diff -r 4ebc2e2fb97c -r 71c04702a3d5 src/hotspot/share/classfile/classLoaderData.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/hotspot/share/classfile/classLoaderData.cpp	Tue Sep 12 19:03:39 2017 +0200
@@ -0,0 +1,1460 @@
+ /*
+ * Copyright (c) 2012, 2017, 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
+// platform, 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/dictionary.hpp"
+#include "classfile/javaClasses.hpp"
+#include "classfile/metadataOnStackMark.hpp"
+#include "classfile/moduleEntry.hpp"
+#include "classfile/packageEntry.hpp"
+#include "classfile/systemDictionary.hpp"
+#include "code/codeCache.hpp"
+#include "gc/shared/gcLocker.hpp"
+#include "logging/log.hpp"
+#include "logging/logStream.hpp"
+#include "memory/metadataFactory.hpp"
+#include "memory/metaspaceShared.hpp"
+#include "memory/oopFactory.hpp"
+#include "memory/resourceArea.hpp"
+#include "oops/objArrayOop.inline.hpp"
+#include "oops/oop.inline.hpp"
+#include "runtime/atomic.hpp"
+#include "runtime/javaCalls.hpp"
+#include "runtime/jniHandles.hpp"
+#include "runtime/mutex.hpp"
+#include "runtime/orderAccess.hpp"
+#include "runtime/safepoint.hpp"
+#include "runtime/synchronizer.hpp"
+#include "utilities/growableArray.hpp"
+#include "utilities/macros.hpp"
+#include "utilities/ostream.hpp"
+#if INCLUDE_ALL_GCS
+#include "gc/g1/g1SATBCardTableModRefBS.hpp"
+#endif // INCLUDE_ALL_GCS
+#if INCLUDE_TRACE
+#include "trace/tracing.hpp"
+#endif
+
+// helper function to avoid in-line casts
+template <typename T> static T* load_ptr_acquire(T* volatile *p) {
+  return static_cast<T*>(OrderAccess::load_ptr_acquire(p));
+}
+
+ClassLoaderData * ClassLoaderData::_the_null_class_loader_data = NULL;
+
+ClassLoaderData::ClassLoaderData(Handle h_class_loader, bool is_anonymous, Dependencies dependencies) :
+  _class_loader(h_class_loader()),
+  _is_anonymous(is_anonymous),
+  // An anonymous class loader data doesn't have anything to keep
+  // it from being unloaded during parsing of the anonymous class.
+  // The null-class-loader should always be kept alive.
+  _keep_alive((is_anonymous || h_class_loader.is_null()) ? 1 : 0),
+  _metaspace(NULL), _unloading(false), _klasses(NULL),
+  _modules(NULL), _packages(NULL),
+  _claimed(0), _jmethod_ids(NULL), _handles(), _deallocate_list(NULL),
+  _next(NULL), _dependencies(dependencies),
+  _metaspace_lock(new Mutex(Monitor::leaf+1, "Metaspace allocation lock", true,
+                            Monitor::_safepoint_check_never)) {
+
+  // A ClassLoaderData created solely for an anonymous class should never have a
+  // ModuleEntryTable or PackageEntryTable created for it. The defining package
+  // and module for an anonymous class will be found in its host class.
+  if (!is_anonymous) {
+    _packages = new PackageEntryTable(PackageEntryTable::_packagetable_entry_size);
+    if (h_class_loader.is_null()) {
+      // Create unnamed module for boot loader
+      _unnamed_module = ModuleEntry::create_boot_unnamed_module(this);
+    } else {
+      // Create unnamed module for all other loaders
+      _unnamed_module = ModuleEntry::create_unnamed_module(this);
+    }
+  } else {
+    _unnamed_module = NULL;
+  }
+
+  if (!is_anonymous) {
+    _dictionary = create_dictionary();
+  } else {
+    _dictionary = NULL;
+  }
+  TRACE_INIT_ID(this);
+}
+
+void ClassLoaderData::init_dependencies(TRAPS) {
+  assert(!Universe::is_fully_initialized(), "should only be called when initializing");
+  assert(is_the_null_class_loader_data(), "should only call this for the null class loader");
+  _dependencies.init(CHECK);
+}
+
+void ClassLoaderData::Dependencies::init(TRAPS) {
+  // Create empty dependencies array to add to. CMS requires this to be
+  // an oop so that it can track additions via card marks.  We think.
