locking/mutexes: Standardize arguments in lock/unlock slowpaths

Just how the locking-end behaves, when unlocking, go ahead and
obtain the proper data structure immediately after the previous
(asm-end) call exits and there are (probably) pending waiters.
This simplifies a bit some of the layering.

Signed-off-by: Davidlohr Bueso <davidlohr@hp.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Cc: jason.low2@hp.com
Cc: aswin@hp.com
Cc: mingo@kernel.org
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: linux-kernel@vger.kernel.org
Link: http://lkml.kernel.org/r/1406752916-3341-1-git-send-email-davidlohr@hp.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

kernel/locking/mutex.c

@@ -679,9 +679,8 @@ EXPORT_SYMBOL_GPL(__ww_mutex_lock_interruptible);
  * Release the lock, slowpath:
  */
 static inline void
-__mutex_unlock_common_slowpath(atomic_t *lock_count, int nested)
+__mutex_unlock_common_slowpath(struct mutex *lock, int nested)
 {
-	struct mutex *lock = container_of(lock_count, struct mutex, count);
 	unsigned long flags;
 
 	/*
@@ -716,7 +715,9 @@ __mutex_unlock_common_slowpath(atomic_t *lock_count, int nested)
 __visible void
 __mutex_unlock_slowpath(atomic_t *lock_count)
 {
-	__mutex_unlock_common_slowpath(lock_count, 1);
+	struct mutex *lock = container_of(lock_count, struct mutex, count);
+
+	__mutex_unlock_common_slowpath(lock, 1);
 }
 
 #ifndef CONFIG_DEBUG_LOCK_ALLOC