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 */ 119