+  _list_head = oopFactory::new_objectArray(2, CHECK);
+}
+
+ClassLoaderData::ChunkedHandleList::~ChunkedHandleList() {
+  Chunk* c = _head;
+  while (c != NULL) {
+    Chunk* next = c->_next;
+    delete c;
+    c = next;
+  }
+}
+
+oop* ClassLoaderData::ChunkedHandleList::add(oop o) {
+  if (_head == NULL || _head->_size == Chunk::CAPACITY) {
+    Chunk* next = new Chunk(_head);
+    OrderAccess::release_store_ptr(&_head, next);
+  }
+  oop* handle = &_head->_data[_head->_size];
+  *handle = o;
+  OrderAccess::release_store(&_head->_size, _head->_size + 1);
+  return handle;
+}
+
+inline void ClassLoaderData::ChunkedHandleList::oops_do_chunk(OopClosure* f, Chunk* c, const juint size) {
+  for (juint i = 0; i < size; i++) {
+    if (c->_data[i] != NULL) {
+      f->do_oop(&c->_data[i]);
+    }
+  }
+}
+
+void ClassLoaderData::ChunkedHandleList::oops_do(OopClosure* f) {
+  Chunk* head = (Chunk*) OrderAccess::load_ptr_acquire(&_head);
+  if (head != NULL) {
+    // Must be careful when reading size of head
+    oops_do_chunk(f, head, OrderAccess::load_acquire(&head->_size));
+    for (Chunk* c = head->_next; c != NULL; c = c->_next) {
+      oops_do_chunk(f, c, c->_size);
+    }
+  }
+}
+
+#ifdef ASSERT
+class VerifyContainsOopClosure : public OopClosure {
+  oop* _target;
+  bool _found;
+
+ public:
+  VerifyContainsOopClosure(oop* target) : _target(target), _found(false) {}
+
+  void do_oop(oop* p) {
+    if (p == _target) {
+      _found = true;
+    }
+  }
+
+  void do_oop(narrowOop* p) {
+    // The ChunkedHandleList should not contain any narrowOop
+    ShouldNotReachHere();
+  }
+
+  bool found() const {
+    return _found;
+  }
+};
+
+bool ClassLoaderData::ChunkedHandleList::contains(oop* p) {
+  VerifyContainsOopClosure cl(p);
+  oops_do(&cl);
+  return cl.found();
+}
+#endif
+
+bool ClassLoaderData::claim() {
+  if (_claimed == 1) {
+    return false;
+  }
+
+  return (int) Atomic::cmpxchg(1, &_claimed, 0) == 0;
+}
+
+// Anonymous classes have their own ClassLoaderData that is marked to keep alive
+// while the class is being parsed, and if the class appears on the module fixup list.
+// Due to the uniqueness that no other class shares the anonymous class' name or
+// ClassLoaderData, no other non-GC thread has knowledge of the anonymous class while
+// it is being defined, therefore _keep_alive is not volatile or atomic.
+void ClassLoaderData::inc_keep_alive() {
+  if (is_anonymous()) {
+    assert(_keep_alive >= 0, "Invalid keep alive increment count");
+    _keep_alive++;
+  }
+}
+
+void ClassLoaderData::dec_keep_alive() {
+  if (is_anonymous()) {
+    assert(_keep_alive > 0, "Invalid keep alive decrement count");
+    _keep_alive--;
+  }
+}
+
+void ClassLoaderData::oops_do(OopClosure* f, KlassClosure* klass_closure, bool must_claim) {
+  if (must_claim && !claim()) {
+    return;
+  }
+
+  f->do_oop(&_class_loader);
+  _dependencies.oops_do(f);
+
+  _handles.oops_do(f);
+
+  if (klass_closure != NULL) {
+    classes_do(klass_closure);
+  }
+}
+
+void ClassLoaderData::Dependencies::oops_do(OopClosure* f) {
+  f->do_oop((oop*)&_list_head);
+}
+
+void ClassLoaderData::classes_do(KlassClosure* klass_closure) {
+  // Lock-free access requires load_ptr_acquire
+  for (Klass* k = load_ptr_acquire(&_klasses); k != NULL; k = k->next_link()) {
+    klass_closure->do_klass(k);
+    assert(k != k->next_link(), "no loops!");
+  }
+}
+
+void ClassLoaderData::classes_do(void f(Klass * const)) {
+  // Lock-free access requires load_ptr_acquire
+  for (Klass* k = load_ptr_acquire(&_klasses); k != NULL; k = k->next_link()) {
+    f(k);
+    assert(k != k->next_link(), "no loops!");
+  }
+}
+
+void ClassLoaderData::methods_do(void f(Method*)) {
+  // Lock-free access requires load_ptr_acquire
+  for (Klass* k = load_ptr_acquire(&_klasses); k != NULL; k = k->next_link()) {
+    if (k->is_instance_klass() && InstanceKlass::cast(k)->is_loaded()) {
+      InstanceKlass::cast(k)->methods_do(f);
+    }
+  }
+}
+
+void ClassLoaderData::loaded_classes_do(KlassClosure* klass_closure) {
+  // Lock-free access requires load_ptr_acquire
+  for (Klass* k = load_ptr_acquire(&_klasses); k != NULL; k = k->next_link()) {
+    // Do not filter ArrayKlass oops here...
+    if (k->is_array_klass() || (k->is_instance_klass() && InstanceKlass::cast(k)->is_loaded())) {
+      klass_closure->do_klass(k);
+    }
+  }
+}
+
+void ClassLoaderData::classes_do(void f(InstanceKlass*)) {
+  // Lock-free access requires load_ptr_acquire
+  for (Klass* k = load_ptr_acquire(&_klasses); k != NULL; k = k->next_link()) {
+    if (k->is_instance_klass()) {
+      f(InstanceKlass::cast(k));
+    }
+    assert(k != k->next_link(), "no loops!");
+  }
+}
+
+void ClassLoaderData::modules_do(void f(ModuleEntry*)) {
+  assert_locked_or_safepoint(Module_lock);
+  if (_unnamed_module != NULL) {
+    f(_unnamed_module);
+  }
+  if (_modules != NULL) {
+    for (int i = 0; i < _modules->table_size(); i++) {
+      for (ModuleEntry* entry = _modules->bucket(i);
+           entry != NULL;
+           entry = entry->next()) {
+        f(entry);
+      }
+    }
+  }
+}
+
+void ClassLoaderData::packages_do(void f(PackageEntry*)) {
+  assert_locked_or_safepoint(Module_lock);
+  if (_packages != NULL) {
+    for (int i = 0; i < _packages->table_size(); i++) {
+      for (PackageEntry* entry = _packages->bucket(i);
+           entry != NULL;
+           entry = entry->next()) {
+        f(entry);
+      }
+    }
+  }
+}
+
+void ClassLoaderData::record_dependency(const Klass* k, TRAPS) {
+  assert(k != NULL, "invariant");
+
+  ClassLoaderData * const from_cld = this;
+  ClassLoaderData * const to_cld = k->class_loader_data();
+
+  // Dependency to the null class loader data doesn't need to be recorded
+  // because the null class loader data never goes away.
