diff options
| author | Nick Piggin <npiggin@suse.de> | 2006-03-23 03:01:02 -0800 |
|---|---|---|
| committer | Linus Torvalds <torvalds@g5.osdl.org> | 2006-03-23 07:38:17 -0800 |
| commit | 0b2fcfdb8b4e7e379192f24ea2203163ddf5df1d (patch) | |
| tree | 1f3995e41ab12ff76e737389e0b59a40c0c73668 /include/asm-s390/atomic.h | |
| parent | 713729e8b993cb880225e2ced50a3f5ac05c2b3f (diff) | |
[PATCH] atomic: add_unless cmpxchg optimise
Without branch hints, the very unlikely chance of the loop repeating due to
cmpxchg failure is unrolled with gcc-4 that I have tested.
Improve this for architectures with a native cas/cmpxchg. llsc archs
should try to implement this natively.
Signed-off-by: Nick Piggin <npiggin@suse.de>
Cc: Andi Kleen <ak@muc.de>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Roman Zippel <zippel@linux-m68k.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'include/asm-s390/atomic.h')
| -rw-r--r-- | include/asm-s390/atomic.h | 18 |
1 files changed, 14 insertions, 4 deletions
diff --git a/include/asm-s390/atomic.h b/include/asm-s390/atomic.h index be6fefe223d..de1d9926aa6 100644 --- a/include/asm-s390/atomic.h +++ b/include/asm-s390/atomic.h @@ -89,10 +89,15 @@ static __inline__ int atomic_cmpxchg(atomic_t *v, int old, int new) static __inline__ int atomic_add_unless(atomic_t *v, int a, int u) { int c, old; - c = atomic_read(v); - while (c != u && (old = atomic_cmpxchg(v, c, c + a)) != c) + for (;;) { + if (unlikely(c == u)) + break; + old = atomic_cmpxchg(v, c, c + a); + if (likely(old == c)) + break; c = old; + } return c != u; } @@ -167,10 +172,15 @@ static __inline__ int atomic64_add_unless(atomic64_t *v, long long a, long long u) { long long c, old; - c = atomic64_read(v); - while (c != u && (old = atomic64_cmpxchg(v, c, c + a)) != c) + for (;;) { + if (unlikely(c == u)) + break; + old = atomic64_cmpxchg(v, c, c + a); + if (likely(old == c)) + break; c = old; + } return c != u; } |