src/hotspot/share/prims/jvmtiGetLoadedClasses.cpp

@@ -1,7 +1,7 @@
 /*
- * Copyright (c) 2003, 2017, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2003, 2018, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
  * under the terms of the GNU General Public License version 2 only, as
  * published by the Free Software Foundation.

@@ -23,10 +23,11 @@
  */
 
 #include "precompiled.hpp"
 #include "classfile/systemDictionary.hpp"
 #include "gc/shared/collectedHeap.hpp"
+#include "gc/g1/g1SATBCardTableModRefBS.hpp"
 #include "memory/universe.inline.hpp"
 #include "prims/jvmtiGetLoadedClasses.hpp"
 #include "runtime/thread.hpp"
 #include "utilities/stack.inline.hpp"
 

@@ -36,18 +37,34 @@
 private:
   Stack<jclass, mtInternal> _classStack;
   JvmtiEnv* _env;
   Thread*   _cur_thread;
 
+private:
+// Tell the GC to keep this klass alive
+static void ensure_klass_alive(oop o) {
+  // A klass that was previously considered dead can be looked up in the 
+  // CLD/SD, and its _java_mirror or _class_loader can be stored in a root
+  // or a reachable object making it alive again.
+  // The SATB part of G1 needs to get notified about this
+  // potential resurrection, otherwise the marking might not find the object.
+#if INCLUDE_ALL_GCS
+  if (UseG1GC && o != NULL) {
+    G1SATBCardTableModRefBS::enqueue(o);
+  }
+#endif
+} 
+
 public:
   LoadedClassesClosure(Thread* thread, JvmtiEnv* env) : _cur_thread(thread), _env(env) {
     assert(_cur_thread == Thread::current(), "must be current thread");
   }
 
   void do_klass(Klass* k) {
     // Collect all jclasses
     _classStack.push((jclass) _env->jni_reference(Handle(_cur_thread, k->java_mirror())));
+    LoadedClassesClosure::ensure_klass_alive(k->java_mirror());
   }
 
   int extract(jclass* result_list) {
     // The size of the Stack will be 0 after extract, so get it here
     int count = (int)_classStack.size();