From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752623AbdJLO0T (ORCPT ); Thu, 12 Oct 2017 10:26:19 -0400 Received: from usa-sjc-mx-foss1.foss.arm.com ([217.140.101.70]:47894 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752213AbdJLO0P (ORCPT ); Thu, 12 Oct 2017 10:26:15 -0400 From: Will Deacon To: paulmck@linux.vnet.ibm.com Cc: linux-kernel@vger.kernel.org, mcree@orcon.net.nz, peterz@infradead.org, rth@twiddle.net, ink@jurassic.park.msu.ru, mattst88@gmail.com, linux-alpha@vger.kernel.org, Will Deacon Subject: [PATCH 3/3] alpha: atomics: Add smp_read_barrier_depends() to release/relaxed atomics Date: Thu, 12 Oct 2017 15:26:17 +0100 Message-Id: <1507818377-7546-4-git-send-email-will.deacon@arm.com> X-Mailer: git-send-email 2.1.4 In-Reply-To: <1507818377-7546-1-git-send-email-will.deacon@arm.com> References: <1507818377-7546-1-git-send-email-will.deacon@arm.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org As part of the fight against smp_read_barrier_depends(), we require dependency ordering to be preserved when a dependency is headed by a load performed using an atomic operation. This patch adds smp_read_barrier_depends() to the _release and _relaxed atomics on alpha, which otherwise lack anything to enforce dependency ordering. Signed-off-by: Will Deacon --- arch/alpha/include/asm/atomic.h | 13 +++++++++++++ 1 file changed, 13 insertions(+) diff --git a/arch/alpha/include/asm/atomic.h b/arch/alpha/include/asm/atomic.h index 498933a7df97..16961a3f45ba 100644 --- a/arch/alpha/include/asm/atomic.h +++ b/arch/alpha/include/asm/atomic.h @@ -13,6 +13,15 @@ * than regular operations. */ +/* + * To ensure dependency ordering is preserved for the _relaxed and + * _release atomics, an smp_read_barrier_depends() is unconditionally + * inserted into the _relaxed variants, which are used to build the + * barriered versions. To avoid redundant back-to-back fences, we can + * define the _acquire and _fence versions explicitly. + */ +#define __atomic_op_acquire(op, args...) op##_relaxed(args) +#define __atomic_op_fence __atomic_op_release #define ATOMIC_INIT(i) { (i) } #define ATOMIC64_INIT(i) { (i) } @@ -60,6 +69,7 @@ static inline int atomic_##op##_return_relaxed(int i, atomic_t *v) \ ".previous" \ :"=&r" (temp), "=m" (v->counter), "=&r" (result) \ :"Ir" (i), "m" (v->counter) : "memory"); \ + smp_read_barrier_depends(); \ return result; \ } @@ -77,6 +87,7 @@ static inline int atomic_fetch_##op##_relaxed(int i, atomic_t *v) \ ".previous" \ :"=&r" (temp), "=m" (v->counter), "=&r" (result) \ :"Ir" (i), "m" (v->counter) : "memory"); \ + smp_read_barrier_depends(); \ return result; \ } @@ -111,6 +122,7 @@ static __inline__ long atomic64_##op##_return_relaxed(long i, atomic64_t * v) \ ".previous" \ :"=&r" (temp), "=m" (v->counter), "=&r" (result) \ :"Ir" (i), "m" (v->counter) : "memory"); \ + smp_read_barrier_depends(); \ return result; \ } @@ -128,6 +140,7 @@ static __inline__ long atomic64_fetch_##op##_relaxed(long i, atomic64_t * v) \ ".previous" \ :"=&r" (temp), "=m" (v->counter), "=&r" (result) \ :"Ir" (i), "m" (v->counter) : "memory"); \ + smp_read_barrier_depends(); \ return result; \ } -- 2.1.4