Linux kernel mirror (for testing)
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1/* SPDX-License-Identifier: GPL-2.0 */
2#ifndef _LINUX_REFCOUNT_H
3#define _LINUX_REFCOUNT_H
4
5#include <linux/atomic.h>
6#include <linux/mutex.h>
7#include <linux/spinlock.h>
8#include <linux/kernel.h>
9
10/**
11 * refcount_t - variant of atomic_t specialized for reference counts
12 * @refs: atomic_t counter field
13 *
14 * The counter saturates at UINT_MAX and will not move once
15 * there. This avoids wrapping the counter and causing 'spurious'
16 * use-after-free bugs.
17 */
18typedef struct refcount_struct {
19 atomic_t refs;
20} refcount_t;
21
22#define REFCOUNT_INIT(n) { .refs = ATOMIC_INIT(n), }
23
24/**
25 * refcount_set - set a refcount's value
26 * @r: the refcount
27 * @n: value to which the refcount will be set
28 */
29static inline void refcount_set(refcount_t *r, unsigned int n)
30{
31 atomic_set(&r->refs, n);
32}
33
34/**
35 * refcount_read - get a refcount's value
36 * @r: the refcount
37 *
38 * Return: the refcount's value
39 */
40static inline unsigned int refcount_read(const refcount_t *r)
41{
42 return atomic_read(&r->refs);
43}
44
45#ifdef CONFIG_REFCOUNT_FULL
46extern __must_check bool refcount_add_not_zero(unsigned int i, refcount_t *r);
47extern void refcount_add(unsigned int i, refcount_t *r);
48
49extern __must_check bool refcount_inc_not_zero(refcount_t *r);
50extern void refcount_inc(refcount_t *r);
51
52extern __must_check bool refcount_sub_and_test(unsigned int i, refcount_t *r);
53
54extern __must_check bool refcount_dec_and_test(refcount_t *r);
55extern void refcount_dec(refcount_t *r);
56#else
57# ifdef CONFIG_ARCH_HAS_REFCOUNT
58# include <asm/refcount.h>
59# else
60static inline __must_check bool refcount_add_not_zero(unsigned int i, refcount_t *r)
61{
62 return atomic_add_unless(&r->refs, i, 0);
63}
64
65static inline void refcount_add(unsigned int i, refcount_t *r)
66{
67 atomic_add(i, &r->refs);
68}
69
70static inline __must_check bool refcount_inc_not_zero(refcount_t *r)
71{
72 return atomic_add_unless(&r->refs, 1, 0);
73}
74
75static inline void refcount_inc(refcount_t *r)
76{
77 atomic_inc(&r->refs);
78}
79
80static inline __must_check bool refcount_sub_and_test(unsigned int i, refcount_t *r)
81{
82 return atomic_sub_and_test(i, &r->refs);
83}
84
85static inline __must_check bool refcount_dec_and_test(refcount_t *r)
86{
87 return atomic_dec_and_test(&r->refs);
88}
89
90static inline void refcount_dec(refcount_t *r)
91{
92 atomic_dec(&r->refs);
93}
94# endif /* !CONFIG_ARCH_HAS_REFCOUNT */
95#endif /* CONFIG_REFCOUNT_FULL */
96
97extern __must_check bool refcount_dec_if_one(refcount_t *r);
98extern __must_check bool refcount_dec_not_one(refcount_t *r);
99extern __must_check bool refcount_dec_and_mutex_lock(refcount_t *r, struct mutex *lock);
100extern __must_check bool refcount_dec_and_lock(refcount_t *r, spinlock_t *lock);
101
102#endif /* _LINUX_REFCOUNT_H */