LXR linux/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 */
  15static 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
  42static 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
  62static 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
  75static 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
  88static 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 */
 105