diff -r 8d161913dfc3 -r db89aa49298f src/share/vm/gc_implementation/shared/concurrentGCThread.cpp
--- a/src/share/vm/gc_implementation/shared/concurrentGCThread.cpp	Fri Oct 21 12:42:42 2011 -0400
+++ b/src/share/vm/gc_implementation/shared/concurrentGCThread.cpp	Thu Oct 20 12:06:20 2011 -0700
@@ -224,6 +224,8 @@
   MutexLockerEx x(&_monitor, Mutex::_no_safepoint_check_flag);
   assert(_buffer == empty, "Should be empty");
   assert(msg != empty, "empty message");
+  assert(!Heap_lock->owned_by_self(), "Heap_lock owned by requesting thread");
+
   _buffer = msg;
   while (_buffer != empty) {
     _monitor.notify();