+  if (to_cld->is_the_null_class_loader_data()) {
+    return;
+  }
+
+  oop to;
+  if (to_cld->is_anonymous()) {
+    // Anonymous class dependencies are through the mirror.
+    to = k->java_mirror();
+  } else {
+    to = to_cld->class_loader();
+
+    // If from_cld is anonymous, even if it's class_loader is a parent of 'to'
+    // we still have to add it.  The class_loader won't keep from_cld alive.
+    if (!from_cld->is_anonymous()) {
+      // Check that this dependency isn't from the same or parent 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
+  // Must handle over GC point.
+  Handle dependency(THREAD, to);
+  from_cld->_dependencies.add(dependency, CHECK);
+}
+
+
+void ClassLoaderData::Dependencies::add(Handle dependency, TRAPS) {
+  // Check first if this dependency is already in the list.
+  // Save a pointer to the last to add to under the lock.
+  objArrayOop ok = _list_head;
+  objArrayOop last = NULL;
+  while (ok != NULL) {
+    last = ok;
+    if (ok->obj_at(0) == dependency()) {
+      // Don't need to add it
+      return;
+    }
+    ok = (objArrayOop)ok->obj_at(1);
+  }
+
+  // Must handle over GC points
+  assert (last != NULL, "dependencies should be initialized");
+  objArrayHandle last_handle(THREAD, last);
+
+  // Create a new dependency node with fields for (class_loader or mirror, next)
+  objArrayOop deps = oopFactory::new_objectArray(2, CHECK);
+  deps->obj_at_put(0, dependency());
+
+  // Must handle over GC points
+  objArrayHandle new_dependency(THREAD, deps);
+
+  // Add the dependency under lock
+  locked_add(last_handle, new_dependency, THREAD);
+}
+
+void ClassLoaderData::Dependencies::locked_add(objArrayHandle last_handle,
+                                               objArrayHandle new_dependency,
+                                               Thread* THREAD) {
+
+  // Have to lock and put the new dependency on the end of the dependency
+  // array so the card mark for CMS sees that this dependency is new.
+  // Can probably do this lock free with some effort.
+  ObjectLocker ol(Handle(THREAD, _list_head), THREAD);
+
+  oop loader_or_mirror = new_dependency->obj_at(0);
+
+  // Since the dependencies are only added, add to the end.
+  objArrayOop end = last_handle();
+  objArrayOop last = NULL;
+  while (end != NULL) {
+    last = end;
+    // check again if another thread added it to the end.
+    if (end->obj_at(0) == loader_or_mirror) {
+      // Don't need to add it
+      return;
+    }
+    end = (objArrayOop)end->obj_at(1);
+  }
+  assert (last != NULL, "dependencies should be initialized");
+  // fill in the first element with the oop in new_dependency.
+  if (last->obj_at(0) == NULL) {
+    last->obj_at_put(0, new_dependency->obj_at(0));
+  } else {
+    last->obj_at_put(1, new_dependency());
+  }
+}
+
+void ClassLoaderDataGraph::clear_claimed_marks() {
+  for (ClassLoaderData* cld = _head; cld != NULL; cld = cld->next()) {
+    cld->clear_claimed();
+  }
+}
+
+void ClassLoaderData::add_class(Klass* k, bool publicize /* true */) {
+  {
+    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, making sure the linked class is stable
+    // since the list can be walked without a lock
+    OrderAccess::release_store_ptr(&_klasses, k);
+  }
+
+  if (publicize && k->class_loader_data() != NULL) {
+    ResourceMark rm;
+    log_trace(class, loader, data)("Adding k: " PTR_FORMAT " %s to CLD: "
+                  PTR_FORMAT " loader: " PTR_FORMAT " %s",
+                  p2i(k),
+                  k->external_name(),
+                  p2i(k->class_loader_data()),
+                  p2i((void *)k->class_loader()),
+                  loader_name());
+  }
+}
+
+// Class iterator used by the compiler.  It gets some number of classes at
+// a safepoint to decay invocation counters on the methods.
+class ClassLoaderDataGraphKlassIteratorStatic {
+  ClassLoaderData* _current_loader_data;
+  Klass*           _current_class_entry;
+ public:
+
+  ClassLoaderDataGraphKlassIteratorStatic() : _current_loader_data(NULL), _current_class_entry(NULL) {}
+
+  InstanceKlass* try_get_next_class() {
+    assert(SafepointSynchronize::is_at_safepoint(), "only called at safepoint");
+    int max_classes = InstanceKlass::number_of_instance_classes();
+    assert(max_classes > 0, "should not be called with no instance classes");
+    for (int i = 0; i < max_classes; ) {
+
+      if (_current_class_entry != NULL) {
+        Klass* k = _current_class_entry;
+        _current_class_entry = _current_class_entry->next_link();
+
+        if (k->is_instance_klass()) {
+          InstanceKlass* ik = InstanceKlass::cast(k);
+          i++;  // count all instance classes found
+          // Not yet loaded classes are counted in max_classes
+          // but only return loaded classes.
