mutex: add atomic_dec_and_mutex_lock(), fix (a511e3f9) · Commits · 戴 / test

include/linux/mutex.h

+1 −23

Original line number	Diff line number	Diff line
		@@ -150,28 +150,6 @@ extern int __must_check mutex_lock_killable(struct mutex *lock);
		*/
		extern int mutex_trylock(struct mutex *lock);
		extern void mutex_unlock(struct mutex *lock);

		/**
		* 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
		*/
		static inline 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;
		}
		extern int atomic_dec_and_mutex_lock(atomic_t cnt, struct mutex lock);

		#endif

+24 −1

Original line number	Diff line number	Diff line
		@@ -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);