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| author | Luca Barbieri <luca@luca-barbieri.com> | 2010-02-26 14:22:41 +0300 |
|---|---|---|
| committer | H. Peter Anvin <hpa@zytor.com> | 2010-03-01 22:38:42 +0300 |
| commit | d7f6de1e9c4a12e11ba7186c70f0f40caa76f590 (patch) | |
| tree | 0f9de2c0666d298a054f2a256da3029f97369d16 /arch/x86/include/asm/atomic.h | |
| parent | 8f4f202b335144bf5be5c9e5b1bc9477ecdae958 (diff) | |
| download | linux-d7f6de1e9c4a12e11ba7186c70f0f40caa76f590.tar.xz | |
x86: Implement atomic[64]_dec_if_positive()
Add support for atomic_dec_if_positive(), and
atomic64_dec_if_positive() for x86-64.
atomic64_dec_if_positive() for x86-32 was already implemented in a previous patch.
Signed-off-by: Luca Barbieri <luca@luca-barbieri.com>
LKML-Reference: <1267183361-20775-2-git-send-email-luca@luca-barbieri.com>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Diffstat (limited to 'arch/x86/include/asm/atomic.h')
| -rw-r--r-- | arch/x86/include/asm/atomic.h | 23 |
1 files changed, 23 insertions, 0 deletions
diff --git a/arch/x86/include/asm/atomic.h b/arch/x86/include/asm/atomic.h index 8f8217b9bdac..706c69492c14 100644 --- a/arch/x86/include/asm/atomic.h +++ b/arch/x86/include/asm/atomic.h @@ -246,6 +246,29 @@ static inline int atomic_add_unless(atomic_t *v, int a, int u) #define atomic_inc_not_zero(v) atomic_add_unless((v), 1, 0) +/* + * 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. + */ +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; +} + /** * atomic_inc_short - increment of a short integer * @v: pointer to type int |