summaryrefslogtreecommitdiff
path: root/arch/x86/include/asm/rwsem.h
diff options
context:
space:
mode:
authorMichel Lespinasse <walken@google.com>2010-07-21 02:19:45 +0400
committerH. Peter Anvin <hpa@linux.intel.com>2010-07-21 04:41:00 +0400
commita751bd858b16dce57f3b6b85ba07946df1bd7be4 (patch)
tree1bd42b7a014003bbd733056dafec27078fed9e7e /arch/x86/include/asm/rwsem.h
parente0959371b4aaddb9b986019d5cfef93f9801d0ff (diff)
downloadlinux-a751bd858b16dce57f3b6b85ba07946df1bd7be4.tar.xz
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.h5
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"