diff -r ee489b336cd9 -r 9b8e9c373740 hotspot/src/share/vm/prims/jvmtiRedefineClasses.hpp
--- a/hotspot/src/share/vm/prims/jvmtiRedefineClasses.hpp	Tue May 17 03:26:07 2016 -0400
+++ b/hotspot/src/share/vm/prims/jvmtiRedefineClasses.hpp	Tue May 17 08:51:05 2016 -0400
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2003, 2015, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2003, 2016, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -489,6 +489,10 @@
 
   void flush_dependent_code(instanceKlassHandle k_h, TRAPS);
 
+  // lock classes to redefine since constant pool merging isn't thread safe.
+  void lock_classes();
+  void unlock_classes();
+
   static void dump_methods();
 
   // Check that there are no old or obsolete methods