hotspot/src/share/vm/classfile/classLoaderData.cpp
changeset 13728 882756847a04
child 14588 8ec26d2d9339
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/hotspot/src/share/vm/classfile/classLoaderData.cpp	Sat Sep 01 13:25:18 2012 -0400
@@ -0,0 +1,640 @@
+/*
+ * Copyright (c) 2012, 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.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ *
+ */
+
+// A ClassLoaderData identifies the full set of class types that a class
+// loader's name resolution strategy produces for a given configuration of the
+// class loader.
+// Class types in the ClassLoaderData may be defined by from class file binaries
+// provided by the class loader, or from other class loader it interacts with
+// according to its name resolution strategy.
+//
+// Class loaders that implement a deterministic name resolution strategy
+// (including with respect to their delegation behavior), such as the boot, the
+// extension, and the system loaders of the JDK's built-in class loader
+// hierarchy, always produce the same linkset for a given configuration.
+//
+// ClassLoaderData carries information related to a linkset (e.g.,
+// metaspace holding its klass definitions).
+// The System Dictionary and related data structures (e.g., placeholder table,
+// loader constraints table) as well as the runtime representation of classes
+// only reference ClassLoaderData.
+//
+// Instances of java.lang.ClassLoader holds a pointer to a ClassLoaderData that
+// that represent the loader's "linking domain" in the JVM.
+//
+// The bootstrap loader (represented by NULL) also has a ClassLoaderData,
+// the singleton class the_null_class_loader_data().
+
+#include "precompiled.hpp"
+#include "classfile/classLoaderData.hpp"
+#include "classfile/classLoaderData.inline.hpp"
+#include "classfile/javaClasses.hpp"
+#include "classfile/systemDictionary.hpp"
+#include "code/codeCache.hpp"
+#include "memory/metadataFactory.hpp"
+#include "memory/metaspaceShared.hpp"
+#include "prims/jvmtiRedefineClasses.hpp"
+#include "runtime/jniHandles.hpp"
+#include "runtime/mutex.hpp"
+#include "runtime/safepoint.hpp"
+#include "runtime/synchronizer.hpp"
+#include "utilities/growableArray.hpp"
+#include "utilities/ostream.hpp"
+
+ClassLoaderData * ClassLoaderData::_the_null_class_loader_data = NULL;
+
+ClassLoaderData::ClassLoaderData(Handle h_class_loader) : _class_loader(h_class_loader()),
+  _metaspace(NULL), _unloading(false), _klasses(NULL),
+  _claimed(0), _jmethod_ids(NULL), _handles(NULL),
+  _deallocate_list(NULL), _next(NULL),
+  _metaspace_lock(new Mutex(Monitor::leaf+1, "Metaspace allocation lock", true)) {
+    // empty
+}
+
+bool ClassLoaderData::claim() {
+  if (_claimed == 1) {
+    return false;
+  }
+
+  return (int) Atomic::cmpxchg(1, &_claimed, 0) == 0;
+}
+
+void ClassLoaderData::oops_do(OopClosure* f, KlassClosure* klass_closure, bool must_claim) {
+  if (must_claim && !claim()) {
+    return;
+  }
+
+  f->do_oop(&_class_loader);
+  _handles->oops_do(f);
+  if (klass_closure != NULL) {
+    classes_do(klass_closure);
+  }
+}
+
+void ClassLoaderData::classes_do(KlassClosure* klass_closure) {
+  for (Klass* k = _klasses; k != NULL; k = k->next_link()) {
+    klass_closure->do_klass(k);
+  }
+}
+
+void ClassLoaderData::classes_do(void f(InstanceKlass*)) {
+  for (Klass* k = _klasses; k != NULL; k = k->next_link()) {
+    if (k->oop_is_instance()) {
+      f(InstanceKlass::cast(k));
+    }
+  }
+}
+
+void ClassLoaderData::record_dependency(Klass* k, TRAPS) {
+  ClassLoaderData * const from_cld = this;
+  ClassLoaderData * const to_cld = k->class_loader_data();
+
+  // Records dependency between non-null class loaders only.
