Messages in this thread Patch in this message | | | Date | Fri, 3 Jul 2009 12:43:17 GMT | From | tip-bot for Eric Dumazet <> | Subject | [tip:perfcounters/urgent] x86: atomic64: Improve cmpxchg8b() |
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Commit-ID: 69237f94e65d3d7f539f1adb98ef68685c595004 Gitweb: http://git.kernel.org/tip/69237f94e65d3d7f539f1adb98ef68685c595004 Author: Eric Dumazet <eric.dumazet@gmail.com> AuthorDate: Fri, 3 Jul 2009 13:26:41 +0200 Committer: Ingo Molnar <mingo@elte.hu> CommitDate: Fri, 3 Jul 2009 13:26:41 +0200
x86: atomic64: Improve cmpxchg8b()
Rewrite cmpxchg8b() to not use %edi register but a generic "+m" constraint, to increase compiler freedom in code generation and possibly better code.
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>
--- arch/x86/lib/atomic64_32.c | 19 +++++++------------ 1 files changed, 7 insertions(+), 12 deletions(-)
diff --git a/arch/x86/lib/atomic64_32.c b/arch/x86/lib/atomic64_32.c index afa5d44..5fc1e2c 100644 --- a/arch/x86/lib/atomic64_32.c +++ b/arch/x86/lib/atomic64_32.c @@ -6,19 +6,14 @@ static inline u64 cmpxchg8b(u64 *ptr, u64 old, u64 new) { - asm volatile( - - LOCK_PREFIX "cmpxchg8b (%[ptr])\n" - - : "=A" (old) - - : [ptr] "D" (ptr), - "A" (old), - "b" (ll_low(new)), - "c" (ll_high(new)) - - : "memory"); + u32 low = new; + u32 high = new >> 32; + asm volatile( + LOCK_PREFIX "cmpxchg8b %1\n" + : "+A" (old), "+m" (*ptr) + : "b" (low), "c" (high) + ); return old; }
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