+          if (ik->is_loaded()) {
+            return ik;
+          }
+        }
+      } else {
+        // Go to next CLD
+        if (_current_loader_data != NULL) {
+          _current_loader_data = _current_loader_data->next();
+        }
+        // Start at the beginning
+        if (_current_loader_data == NULL) {
+          _current_loader_data = ClassLoaderDataGraph::_head;
+        }
+
+        _current_class_entry = _current_loader_data->klasses();
+      }
+    }
+    // Should never be reached unless all instance classes have failed or are not fully loaded.
+    // Caller handles NULL.
+    return NULL;
+  }
+
+  // If the current class for the static iterator is a class being unloaded or
+  // deallocated, adjust the current class.
+  void adjust_saved_class(ClassLoaderData* cld) {
+    if (_current_loader_data == cld) {
+      _current_loader_data = cld->next();
+      if (_current_loader_data != NULL) {
+        _current_class_entry = _current_loader_data->klasses();
+      }  // else try_get_next_class will start at the head
+    }
+  }
+
+  void adjust_saved_class(Klass* klass) {
+    if (_current_class_entry == klass) {
+      _current_class_entry = klass->next_link();
+    }
+  }
+};
+
+static ClassLoaderDataGraphKlassIteratorStatic static_klass_iterator;
+
+InstanceKlass* ClassLoaderDataGraph::try_get_next_class() {
+  return static_klass_iterator.try_get_next_class();
+}
+
+
+// Remove a klass from the _klasses list for scratch_class during redefinition
+// or parsed class in the case of an error.
+void ClassLoaderData::remove_class(Klass* scratch_class) {
+  assert(SafepointSynchronize::is_at_safepoint(), "only called at safepoint");
+
+  // Adjust global class iterator.
+  static_klass_iterator.adjust_saved_class(scratch_class);
+
+  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;
+    assert(k != k->next_link(), "no loops!");
+  }
+  ShouldNotReachHere();   // should have found this class!!
+}
+
+void ClassLoaderData::unload() {
+  _unloading = true;
+
+  // Tell serviceability tools these classes are unloading
+  classes_do(InstanceKlass::notify_unload_class);
+
+  LogTarget(Debug, class, loader, data) lt;
+  if (lt.is_enabled()) {
+    ResourceMark rm;
+    LogStream ls(lt);
+    ls.print(": unload loader data " INTPTR_FORMAT, p2i(this));
+    ls.print(" for instance " INTPTR_FORMAT " of %s", p2i((void *)class_loader()),
+               loader_name());
+    if (is_anonymous()) {
+      ls.print(" for anonymous class  " INTPTR_FORMAT " ", p2i(_klasses));
+    }
+    ls.cr();
+  }
+
+  // In some rare cases items added to this list will not be freed elsewhere.
+  // To keep it simple, just free everything in it here.
+  free_deallocate_list();
+
+  // Clean up global class iterator for compiler
+  static_klass_iterator.adjust_saved_class(this);
+}
+
+ModuleEntryTable* ClassLoaderData::modules() {
+  // Lazily create the module entry table at first request.
+  // Lock-free access requires load_ptr_acquire.
+  ModuleEntryTable* modules = load_ptr_acquire(&_modules);
+  if (modules == NULL) {
+    MutexLocker m1(Module_lock);
+    // Check if _modules got allocated while we were waiting for this lock.
+    if ((modules = _modules) == NULL) {
+      modules = new ModuleEntryTable(ModuleEntryTable::_moduletable_entry_size);
+
+      {
+        MutexLockerEx m1(metaspace_lock(), Mutex::_no_safepoint_check_flag);
+        // Ensure _modules is stable, since it is examined without a lock
+        OrderAccess::release_store_ptr(&_modules, modules);
+      }
+    }
+  }
+  return modules;
+}
+
+const int _boot_loader_dictionary_size    = 1009;
+const int _default_loader_dictionary_size = 107;
+const int _prime_array_size         = 8;                       // array of primes for system dictionary size
+const int _average_depth_goal       = 3;                       // goal for lookup length
+const int _primelist[_prime_array_size] = {107, 1009, 2017, 4049, 5051, 10103, 20201, 40423};
+
+// Calculate a "good" dictionary size based
+// on predicted or current loaded classes count.
+static int calculate_dictionary_size(int classcount) {
+  int newsize = _primelist[0];
+  if (classcount > 0 && !DumpSharedSpaces) {
+    int index = 0;
+    int desiredsize = classcount/_average_depth_goal;
+    for (newsize = _primelist[index]; index < _prime_array_size -1;
+         newsize = _primelist[++index]) {
+      if (desiredsize <=  newsize) {
+        break;
+      }
+    }
+  }
+  return newsize;
+}
+
+Dictionary* ClassLoaderData::create_dictionary() {
+  assert(!is_anonymous(), "anonymous class loader data do not have a dictionary");
+  int size;
+  if (_the_null_class_loader_data == NULL) {
+    size = _boot_loader_dictionary_size;
+  } else if (class_loader()->is_a(SystemDictionary::reflect_DelegatingClassLoader_klass())) {
+    size = 1;  // there's only one class in relection class loader and no initiated classes
+  } else if (is_system_class_loader_data()) {
+    size = calculate_dictionary_size(PredictedLoadedClassCount);
+  } else {
+    size = _default_loader_dictionary_size;
+  }
+  return new Dictionary(this, size);
+}
+
+// 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();
+}
+
+bool ClassLoaderData::is_alive(BoolObjectClosure* is_alive_closure) const {
+  bool alive = keep_alive() // null class loader and incomplete anonymous klasses.
