From: Peter Zijlstra <peterz@xxxxxxxxxxxxx> commit 1b367ece0d7e696cab1c8501bab282cc6a538b3f upstream. Since the futex_q can dissapear the instruction after assigning NULL, this really should be a RELEASE barrier. That stops loads from hitting dead memory too. Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx> Cc: juri.lelli@xxxxxxx Cc: bigeasy@xxxxxxxxxxxxx Cc: xlpang@xxxxxxxxxx Cc: rostedt@xxxxxxxxxxx Cc: mathieu.desnoyers@xxxxxxxxxxxx Cc: jdesfossez@xxxxxxxxxxxx Cc: dvhart@xxxxxxxxxxxxx Cc: bristot@xxxxxxxxxx Link: http://lkml.kernel.org/r/20170322104151.604296452@xxxxxxxxxxxxx Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx> --- kernel/futex.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) diff --git a/kernel/futex.c b/kernel/futex.c index 796b1c860839..e112a9d4c84f 100644 --- a/kernel/futex.c +++ b/kernel/futex.c @@ -1565,8 +1565,7 @@ static void mark_wake_futex(struct wake_q_head *wake_q, struct futex_q *q) * memory barrier is required here to prevent the following * store to lock_ptr from getting ahead of the plist_del. */ - smp_wmb(); - q->lock_ptr = NULL; + smp_store_release(&q->lock_ptr, NULL); } /*
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