Fix del_timer_sync() SMP memory ordering (from Tejun Huh <tejun@aratech.co.kr>)

From Tejun's posting:
>
> 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.

1 files changed, 1 insertions, 0 deletions

diff --git a/kernel/timer.c b/kernel/timer.c
index ab083d12eb3a..2c8d770c5876 100644
--- a/kernel/timer.c
+++ b/kernel/timer.c
@@ -338,6 +338,7 @@ del_again:
 			break;
 		}
 	}
+	smp_rmb();
 	if (timer_pending(timer))
 		goto del_again;