include/linux/refcount.h

   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 */