From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.linuxfoundation.org ([140.211.169.12]:45338 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933644AbcIVNeO (ORCPT ); Thu, 22 Sep 2016 09:34:14 -0400 Subject: Patch "arm64: spinlocks: implement smp_mb__before_spinlock() as smp_mb()" has been added to the 4.7-stable tree To: will.deacon@arm.com, catalin.marinas@arm.com, gregkh@linuxfoundation.org, peterz@infradead.org, stern@rowland.harvard.edu Cc: , From: Date: Thu, 22 Sep 2016 15:34:02 +0200 Message-ID: <147455124222666@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 arm64: spinlocks: implement smp_mb__before_spinlock() as smp_mb() to the 4.7-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: arm64-spinlocks-implement-smp_mb__before_spinlock-as-smp_mb.patch and it can be found in the queue-4.7 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let know about it. >>From 872c63fbf9e153146b07f0cece4da0d70b283eeb Mon Sep 17 00:00:00 2001 From: Will Deacon Date: Mon, 5 Sep 2016 11:56:05 +0100 Subject: arm64: spinlocks: implement smp_mb__before_spinlock() as smp_mb() From: Will Deacon commit 872c63fbf9e153146b07f0cece4da0d70b283eeb upstream. smp_mb__before_spinlock() is intended to upgrade a spin_lock() operation to a full barrier, such that prior stores are ordered with respect to loads and stores occuring inside the critical section. Unfortunately, the core code defines the barrier as smp_wmb(), which is insufficient to provide the required ordering guarantees when used in conjunction with our load-acquire-based spinlock implementation. This patch overrides the arm64 definition of smp_mb__before_spinlock() to map to a full smp_mb(). Cc: Peter Zijlstra Reported-by: Alan Stern Signed-off-by: Will Deacon Signed-off-by: Catalin Marinas Signed-off-by: Greg Kroah-Hartman --- arch/arm64/include/asm/spinlock.h | 10 ++++++++++ 1 file changed, 10 insertions(+) --- a/arch/arm64/include/asm/spinlock.h +++ b/arch/arm64/include/asm/spinlock.h @@ -363,4 +363,14 @@ static inline int arch_read_trylock(arch #define arch_read_relax(lock) cpu_relax() #define arch_write_relax(lock) cpu_relax() +/* + * Accesses appearing in program order before a spin_lock() operation + * can be reordered with accesses inside the critical section, by virtue + * of arch_spin_lock being constructed using acquire semantics. + * + * In cases where this is problematic (e.g. try_to_wake_up), an + * smp_mb__before_spinlock() can restore the required ordering. + */ +#define smp_mb__before_spinlock() smp_mb() + #endif /* __ASM_SPINLOCK_H */ Patches currently in stable-queue which might be from will.deacon@arm.com are queue-4.7/arm64-spinlocks-implement-smp_mb__before_spinlock-as-smp_mb.patch