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| author | Michel Lespinasse <walken@google.com> | 2010-07-21 00:19:45 +0200 |
|---|---|---|
| committer | H. Peter Anvin <hpa@linux.intel.com> | 2010-07-21 02:41:00 +0200 |
| commit | a751bd858b16dce57f3b6b85ba07946df1bd7be4 (patch) | |
| tree | 1bd42b7a014003bbd733056dafec27078fed9e7e /arch/x86/include/asm/rwsem.h | |
| parent | Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/sag... (diff) | |
| download | linux-a751bd858b16dce57f3b6b85ba07946df1bd7be4.tar.xz linux-a751bd858b16dce57f3b6b85ba07946df1bd7be4.zip | |
x86, rwsem: Stay on fast path when count > 0 in __up_write()
When count > 0 there is no need to take the call_rwsem_wake path. If
we did take that path, it would just return without doing anything due
to the active count not being zero.
Signed-off-by: Michel Lespinasse <walken@google.com>
LKML-Reference: <201007202219.o6KMJj9x021042@imap1.linux-foundation.org>
Acked-by: David Howells <dhowells@redhat.com>
Cc: Mike Waychison <mikew@google.com>
Cc: Suleiman Souhlal <suleiman@google.com>
Cc: Ying Han <yinghan@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
Diffstat (limited to 'arch/x86/include/asm/rwsem.h')
| -rw-r--r-- | arch/x86/include/asm/rwsem.h | 5 |
1 files changed, 2 insertions, 3 deletions
diff --git a/arch/x86/include/asm/rwsem.h b/arch/x86/include/asm/rwsem.h index 606ede126972..5bf5e04e497f 100644 --- a/arch/x86/include/asm/rwsem.h +++ b/arch/x86/include/asm/rwsem.h @@ -216,9 +216,8 @@ static inline void __up_write(struct rw_semaphore *sem) rwsem_count_t tmp; asm volatile("# beginning __up_write\n\t" LOCK_PREFIX " xadd %1,(%2)\n\t" - /* tries to transition - 0xffff0001 -> 0x00000000 */ - " jz 1f\n" + /* subtracts 0xffff0001, returns the old value */ + " jns 1f\n\t" " call call_rwsem_wake\n" "1:\n\t" "# ending __up_write\n" |