrong.  TIA.

-- 
tejun

diff -Nru a/kernel/timer.c b/kernel/timer.c
--- a/kernel/timer.c	Tue Sep  2 11:56:58 2003
+++ b/kernel/timer.c	Tue Sep  2 11:56:58 2003
@@ -338,6 +338,7 @@
 			break;
 		}
 	}
+	smp_rmb();
 	if (timer_pending(timer))
 		goto del_again;