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| author | Frederic Weisbecker <fweisbec@gmail.com> | 2009-01-25 12:50:13 -0800 |
|---|---|---|
| committer | Ingo Molnar <mingo@elte.hu> | 2009-01-26 14:06:36 +0100 |
| commit | 2d4d57db692ea790e185656516e6ebe8791f1788 (patch) | |
| tree | f7ad21dbcb4d5de2f0eb63024c1b5f1bf5321d76 /arch/x86/include/asm/spinlock.h | |
| parent | 7106a5ab89c50c6b5aadea0850b40323804a922d (diff) | |
| download | linux-0-day-2d4d57db692ea790e185656516e6ebe8791f1788.tar.gz linux-0-day-2d4d57db692ea790e185656516e6ebe8791f1788.tar.xz | |
x86: micro-optimize __raw_read_trylock()
The current version of __raw_read_trylock starts with decrementing the lock
and read its new value as a separate operation after that.
That makes 3 dereferences (read, write (after sub), read) whereas
a single atomic_dec_return does only two pointers dereferences (read, write).
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'arch/x86/include/asm/spinlock.h')
| -rw-r--r-- | arch/x86/include/asm/spinlock.h | 3 |
1 files changed, 1 insertions, 2 deletions
diff --git a/arch/x86/include/asm/spinlock.h b/arch/x86/include/asm/spinlock.h index d17c91981da2f..4d3dcc51cacdf 100644 --- a/arch/x86/include/asm/spinlock.h +++ b/arch/x86/include/asm/spinlock.h @@ -329,8 +329,7 @@ static inline int __raw_read_trylock(raw_rwlock_t *lock) { atomic_t *count = (atomic_t *)lock; - atomic_dec(count); - if (atomic_read(count) >= 0) + if (atomic_dec_return(count) >= 0) return 1; atomic_inc(count); return 0; |