+  if (to_cld->is_the_null_class_loader_data() || from_cld->is_the_null_class_loader_data()) {
+    return;
+  }
+
+  // Check that this dependency isn't from the same or parent class_loader
+  oop to = to_cld->class_loader();
+  oop from = from_cld->class_loader();
+
+  oop curr = from;
+  while (curr != NULL) {
+    if (curr == to) {
+      return; // this class loader is in the parent list, no need to add it.
+    }
+    curr = java_lang_ClassLoader::parent(curr);
+  }
+
+  // It's a dependency we won't find through GC, add it. This is relatively rare
+  from_cld->add_dependency(to_cld, CHECK);
+}
+
+bool ClassLoaderData::has_dependency(ClassLoaderData* dependency) {
+  oop loader = dependency->class_loader();
+
+  // Get objArrayOop out of the class_loader oop and see if this dependency
+  // is there.  Don't safepoint!  These are all oops.
+  // Dependency list is (oop class_loader, objArrayOop next)
+  objArrayOop ok = (objArrayOop)java_lang_ClassLoader::dependencies(class_loader());
+  while (ok != NULL) {
+    if (ok->obj_at(0) == loader) {
+      return true;
+    }
+    ok = (objArrayOop)ok->obj_at(1);
+  }
+  return false;
+}
+
+void ClassLoaderData::add_dependency(ClassLoaderData* dependency, TRAPS) {
+  // Minimize the number of duplicates in the list.
+  if (has_dependency(dependency)) {
+    return;
+  }
+
+  // Create a new dependency node with fields for (class_loader, next)
+  objArrayOop deps = oopFactory::new_objectArray(2, CHECK);
+  deps->obj_at_put(0, dependency->class_loader());
+
+  // Add this lock free, using compare and exchange, need barriers for GC
+  // Do the barrier first.
+  HeapWord* addr = java_lang_ClassLoader::dependencies_addr(class_loader());
+  while (true) {
+    oop old_dependency = java_lang_ClassLoader::dependencies(class_loader());
+    deps->obj_at_put(1, old_dependency);
+
+    oop newold = oopDesc::atomic_compare_exchange_oop((oop)deps, addr, old_dependency, true);
+    if (newold == old_dependency) {
+      update_barrier_set((void*)addr, (oop)deps);
+      // we won the race to add this dependency
+      break;
+    }
+  }
+}
+
+
+void ClassLoaderDataGraph::clear_claimed_marks() {
+  for (ClassLoaderData* cld = _head; cld != NULL; cld = cld->next()) {
+    cld->clear_claimed();
+  }
+}
+
+void ClassLoaderData::add_class(Klass* k) {
+  MutexLockerEx ml(metaspace_lock(),  Mutex::_no_safepoint_check_flag);
+  Klass* old_value = _klasses;
+  k->set_next_link(old_value);
+  // link the new item into the list
+  _klasses = k;
+
+  if (TraceClassLoaderData && k->class_loader_data() != NULL) {
+    ResourceMark rm;
+    tty->print_cr("[TraceClassLoaderData] Adding k: " PTR_FORMAT " %s to CLD: "
+                  PTR_FORMAT " loader: " PTR_FORMAT " %s",
+                  k,
+                  k->external_name(),
+                  k->class_loader_data(),
+                  k->class_loader(),
+                  k->class_loader() != NULL ? k->class_loader()->klass()->external_name() : "NULL"
+      );
+  }
+}
+
+// This is called by InstanceKlass::deallocate_contents() to remove the
+// scratch_class for redefine classes.  We need a lock because there it may not
+// be called at a safepoint if there's an error.
+void ClassLoaderData::remove_class(Klass* scratch_class) {
+  MutexLockerEx ml(metaspace_lock(),  Mutex::_no_safepoint_check_flag);
+  Klass* prev = NULL;
+  for (Klass* k = _klasses; k != NULL; k = k->next_link()) {
+    if (k == scratch_class) {
+      if (prev == NULL) {
+        _klasses = k->next_link();
+      } else {
+        Klass* next = k->next_link();
+        prev->set_next_link(next);
+      }
+      return;
+    }
+    prev = k;
+  }
+  ShouldNotReachHere();   // should have found this class!!
