Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S966628Ab3DQTXw (ORCPT ); Wed, 17 Apr 2013 15:23:52 -0400 Received: from g1t0027.austin.hp.com ([15.216.28.34]:29538 "EHLO g1t0027.austin.hp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S936356Ab3DQTXp (ORCPT ); Wed, 17 Apr 2013 15:23:45 -0400 From: Waiman Long Cc: Waiman Long , linux-kernel@vger.kernel.org, x86@kernel.org, linux-arch@vger.kernel.org, "Chandramouleeswaran, Aswin" , Davidlohr Bueso , "Norton, Scott J" , Rik van Riel Subject: [PATCH v4 optional 4/4] mutex: back out architecture specific check for negative mutex count Date: Wed, 17 Apr 2013 15:23:14 -0400 Message-Id: <1366226594-5506-5-git-send-email-Waiman.Long@hp.com> X-Mailer: git-send-email 1.7.1 In-Reply-To: <1366226594-5506-1-git-send-email-Waiman.Long@hp.com> References: <1366226594-5506-1-git-send-email-Waiman.Long@hp.com> To: Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , "Paul E. McKenney" , David Howells , Dave Jones , Clark Williams , Peter Zijlstra Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2026 Lines: 62 If it is confirmed that all the supported architectures can allow a negative mutex count without incorrect behavior, we can then back out the architecture specific change and allow the mutex count to go to any negative number. That should further reduce contention for non-x86 architecture. If this is not the case, this patch should be dropped. Signed-off-by: Waiman Long --- arch/x86/include/asm/mutex.h | 10 ---------- kernel/mutex.c | 9 ++------- 2 files changed, 2 insertions(+), 17 deletions(-) diff --git a/arch/x86/include/asm/mutex.h b/arch/x86/include/asm/mutex.h index bc2a0b0..7d3a482 100644 --- a/arch/x86/include/asm/mutex.h +++ b/arch/x86/include/asm/mutex.h @@ -3,13 +3,3 @@ #else # include #endif - -#ifndef __ASM_MUTEX_H -#define __ASM_MUTEX_H -/* - * For the x86 architecture, it allows any negative number (besides -1) in - * the mutex count to indicate that some other threads are waiting on the - * mutex. - */ -#define __ARCH_ALLOW_ANY_NEGATIVE_MUTEX_COUNT 1 -#endif diff --git a/kernel/mutex.c b/kernel/mutex.c index 1dbd421..ad53a66 100644 --- a/kernel/mutex.c +++ b/kernel/mutex.c @@ -38,15 +38,10 @@ #endif /* - * A mutex count of -1 indicates that waiters are sleeping waiting for the - * mutex. Some architectures can allow any negative number, not just -1, for - * this purpose. + * A negative mutex count indicates that waiters are sleeping waiting for the + * mutex. */ -#ifdef __ARCH_ALLOW_ANY_NEGATIVE_MUTEX_COUNT #define MUTEX_SHOW_NO_WAITER(mutex) (atomic_read(&(mutex)->count) >= 0) -#else -#define MUTEX_SHOW_NO_WAITER(mutex) (atomic_read(&(mutex)->count) != -1) -#endif void __mutex_init(struct mutex *lock, const char *name, struct lock_class_key *key) -- 1.7.1 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/