From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754848AbaKYMi7 (ORCPT ); Tue, 25 Nov 2014 07:38:59 -0500 Received: from e06smtp14.uk.ibm.com ([195.75.94.110]:43374 "EHLO e06smtp14.uk.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754173AbaKYMir (ORCPT ); Tue, 25 Nov 2014 07:38:47 -0500 From: Christian Borntraeger To: linux-kernel@vger.kernel.org Cc: "linux-arch@vger.kernel.org, linux-mips@linux-mips.org, linux-x86_64@vger.kernel.org, linux-s390"@vger.kernel.org, Paolo Bonzini , paulmck@linux.vnet.ibm.com, mingo@kernel.org, torvalds@linux-foundation.org, Catalin Marinas , Will Deacon , Alexei Starovoitov , David Howells , Russell King , Christian Borntraeger Subject: [PATCHv2 08/10] arm: Replace ACCESS_ONCE for spinlock code with READ_ONCE Date: Tue, 25 Nov 2014 13:38:35 +0100 Message-Id: <1416919117-50652-9-git-send-email-borntraeger@de.ibm.com> X-Mailer: git-send-email 1.9.3 In-Reply-To: <1416919117-50652-1-git-send-email-borntraeger@de.ibm.com> References: <1416919117-50652-1-git-send-email-borntraeger@de.ibm.com> X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 14112512-0017-0000-0000-000001F84C73 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org ACCESS_ONCE does not work reliably on non-scalar types. For example gcc 4.6 and 4.7 might remove the volatile tag for such accesses during the SRA (scalar replacement of aggregates) step (https://gcc.gnu.org/bugzilla/show_bug.cgi?id=58145) Change the spinlock code to replace ACCESS_ONCE with READ_ONCE. Signed-off-by: Christian Borntraeger --- arch/arm/include/asm/spinlock.h | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/arch/arm/include/asm/spinlock.h b/arch/arm/include/asm/spinlock.h index ac4bfae..0fa4184 100644 --- a/arch/arm/include/asm/spinlock.h +++ b/arch/arm/include/asm/spinlock.h @@ -120,12 +120,12 @@ static inline int arch_spin_value_unlocked(arch_spinlock_t lock) static inline int arch_spin_is_locked(arch_spinlock_t *lock) { - return !arch_spin_value_unlocked(ACCESS_ONCE(*lock)); + return !arch_spin_value_unlocked(READ_ONCE(*lock)); } static inline int arch_spin_is_contended(arch_spinlock_t *lock) { - struct __raw_tickets tickets = ACCESS_ONCE(lock->tickets); + struct __raw_tickets tickets = READ_ONCE(lock->tickets); return (tickets.next - tickets.owner) > 1; } #define arch_spin_is_contended arch_spin_is_contended -- 1.9.3