[PATCH 1/1] ptrace: task_clear_jobctl_trapping()->wake_up_bit() needs mb()

[Oleg Nesterov]

__wake_up_bit() checks waitqueue_active() and thus the caller needs
mb() as wake_up_bit() documents, fix task_clear_jobctl_trapping().

Signed-off-by: Oleg Nesterov <oleg@xxxxxxxxxx>
---
 kernel/signal.c |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)

diff --git a/kernel/signal.c b/kernel/signal.c
index c2a8542..f4c4119 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -277,6 +277,7 @@ void task_clear_jobctl_trapping(struct task_struct *task)
 {
 	if (unlikely(task->jobctl & JOBCTL_TRAPPING)) {
 		task->jobctl &= ~JOBCTL_TRAPPING;
+		smp_mb();	/* advised by wake_up_bit() */
 		wake_up_bit(&task->jobctl, JOBCTL_TRAPPING_BIT);
 	}
 }
-- 
1.5.5.1


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