--- old/src/share/vm/gc/shared/genCollectedHeap.cpp	2016-04-29 23:00:36.290427916 +0900
+++ new/src/share/vm/gc/shared/genCollectedHeap.cpp	2016-04-29 23:00:36.135428437 +0900
@@ -1089,6 +1089,8 @@
 }
 
 void GenCollectedHeap::print_on(outputStream* st) const {
+  assert_locked_or_safepoint(Heap_lock);
+
   _young_gen->print_on(st);
   _old_gen->print_on(st);
   MetaspaceAux::print_on(st);