Commit 1b367ece authored Mar 22, 2017 by Peter Zijlstra Committed by Thomas Gleixner Mar 23, 2017

futex: Use smp_store_release() in mark_wake_futex()



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>

parent 499f5aca

kernel/futex.c

+1 −2

Original line number	Diff line number	Diff line
		@@ -1290,8 +1290,7 @@ 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,