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Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
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linux
1#ifndef _LINUX_CALL_ONCE_H
2#define _LINUX_CALL_ONCE_H
3
4#include <linux/types.h>
5#include <linux/mutex.h>
6
7#define ONCE_NOT_STARTED 0
8#define ONCE_RUNNING 1
9#define ONCE_COMPLETED 2
10
11struct once {
12 atomic_t state;
13 struct mutex lock;
14};
15
16static inline void __once_init(struct once *once, const char *name,
17 struct lock_class_key *key)
18{
19 atomic_set(&once->state, ONCE_NOT_STARTED);
20 __mutex_init(&once->lock, name, key);
21}
22
23#define once_init(once) \
24do { \
25 static struct lock_class_key __key; \
26 __once_init((once), #once, &__key); \
27} while (0)
28
29static inline void call_once(struct once *once, void (*cb)(struct once *))
30{
31 /* Pairs with atomic_set_release() below. */
32 if (atomic_read_acquire(&once->state) == ONCE_COMPLETED)
33 return;
34
35 guard(mutex)(&once->lock);
36 WARN_ON(atomic_read(&once->state) == ONCE_RUNNING);
37 if (atomic_read(&once->state) != ONCE_NOT_STARTED)
38 return;
39
40 atomic_set(&once->state, ONCE_RUNNING);
41 cb(once);
42 atomic_set_release(&once->state, ONCE_COMPLETED);
43}
44
45#endif /* _LINUX_CALL_ONCE_H */