X-Git-Url: http://git.cascardo.eti.br/?a=blobdiff_plain;f=kernel%2Fmutex.c;h=947b3ad551f8a925c39ef6f53f4f37c16f8a3ea3;hb=31950eb66ff47c946fd9c65c2f8c94b6b7ba13fc;hp=6ca5fe96e393a5176428e95b34d6aa9fcc20de2b;hpb=be15f9d63b97da0065187696962331de6cd9de9e;p=cascardo%2Flinux.git

diff --git a/kernel/mutex.c b/kernel/mutex.c
index 6ca5fe96e393..947b3ad551f8 100644
--- a/kernel/mutex.c
+++ b/kernel/mutex.c
@@ -89,7 +89,7 @@ __mutex_lock_slowpath(atomic_t *lock_count);
  *
  * This function is similar to (but not equivalent to) down().
  */
-void inline __sched mutex_lock(struct mutex *lock)
+void __sched mutex_lock(struct mutex *lock)
 {
 	might_sleep();
 	/*
@@ -473,5 +473,28 @@ 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);