--- a/hotspot/src/cpu/x86/vm/assembler_x86.cpp	Thu Nov 06 20:00:03 2008 -0800
+++ b/hotspot/src/cpu/x86/vm/assembler_x86.cpp	Fri Nov 07 09:29:38 2008 -0800
@@ -621,6 +621,10 @@
     debug_only(has_disp32 = true);
     break;
 
+  case 0xF0:                    // Lock
+    assert(os::is_MP(), "only on MP");
+    goto again_after_prefix;
+
   case 0xF3:                    // For SSE
   case 0xF2:                    // For SSE2
     switch (0xFF & *ip++) {