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/mutex.h>
   7 #include <linux/spinlock.h>
   8 #include <linux/kernel.h>
   9
  10 /**
  11  * refcount_t - variant of atomic_t specialized for reference counts
  12  * @refs: atomic_t counter field
  13  *
  14  * The counter saturates at UINT_MAX and will not move once
  15  * there. This avoids wrapping the counter and causing 'spurious'
  16  * use-after-free bugs.
  17  */
  18 typedef struct refcount_struct {
  19         atomic_t refs;
  20 } refcount_t;
  21
  22 #define REFCOUNT_INIT(n)        { .refs = ATOMIC_INIT(n), }
  23
  24 /**
  25  * refcount_set - set a refcount's value
  26  * @r: the refcount
  27  * @n: value to which the refcount will be set
  28  */
  29 static inline void refcount_set(refcount_t *r, unsigned int n)
  30 {
  31         atomic_set(&r->refs, n);
  32 }
  33
  34 /**
  35  * refcount_read - get a refcount's value
  36  * @r: the refcount
  37  *
  38  * Return: the refcount's value
  39  */
  40 static inline unsigned int refcount_read(const refcount_t *r)
  41 {
  42         return atomic_read(&r->refs);
  43 }
  44
  45 #ifdef CONFIG_REFCOUNT_FULL
  46 extern __must_check bool refcount_add_not_zero(unsigned int i, refcount_t *r);
  47 extern void refcount_add(unsigned int i, refcount_t *r);
  48
  49 extern __must_check bool refcount_inc_not_zero(refcount_t *r);
  50 extern void refcount_inc(refcount_t *r);
  51
  52 extern __must_check bool refcount_sub_and_test(unsigned int i, refcount_t *r);
  53
  54 extern __must_check bool refcount_dec_and_test(refcount_t *r);
  55 extern void refcount_dec(refcount_t *r);
  56 #else
  57 # ifdef CONFIG_ARCH_HAS_REFCOUNT
  58 #  include <asm/refcount.h>
  59 # else
  60 static inline __must_check bool refcount_add_not_zero(unsigned int i, refcount_t *r)
  61 {
  62         return atomic_add_unless(&r->refs, i, 0);
  63 }
  64
  65 static inline void refcount_add(unsigned int i, refcount_t *r)
  66 {
  67         atomic_add(i, &r->refs);
  68 }
  69
  70 static inline __must_check bool refcount_inc_not_zero(refcount_t *r)
  71 {
  72         return atomic_add_unless(&r->refs, 1, 0);
  73 }
  74
  75 static inline void refcount_inc(refcount_t *r)
  76 {
  77         atomic_inc(&r->refs);
  78 }
  79
  80 static inline __must_check bool refcount_sub_and_test(unsigned int i, refcount_t *r)
  81 {
  82         return atomic_sub_and_test(i, &r->refs);
  83 }
  84
  85 static inline __must_check bool refcount_dec_and_test(refcount_t *r)
  86 {
  87         return atomic_dec_and_test(&r->refs);
  88 }
  89
  90 static inline void refcount_dec(refcount_t *r)
  91 {
  92         atomic_dec(&r->refs);
  93 }
  94 # endif /* !CONFIG_ARCH_HAS_REFCOUNT */
  95 #endif /* CONFIG_REFCOUNT_FULL */
  96
  97 extern __must_check bool refcount_dec_if_one(refcount_t *r);
  98 extern __must_check bool refcount_dec_not_one(refcount_t *r);
  99 extern __must_check bool refcount_dec_and_mutex_lock(refcount_t *r, struct mutex *lock);
 100 extern __must_check bool refcount_dec_and_lock(refcount_t *r, spinlock_t *lock);
 101
 102 #endif /* _LINUX_REFCOUNT_H */