Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752992AbcJCJZ1 (ORCPT ); Mon, 3 Oct 2016 05:25:27 -0400 Received: from merlin.infradead.org ([205.233.59.134]:58410 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752464AbcJCJYp (ORCPT ); Mon, 3 Oct 2016 05:24:45 -0400 Message-Id: <20161003091847.527807466@infradead.org> User-Agent: quilt/0.63-1 Date: Mon, 03 Oct 2016 11:12:36 +0200 From: Peter Zijlstra To: mingo@kernel.org, tglx@linutronix.de, juri.lelli@arm.com, rostedt@goodmis.org, xlpang@redhat.com, bigeasy@linutronix.de Cc: linux-kernel@vger.kernel.org, mathieu.desnoyers@efficios.com, jdesfossez@efficios.com, bristot@redhat.com, peterz@infradead.org Subject: [RFC][PATCH 2/4] futex: Use smp_store_release() in mark_wake_futex() References: <20161003091234.879763059@infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline; filename=peterz-futex-mark_wake_futex.patch Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 698 Lines: 22 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) --- kernel/futex.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) --- a/kernel/futex.c +++ b/kernel/futex.c @@ -1288,8 +1288,7 @@ 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); } static int wake_futex_pi(u32 __user *uaddr, u32 uval, struct futex_q *top_waiter,