+      || is_alive_closure->do_object_b(keep_alive_object());
+
+  return alive;
+}
+
+ClassLoaderData::~ClassLoaderData() {
+  // Release C heap structures for all the classes.
+  classes_do(InstanceKlass::release_C_heap_structures);
+
+  // Release C heap allocated hashtable for all the packages.
+  if (_packages != NULL) {
+    // Destroy the table itself
+    delete _packages;
+    _packages = NULL;
+  }
+
+  // Release C heap allocated hashtable for all the modules.
+  if (_modules != NULL) {
+    // Destroy the table itself
+    delete _modules;
+    _modules = NULL;
+  }
+
+  // Release C heap allocated hashtable for the dictionary
+  if (_dictionary != NULL) {
+    // Destroy the table itself
+    delete _dictionary;
+    _dictionary = NULL;
+  }
+
+  if (_unnamed_module != NULL) {
+    _unnamed_module->delete_unnamed_module();
+    _unnamed_module = NULL;
+  }
+
+  // release the metaspace
+  Metaspace *m = _metaspace;
+  if (m != NULL) {
+    _metaspace = NULL;
+    delete m;
+  }
+  // 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;
+  }
+}
+
+// Returns true if this class loader data is for the system class loader.
+bool ClassLoaderData::is_system_class_loader_data() const {
+  return SystemDictionary::is_system_class_loader(class_loader());
+}
+
+// Returns true if this class loader data is for the platform class loader.
+bool ClassLoaderData::is_platform_class_loader_data() const {
+  return SystemDictionary::is_platform_class_loader(class_loader());
+}
+
+// Returns true if this class loader data is one of the 3 builtin
+// (boot, application/system or platform) class loaders. Note, the
+// builtin loaders are not freed by a GC.
+bool ClassLoaderData::is_builtin_class_loader_data() const {
+  return (is_the_null_class_loader_data() ||
+          SystemDictionary::is_system_class_loader(class_loader()) ||
+          SystemDictionary::is_platform_class_loader(class_loader()));
+}
+
+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.
+  // Lock-free access requires load_ptr_acquire.
+  Metaspace* metaspace = load_ptr_acquire(&_metaspace);
+  if (metaspace == NULL) {
+    MutexLockerEx ml(_metaspace_lock,  Mutex::_no_safepoint_check_flag);
+    // Check if _metaspace got allocated while we were waiting for this lock.
+    if ((metaspace = _metaspace) == NULL) {
+      if (this == the_null_class_loader_data()) {
+        assert (class_loader() == NULL, "Must be");
+        metaspace = new Metaspace(_metaspace_lock, Metaspace::BootMetaspaceType);
+      } else if (is_anonymous()) {
+        if (class_loader() != NULL) {
+          log_trace(class, loader, data)("is_anonymous: %s", class_loader()->klass()->internal_name());
+        }
+        metaspace = new Metaspace(_metaspace_lock, Metaspace::AnonymousMetaspaceType);
+      } else if (class_loader()->is_a(SystemDictionary::reflect_DelegatingClassLoader_klass())) {
+        if (class_loader() != NULL) {
+          log_trace(class, loader, data)("is_reflection: %s", class_loader()->klass()->internal_name());
+        }
+        metaspace = new Metaspace(_metaspace_lock, Metaspace::ReflectionMetaspaceType);
+      } else {
+        metaspace = new Metaspace(_metaspace_lock, Metaspace::StandardMetaspaceType);
+      }
+      // Ensure _metaspace is stable, since it is examined without a lock
+      OrderAccess::release_store_ptr(&_metaspace, metaspace);
+    }
+  }
+  return metaspace;
+}
+
+OopHandle ClassLoaderData::add_handle(Handle h) {
+  MutexLockerEx ml(metaspace_lock(),  Mutex::_no_safepoint_check_flag);
+  return OopHandle(_handles.add(h()));
+}
+
+void ClassLoaderData::remove_handle(OopHandle h) {
+  oop* ptr = h.ptr_raw();
+  if (ptr != NULL) {
+    assert(_handles.contains(ptr), "Got unexpected handle " PTR_FORMAT, p2i(ptr));
+#if INCLUDE_ALL_GCS
+    // This barrier is used by G1 to remember the old oop values, so
+    // that we don't forget any objects that were live at the snapshot at
+    // the beginning.
+    if (UseG1GC) {
+      oop obj = *ptr;
+      if (obj != NULL) {
+        G1SATBCardTableModRefBS::enqueue(obj);
+      }
+    }
+#endif
+    *ptr = NULL;
+  }
+}
+
+void ClassLoaderData::init_handle_locked(OopHandle& dest, Handle h) {
+  MutexLockerEx ml(metaspace_lock(),  Mutex::_no_safepoint_check_flag);
+  if (dest.resolve() != NULL) {
+    return;
+  } else {
+    dest = _handles.add(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();
+      }
+    } else {
+      // Metadata is alive.
+      // If scratch_class is on stack then it shouldn't be on this list!
+      assert(!m->is_klass() || !((InstanceKlass*)m)->is_scratch_class(),
+             "scratch classes on this list should be dead");
+      // Also should assert that other metadata on the list was found in handles.
