1 files changed, 27 insertions, 2 deletions

diff --git a/kernel/mutex.c b/kernel/mutex.c
index 507cf2b5e9f1..e5cc0cd28d54 100644
--- a/kernel/mutex.c
+++ b/kernel/mutex.c
@@ -249,7 +249,9 @@ __mutex_lock_common(struct mutex *lock, long state, unsigned int subclass,
 
                 /* didnt get the lock, go to sleep: */
                 spin_unlock_mutex(&lock->wait_lock, flags);
-                __schedule();
+                preempt_enable_no_resched();
+                schedule();
+                preempt_disable();
                 spin_lock_mutex(&lock->wait_lock, flags);
         }
 
@@ -471,5 +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);