+}
+
+ClassLoaderData::~ClassLoaderData() {
+  Metaspace *m = _metaspace;
+  if (m != NULL) {
+    _metaspace = NULL;
+    // release the metaspace
+    delete m;
+    // release the handles
+    if (_handles != NULL) {
+      JNIHandleBlock::release_block(_handles);
+      _handles = NULL;
+    }
+  }
+
+  // Clear all the JNI handles for methods
+  // These aren't deallocated and are going to look like a leak, but that's
+  // needed because we can't really get rid of jmethodIDs because we don't
+  // know when native code is going to stop using them.  The spec says that
+  // they're "invalid" but existing programs likely rely on their being
+  // NULL after class unloading.
+  if (_jmethod_ids != NULL) {
+    Method::clear_jmethod_ids(this);
+  }
+  // Delete lock
+  delete _metaspace_lock;
+
+  // Delete free list
+  if (_deallocate_list != NULL) {
+    delete _deallocate_list;
+  }
+}
+
+Metaspace* ClassLoaderData::metaspace_non_null() {
+  // If the metaspace has not been allocated, create a new one.  Might want
+  // to create smaller arena for Reflection class loaders also.
+  // The reason for the delayed allocation is because some class loaders are
+  // simply for delegating with no metadata of their own.
+  if (_metaspace == NULL) {
+    MutexLockerEx ml(metaspace_lock(),  Mutex::_no_safepoint_check_flag);
+    // Check again if metaspace has been allocated while we were getting this lock.
+    if (_metaspace != NULL) {
+      return _metaspace;
+    }
+    if (class_loader() == NULL) {
+      assert(this == the_null_class_loader_data(), "Must be");
+      size_t word_size = Metaspace::first_chunk_word_size();
+      set_metaspace(new Metaspace(_metaspace_lock, word_size));
+    } else {
+      set_metaspace(new Metaspace(_metaspace_lock));  // default size for now.
+    }
+  }
+  return _metaspace;
+}
+
+JNIHandleBlock* ClassLoaderData::handles() const           { return _handles; }
+void ClassLoaderData::set_handles(JNIHandleBlock* handles) { _handles = handles; }
+
+jobject ClassLoaderData::add_handle(Handle h) {
+  MutexLockerEx ml(metaspace_lock(),  Mutex::_no_safepoint_check_flag);
+  if (handles() == NULL) {
+    set_handles(JNIHandleBlock::allocate_block());
+  }
+  return handles()->allocate_handle(h());
+}
+
+// Add this metadata pointer to be freed when it's safe.  This is only during
+// class unloading because Handles might point to this metadata field.
+void ClassLoaderData::add_to_deallocate_list(Metadata* m) {
+  // Metadata in shared region isn't deleted.
+  if (!m->is_shared()) {
+    MutexLockerEx ml(metaspace_lock(),  Mutex::_no_safepoint_check_flag);
+    if (_deallocate_list == NULL) {
+      _deallocate_list = new (ResourceObj::C_HEAP, mtClass) GrowableArray<Metadata*>(100, true);
+    }
+    _deallocate_list->append_if_missing(m);
+  }
+}
+
+// Deallocate free metadata on the free list.  How useful the PermGen was!
+void ClassLoaderData::free_deallocate_list() {
+  // Don't need lock, at safepoint
+  assert(SafepointSynchronize::is_at_safepoint(), "only called at safepoint");
+  if (_deallocate_list == NULL) {
+    return;
+  }
+  // Go backwards because this removes entries that are freed.
+  for (int i = _deallocate_list->length() - 1; i >= 0; i--) {
+    Metadata* m = _deallocate_list->at(i);
+    if (!m->on_stack()) {
+      _deallocate_list->remove_at(i);
+      // There are only three types of metadata that we deallocate directly.
+      // Cast them so they can be used by the template function.
