projects/linux·blob v4.12 · refs

61 lines · 1.7 KiB

1#ifndef _LINUX_REFCOUNT_H
2#define _LINUX_REFCOUNT_H
3
4#include <linux/atomic.h>
5#include <linux/mutex.h>
6#include <linux/spinlock.h>
7#include <linux/kernel.h>
8
9/**
10 * refcount_t - variant of atomic_t specialized for reference counts
11 * @refs: atomic_t counter field
12 *
13 * The counter saturates at UINT_MAX and will not move once
14 * there. This avoids wrapping the counter and causing 'spurious'
15 * use-after-free bugs.
16 */
17typedef struct refcount_struct {
18 atomic_t refs;
19} refcount_t;
20
21#define REFCOUNT_INIT(n) { .refs = ATOMIC_INIT(n), }
22
23/**
24 * refcount_set - set a refcount's value
25 * @r: the refcount
26 * @n: value to which the refcount will be set
27 */
28static inline void refcount_set(refcount_t *r, unsigned int n)
29{
30 atomic_set(&r->refs, n);
31}
32
33/**
34 * refcount_read - get a refcount's value
35 * @r: the refcount
36 *
37 * Return: the refcount's value
38 */
39static inline unsigned int refcount_read(const refcount_t *r)
40{
41 return atomic_read(&r->refs);
42}
43
44extern __must_check bool refcount_add_not_zero(unsigned int i, refcount_t *r);
45extern void refcount_add(unsigned int i, refcount_t *r);
46
47extern __must_check bool refcount_inc_not_zero(refcount_t *r);
48extern void refcount_inc(refcount_t *r);
49
50extern __must_check bool refcount_sub_and_test(unsigned int i, refcount_t *r);
51extern void refcount_sub(unsigned int i, refcount_t *r);
52
53extern __must_check bool refcount_dec_and_test(refcount_t *r);
54extern void refcount_dec(refcount_t *r);
55
56extern __must_check bool refcount_dec_if_one(refcount_t *r);
57extern __must_check bool refcount_dec_not_one(refcount_t *r);
58extern __must_check bool refcount_dec_and_mutex_lock(refcount_t *r, struct mutex *lock);
59extern __must_check bool refcount_dec_and_lock(refcount_t *r, spinlock_t *lock);
60
61#endif /* _LINUX_REFCOUNT_H */