From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.linuxfoundation.org ([140.211.169.12]:58312 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753056AbcLLWrA (ORCPT ); Mon, 12 Dec 2016 17:47:00 -0500 Subject: Patch "locking/rtmutex: Use READ_ONCE() in rt_mutex_owner()" has been added to the 4.4-stable tree To: tglx@linutronix.de, bigeasy@linutronix.de, ddaney@caviumnetworks.com, gregkh@linuxfoundation.org, mark.rutland@arm.com, mingo@kernel.org, peterz@infradead.org, rostedt@goodmis.org, torvalds@linux-foundation.org, will.deacon@arm.com Cc: , From: Date: Mon, 12 Dec 2016 14:47:09 -0800 Message-ID: <14815828296683@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=ANSI_X3.4-1968 Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org List-ID: This is a note to let you know that I've just added the patch titled locking/rtmutex: Use READ_ONCE() in rt_mutex_owner() to the 4.4-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: locking-rtmutex-use-read_once-in-rt_mutex_owner.patch and it can be found in the queue-4.4 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let know about it. >>From 1be5d4fa0af34fb7bafa205aeb59f5c7cc7a089d Mon Sep 17 00:00:00 2001 From: Thomas Gleixner Date: Wed, 30 Nov 2016 21:04:42 +0000 Subject: locking/rtmutex: Use READ_ONCE() in rt_mutex_owner() From: Thomas Gleixner commit 1be5d4fa0af34fb7bafa205aeb59f5c7cc7a089d upstream. While debugging the rtmutex unlock vs. dequeue race Will suggested to use READ_ONCE() in rt_mutex_owner() as it might race against the cmpxchg_release() in unlock_rt_mutex_safe(). Will: "It's a minor thing which will most likely not matter in practice" Careful search did not unearth an actual problem in todays code, but it's better to be safe than surprised. Suggested-by: Will Deacon Signed-off-by: Thomas Gleixner Acked-by: Peter Zijlstra (Intel) Cc: David Daney Cc: Linus Torvalds Cc: Mark Rutland Cc: Peter Zijlstra Cc: Sebastian Siewior Cc: Steven Rostedt Link: http://lkml.kernel.org/r/20161130210030.431379999@linutronix.de Signed-off-by: Ingo Molnar Signed-off-by: Greg Kroah-Hartman --- kernel/locking/rtmutex_common.h | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) --- a/kernel/locking/rtmutex_common.h +++ b/kernel/locking/rtmutex_common.h @@ -75,8 +75,9 @@ task_top_pi_waiter(struct task_struct *p static inline struct task_struct *rt_mutex_owner(struct rt_mutex *lock) { - return (struct task_struct *) - ((unsigned long)lock->owner & ~RT_MUTEX_OWNER_MASKALL); + unsigned long owner = (unsigned long) READ_ONCE(lock->owner); + + return (struct task_struct *) (owner & ~RT_MUTEX_OWNER_MASKALL); } /* Patches currently in stable-queue which might be from tglx@linutronix.de are queue-4.4/locking-rtmutex-prevent-dequeue-vs.-unlock-race.patch queue-4.4/perf-x86-fix-full-width-counter-counter-overflow.patch queue-4.4/locking-rtmutex-use-read_once-in-rt_mutex_owner.patch