include/asm-generic/qrwlock.h

3  * Queue read/write lock
28 #define	_QW_LOCKED	0x0ff		/* A writer holds the lock */
36 extern void queued_read_lock_slowpath(struct qrwlock *lock);
37 extern void queued_write_lock_slowpath(struct qrwlock *lock);
40  * queued_read_trylock - try to acquire read lock of a queued rwlock
41  * @lock : Pointer to queued rwlock structure
42  * Return: 1 if lock acquired, 0 if failed
44 static inline int queued_read_trylock(struct qrwlock *lock)
48 	cnts = atomic_read(&lock->cnts);
50 		cnts = (u32)atomic_add_return_acquire(_QR_BIAS, &lock->cnts);
53 		atomic_sub(_QR_BIAS, &lock->cnts);
59  * queued_write_trylock - try to acquire write lock of a queued rwlock
60  * @lock : Pointer to queued rwlock structure
61  * Return: 1 if lock acquired, 0 if failed
63 static inline int queued_write_trylock(struct qrwlock *lock)
67 	cnts = atomic_read(&lock->cnts);
71 	return likely(atomic_try_cmpxchg_acquire(&lock->cnts, &cnts,
75  * queued_read_lock - acquire read lock of a queued rwlock
76  * @lock: Pointer to queued rwlock structure
78 static inline void queued_read_lock(struct qrwlock *lock)
82 	cnts = atomic_add_return_acquire(_QR_BIAS, &lock->cnts);
87 	queued_read_lock_slowpath(lock);
91  * queued_write_lock - acquire write lock of a queued rwlock
92  * @lock : Pointer to queued rwlock structure
94 static inline void queued_write_lock(struct qrwlock *lock)
97 	/* Optimize for the unfair lock case where the fair flag is 0. */
98 	if (likely(atomic_try_cmpxchg_acquire(&lock->cnts, &cnts, _QW_LOCKED)))
101 	queued_write_lock_slowpath(lock);
105  * queued_read_unlock - release read lock of a queued rwlock
106  * @lock : Pointer to queued rwlock structure
108 static inline void queued_read_unlock(struct qrwlock *lock)
113 	(void)atomic_sub_return_release(_QR_BIAS, &lock->cnts);
117  * queued_write_unlock - release write lock of a queued rwlock
118  * @lock : Pointer to queued rwlock structure
120 static inline void queued_write_unlock(struct qrwlock *lock)
122 	smp_store_release(&lock->wlocked, 0);
126  * queued_rwlock_is_contended - check if the lock is contended
127  * @lock : Pointer to queued rwlock structure
128  * Return: 1 if lock contended, 0 otherwise
130 static inline int queued_rwlock_is_contended(struct qrwlock *lock)
132 	return arch_spin_is_locked(&lock->wait_lock);