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#ifndef _LINUX_CALL_ONCE_H
#define _LINUX_CALL_ONCE_H
#include <linux/types.h>
#include <linux/mutex.h>
#define ONCE_NOT_STARTED 0
#define ONCE_RUNNING 1
#define ONCE_COMPLETED 2
struct once {
atomic_t state;
struct mutex lock;
};
static inline void __once_init(struct once *once, const char *name,
struct lock_class_key *key)
{
atomic_set(&once->state, ONCE_NOT_STARTED);
__mutex_init(&once->lock, name, key);
}
#define once_init(once) \
do { \
static struct lock_class_key __key; \
__once_init((once), #once, &__key); \
} while (0)
static inline void call_once(struct once *once, void (*cb)(struct once *))
{
/* Pairs with atomic_set_release() below. */
if (atomic_read_acquire(&once->state) == ONCE_COMPLETED)
return;
guard(mutex)(&once->lock);
WARN_ON(atomic_read(&once->state) == ONCE_RUNNING);
if (atomic_read(&once->state) != ONCE_NOT_STARTED)
return;
atomic_set(&once->state, ONCE_RUNNING);
cb(once);
atomic_set_release(&once->state, ONCE_COMPLETED);
}
#endif /* _LINUX_CALL_ONCE_H */
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