From cc189d2513d1f45cde87a9043fe3be28559c7490 Mon Sep 17 00:00:00 2001 From: Waiman Long Date: Wed, 17 Apr 2013 15:23:14 -0400 Subject: [PATCH] mutex: Back out architecture specific check for negative mutex count Linus suggested that probably all the supported architectures can allow a negative mutex count without incorrect behavior, so 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. Suggested-by: Linus Torvalds Signed-off-by: Waiman Long Cc: Andrew Morton Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: Chandramouleeswaran Aswin Cc: Davidlohr Bueso Cc: Norton Scott J Cc: Rik van Riel Cc: Paul E. McKenney Cc: David Howells Cc: Dave Jones Cc: Clark Williams Cc: Peter Zijlstra Link: http://lkml.kernel.org/r/1366226594-5506-5-git-send-email-Waiman.Long@hp.com Signed-off-by: Ingo Molnar --- 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 bc2a0b0dcea6..7d3a48275394 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 1dbd4210baef..ad53a664f113 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) -- 2.30.2