From 038bb2d149e5a561a9725f7f21f80a2b21b02bb5 Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Sun, 28 Mar 2021 22:40:54 +0200 Subject: [PATCH] futex: Use smp_store_release() in mark_wake_futex() 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) 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 Signed-off-by: Ben Hutchings Signed-off-by: Greg Kroah-Hartman --- 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); } /*