include/linux/refcount.h

   1 #ifndef _LINUX_REFCOUNT_H
   2 #define _LINUX_REFCOUNT_H
   3
   4 #include <linux/atomic.h>
   5 #include <linux/mutex.h>
   6 #include <linux/spinlock.h>
   7 #include <linux/kernel.h>
   8
   9 /**
  10  * refcount_t - variant of atomic_t specialized for reference counts
  11  * @refs: atomic_t counter field
  12  *
  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.
  16  */
  17 typedef struct refcount_struct {
  18         atomic_t refs;
  19 } refcount_t;
  20
  21 #define REFCOUNT_INIT(n)        { .refs = ATOMIC_INIT(n), }
  22
  23 /**
  24  * refcount_set - set a refcount's value
  25  * @r: the refcount
  26  * @n: value to which the refcount will be set
  27  */
  28 static inline void refcount_set(refcount_t *r, unsigned int n)
  29 {
  30         atomic_set(&r->refs, n);
  31 }
  32
  33 /**
  34  * refcount_read - get a refcount's value
  35  * @r: the refcount
  36  *
  37  * Return: the refcount's value
  38  */
  39 static inline unsigned int refcount_read(const refcount_t *r)
  40 {
  41         return atomic_read(&r->refs);
  42 }
  43
  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);
  47
  48 extern __must_check bool refcount_inc_not_zero(refcount_t *r);
  49 extern void refcount_inc(refcount_t *r);
  50
  51 extern __must_check bool refcount_sub_and_test(unsigned int i, refcount_t *r);
  52
  53 extern __must_check bool refcount_dec_and_test(refcount_t *r);
  54 extern void refcount_dec(refcount_t *r);
  55 #else
  56 static inline __must_check bool refcount_add_not_zero(unsigned int i, refcount_t *r)
  57 {
  58         return atomic_add_unless(&r->refs, i, 0);
  59 }
  60
  61 static inline void refcount_add(unsigned int i, refcount_t *r)
  62 {
  63         atomic_add(i, &r->refs);
  64 }
  65
  66 static inline __must_check bool refcount_inc_not_zero(refcount_t *r)
  67 {
  68         return atomic_add_unless(&r->refs, 1, 0);
  69 }
  70
  71 static inline void refcount_inc(refcount_t *r)
  72 {
  73         atomic_inc(&r->refs);
  74 }
  75
  76 static inline __must_check bool refcount_sub_and_test(unsigned int i, refcount_t *r)
  77 {
  78         return atomic_sub_and_test(i, &r->refs);
  79 }
  80
  81 static inline __must_check bool refcount_dec_and_test(refcount_t *r)
  82 {
  83         return atomic_dec_and_test(&r->refs);
  84 }
  85
  86 static inline void refcount_dec(refcount_t *r)
  87 {
  88         atomic_dec(&r->refs);
  89 }
  90 #endif /* CONFIG_REFCOUNT_FULL */
  91
  92 extern __must_check bool refcount_dec_if_one(refcount_t *r);
  93 extern __must_check bool refcount_dec_not_one(refcount_t *r);
  94 extern __must_check bool refcount_dec_and_mutex_lock(refcount_t *r, struct mutex *lock);
  95 extern __must_check bool refcount_dec_and_lock(refcount_t *r, spinlock_t *lock);
  96
  97 #endif /* _LINUX_REFCOUNT_H */