+    }
+  }
+}
+
+// These anonymous class loaders are to contain classes used for JSR292
+ClassLoaderData* ClassLoaderData::anonymous_class_loader_data(oop loader, TRAPS) {
+  // Add a new class loader data to the graph.
+  Handle lh(THREAD, loader);
+  return ClassLoaderDataGraph::add(lh, true, THREAD);
+}
+
+const char* ClassLoaderData::loader_name() {
+  // Handles null class loader
+  return SystemDictionary::loader_name(class_loader());
+}
+
+#ifndef PRODUCT
+// Define to dump klasses
+#undef CLD_DUMP_KLASSES
+
+void ClassLoaderData::dump(outputStream * const out) {
+  out->print("ClassLoaderData CLD: " PTR_FORMAT ", loader: " PTR_FORMAT ", loader_klass: " PTR_FORMAT " %s {",
+      p2i(this), p2i((void *)class_loader()),
+      p2i(class_loader() != NULL ? class_loader()->klass() : NULL), loader_name());
+  if (claimed()) out->print(" claimed ");
+  if (is_unloading()) out->print(" unloading ");
+  out->cr();
+  if (metaspace_or_null() != NULL) {
+    out->print_cr("metaspace: " INTPTR_FORMAT, p2i(metaspace_or_null()));
+    metaspace_or_null()->dump(out);
+  } else {
+    out->print_cr("metaspace: NULL");
+  }
+
+#ifdef CLD_DUMP_KLASSES
+  if (Verbose) {
+    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());
+      assert(k != k->next_link(), "no loops!");
+      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() {
+  assert_locked_or_safepoint(_metaspace_lock);
+  oop cl = class_loader();
+
+  guarantee(this == class_loader_data(cl) || is_anonymous(), "Must be the same");
+  guarantee(cl != NULL || this == ClassLoaderData::the_null_class_loader_data() || is_anonymous(), "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();
+    assert(k != k->next_link(), "no loops!");
+  }
+}
+
+bool ClassLoaderData::contains_klass(Klass* klass) {
+  // Lock-free access requires load_ptr_acquire
+  for (Klass* k = load_ptr_acquire(&_klasses); k != NULL; k = k->next_link()) {
+    if (k == klass) return true;
+  }
+  return false;
+}
+
+
+// GC root of class loader data created.
+ClassLoaderData* ClassLoaderDataGraph::_head = NULL;
+ClassLoaderData* ClassLoaderDataGraph::_unloading = NULL;
+ClassLoaderData* ClassLoaderDataGraph::_saved_unloading = NULL;
+ClassLoaderData* ClassLoaderDataGraph::_saved_head = NULL;
+
+bool ClassLoaderDataGraph::_should_purge = false;
+bool ClassLoaderDataGraph::_metaspace_oom = false;
+
+// 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(Handle loader, bool is_anonymous, TRAPS) {
+  // We need to allocate all the oops for the ClassLoaderData before allocating the
+  // actual ClassLoaderData object.
+  ClassLoaderData::Dependencies dependencies(CHECK_NULL);
+
+  NoSafepointVerifier no_safepoints; // we mustn't GC until we've installed the
+                                     // ClassLoaderData in the graph since the CLD
+                                     // contains unhandled oops
+
+  ClassLoaderData* cld = new ClassLoaderData(loader, is_anonymous, dependencies);
+
+
+  if (!is_anonymous) {
+    ClassLoaderData** cld_addr = java_lang_ClassLoader::loader_data_addr(loader());
+    // 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
+  ClassLoaderData** list_head = &_head;
+  ClassLoaderData* next = _head;
+
+  do {
+    cld->set_next(next);
+    ClassLoaderData* exchanged = (ClassLoaderData*)Atomic::cmpxchg_ptr(cld, list_head, next);
+    if (exchanged == next) {
+      LogTarget(Debug, class, loader, data) lt;
+      if (lt.is_enabled()) {
+       PauseNoSafepointVerifier pnsv(&no_safepoints); // Need safe points for JavaCalls::call_virtual
+       LogStream ls(lt);
+       print_creation(&ls, loader, cld, CHECK_NULL);
+      }
+      return cld;
+    }
+    next = exchanged;
+  } while (true);
+}
+
+void ClassLoaderDataGraph::print_creation(outputStream* out, Handle loader, ClassLoaderData* cld, TRAPS) {
+  Handle string;
+  if (loader.not_null()) {
+    // Include the result of loader.toString() in the output. This allows
+    // the user of the log to identify the class loader instance.
