From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755953AbaCYSAI (ORCPT ); Tue, 25 Mar 2014 14:00:08 -0400 Received: from youngberry.canonical.com ([91.189.89.112]:55651 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754208AbaCYRRS (ORCPT ); Tue, 25 Mar 2014 13:17:18 -0400 From: Kamal Mostafa To: linux-kernel@vger.kernel.org, stable@vger.kernel.org, kernel-team@lists.ubuntu.com Cc: Will Deacon , Russell King , Kamal Mostafa Subject: [PATCH 3.8 08/81] ARM: 7955/1: spinlock: ensure we have a compiler barrier before sev Date: Tue, 25 Mar 2014 10:15:21 -0700 Message-Id: <1395767794-5012-9-git-send-email-kamal@canonical.com> X-Mailer: git-send-email 1.8.3.2 In-Reply-To: <1395767794-5012-1-git-send-email-kamal@canonical.com> References: <1395767794-5012-1-git-send-email-kamal@canonical.com> X-Extended-Stable: 3.8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.8.13.20 -stable review patch. If anyone has any objections, please let me know. ------------------ From: Will Deacon commit 7c8746a9eb287642deaad0e7c2cdf482dce5e4be upstream. When unlocking a spinlock, we require the following, strictly ordered sequence of events: /* dmb */ /* dsb */ Whilst the code does indeed reflect this in terms of the architecture, the final + have been contracted into a single inline asm without a "memory" clobber, therefore the compiler is at liberty to reorder the unlock to the end of the above sequence. In such a case, a waiting CPU may be woken up before the lock has been unlocked, leading to extremely poor performance. This patch reworks the dsb_sev() function to make use of the dsb() macro and ensure ordering against the unlock. Reported-by: Mark Rutland Signed-off-by: Will Deacon Signed-off-by: Russell King Signed-off-by: Kamal Mostafa --- arch/arm/include/asm/spinlock.h | 15 +++------------ 1 file changed, 3 insertions(+), 12 deletions(-) diff --git a/arch/arm/include/asm/spinlock.h b/arch/arm/include/asm/spinlock.h index b4ca707..d429475 100644 --- a/arch/arm/include/asm/spinlock.h +++ b/arch/arm/include/asm/spinlock.h @@ -44,18 +44,9 @@ static inline void dsb_sev(void) { -#if __LINUX_ARM_ARCH__ >= 7 - __asm__ __volatile__ ( - "dsb\n" - SEV - ); -#else - __asm__ __volatile__ ( - "mcr p15, 0, %0, c7, c10, 4\n" - SEV - : : "r" (0) - ); -#endif + + dsb(ishst); + __asm__(SEV); } /* -- 1.8.3.2