1 #ifndef _LINUX_REFCOUNT_H
2 #define _LINUX_REFCOUNT_H
4 #include <linux/atomic.h>
5 #include <linux/mutex.h>
6 #include <linux/spinlock.h>
7 #include <linux/kernel.h>
10 * refcount_t - variant of atomic_t specialized for reference counts
11 * @refs: atomic_t counter field
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.
17 typedef struct refcount_struct {
21 #define REFCOUNT_INIT(n) { .refs = ATOMIC_INIT(n), }
24 * refcount_set - set a refcount's value
26 * @n: value to which the refcount will be set
28 static inline void refcount_set(refcount_t *r, unsigned int n)
30 atomic_set(&r->refs, n);
34 * refcount_read - get a refcount's value
37 * Return: the refcount's value
39 static inline unsigned int refcount_read(const refcount_t *r)
41 return atomic_read(&r->refs);
44 #ifdef CONFIG_REFCOUNT_FULL
45 extern __must_check bool refcount_add_not_zero(unsigned int i, refcount_t *r);
46 extern void refcount_add(unsigned int i, refcount_t *r);
48 extern __must_check bool refcount_inc_not_zero(refcount_t *r);
49 extern void refcount_inc(refcount_t *r);
51 extern __must_check bool refcount_sub_and_test(unsigned int i, refcount_t *r);
53 extern __must_check bool refcount_dec_and_test(refcount_t *r);
54 extern void refcount_dec(refcount_t *r);
56 # ifdef CONFIG_ARCH_HAS_REFCOUNT
57 # include <asm/refcount.h>
59 static inline __must_check bool refcount_add_not_zero(unsigned int i, refcount_t *r)
61 return atomic_add_unless(&r->refs, i, 0);
64 static inline void refcount_add(unsigned int i, refcount_t *r)
66 atomic_add(i, &r->refs);
69 static inline __must_check bool refcount_inc_not_zero(refcount_t *r)
71 return atomic_add_unless(&r->refs, 1, 0);
74 static inline void refcount_inc(refcount_t *r)
79 static inline __must_check bool refcount_sub_and_test(unsigned int i, refcount_t *r)
81 return atomic_sub_and_test(i, &r->refs);
84 static inline __must_check bool refcount_dec_and_test(refcount_t *r)
86 return atomic_dec_and_test(&r->refs);
89 static inline void refcount_dec(refcount_t *r)
93 # endif /* !CONFIG_ARCH_HAS_REFCOUNT */
94 #endif /* CONFIG_REFCOUNT_FULL */
96 extern __must_check bool refcount_dec_if_one(refcount_t *r);
97 extern __must_check bool refcount_dec_not_one(refcount_t *r);
98 extern __must_check bool refcount_dec_and_mutex_lock(refcount_t *r, struct mutex *lock);
99 extern __must_check bool refcount_dec_and_lock(refcount_t *r, spinlock_t *lock);
101 #endif /* _LINUX_REFCOUNT_H */