diff options
Diffstat (limited to 'include/linux')
| -rw-r--r-- | include/linux/atomic.h | 25 |
1 files changed, 25 insertions, 0 deletions
diff --git a/include/linux/atomic.h b/include/linux/atomic.h index 70cfcb2d63c..5b08a8540ec 100644 --- a/include/linux/atomic.h +++ b/include/linux/atomic.h @@ -86,6 +86,31 @@ static inline int atomic_dec_unless_positive(atomic_t *p) } #endif +/* + * atomic_dec_if_positive - decrement by 1 if old value positive + * @v: pointer of type atomic_t + * + * The function returns the old value of *v minus 1, even if + * the atomic variable, v, was not decremented. + */ +#ifndef atomic_dec_if_positive +static inline int atomic_dec_if_positive(atomic_t *v) +{ + int c, old, dec; + c = atomic_read(v); + for (;;) { + dec = c - 1; + if (unlikely(dec < 0)) + break; + old = atomic_cmpxchg((v), c, dec); + if (likely(old == c)) + break; + c = old; + } + return dec; +} +#endif + #ifndef CONFIG_ARCH_HAS_ATOMIC_OR static inline void atomic_or(int i, atomic_t *v) { |