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[92.220.88.11]) by smtp.gmail.com with ESMTPSA id u65sm1265576lff.54.2018.11.09.02.07.53 (version=TLS1_2 cipher=ECDHE-RSA-AES128-SHA bits=128/128); Fri, 09 Nov 2018 02:07:53 -0800 (PST) From: Henrik Austad To: Linux Kernel Mailing List Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Henrik Austad , Peter Zijlstra , juri.lelli@arm.com, bigeasy@linutronix.de, xlpang@redhat.com, rostedt@goodmis.org, mathieu.desnoyers@efficios.com, jdesfossez@efficios.com, dvhart@infradead.org, bristot@redhat.com, Thomas Gleixner Subject: [PATCH 02/17] futex: Use smp_store_release() in mark_wake_futex() Date: Fri, 9 Nov 2018 11:07:30 +0100 Message-Id: <1541758065-10952-3-git-send-email-henrik@austad.us> X-Mailer: git-send-email 2.7.4 In-Reply-To: <1541758065-10952-1-git-send-email-henrik@austad.us> References: <1541758065-10952-1-git-send-email-henrik@austad.us> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Peter Zijlstra 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 Tested-by: Henrik Austad --- kernel/futex.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) diff --git a/kernel/futex.c b/kernel/futex.c index bb87324..9e92f12 100644 --- a/kernel/futex.c +++ b/kernel/futex.c @@ -1284,8 +1284,7 @@ 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, -- 2.7.4