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authorWaiman Long <Waiman.Long@hp.com>2013-04-17 15:23:14 -0400
committerIngo Molnar <mingo@kernel.org>2013-04-19 09:33:36 +0200
commitcc189d2513d1f45cde87a9043fe3be28559c7490 (patch)
tree064796cc597cfae5cc657d8bdc212774ea5251ff
parent2bd2c92cf07cc4a373bf316c75b78ac465fefd35 (diff)
downloadlinaro-lsk-cc189d2513d1f45cde87a9043fe3be28559c7490.tar.gz
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 <torvalds@linux-foundation.org> Signed-off-by: Waiman Long <Waiman.Long@hp.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Chandramouleeswaran Aswin <aswin@hp.com> Cc: Davidlohr Bueso <davidlohr.bueso@hp.com> Cc: Norton Scott J <scott.norton@hp.com> Cc: Rik van Riel <riel@redhat.com> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: David Howells <dhowells@redhat.com> Cc: Dave Jones <davej@redhat.com> Cc: Clark Williams <williams@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/r/1366226594-5506-5-git-send-email-Waiman.Long@hp.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
-rw-r--r--arch/x86/include/asm/mutex.h10
-rw-r--r--kernel/mutex.c9
2 files changed, 2 insertions, 17 deletions
diff --git a/arch/x86/include/asm/mutex.h b/arch/x86/include/asm/mutex.h
index bc2a0b0dcea..7d3a4827539 100644
--- a/arch/x86/include/asm/mutex.h
+++ b/arch/x86/include/asm/mutex.h
@@ -3,13 +3,3 @@
#else
# include <asm/mutex_64.h>
#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 1dbd4210bae..ad53a664f11 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)