--- a/hotspot/src/share/vm/memory/freeBlockDictionary.hpp	Fri Aug 31 16:39:35 2012 -0700
+++ b/hotspot/src/share/vm/memory/freeBlockDictionary.hpp	Sat Sep 01 13:25:18 2012 -0400
@@ -48,6 +48,10 @@
   };
 
  private:
+  // This field is added and can be set to point to the
+  // the Mutex used to synchronize access to the
+  // dictionary so that assertion checking can be done.
+  // For example it is set to point to _parDictionaryAllocLock.
   NOT_PRODUCT(Mutex* _lock;)
 
  public: