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author | Linus Torvalds <torvalds@linux-foundation.org> | 2010-05-18 08:40:05 -0700 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2010-05-18 08:40:05 -0700 |
commit | 93c9d7f60c0cb7715890b1f9e159da6f4d1f5a65 (patch) | |
tree | 6be428ca5fe52f14ebb78a8e695cec59d2f21c26 /arch/x86/include/asm/atomic.h | |
parent | 7421a10de7a525f67cc082fca7a91011d00eada4 (diff) | |
parent | d9c5841e22231e4e49fd0a1004164e6fce59b7a6 (diff) | |
download | linux-93c9d7f60c0cb7715890b1f9e159da6f4d1f5a65.tar.bz2 |
Merge branch 'x86-atomic-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip
* 'x86-atomic-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
x86: Fix LOCK_PREFIX_HERE for uniprocessor build
x86, atomic64: In selftest, distinguish x86-64 from 586+
x86-32: Fix atomic64_inc_not_zero return value convention
lib: Fix atomic64_inc_not_zero test
lib: Fix atomic64_add_unless return value convention
x86-32: Fix atomic64_add_unless return value convention
lib: Fix atomic64_add_unless test
x86: Implement atomic[64]_dec_if_positive()
lib: Only test atomic64_dec_if_positive on archs having it
x86-32: Rewrite 32-bit atomic64 functions in assembly
lib: Add self-test for atomic64_t
x86-32: Allow UP/SMP lock replacement in cmpxchg64
x86: Add support for lock prefix in alternatives
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 37b39d27abe0..952a826ac4e5 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 |