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authorIngo Molnar <mingo@elte.hu>2009-05-06 08:46:27 +0200
committerIngo Molnar <mingo@elte.hu>2009-05-06 08:47:26 +0200
commit3611dfb8eda847c1c8e1a052f57206f7fddc6a7c (patch)
tree74b5d689be8bfca2ec0fe18961ccaf6953c21dba /kernel/mutex.c
parent16c8a10932aef971292c9570eb5f60b5d4e83ed2 (diff)
parenta511e3f968c462a55ef58697257f5347c73d306e (diff)
downloadlinaro-lsk-3611dfb8eda847c1c8e1a052f57206f7fddc6a7c.tar.gz
Merge branch 'core/locking' into perfcounters/core
Merge reason: we moved a mutex.h commit that originated from the perfcounters tree into core/locking - but now merge back that branch to solve a merge artifact and to pick up cleanups of this commit that happened in core/locking. Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'kernel/mutex.c')
-rw-r--r--kernel/mutex.c25
1 files changed, 24 insertions, 1 deletions
diff --git a/kernel/mutex.c b/kernel/mutex.c
index f415e80a911..f788a5ace24 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);