1 files changed, 26 insertions, 27 deletions

diff --git a/include/asm-generic/mutex-xchg.h b/include/asm-generic/mutex-xchg.h
index 1d24f47e6c4..f169ec06478 100644
--- a/include/asm-generic/mutex-xchg.h
+++ b/include/asm-generic/mutex-xchg.h
@@ -1,9 +1,9 @@
 /*
- * asm-generic/mutex-xchg.h
+ * include/asm-generic/mutex-xchg.h
  *
  * Generic implementation of the mutex fastpath, based on xchg().
  *
- * NOTE: An xchg based implementation is less optimal than an atomic
+ * NOTE: An xchg based implementation might be less optimal than an atomic
  *       decrement/increment based implementation. If your architecture
  *       has a reasonable atomic dec/inc then you should probably use
  *	 asm-generic/mutex-dec.h instead, or you could open-code an
@@ -22,34 +22,34 @@
  * wasn't 1 originally. This function MUST leave the value lower than 1
  * even when the "1" assertion wasn't true.
  */
-#define __mutex_fastpath_lock(count, fail_fn)				\
-do {									\
-	if (unlikely(atomic_xchg(count, 0) != 1))			\
-		fail_fn(count);						\
-	else								\
-		smp_mb();						\
-} while (0)
-
+static inline void
+__mutex_fastpath_lock(atomic_t *count, void (*fail_fn)(atomic_t *))
+{
+	if (unlikely(atomic_xchg(count, 0) != 1))
+		/*
+		 * We failed to acquire the lock, so mark it contended
+		 * to ensure that any waiting tasks are woken up by the
+		 * unlock slow path.
+		 */
+		if (likely(atomic_xchg(count, -1) != 1))
+			fail_fn(count);
+}
 
 /**
  *  __mutex_fastpath_lock_retval - try to take the lock by moving the count
  *                                 from 1 to a 0 value
  *  @count: pointer of type atomic_t
- *  @fail_fn: function to call if the original value was not 1
  *
- * Change the count from 1 to a value lower than 1, and call <fail_fn> if it
- * wasn't 1 originally. This function returns 0 if the fastpath succeeds,
- * or anything the slow path function returns
+ * Change the count from 1 to a value lower than 1. This function returns 0
+ * if the fastpath succeeds, or -1 otherwise.
  */
 static inline int
-__mutex_fastpath_lock_retval(atomic_t *count, int (*fail_fn)(atomic_t *))
+__mutex_fastpath_lock_retval(atomic_t *count)
 {
 	if (unlikely(atomic_xchg(count, 0) != 1))
-		return fail_fn(count);
-	else {
-		smp_mb();
-		return 0;
-	}
+		if (likely(atomic_xchg(count, -1) != 1))
+			return -1;
+	return 0;
 }
 
 /**
@@ -64,12 +64,12 @@ __mutex_fastpath_lock_retval(atomic_t *count, int (*fail_fn)(atomic_t *))
  * __mutex_slowpath_needs_to_unlock() macro needs to return 1, it needs
  * to return 0 otherwise.
  */
-#define __mutex_fastpath_unlock(count, fail_fn)				\
-do {									\
-	smp_mb();							\
-	if (unlikely(atomic_xchg(count, 1) != 0))			\
-		fail_fn(count);						\
-} while (0)
+static inline void
+__mutex_fastpath_unlock(atomic_t *count, void (*fail_fn)(atomic_t *))
+{
+	if (unlikely(atomic_xchg(count, 1) != 0))
+		fail_fn(count);
+}
 
 #define __mutex_slowpath_needs_to_unlock()		0
 
@@ -109,7 +109,6 @@ __mutex_fastpath_trylock(atomic_t *count, int (*fail_fn)(atomic_t *))
 		if (prev < 0)
 			prev = 0;
 	}
-	smp_mb();
 
 	return prev;
 }