diff -Naur postgresql-8.1.4.orig/src/include/storage/s_lock.h postgresql-8.1.4/src/include/storage/s_lock.h
--- postgresql-8.1.4.orig/src/include/storage/s_lock.h	2005-10-11 22:41:32.000000000 +0200
+++ postgresql-8.1.4/src/include/storage/s_lock.h	2006-05-31 09:19:04.000000000 +0200
@@ -125,12 +125,9 @@
 	 * extra test appears to be a small loss on some x86 platforms and a small
 	 * win on others; it's by no means clear that we should keep it.
 	 */
+	/* xchg implies a LOCK prefix, so no need to say LOCK explicitly */
 	__asm__ __volatile__(
-		"	cmpb	$0,%1	\n"
-		"	jne		1f		\n"
-		"	lock			\n"
 		"	xchgb	%0,%1	\n"
-		"1: \n"
 :		"+q"(_res), "+m"(*lock)
 :
 :		"memory", "cc");
@@ -189,8 +186,8 @@
 	 * is a huge loss.  On EM64T, it appears to be a wash or small loss,
 	 * so we needn't bother to try to distinguish the sub-architectures.
 	 */
+	/* xchg implies a LOCK prefix, so no need to say LOCK explicitly */
 	__asm__ __volatile__(
-		"	lock			\n"
 		"	xchgb	%0,%1	\n"
 :		"+q"(_res), "+m"(*lock)
 :