include/linux/atomic.h

   1 #ifndef _LINUX_ATOMIC_H
   2 #define _LINUX_ATOMIC_H
   3 #include <asm/atomic.h>
   4
   5 /**
   6  * atomic_inc_not_zero - increment unless the number is zero
   7  * @v: pointer of type atomic_t
   8  *
   9  * Atomically increments @v by 1, so long as @v is non-zero.
  10  * Returns non-zero if @v was non-zero, and zero otherwise.
  11  */
  12 #define atomic_inc_not_zero(v)          atomic_add_unless((v), 1, 0)
  13
  14 /**
  15  * atomic_inc_not_zero_hint - increment if not null
  16  * @v: pointer of type atomic_t
  17  * @hint: probable value of the atomic before the increment
  18  *
  19  * This version of atomic_inc_not_zero() gives a hint of probable
  20  * value of the atomic. This helps processor to not read the memory
  21  * before doing the atomic read/modify/write cycle, lowering
  22  * number of bus transactions on some arches.
  23  *
  24  * Returns: 0 if increment was not done, 1 otherwise.
  25  */
  26 #ifndef atomic_inc_not_zero_hint
  27 static inline int atomic_inc_not_zero_hint(atomic_t *v, int hint)
  28 {
  29         int val, c = hint;
  30
  31         /* sanity test, should be removed by compiler if hint is a constant */
  32         if (!hint)
  33                 return atomic_inc_not_zero(v);
  34
  35         do {
  36                 val = atomic_cmpxchg(v, c, c + 1);
  37                 if (val == c)
  38                         return 1;
  39                 c = val;
  40         } while (c);
  41
  42         return 0;
  43 }
  44 #endif
  45
  46 #ifndef atomic_inc_unless_negative
  47 static inline int atomic_inc_unless_negative(atomic_t *p)
  48 {
  49         int v, v1;
  50         for (v = 0; v >= 0; v = v1) {
  51                 v1 = atomic_cmpxchg(p, v, v + 1);
  52                 if (likely(v1 == v))
  53                         return 1;
  54         }
  55         return 0;
  56 }
  57 #endif
  58
  59 #ifndef atomic_dec_unless_positive
  60 static inline int atomic_dec_unless_positive(atomic_t *p)
  61 {
  62         int v, v1;
  63         for (v = 0; v <= 0; v = v1) {
  64                 v1 = atomic_cmpxchg(p, v, v - 1);
  65                 if (likely(v1 == v))
  66                         return 1;
  67         }
  68         return 0;
  69 }
  70 #endif
  71
  72 #ifndef CONFIG_ARCH_HAS_ATOMIC_OR
  73 static inline void atomic_or(int i, atomic_t *v)
  74 {
  75         int old;
  76         int new;
  77
  78         do {
  79                 old = atomic_read(v);
  80                 new = old | i;
  81         } while (atomic_cmpxchg(v, old, new) != old);
  82 }
  83 #endif /* #ifndef CONFIG_ARCH_HAS_ATOMIC_OR */
  84
  85 #endif /* _LINUX_ATOMIC_H */