From mboxrd@z Thu Jan 1 00:00:00 1970 From: Waiman Long Subject: [RFC PATCH-tip v2 1/6] locking/osq: Make lock/unlock proper acquire/release barrier Date: Tue, 14 Jun 2016 18:48:04 -0400 Message-ID: <1465944489-43440-2-git-send-email-Waiman.Long@hpe.com> References: <1465944489-43440-1-git-send-email-Waiman.Long@hpe.com> Return-path: In-Reply-To: <1465944489-43440-1-git-send-email-Waiman.Long@hpe.com> Sender: linux-ia64-owner@vger.kernel.org To: Peter Zijlstra , Ingo Molnar Cc: linux-kernel@vger.kernel.org, x86@kernel.org, linux-alpha@vger.kernel.org, linux-ia64@vger.kernel.org, linux-s390@vger.kernel.org, linux-arch@vger.kernel.org, Davidlohr Bueso , Jason Low , Dave Chinner , Scott J Norton , Douglas Hatch , Waiman Long List-Id: linux-arch.vger.kernel.org The osq_lock() and osq_unlock() function may not provide the necessary acquire and release barrier in some cases. This patch makes sure that the proper barriers are provided when osq_lock() is successful or when osq_unlock() is called. Signed-off-by: Waiman Long --- kernel/locking/osq_lock.c | 4 ++-- 1 files changed, 2 insertions(+), 2 deletions(-) diff --git a/kernel/locking/osq_lock.c b/kernel/locking/osq_lock.c index 05a3785..7dd4ee5 100644 --- a/kernel/locking/osq_lock.c +++ b/kernel/locking/osq_lock.c @@ -115,7 +115,7 @@ bool osq_lock(struct optimistic_spin_queue *lock) * cmpxchg in an attempt to undo our queueing. */ - while (!READ_ONCE(node->locked)) { + while (!smp_load_acquire(&node->locked)) { /* * If we need to reschedule bail... so we can block. */ @@ -198,7 +198,7 @@ void osq_unlock(struct optimistic_spin_queue *lock) * Second most likely case. */ node = this_cpu_ptr(&osq_node); - next = xchg(&node->next, NULL); + next = xchg_release(&node->next, NULL); if (next) { WRITE_ONCE(next->locked, 1); return; -- 1.7.1 From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from g9t5009.houston.hpe.com ([15.241.48.73]:58345 "EHLO g9t5009.houston.hpe.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751339AbcFNWsc (ORCPT ); Tue, 14 Jun 2016 18:48:32 -0400 From: Waiman Long Subject: [RFC PATCH-tip v2 1/6] locking/osq: Make lock/unlock proper acquire/release barrier Date: Tue, 14 Jun 2016 18:48:04 -0400 Message-ID: <1465944489-43440-2-git-send-email-Waiman.Long@hpe.com> In-Reply-To: <1465944489-43440-1-git-send-email-Waiman.Long@hpe.com> References: <1465944489-43440-1-git-send-email-Waiman.Long@hpe.com> Sender: linux-arch-owner@vger.kernel.org List-ID: To: Peter Zijlstra , Ingo Molnar Cc: linux-kernel@vger.kernel.org, x86@kernel.org, linux-alpha@vger.kernel.org, linux-ia64@vger.kernel.org, linux-s390@vger.kernel.org, linux-arch@vger.kernel.org, Davidlohr Bueso , Jason Low , Dave Chinner , Scott J Norton , Douglas Hatch , Waiman Long Message-ID: <20160614224804.TXWZgdEuHQ_MF2rxBFVq4tu5bHaQtAbpASUctAabKpc@z> The osq_lock() and osq_unlock() function may not provide the necessary acquire and release barrier in some cases. This patch makes sure that the proper barriers are provided when osq_lock() is successful or when osq_unlock() is called. Signed-off-by: Waiman Long --- kernel/locking/osq_lock.c | 4 ++-- 1 files changed, 2 insertions(+), 2 deletions(-) diff --git a/kernel/locking/osq_lock.c b/kernel/locking/osq_lock.c index 05a3785..7dd4ee5 100644 --- a/kernel/locking/osq_lock.c +++ b/kernel/locking/osq_lock.c @@ -115,7 +115,7 @@ bool osq_lock(struct optimistic_spin_queue *lock) * cmpxchg in an attempt to undo our queueing. */ - while (!READ_ONCE(node->locked)) { + while (!smp_load_acquire(&node->locked)) { /* * If we need to reschedule bail... so we can block. */ @@ -198,7 +198,7 @@ void osq_unlock(struct optimistic_spin_queue *lock) * Second most likely case. */ node = this_cpu_ptr(&osq_node); - next = xchg(&node->next, NULL); + next = xchg_release(&node->next, NULL); if (next) { WRITE_ONCE(next->locked, 1); return; -- 1.7.1