include/linux/atomic.h

   1 /* Atomic operations usable in machine independent code */
   2 #ifndef _LINUX_ATOMIC_H
   3 #define _LINUX_ATOMIC_H
   4 #include <asm/atomic.h>
   5
   6 /**
   7  * atomic_add_unless - add unless the number is already a given value
   8  * @v: pointer of type atomic_t
   9  * @a: the amount to add to v...
  10  * @u: ...unless v is equal to u.
  11  *
  12  * Atomically adds @a to @v, so long as @v was not already @u.
  13  * Returns non-zero if @v was not @u, and zero otherwise.
  14  */
  15 static inline int atomic_add_unless(atomic_t *v, int a, int u)
  16 {
  17         return __atomic_add_unless(v, a, u) != u;
  18 }
  19
  20 /**
  21  * atomic_inc_not_zero - increment unless the number is zero
  22  * @v: pointer of type atomic_t
  23  *
  24  * Atomically increments @v by 1, so long as @v is non-zero.
  25  * Returns non-zero if @v was non-zero, and zero otherwise.
  26  */
  27 #define atomic_inc_not_zero(v)          atomic_add_unless((v), 1, 0)
  28
  29 /**
  30  * atomic_inc_not_zero_hint - increment if not null
  31  * @v: pointer of type atomic_t
  32  * @hint: probable value of the atomic before the increment
  33  *
  34  * This version of atomic_inc_not_zero() gives a hint of probable
  35  * value of the atomic. This helps processor to not read the memory
  36  * before doing the atomic read/modify/write cycle, lowering
  37  * number of bus transactions on some arches.
  38  *
  39  * Returns: 0 if increment was not done, 1 otherwise.
  40  */
  41 #ifndef atomic_inc_not_zero_hint
  42 static inline int atomic_inc_not_zero_hint(atomic_t *v, int hint)
  43 {
  44         int val, c = hint;
  45
  46         /* sanity test, should be removed by compiler if hint is a constant */
  47         if (!hint)
  48                 return atomic_inc_not_zero(v);
  49
  50         do {
  51                 val = atomic_cmpxchg(v, c, c + 1);
  52                 if (val == c)
  53                         return 1;
  54                 c = val;
  55         } while (c);
  56
  57         return 0;
  58 }
  59 #endif
  60
  61 #ifndef atomic_inc_unless_negative
  62 static inline int atomic_inc_unless_negative(atomic_t *p)
  63 {
  64         int v, v1;
  65         for (v = 0; v >= 0; v = v1) {
  66                 v1 = atomic_cmpxchg(p, v, v + 1);
  67                 if (likely(v1 == v))
  68                         return 1;
  69         }
  70         return 0;
  71 }
  72 #endif
  73
  74 #ifndef atomic_dec_unless_positive
  75 static inline int atomic_dec_unless_positive(atomic_t *p)
  76 {
  77         int v, v1;
  78         for (v = 0; v <= 0; v = v1) {
  79                 v1 = atomic_cmpxchg(p, v, v - 1);
  80                 if (likely(v1 == v))
  81                         return 1;
  82         }
  83         return 0;
  84 }
  85 #endif
  86
  87 #ifndef CONFIG_ARCH_HAS_ATOMIC_OR
  88 static inline void atomic_or(int i, atomic_t *v)
  89 {
  90         int old;
  91         int new;
  92
  93         do {
  94                 old = atomic_read(v);
  95                 new = old | i;
  96         } while (atomic_cmpxchg(v, old, new) != old);
  97 }
  98 #endif /* #ifndef CONFIG_ARCH_HAS_ATOMIC_OR */
  99
 100 #include <asm-generic/atomic-long.h>
 101 #ifdef CONFIG_GENERIC_ATOMIC64
 102 #include <asm-generic/atomic64.h>
 103 #endif
 104 #endif /* _LINUX_ATOMIC_H */