From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758291AbcDMLe3 (ORCPT ); Wed, 13 Apr 2016 07:34:29 -0400 Received: from terminus.zytor.com ([198.137.202.10]:55952 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750945AbcDMLe1 (ORCPT ); Wed, 13 Apr 2016 07:34:27 -0400 Date: Wed, 13 Apr 2016 04:32:38 -0700 From: tip-bot for Michal Hocko Message-ID: Cc: torvalds@linux-foundation.org, dbueso@suse.de, davem@davemloft.net, jcmvbkbc@gmail.com, mingo@kernel.org, mhocko@suse.com, tony.luck@intel.com, akpm@linux-foundation.org, jason.low2@hp.com, hpa@zytor.com, peterz@infradead.org, paulmck@linux.vnet.ibm.com, chris@zankel.net, tglx@linutronix.de, linux-kernel@vger.kernel.org Reply-To: dbueso@suse.de, torvalds@linux-foundation.org, davem@davemloft.net, mingo@kernel.org, jcmvbkbc@gmail.com, mhocko@suse.com, tony.luck@intel.com, akpm@linux-foundation.org, jason.low2@hp.com, hpa@zytor.com, peterz@infradead.org, paulmck@linux.vnet.ibm.com, chris@zankel.net, tglx@linutronix.de, linux-kernel@vger.kernel.org In-Reply-To: <1460041951-22347-3-git-send-email-mhocko@kernel.org> References: <1460041951-22347-3-git-send-email-mhocko@kernel.org> To: linux-tip-commits@vger.kernel.org Subject: [tip:locking/rwsem] locking/rwsem: Drop explicit memory barriers Git-Commit-ID: 2e927c6422fea5ce36b24b00c2c84f2e9ead31b6 X-Mailer: tip-git-log-daemon Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Commit-ID: 2e927c6422fea5ce36b24b00c2c84f2e9ead31b6 Gitweb: http://git.kernel.org/tip/2e927c6422fea5ce36b24b00c2c84f2e9ead31b6 Author: Michal Hocko AuthorDate: Thu, 7 Apr 2016 17:12:22 +0200 Committer: Ingo Molnar CommitDate: Wed, 13 Apr 2016 10:42:18 +0200 locking/rwsem: Drop explicit memory barriers sh and xtensa seem to be the only architectures which use explicit memory barriers for rw_semaphore operations even though they are not really needed because there is the full memory barrier is always implied by atomic_{inc,dec,add,sub}_return() resp. cmpxchg(). Remove them. Signed-off-by: Michal Hocko Cc: Andrew Morton Cc: Chris Zankel Cc: David S. Miller Cc: Linus Torvalds Cc: Max Filippov Cc: Paul E. McKenney Cc: Peter Zijlstra Cc: Signed-off-by: Davidlohr Bueso Cc: Signed-off-by: Jason Low Cc: Thomas Gleixner Cc: Tony Luck Cc: linux-alpha@vger.kernel.org Cc: linux-arch@vger.kernel.org Cc: linux-ia64@vger.kernel.org Cc: linux-s390@vger.kernel.org Cc: linux-sh@vger.kernel.org Cc: linux-xtensa@linux-xtensa.org Cc: sparclinux@vger.kernel.org Link: http://lkml.kernel.org/r/1460041951-22347-3-git-send-email-mhocko@kernel.org Signed-off-by: Ingo Molnar --- arch/sh/include/asm/rwsem.h | 14 ++------------ arch/xtensa/include/asm/rwsem.h | 14 ++------------ 2 files changed, 4 insertions(+), 24 deletions(-) diff --git a/arch/sh/include/asm/rwsem.h b/arch/sh/include/asm/rwsem.h index a5104be..f6c951c 100644 --- a/arch/sh/include/asm/rwsem.h +++ b/arch/sh/include/asm/rwsem.h @@ -24,9 +24,7 @@ */ static inline void __down_read(struct rw_semaphore *sem) { - if (atomic_inc_return((atomic_t *)(&sem->count)) > 0) - smp_wmb(); - else + if (atomic_inc_return((atomic_t *)(&sem->count)) <= 0) rwsem_down_read_failed(sem); } @@ -37,7 +35,6 @@ static inline int __down_read_trylock(struct rw_semaphore *sem) while ((tmp = sem->count) >= 0) { if (tmp == cmpxchg(&sem->count, tmp, tmp + RWSEM_ACTIVE_READ_BIAS)) { - smp_wmb(); return 1; } } @@ -53,9 +50,7 @@ static inline void __down_write(struct