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| author | Eric Dumazet <eric.dumazet@gmail.com> | 2009-07-03 13:23:02 +0200 |
|---|---|---|
| committer | Ingo Molnar <mingo@elte.hu> | 2009-07-03 14:42:59 +0200 |
| commit | 67d7178f8fc64b7f68d7dd8a1b21dfa0d42c220c (patch) | |
| tree | d14adbf73d928b9c954d8ade1a3df8c61183fd95 /arch/x86 | |
| parent | 8e049ef054f1cc765f05f13e1396bb9a17c19e66 (diff) | |
| download | op-kernel-dev-67d7178f8fc64b7f68d7dd8a1b21dfa0d42c220c.zip op-kernel-dev-67d7178f8fc64b7f68d7dd8a1b21dfa0d42c220c.tar.gz | |
x86: atomic64: Improve atomic64_read()
Optimize atomic64_read() as a special open-coded
cmpxchg8b variant. This generates nicer code:
arch/x86/lib/atomic64_32.o:
text data bss dec hex filename
435 0 0 435 1b3 atomic64_32.o.before
431 0 0 431 1af atomic64_32.o.after
md5:
bd8ab95e69c93518578bfaf0ea3be4d9 atomic64_32.o.before.asm
2bdfd4bd1f6b7b61b7fc127aef90ce3b atomic64_32.o.after.asm
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Arnd Bergmann <arnd@arndb.de>
LKML-Reference: <alpine.LFD.2.01.0907021653030.3210@localhost.localdomain>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'arch/x86')
| -rw-r--r-- | arch/x86/lib/atomic64_32.c | 12 |
1 files changed, 10 insertions, 2 deletions
diff --git a/arch/x86/lib/atomic64_32.c b/arch/x86/lib/atomic64_32.c index fd28fd3..cd11803 100644 --- a/arch/x86/lib/atomic64_32.c +++ b/arch/x86/lib/atomic64_32.c @@ -62,9 +62,17 @@ void atomic64_set(atomic64_t *ptr, u64 new_val) */ u64 atomic64_read(atomic64_t *ptr) { - u64 old = 1LL << 32; + u64 res; - return cmpxchg8b(&ptr->counter, old, old); + asm volatile( + "mov %%ebx, %%eax\n\t" + "mov %%ecx, %%edx\n\t" + LOCK_PREFIX "cmpxchg8b %1\n" + : "+A" (res) + : "m" (*ptr) + ); + + return res; } /** |