+    JavaValue result(T_OBJECT);
+    Klass* spec_klass = SystemDictionary::ClassLoader_klass();
+    JavaCalls::call_virtual(&result,
+                            loader,
+                            spec_klass,
+                            vmSymbols::toString_name(),
+                            vmSymbols::void_string_signature(),
+                            CHECK);
+    assert(result.get_type() == T_OBJECT, "just checking");
+    string = Handle(THREAD, (oop)result.get_jobject());
+  }
+
+  ResourceMark rm;
+  out->print("create class loader data " INTPTR_FORMAT, p2i(cld));
+  out->print(" for instance " INTPTR_FORMAT " of %s", p2i((void *)cld->class_loader()),
+             cld->loader_name());
+
+  if (string.not_null()) {
+    out->print(": ");
+    java_lang_String::print(string(), out);
+  }
+  out->cr();
+}
+
+
+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::keep_alive_oops_do(OopClosure* f, KlassClosure* klass_closure, bool must_claim) {
+  for (ClassLoaderData* cld = _head; cld != NULL; cld = cld->next()) {
+    if (cld->keep_alive()) {
+      cld->oops_do(f, klass_closure, must_claim);
+    }
+  }
+}
+
+void ClassLoaderDataGraph::always_strong_oops_do(OopClosure* f, KlassClosure* klass_closure, bool must_claim) {
+  if (ClassUnloading) {
+    keep_alive_oops_do(f, klass_closure, must_claim);
+  } else {
+    oops_do(f, klass_closure, must_claim);
+  }
+}
+
+void ClassLoaderDataGraph::cld_do(CLDClosure* cl) {
+  for (ClassLoaderData* cld = _head; cl != NULL && cld != NULL; cld = cld->next()) {
+    cl->do_cld(cld);
+  }
+}
+
+void ClassLoaderDataGraph::cld_unloading_do(CLDClosure* cl) {
+  assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint!");
+  // Only walk the head until any clds not purged from prior unloading
+  // (CMS doesn't purge right away).
+  for (ClassLoaderData* cld = _unloading; cld != _saved_unloading; cld = cld->next()) {
+    assert(cld->is_unloading(), "invariant");
+    cl->do_cld(cld);
+  }
+}
+
+void ClassLoaderDataGraph::roots_cld_do(CLDClosure* strong, CLDClosure* weak) {
+  for (ClassLoaderData* cld = _head;  cld != NULL; cld = cld->_next) {
+    CLDClosure* closure = cld->keep_alive() ? strong : weak;
+    if (closure != NULL) {
+      closure->do_cld(cld);
+    }
+  }
+}
+
+void ClassLoaderDataGraph::keep_alive_cld_do(CLDClosure* cl) {
+  roots_cld_do(cl, NULL);
+}
+
+void ClassLoaderDataGraph::always_strong_cld_do(CLDClosure* cl) {
+  if (ClassUnloading) {
+    keep_alive_cld_do(cl);
+  } else {
+    cld_do(cl);
+  }
+}
+
+void ClassLoaderDataGraph::classes_do(KlassClosure* klass_closure) {
+  for (ClassLoaderData* cld = _head; cld != NULL; cld = cld->next()) {
+    cld->classes_do(klass_closure);
+  }
+}
+
+void ClassLoaderDataGraph::classes_do(void f(Klass* const)) {
+  for (ClassLoaderData* cld = _head; cld != NULL; cld = cld->next()) {
+    cld->classes_do(f);
+  }
+}
+
+void ClassLoaderDataGraph::methods_do(void f(Method*)) {
+  for (ClassLoaderData* cld = _head; cld != NULL; cld = cld->next()) {
+    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->modules_do(f);
+  }
+}
+
+void ClassLoaderDataGraph::modules_unloading_do(void f(ModuleEntry*)) {
+  assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint!");
+  // Only walk the head until any clds not purged from prior unloading
+  // (CMS doesn't purge right away).
+  for (ClassLoaderData* cld = _unloading; cld != _saved_unloading; cld = cld->next()) {
+    assert(cld->is_unloading(), "invariant");
+    cld->modules_do(f);
+  }
+}
+
+void ClassLoaderDataGraph::packages_do(void f(PackageEntry*)) {
+  assert_locked_or_safepoint(Module_lock);
+  for (ClassLoaderData* cld = _head; cld != NULL; cld = cld->next()) {
+    cld->packages_do(f);
+  }
+}
+
+void ClassLoaderDataGraph::packages_unloading_do(void f(PackageEntry*)) {
+  assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint!");
+  // Only walk the head until any clds not purged from prior unloading
+  // (CMS doesn't purge right away).
+  for (ClassLoaderData* cld = _unloading; cld != _saved_unloading; cld = cld->next()) {
+    assert(cld->is_unloading(), "invariant");
+    cld->packages_do(f);
+  }
+}
+
+void ClassLoaderDataGraph::loaded_classes_do(KlassClosure* klass_closure) {
+  for (ClassLoaderData* cld = _head; cld != NULL; cld = cld->next()) {
+    cld->loaded_classes_do(klass_closure);
+  }
+}
+
+void ClassLoaderDataGraph::classes_unloading_do(void f(Klass* const)) {
+  assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint!");
+  // Only walk the head until any clds not purged from prior unloading
+  // (CMS doesn't purge right away).
