src/hotspot/share/classfile/classLoaderData.cpp

*** 594,603 ****
--- 594,616 ----
      resizable = false;
    }
    return new Dictionary(this, size, resizable);
  }
  
+ // Tell the GC to keep this klass alive while iterating ClassLoaderDataGraph
+ void ClassLoaderData::ensure_loader_alive() {
+   // 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 (!keep_alive()) {
+     oop* o = is_anonymous() ? _klasses->java_mirror_handle().ptr_raw() : &_class_loader;
+     (void)RootAccess<ON_PHANTOM_OOP_REF>::oop_load(o);
+   }
+ }
+ 
  // Unloading support
  oop ClassLoaderData::keep_alive_object() const {
    assert_locked_or_safepoint(_metaspace_lock);
    assert(!keep_alive(), "Don't use with CLDs that are artificially kept alive");
    return is_anonymous() ? _klasses->java_mirror() : class_loader();
*** 1033,1061 ****
--- 1046,1078 ----
    }
  }
  
  void ClassLoaderDataGraph::classes_do(KlassClosure* klass_closure) {
    for (ClassLoaderData* cld = _head; cld != NULL; cld = cld->next()) {
+     cld->ensure_loader_alive();
      cld->classes_do(klass_closure);
    }
  }
  
  void ClassLoaderDataGraph::classes_do(void f(Klass* const)) {
    for (ClassLoaderData* cld = _head; cld != NULL; cld = cld->next()) {
+     cld->ensure_loader_alive();
      cld->classes_do(f);
    }
  }
  
  void ClassLoaderDataGraph::methods_do(void f(Method*)) {
    for (ClassLoaderData* cld = _head; cld != NULL; cld = cld->next()) {
+     cld->ensure_loader_alive();
      cld->methods_do(f);
    }
  }
  
  void ClassLoaderDataGraph::modules_do(void f(ModuleEntry*)) {
    assert_locked_or_safepoint(Module_lock);
    for (ClassLoaderData* cld = _head; cld != NULL; cld = cld->next()) {
+     cld->ensure_loader_alive();
      cld->modules_do(f);
    }
  }
  
  void ClassLoaderDataGraph::modules_unloading_do(void f(ModuleEntry*)) {
*** 1069,1078 ****
--- 1086,1096 ----
  }
  
  void ClassLoaderDataGraph::packages_do(void f(PackageEntry*)) {
    assert_locked_or_safepoint(Module_lock);
    for (ClassLoaderData* cld = _head; cld != NULL; cld = cld->next()) {
+     cld->ensure_loader_alive();
      cld->packages_do(f);
    }
  }
  
  void ClassLoaderDataGraph::packages_unloading_do(void f(PackageEntry*)) {
*** 1085,1094 ****
--- 1103,1113 ----
    }
  }
  
  void ClassLoaderDataGraph::loaded_classes_do(KlassClosure* klass_closure) {
    for (ClassLoaderData* cld = _head; cld != NULL; cld = cld->next()) {
+     cld->ensure_loader_alive();
      cld->loaded_classes_do(klass_closure);
    }
  }
  
  void ClassLoaderDataGraph::classes_unloading_do(void f(Klass* const)) {
*** 1106,1135 ****
--- 1125,1158 ----
  
  // Walk classes in the loaded class dictionaries in various forms.
  // Only walks the classes defined in this class loader.
  void ClassLoaderDataGraph::dictionary_classes_do(void f(InstanceKlass*)) {
    FOR_ALL_DICTIONARY(cld) {
+     cld->ensure_loader_alive();
      cld->dictionary()->classes_do(f);
    }
  }
  
  // Only walks the classes defined in this class loader.
  void ClassLoaderDataGraph::dictionary_classes_do(void f(InstanceKlass*, TRAPS), TRAPS) {
    FOR_ALL_DICTIONARY(cld) {
+     cld->ensure_loader_alive();
      cld->dictionary()->classes_do(f, CHECK);
    }
  }
  
  // Walks all entries in the dictionary including entries initiated by this class loader.
  void ClassLoaderDataGraph::dictionary_all_entries_do(void f(InstanceKlass*, ClassLoaderData*)) {
    FOR_ALL_DICTIONARY(cld) {
+     cld->ensure_loader_alive();
      cld->dictionary()->all_entries_do(f);
    }
  }
  
  void ClassLoaderDataGraph::verify_dictionary() {
    FOR_ALL_DICTIONARY(cld) {
+     cld->ensure_loader_alive();
      cld->dictionary()->verify();
    }
  }
  
  void ClassLoaderDataGraph::print_dictionary(outputStream* st) {