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>

1 files changed, 2 insertions, 7 deletions

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)