From: Peter Zijlstra <pet...@infradead.org> 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) <pet...@infradead.org> Cc: juri.le...@arm.com Cc: bige...@linutronix.de Cc: xlp...@redhat.com Cc: rost...@goodmis.org Cc: mathieu.desnoy...@efficios.com Cc: jdesfos...@efficios.com Cc: dvh...@infradead.org Cc: bris...@redhat.com Link: http://lkml.kernel.org/r/20170322104151.604296...@infradead.org Signed-off-by: Thomas Gleixner <t...@linutronix.de> Tested-by: Henrik Austad <haus...@cisco.com> --- kernel/futex.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) diff --git a/kernel/futex.c b/kernel/futex.c index bb87324..9e92f12 100644 --- a/kernel/futex.c +++ b/kernel/futex.c @@ -1284,8 +1284,7 @@ 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); } static int wake_futex_pi(u32 __user *uaddr, u32 uval, struct futex_q *top_waiter, -- 2.7.4
