--- a/src/hotspot/share/prims/jvmtiEnvBase.cpp	Fri Aug 31 12:41:00 2018 +0200
+++ b/src/hotspot/share/prims/jvmtiEnvBase.cpp	Fri Aug 31 07:03:46 2018 -0400
@@ -1489,6 +1489,7 @@
 jvmtiError
 JvmtiModuleClosure::get_all_modules(JvmtiEnv* env, jint* module_count_ptr, jobject** modules_ptr) {
   ResourceMark rm;
+  MutexLocker mcld(ClassLoaderDataGraph_lock);
   MutexLocker ml(Module_lock);
 
   _tbl = new GrowableArray<OopHandle>(77);