+      if (m->is_method()) {
+        MetadataFactory::free_metadata(this, (Method*)m);
+      } else if (m->is_constantPool()) {
+        MetadataFactory::free_metadata(this, (ConstantPool*)m);
+      } else if (m->is_klass()) {
+        MetadataFactory::free_metadata(this, (InstanceKlass*)m);
+      } else {
+        ShouldNotReachHere();
+      }
+    }
+  }
+}
+
+#ifndef PRODUCT
+void ClassLoaderData::print_loader(ClassLoaderData *loader_data, outputStream* out) {
+  oop class_loader = loader_data->class_loader();
+  out->print("%s", SystemDictionary::loader_name(class_loader));
+}
+
+// Define to dump klasses
+#undef CLD_DUMP_KLASSES
+
+void ClassLoaderData::dump(outputStream * const out) {
+  ResourceMark rm;
+  out->print("ClassLoaderData CLD: "PTR_FORMAT", loader: "PTR_FORMAT", loader_klass: "PTR_FORMAT" %s {",
+      this, class_loader(),
+      class_loader() != NULL ? class_loader()->klass() : NULL,
+      class_loader() != NULL ? class_loader()->klass()->external_name() : "NULL");
+  if (claimed()) out->print(" claimed ");
+  if (is_unloading()) out->print(" unloading ");
+  out->print(" handles " INTPTR_FORMAT, handles());
+  out->cr();
+  if (metaspace_or_null() != NULL) {
+    out->print_cr("metaspace: " PTR_FORMAT, metaspace_or_null());
+    metaspace_or_null()->dump(out);
+  } else {
+    out->print_cr("metaspace: NULL");
+  }
+
+#ifdef CLD_DUMP_KLASSES
+  if (Verbose) {
+    ResourceMark rm;
+    Klass* k = _klasses;
+    while (k != NULL) {
+      out->print_cr("klass "PTR_FORMAT", %s, CT: %d, MUT: %d", k, k->name()->as_C_string(),
+          k->has_modified_oops(), k->has_accumulated_modified_oops());
+      k = k->next_link();
+    }
+  }
+#endif  // CLD_DUMP_KLASSES
+#undef CLD_DUMP_KLASSES
+  if (_jmethod_ids != NULL) {
+    Method::print_jmethod_ids(this, out);
+  }
+  out->print_cr("}");
+}
+#endif // PRODUCT
+
+void ClassLoaderData::verify() {
+  oop cl = class_loader();
+
+  guarantee(this == class_loader_data(cl), "Must be the same");
+  guarantee(cl != NULL || this == ClassLoaderData::the_null_class_loader_data(), "must be");
+
+  // Verify the integrity of the allocated space.
+  if (metaspace_or_null() != NULL) {
+    metaspace_or_null()->verify();
+  }
+
+  for (Klass* k = _klasses; k != NULL; k = k->next_link()) {
+    guarantee(k->class_loader_data() == this, "Must be the same");
+    k->verify();
+  }
+}
+
+// GC root of class loader data created.
+ClassLoaderData* ClassLoaderDataGraph::_head = NULL;
+ClassLoaderData* ClassLoaderDataGraph::_unloading = NULL;
+ClassLoaderData* ClassLoaderDataGraph::_saved_head = NULL;
+
+
+// Add a new class loader data node to the list.  Assign the newly created
+// ClassLoaderData into the java/lang/ClassLoader object as a hidden field
+ClassLoaderData* ClassLoaderDataGraph::add(ClassLoaderData** cld_addr, Handle loader_data) {
+  // Not assigned a class loader data yet.
+  // Create one.
+  ClassLoaderData* *list_head = &_head;
+  ClassLoaderData* next = _head;
+  ClassLoaderData* cld = new ClassLoaderData(loader_data);
+
+  // First, Atomically set it.
+  ClassLoaderData* old = (ClassLoaderData*) Atomic::cmpxchg_ptr(cld, cld_addr, NULL);
+  if (old != NULL) {
+    delete cld;
+    // Returns the data.
