From: Peter Zijlstra peterz@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) peterz@infradead.org Cc: juri.lelli@arm.com Cc: bigeasy@linutronix.de Cc: xlpang@redhat.com Cc: rostedt@goodmis.org Cc: mathieu.desnoyers@efficios.com Cc: jdesfossez@efficios.com Cc: dvhart@infradead.org Cc: bristot@redhat.com Link: http://lkml.kernel.org/r/20170322104151.604296452@infradead.org Signed-off-by: Thomas Gleixner tglx@linutronix.de Signed-off-by: Ben Hutchings ben@decadent.org.uk Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- kernel/futex.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-)
--- a/kernel/futex.c +++ b/kernel/futex.c @@ -1565,8 +1565,7 @@ static void mark_wake_futex(struct wake_ * 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); }
/*