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_hint - increment if not null
   7  * @v: pointer of type atomic_t
   8  * @hint: probable value of the atomic before the increment
   9  *
  10  * This version of atomic_inc_not_zero() gives a hint of probable
  11  * value of the atomic. This helps processor to not read the memory
  12  * before doing the atomic read/modify/write cycle, lowering
  13  * number of bus transactions on some arches.
  14  *
  15  * Returns: 0 if increment was not done, 1 otherwise.
  16  */
  17 #ifndef atomic_inc_not_zero_hint
  18 static inline int atomic_inc_not_zero_hint(atomic_t *v, int hint)
  19 {
  20         int val, c = hint;
  21
  22         /* sanity test, should be removed by compiler if hint is a constant */
  23         if (!hint)
  24                 return atomic_inc_not_zero(v);
  25
  26         do {
  27                 val = atomic_cmpxchg(v, c, c + 1);
  28                 if (val == c)
  29                         return 1;
  30                 c = val;
  31         } while (c);
  32
  33         return 0;
  34 }
  35 #endif
  36
  37 #endif /* _LINUX_ATOMIC_H */