src/share/vm/memory/universe.cpp

@@ -1068,17 +1068,17 @@
 void Universe::compute_base_vtable_size() {
   _base_vtable_size = ClassLoader::compute_Object_vtable();
 }
 
 void Universe::print_on(outputStream* st) {
+  GCMutexLocker hl(Heap_lock); // Heap_lock might be locked by caller thread.
   st->print_cr("Heap");
   heap()->print_on(st);
 }
 
 void Universe::print_heap_at_SIGBREAK() {
   if (PrintHeapAtSIGBREAK) {
-    MutexLocker hl(Heap_lock);
     print_on(tty);
     tty->cr();
     tty->flush();
   }
 }