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/compiler.h>
7#include <linux/spinlock_types.h>
8
9struct mutex;
10
11/**
12 * struct refcount_t - variant of atomic_t specialized for reference counts
13 * @refs: atomic_t counter field
14 *
15 * The counter saturates at UINT_MAX and will not move once
16 * there. This avoids wrapping the counter and causing 'spurious'
17 * use-after-free bugs.
18 */
19typedef struct refcount_struct {
20 atomic_t refs;
21} refcount_t;
22
23#define REFCOUNT_INIT(n) { .refs = ATOMIC_INIT(n), }
24
25/**
26 * refcount_set - set a refcount's value
27 * @r: the refcount
28 * @n: value to which the refcount will be set
29 */
30static inline void refcount_set(refcount_t *r, unsigned int n)
31{
32 atomic_set(&r->refs, n);
33}
34
35/**
36 * refcount_read - get a refcount's value
37 * @r: the refcount
38 *
39 * Return: the refcount's value
40 */
41static inline unsigned int refcount_read(const refcount_t *r)
42{
43 return atomic_read(&r->refs);
44}
45
46extern __must_check bool refcount_add_not_zero_checked(unsigned int i, refcount_t *r);
47extern void refcount_add_checked(unsigned int i, refcount_t *r);
48
49extern __must_check bool refcount_inc_not_zero_checked(refcount_t *r);
50extern void refcount_inc_checked(refcount_t *r);
51
52extern __must_check bool refcount_sub_and_test_checked(unsigned int i, refcount_t *r);
53
54extern __must_check bool refcount_dec_and_test_checked(refcount_t *r);
55extern void refcount_dec_checked(refcount_t *r);
56
57#ifdef CONFIG_REFCOUNT_FULL
58
59#define refcount_add_not_zero refcount_add_not_zero_checked
60#define refcount_add refcount_add_checked
61
62#define refcount_inc_not_zero refcount_inc_not_zero_checked
63#define refcount_inc refcount_inc_checked
64
65#define refcount_sub_and_test refcount_sub_and_test_checked
66
67#define refcount_dec_and_test refcount_dec_and_test_checked
68#define refcount_dec refcount_dec_checked
69
70#else
71# ifdef CONFIG_ARCH_HAS_REFCOUNT
72# include <asm/refcount.h>
73# else
74static inline __must_check bool refcount_add_not_zero(unsigned int i, refcount_t *r)
75{
76 return atomic_add_unless(&r->refs, i, 0);
77}
78
79static inline void refcount_add(unsigned int i, refcount_t *r)
80{
81 atomic_add(i, &r->refs);
82}
83
84static inline __must_check bool refcount_inc_not_zero(refcount_t *r)
85{
86 return atomic_add_unless(&r->refs, 1, 0);
87}
88
89static inline void refcount_inc(refcount_t *r)
90{
91 atomic_inc(&r->refs);
92}
93
94static inline __must_check bool refcount_sub_and_test(unsigned int i, refcount_t *r)
95{
96 return atomic_sub_and_test(i, &r->refs);
97}
98
99static inline __must_check bool refcount_dec_and_test(refcount_t *r)
100{
101 return atomic_dec_and_test(&r->refs);
102}
103
104static inline void refcount_dec(refcount_t *r)
105{
106 atomic_dec(&r->refs);
107}
108# endif /* !CONFIG_ARCH_HAS_REFCOUNT */
109#endif /* CONFIG_REFCOUNT_FULL */
110
111extern __must_check bool refcount_dec_if_one(refcount_t *r);
112extern __must_check bool refcount_dec_not_one(refcount_t *r);
113extern __must_check bool refcount_dec_and_mutex_lock(refcount_t *r, struct mutex *lock);
114extern __must_check bool refcount_dec_and_lock(refcount_t *r, spinlock_t *lock);
115extern __must_check bool refcount_dec_and_lock_irqsave(refcount_t *r,
116 spinlock_t *lock,
117 unsigned long *flags);
118#endif /* _LINUX_REFCOUNT_H */
119