From a751bd858b16dce57f3b6b85ba07946df1bd7be4 Mon Sep 17 00:00:00 2001 From: Michel Lespinasse Date: Tue, 20 Jul 2010 15:19:45 -0700 Subject: [PATCH] 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 LKML-Reference: <201007202219.o6KMJj9x021042@imap1.linux-foundation.org> Acked-by: David Howells Cc: Mike Waychison Cc: Suleiman Souhlal Cc: Ying Han Signed-off-by: Andrew Morton Signed-off-by: H. Peter Anvin --- arch/x86/include/asm/rwsem.h | 5 ++--- 1 file 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" -- 2.20.1