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
9 struct 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 */
19 typedef 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 */
refcount_set(refcount_t * r,unsigned int n)30 static 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 */
refcount_read(const refcount_t * r)41 static inline unsigned int refcount_read(const refcount_t *r)
42 {
43 return atomic_read(&r->refs);
44 }
45
46 extern __must_check bool refcount_add_not_zero_checked(unsigned int i, refcount_t *r);
47 extern void refcount_add_checked(unsigned int i, refcount_t *r);
48
49 extern __must_check bool refcount_inc_not_zero_checked(refcount_t *r);
50 extern void refcount_inc_checked(refcount_t *r);
51
52 extern __must_check bool refcount_sub_and_test_checked(unsigned int i, refcount_t *r);
53
54 extern __must_check bool refcount_dec_and_test_checked(refcount_t *r);
55 extern 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
refcount_add_not_zero(unsigned int i,refcount_t * r)74 static 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
refcount_add(unsigned int i,refcount_t * r)79 static inline void refcount_add(unsigned int i, refcount_t *r)
80 {
81 atomic_add(i, &r->refs);
82 }
83
refcount_inc_not_zero(refcount_t * r)84 static inline __must_check bool refcount_inc_not_zero(refcount_t *r)
85 {
86 return atomic_add_unless(&r->refs, 1, 0);
87 }
88
refcount_inc(refcount_t * r)89 static inline void refcount_inc(refcount_t *r)
90 {
91 atomic_inc(&r->refs);
92 }
93
refcount_sub_and_test(unsigned int i,refcount_t * r)94 static 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
refcount_dec_and_test(refcount_t * r)99 static inline __must_check bool refcount_dec_and_test(refcount_t *r)
100 {
101 return atomic_dec_and_test(&r->refs);
102 }
103
refcount_dec(refcount_t * r)104 static 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
111 extern __must_check bool refcount_dec_if_one(refcount_t *r);
112 extern __must_check bool refcount_dec_not_one(refcount_t *r);
113 extern __must_check bool refcount_dec_and_mutex_lock(refcount_t *r, struct mutex *lock);
114 extern __must_check bool refcount_dec_and_lock(refcount_t *r, spinlock_t *lock);
115 extern __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