11 struct once {  struct
16 static inline void __once_init(struct once *once, const char *name,  in __once_init()  argument
19         atomic_set(&once->state, ONCE_NOT_STARTED);  in __once_init()
20         __mutex_init(&once->lock, name, key);  in __once_init()
23 #define once_init(once)							\  argument
26 	__once_init((once), #once, &__key);				\
30  * call_once - Ensure a function has been called exactly once
32  * @once: Tracking struct
35  * If @once has never completed successfully before, call @cb and, if
36  * it returns a zero or positive value, mark @once as completed.  Return
39  * If @once has completed succesfully before, return 0.
44 static inline int call_once(struct once *once, int (*cb)(struct once *))  in call_once()  argument
49 	if (atomic_read_acquire(&once->state) == ONCE_COMPLETED)  in call_once()
52 	guard(mutex)(&once->lock);  in call_once()
53 	state = atomic_read(&once->state);  in call_once()
57 	atomic_set(&once->state, ONCE_RUNNING);  in call_once()
58 	r = cb(once);  in call_once()
60 		atomic_set(&once->state, ONCE_NOT_STARTED);  in call_once()
62 		atomic_set_release(&once->state, ONCE_COMPLETED);  in call_once()