rw_semaphore *sem) tmp = atomic_add_return(RWSEM_ACTIVE_WRITE_BIAS, (atomic_t *)(&sem->count)); - if (tmp == RWSEM_ACTIVE_WRITE_BIAS) - smp_wmb(); - else + if (tmp != RWSEM_ACTIVE_WRITE_BIAS) rwsem_down_write_failed(sem); } @@ -65,7 +60,6 @@ static inline int __down_write_trylock(struct rw_semaphore *sem) tmp = cmpxchg(&sem->count, RWSEM_UNLOCKED_VALUE, RWSEM_ACTIVE_WRITE_BIAS); - smp_wmb(); return tmp == RWSEM_UNLOCKED_VALUE; } @@ -76,7 +70,6 @@ static inline void __up_read(struct rw_semaphore *sem) { int tmp; - smp_wmb(); tmp = atomic_dec_return((atomic_t *)(&sem->count)); if (tmp < -1 && (tmp & RWSEM_ACTIVE_MASK) == 0) rwsem_wake(sem); @@ -87,7 +80,6 @@ static inline void __up_read(struct rw_semaphore *sem) */ static inline void __up_write(struct rw_semaphore *sem) { - smp_wmb(); if (atomic_sub_return(RWSEM_ACTIVE_WRITE_BIAS, (atomic_t *)(&sem->count)) < 0) rwsem_wake(sem); @@ -108,7 +100,6 @@ static inline void __downgrade_write(struct rw_semaphore *sem) { int tmp; - smp_wmb(); tmp = atomic_add_return(-RWSEM_WAITING_BIAS, (atomic_t *)(&sem->count)); if (tmp < 0) rwsem_downgrade_wake(sem); @@ -119,7 +110,6 @@ static inline void __downgrade_write(struct rw_semaphore *sem) */ static inline int rwsem_atomic_update(int delta, struct rw_semaphore *sem) { - smp_mb(); return atomic_add_return(delta, (atomic_t *)(&sem->count)); } diff --git a/arch/xtensa/include/asm/rwsem.h b/arch/xtensa/include/asm/rwsem.h index 249619e..593483f 100644 --- a/arch/xtensa/include/asm/rwsem.h +++ b/arch/xtensa/include/asm/rwsem.h @@ -29,9 +29,7 @@ */ static inline void __down_read(struct rw_semaphore *sem) { - if (atomic_add_return(1,(atomic_t *)(&sem->count)) > 0) - smp_wmb(); - else + if (atomic_add_return(1,(atomic_t *)(&sem->count)) <= 0) rwsem_down_read_failed(sem); } @@ -42,7 +40,6 @@ static inline int __down_read_trylock(struct rw_semaphore *sem) while ((tmp = sem->count) >= 0) { if (tmp == cmpxchg(&sem->count, tmp, tmp + RWSEM_ACTIVE_READ_BIAS)) { - smp_wmb(); return 1; } } @@ -58,9 +55,7 @@ static inline void __down_write(struct rw_semaphore *sem) tmp = atomic_add_return(RWSEM_ACTIVE_WRITE_BIAS, (atomic_t *)(&sem->count)); - if (tmp == RWSEM_ACTIVE_WRITE_BIAS) - smp_wmb(); - else + if (tmp != RWSEM_ACTIVE_WRITE_BIAS) rwsem_down_write_failed(sem); } @@ -70,7 +65,6 @@ static inline int __down_write_trylock(struct rw_semaphore *sem) tmp = cmpxchg(&sem->count, RWSEM_UNLOCKED_VALUE, RWSEM_ACTIVE_WRITE_BIAS); - smp_wmb(); return tmp == RWSEM_UNLOCKED_VALUE; } @@ -81,7 +75,6 @@ static inline void __up_read(struct rw_semaphore *sem) { int tmp; - smp_wmb(); tmp = atomic_sub_return(1,(atomic_t *)(&sem->count)); if (tmp < -1 && (tmp & RWSEM_ACTIVE_MASK) == 0) rwsem_wake(sem); @@ -92,7 +85,6 @@ static inline void __up_read(struct rw_semaphore *sem) */ static inline void __up_write(struct rw_semaphore *sem) { - smp_wmb(); if (atomic_sub_return(RWSEM_ACTIVE_WRITE_BIAS, (atomic_t *)(&sem->count)) < 0) rwsem_wake(sem); @@ -113,7 +105,6 @@ static inline void __downgrade_write(struct rw_semaphore *sem) { int tmp; - smp_wmb(); tmp = atomic_add_return(-RWSEM_WAITING_BIAS, (atomic_t *)(&sem->count)); if (tmp < 0) rwsem_downgrade_wake(sem); @@ -124,7 +115,6 @@ static inline void __downgrade_write(struct rw_semaphore *sem) */ static inline int rwsem_atomic_update(int delta, struct rw_semaphore *sem) { - smp_mb(); return atomic_add_return(delta, (atomic_t *)(&sem->count)); }