+    return old;
+  }
+
+  // We won the race, and therefore the task of adding the data to the list of
+  // class loader data
+  do {
+    cld->set_next(next);
+    ClassLoaderData* exchanged = (ClassLoaderData*)Atomic::cmpxchg_ptr(cld, list_head, next);
+    if (exchanged == next) {
+      if (TraceClassLoaderData) {
+        tty->print("[ClassLoaderData: ");
+        tty->print("create class loader data "PTR_FORMAT, cld);
+        tty->print(" for instance "PTR_FORMAT" of ", cld->class_loader());
+        loader_data->klass()->name()->print_symbol_on(tty);
+        tty->print_cr("]");
+      }
+      return cld;
+    }
+    next = exchanged;
+  } while (true);
+}
+
+void ClassLoaderDataGraph::oops_do(OopClosure* f, KlassClosure* klass_closure, bool must_claim) {
+  for (ClassLoaderData* cld = _head; cld != NULL; cld = cld->next()) {
+    cld->oops_do(f, klass_closure, must_claim);
+  }
+}
+
+void ClassLoaderDataGraph::always_strong_oops_do(OopClosure* f, KlassClosure* klass_closure, bool must_claim) {
+  if (ClassUnloading) {
+    ClassLoaderData::the_null_class_loader_data()->oops_do(f, klass_closure, must_claim);
+  } else {
+    ClassLoaderDataGraph::oops_do(f, klass_closure, must_claim);
+  }
+}
+
+void ClassLoaderDataGraph::classes_do(KlassClosure* klass_closure) {
+  for (ClassLoaderData* cld = _head; cld != NULL; cld = cld->next()) {
+    cld->classes_do(klass_closure);
+  }
+}
+
+GrowableArray<ClassLoaderData*>* ClassLoaderDataGraph::new_clds() {
+  assert(_head == NULL || _saved_head != NULL, "remember_new_clds(true) not called?");
+
+  GrowableArray<ClassLoaderData*>* array = new GrowableArray<ClassLoaderData*>();
+
+  // The CLDs in [_head, _saved_head] were all added during last call to remember_new_clds(true);
+  ClassLoaderData* curr = _head;
+  while (curr != _saved_head) {
+    if (!curr->claimed()) {
+      array->push(curr);
+
+      if (TraceClassLoaderData) {
+        tty->print("[ClassLoaderData] found new CLD: ");
+        curr->print_value_on(tty);
+        tty->cr();
+      }
+    }
+
+    curr = curr->_next;
+  }
+
+  return array;
+}
+
+#ifndef PRODUCT
+// for debugging and hsfind(x)
+bool ClassLoaderDataGraph::contains(address x) {
+  // I think we need the _metaspace_lock taken here because the class loader
+  // data graph could be changing while we are walking it (new entries added,
+  // new entries being unloaded, etc).
+  if (DumpSharedSpaces) {
+    // There are only two metaspaces to worry about.
+    ClassLoaderData* ncld = ClassLoaderData::the_null_class_loader_data();
+    return (ncld->ro_metaspace()->contains(x) || ncld->rw_metaspace()->contains(x));
+  }
+
+  if (UseSharedSpaces && MetaspaceShared::is_in_shared_space(x)) {
+    return true;
+  }
+
+  for (ClassLoaderData* cld = _head; cld != NULL; cld = cld->next()) {
+    if (cld->metaspace_or_null() != NULL && cld->metaspace_or_null()->contains(x)) {
+      return true;
+    }
+  }
+
+  // Could also be on an unloading list which is okay, ie. still allocated
+  // for a little while.
+  for (ClassLoaderData* ucld = _unloading; ucld != NULL; ucld = ucld->next()) {
+    if (ucld->metaspace_or_null() != NULL && ucld->metaspace_or_null()->contains(x)) {
+      return true;
+    }
+  }
+  return false;
+}
+
+bool ClassLoaderDataGraph::contains_loader_data(ClassLoaderData* loader_data) {
+  for (ClassLoaderData* data = _head; data != NULL; data = data->next()) {
+    if (loader_data == data) {
+      return true;
+    }
+  }
+
+  return false;
+}
+#endif // PRODUCT
+
+// Move class loader data from main list to the unloaded list for unloading
+// and deallocation later.
+bool ClassLoaderDataGraph::do_unloading(BoolObjectClosure* is_alive) {
+  ClassLoaderData* data = _head;
+  ClassLoaderData* prev = NULL;
+  bool seen_dead_loader = false;
+  // mark metadata seen on the stack and code cache so we can delete
+  // unneeded entries.
