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 #ifdef CONFIG_REFCOUNT_FULL 47 extern __must_check bool refcount_add_not_zero(unsigned int i, refcount_t *r); 48 extern void refcount_add(unsigned int i, refcount_t *r); 49 50 extern __must_check bool refcount_inc_not_zero(refcount_t *r); 51 extern void refcount_inc(refcount_t *r); 52 53 extern __must_check bool refcount_sub_and_test(unsigned int i, refcount_t *r); 54 55 extern __must_check bool refcount_dec_and_test(refcount_t *r); 56 extern void refcount_dec(refcount_t *r); 57 #else 58 # ifdef CONFIG_ARCH_HAS_REFCOUNT 59 # include <asm/refcount.h> 60 # else 61 static inline __must_check bool refcount_add_not_zero(unsigned int i, refcount_t *r) 62 { 63 return atomic_add_unless(&r->refs, i, 0); 64 } 65 66 static inline void refcount_add(unsigned int i, refcount_t *r) 67 { 68 atomic_add(i, &r->refs); 69 } 70 71 static inline __must_check bool refcount_inc_not_zero(refcount_t *r) 72 { 73 return atomic_add_unless(&r->refs, 1, 0); 74 } 75 76 static inline void refcount_inc(refcount_t *r) 77 { 78 atomic_inc(&r->refs); 79 } 80 81 static inline __must_check bool refcount_sub_and_test(unsigned int i, refcount_t *r) 82 { 83 return atomic_sub_and_test(i, &r->refs); 84 } 85 86 static inline __must_check bool refcount_dec_and_test(refcount_t *r) 87 { 88 return atomic_dec_and_test(&r->refs); 89 } 90 91 static inline void refcount_dec(refcount_t *r) 92 { 93 atomic_dec(&r->refs); 94 } 95 # endif /* !CONFIG_ARCH_HAS_REFCOUNT */ 96 #endif /* CONFIG_REFCOUNT_FULL */ 97 98 extern __must_check bool refcount_dec_if_one(refcount_t *r); 99 extern __must_check bool refcount_dec_not_one(refcount_t *r); 100 extern __must_check bool refcount_dec_and_mutex_lock(refcount_t *r, struct mutex *lock); 101 extern __must_check bool refcount_dec_and_lock(refcount_t *r, spinlock_t *lock); 102 103 #endif /* _LINUX_REFCOUNT_H */ 104