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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/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 | */ | |
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 | */ | |
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 | |
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 | ||
79 | static inline void refcount_add(unsigned int i, refcount_t *r) | |
80 | { | |
81 | atomic_add(i, &r->refs); | |
82 | } | |
83 | ||
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 | ||
89 | static inline void refcount_inc(refcount_t *r) | |
90 | { | |
91 | atomic_inc(&r->refs); | |
92 | } | |
93 | ||
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 | ||
99 | static inline __must_check bool refcount_dec_and_test(refcount_t *r) | |
100 | { | |
101 | return atomic_dec_and_test(&r->refs); | |
102 | } | |
103 | ||
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 */ |