From 409d738bbd827ba99109a29591286b301a0785e6 Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Wed, 22 Mar 2017 11:35:49 +0100 Subject: [PATCH 006/365] futex: Use smp_store_release() in mark_wake_futex() Upstream commit 1b367ece0d7e696cab1c8501bab282cc6a538b3f 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: Sebastian Andrzej Siewior --- kernel/futex.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) diff --git a/kernel/futex.c b/kernel/futex.c index 8466f16dedf9..b4cba6dbf608 100644 --- a/kernel/futex.c +++ b/kernel/futex.c @@ -1306,8 +1306,7 @@ 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, -- 2.28.0