+  bool has_redefined_a_class = JvmtiExport::has_redefined_a_class();
+  MetadataOnStackMark md_on_stack;
+  while (data != NULL) {
+    if (data->class_loader() == NULL || is_alive->do_object_b(data->class_loader())) {
+      assert(data->claimed(), "class loader data must have been claimed");
+      if (has_redefined_a_class) {
+        data->classes_do(InstanceKlass::purge_previous_versions);
+      }
+      data->free_deallocate_list();
+      prev = data;
+      data = data->next();
+      continue;
+    }
+    seen_dead_loader = true;
+    ClassLoaderData* dead = data;
+    dead->mark_for_unload();
+    if (TraceClassLoaderData) {
+      tty->print("[ClassLoaderData: unload loader data "PTR_FORMAT, dead);
+      tty->print(" for instance "PTR_FORMAT" of ", dead->class_loader());
+      dead->class_loader()->klass()->name()->print_symbol_on(tty);
+      tty->print_cr("]");
+    }
+    data = data->next();
+    // Remove from loader list.
+    if (prev != NULL) {
+      prev->set_next(data);
+    } else {
+      assert(dead == _head, "sanity check");
+      _head = data;
+    }
+    dead->set_next(_unloading);
+    _unloading = dead;
+  }
+  return seen_dead_loader;
+}
+
+void ClassLoaderDataGraph::purge() {
+  ClassLoaderData* list = _unloading;
+  _unloading = NULL;
+  ClassLoaderData* next = list;
+  while (next != NULL) {
+    ClassLoaderData* purge_me = next;
+    next = purge_me->next();
+    delete purge_me;
+  }
+}
+
+// CDS support
+
+// Global metaspaces for writing information to the shared archive.  When
+// application CDS is supported, we may need one per metaspace, so this
+// sort of looks like it.
+Metaspace* ClassLoaderData::_ro_metaspace = NULL;
+Metaspace* ClassLoaderData::_rw_metaspace = NULL;
+static bool _shared_metaspaces_initialized = false;
+
+// Initialize shared metaspaces (change to call from somewhere not lazily)
+void ClassLoaderData::initialize_shared_metaspaces() {
+  assert(DumpSharedSpaces, "only use this for dumping shared spaces");
+  assert(this == ClassLoaderData::the_null_class_loader_data(),
+         "only supported for null loader data for now");
+  assert (!_shared_metaspaces_initialized, "only initialize once");
+  MutexLockerEx ml(metaspace_lock(),  Mutex::_no_safepoint_check_flag);
+  _ro_metaspace = new Metaspace(_metaspace_lock, SharedReadOnlySize/wordSize);
+  _rw_metaspace = new Metaspace(_metaspace_lock, SharedReadWriteSize/wordSize);
+  _shared_metaspaces_initialized = true;
+}
+
+Metaspace* ClassLoaderData::ro_metaspace() {
+  assert(_ro_metaspace != NULL, "should already be initialized");
+  return _ro_metaspace;
+}
+
+Metaspace* ClassLoaderData::rw_metaspace() {
+  assert(_rw_metaspace != NULL, "should already be initialized");
+  return _rw_metaspace;
+}
+
+
+ClassLoaderDataGraphMetaspaceIterator::ClassLoaderDataGraphMetaspaceIterator() {
+  _data = ClassLoaderDataGraph::_head;
+}
+
+ClassLoaderDataGraphMetaspaceIterator::~ClassLoaderDataGraphMetaspaceIterator() {}
+
+#ifndef PRODUCT
+// callable from debugger
+extern "C" int print_loader_data_graph() {
+  ClassLoaderDataGraph::dump_on(tty);
+  return 0;
+}
+
+void ClassLoaderDataGraph::verify() {
+  for (ClassLoaderData* data = _head; data != NULL; data = data->next()) {
+    data->verify();
+  }
+}
+
+void ClassLoaderDataGraph::dump_on(outputStream * const out) {
+  for (ClassLoaderData* data = _head; data != NULL; data = data->next()) {
+    data->dump(out);
+  }
+  MetaspaceAux::dump(out);
+}
+
+void ClassLoaderData::print_value_on(outputStream* out) const {
+  if (class_loader() == NULL) {
+    out->print_cr("NULL class_loader");
+  } else {
+    out->print("class loader "PTR_FORMAT, this);
+    class_loader()->print_value_on(out);
+  }
+}
+#endif // PRODUCT