aboutsummaryrefslogtreecommitdiffstats
diff options
context:
space:
mode:
-rw-r--r--include/linux/mutex.h24
-rw-r--r--kernel/mutex.c25
2 files changed, 25 insertions, 24 deletions
diff --git a/include/linux/mutex.h b/include/linux/mutex.h
index 93054fc3635c..878cab4f5fcc 100644
--- a/include/linux/mutex.h
+++ b/include/linux/mutex.h
@@ -150,28 +150,6 @@ extern int __must_check mutex_lock_killable(struct mutex *lock);
150 */ 150 */
151extern int mutex_trylock(struct mutex *lock); 151extern int mutex_trylock(struct mutex *lock);
152extern void mutex_unlock(struct mutex *lock); 152extern void mutex_unlock(struct mutex *lock);
153 153extern int atomic_dec_and_mutex_lock(atomic_t *cnt, struct mutex *lock);
154/**
155 * atomic_dec_and_mutex_lock - return holding mutex if we dec to 0
156 * @cnt: the atomic which we are to dec
157 * @lock: the mutex to return holding if we dec to 0
158 *
159 * return true and hold lock if we dec to 0, return false otherwise
160 */
161static inline int atomic_dec_and_mutex_lock(atomic_t *cnt, struct mutex *lock)
162{
163 /* dec if we can't possibly hit 0 */
164 if (atomic_add_unless(cnt, -1, 1))
165 return 0;
166 /* we might hit 0, so take the lock */
167 mutex_lock(lock);
168 if (!atomic_dec_and_test(cnt)) {
169 /* when we actually did the dec, we didn't hit 0 */
170 mutex_unlock(lock);
171 return 0;
172 }
173 /* we hit 0, and we hold the lock */
174 return 1;
175}
176 154
177#endif 155#endif
diff --git a/kernel/mutex.c b/kernel/mutex.c
index 507cf2b5e9f1..e2d25e9e62ae 100644
--- a/kernel/mutex.c
+++ b/kernel/mutex.c
@@ -471,5 +471,28 @@ int __sched mutex_trylock(struct mutex *lock)
471 471
472 return ret; 472 return ret;
473} 473}
474
475EXPORT_SYMBOL(mutex_trylock); 474EXPORT_SYMBOL(mutex_trylock);
475
476/**
477 * atomic_dec_and_mutex_lock - return holding mutex if we dec to 0
478 * @cnt: the atomic which we are to dec
479 * @lock: the mutex to return holding if we dec to 0
480 *
481 * return true and hold lock if we dec to 0, return false otherwise
482 */
483int atomic_dec_and_mutex_lock(atomic_t *cnt, struct mutex *lock)
484{
485 /* dec if we can't possibly hit 0 */
486 if (atomic_add_unless(cnt, -1, 1))
487 return 0;
488 /* we might hit 0, so take the lock */
489 mutex_lock(lock);
490 if (!atomic_dec_and_test(cnt)) {
491 /* when we actually did the dec, we didn't hit 0 */
492 mutex_unlock(lock);
493 return 0;
494 }
495 /* we hit 0, and we hold the lock */
496 return 1;
497}
498EXPORT_SYMBOL(atomic_dec_and_mutex_lock);