--- old/src/share/vm/gc/shared/workgroup.cpp	Tue May  3 04:08:15 2016
+++ new/src/share/vm/gc/shared/workgroup.cpp	Tue May  3 04:08:14 2016
@@ -267,6 +267,7 @@
 void AbstractGangWorker::run() {
   initialize();
   loop();
+  NOT_PRODUCT(ShouldNotReachHere());  // should never return from loop()
 }
 
 void AbstractGangWorker::initialize() {