2 files changed, 28 insertions, 5 deletions

diff --git a/kernel/mutex.c b/kernel/mutex.c
index f415e80a9119..f788a5ace24b 100644
--- a/kernel/mutex.c
+++ b/kernel/mutex.c
@@ -471,5 +471,28 @@ int __sched mutex_trylock(struct mutex *lock)
 
         return ret;
 }
-
 EXPORT_SYMBOL(mutex_trylock);
+
+/**
+ * atomic_dec_and_mutex_lock - return holding mutex if we dec to 0
+ * @cnt: the atomic which we are to dec
+ * @lock: the mutex to return holding if we dec to 0
+ *
+ * return true and hold lock if we dec to 0, return false otherwise
+ */
+int atomic_dec_and_mutex_lock(atomic_t *cnt, struct mutex *lock)
+{
+        /* dec if we can't possibly hit 0 */
+        if (atomic_add_unless(cnt, -1, 1))
+                return 0;
+        /* we might hit 0, so take the lock */
+        mutex_lock(lock);
+        if (!atomic_dec_and_test(cnt)) {
+                /* when we actually did the dec, we didn't hit 0 */
+                mutex_unlock(lock);
+                return 0;
+        }
+        /* we hit 0, and we hold the lock */
+        return 1;
+}
+EXPORT_SYMBOL(atomic_dec_and_mutex_lock);
diff --git a/kernel/rtmutex.c b/kernel/rtmutex.c
index 69d9cb921ffa..013882e83497 100644
--- a/kernel/rtmutex.c
+++ b/kernel/rtmutex.c
@@ -864,9 +864,9 @@ int __sched rt_mutex_lock_interruptible(struct rt_mutex *lock,
 EXPORT_SYMBOL_GPL(rt_mutex_lock_interruptible);
 
 /**
- * rt_mutex_lock_interruptible_ktime - lock a rt_mutex interruptible
- *                                     the timeout structure is provided
- *                                     by the caller
+ * rt_mutex_timed_lock - lock a rt_mutex interruptible
+ *                      the timeout structure is provided
+ *                      by the caller
  *
  * @lock:               the rt_mutex to be locked
  * @timeout:            timeout structure or NULL (no timeout)
@@ -913,7 +913,7 @@ void __sched rt_mutex_unlock(struct rt_mutex *lock)
 }
 EXPORT_SYMBOL_GPL(rt_mutex_unlock);
 
-/***
+/**
  * rt_mutex_destroy - mark a mutex unusable
  * @lock: the mutex to be destroyed
  *