+  for (ClassLoaderData* cld = _unloading; cld != _saved_unloading; cld = cld->next()) {
+    assert(cld->is_unloading(), "invariant");
+    cld->classes_do(f);
+  }
+}
+
+#define FOR_ALL_DICTIONARY(X) for (ClassLoaderData* X = _head; X != NULL; X = X->next()) \
+                                if (X->dictionary() != NULL)
+
+// 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->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->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->dictionary()->all_entries_do(f);
+  }
+}
+
+void ClassLoaderDataGraph::verify_dictionary() {
+  FOR_ALL_DICTIONARY(cld) {
+    cld->dictionary()->verify();
+  }
+}
+
+void ClassLoaderDataGraph::print_dictionary(outputStream* st) {
+  FOR_ALL_DICTIONARY(cld) {
+    st->print("Dictionary for ");
+    cld->print_value_on(st);
+    st->cr();
+    cld->dictionary()->print_on(st);
+    st->cr();
+  }
+}
+
+void ClassLoaderDataGraph::print_dictionary_statistics(outputStream* st) {
+  FOR_ALL_DICTIONARY(cld) {
+    ResourceMark rm;
+    stringStream tempst;
+    tempst.print("System Dictionary for %s", cld->loader_name());
+    cld->dictionary()->print_table_statistics(st, tempst.as_string());
+  }
+}
+
+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);
+      LogTarget(Debug, class, loader, data) lt;
+      if (lt.is_enabled()) {
+        LogStream ls(lt);
+        ls.print("found new CLD: ");
+        curr->print_value_on(&ls);
+        ls.cr();
+      }
+    }
+
+    curr = curr->_next;
+  }
+
+  return array;
+}
+
+bool ClassLoaderDataGraph::unload_list_contains(const void* x) {
+  assert(SafepointSynchronize::is_at_safepoint(), "only safe to call at safepoint");
+  for (ClassLoaderData* cld = _unloading; cld != NULL; cld = cld->next()) {
+    if (cld->metaspace_or_null() != NULL && cld->metaspace_or_null()->contains(x)) {
+      return true;
+    }
+  }
+  return false;
+}
+
+#ifndef PRODUCT
+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_closure,
+                                        bool clean_previous_versions) {
+
+  ClassLoaderData* data = _head;
+  ClassLoaderData* prev = NULL;
+  bool seen_dead_loader = false;
+
+  // Mark metadata seen on the stack only so we can delete unneeded entries.
+  // Only walk all metadata, including the expensive code cache walk, for Full GC
+  // and only if class redefinition and if there's previous versions of
+  // Klasses to delete.
+  bool walk_all_metadata = clean_previous_versions &&
+                           JvmtiExport::has_redefined_a_class() &&
+                           InstanceKlass::has_previous_versions_and_reset();
+  MetadataOnStackMark md_on_stack(walk_all_metadata);
+
+  // Save previous _unloading pointer for CMS which may add to unloading list before
+  // purging and we don't want to rewalk the previously unloaded class loader data.
+  _saved_unloading = _unloading;
+
+  data = _head;
+  while (data != NULL) {
+    if (data->is_alive(is_alive_closure)) {
+      // clean metaspace
+      if (walk_all_metadata) {
+        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->unload();
+    data = data->next();
+    // Remove from loader list.
+    // This class loader data will no longer be found
+    // in the ClassLoaderDataGraph.
+    if (prev != NULL) {
+      prev->set_next(data);
+    } else {
+      assert(dead == _head, "sanity check");
+      _head = data;
+    }
+    dead->set_next(_unloading);
+    _unloading = dead;
+  }
+
+  if (seen_dead_loader) {
+    data = _head;
+    while (data != NULL) {
+      // Remove entries in the dictionary of live class loader that have
+      // initiated loading classes in a dead class loader.
+      if (data->dictionary() != NULL) {
+        data->dictionary()->do_unloading();
+      }
+      // Walk a ModuleEntry's reads, and a PackageEntry's exports
+      // lists to determine if there are modules on those lists that are now
+      // dead and should be removed.  A module's life cycle is equivalent
+      // to its defining class loader's life cycle.  Since a module is
+      // considered dead if its class loader is dead, these walks must
+      // occur after each class loader's aliveness is determined.
+      if (data->packages() != NULL) {
+        data->packages()->purge_all_package_exports();
+      }
+      if (data->modules_defined()) {
+        data->modules()->purge_all_module_reads();
+      }
+      data = data->next();
+    }
+
+    post_class_unload_events();
+  }
+
+  return seen_dead_loader;
+}
+
+void ClassLoaderDataGraph::purge() {
+  assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint!");
+  ClassLoaderData* list = _unloading;
+  _unloading = NULL;
+  ClassLoaderData* next = list;
+  bool classes_unloaded = false;
+  while (next != NULL) {
+    ClassLoaderData* purge_me = next;
+    next = purge_me->next();
+    delete purge_me;
+    classes_unloaded = true;
+  }
+  if (classes_unloaded) {
+    Metaspace::purge();
+    set_metaspace_oom(false);
+  }
+}
+
+void ClassLoaderDataGraph::post_class_unload_events() {
+#if INCLUDE_TRACE
+  assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint!");
+  if (Tracing::enabled()) {
+    if (Tracing::is_event_enabled(TraceClassUnloadEvent)) {
+      assert(_unloading != NULL, "need class loader data unload list!");
+      _class_unload_time = Ticks::now();
+      classes_unloading_do(&class_unload_event);
+    }
+    Tracing::on_unloading_classes();
+  }
+#endif
+}
+
+ClassLoaderDataGraphKlassIteratorAtomic::ClassLoaderDataGraphKlassIteratorAtomic()
+    : _next_klass(NULL) {
+  ClassLoaderData* cld = ClassLoaderDataGraph::_head;
+  Klass* klass = NULL;
+
+  // Find the first klass in the CLDG.
+  while (cld != NULL) {
+    assert_locked_or_safepoint(cld->metaspace_lock());
+    klass = cld->_klasses;
+    if (klass != NULL) {
+      _next_klass = klass;
+      return;
+    }
+    cld = cld->next();
+  }
+}
+
+Klass* ClassLoaderDataGraphKlassIteratorAtomic::next_klass_in_cldg(Klass* klass) {
+  Klass* next = klass->next_link();
+  if (next != NULL) {
+    return next;
+  }
+
+  // No more klasses in the current CLD. Time to find a new CLD.
+  ClassLoaderData* cld = klass->class_loader_data();
+  assert_locked_or_safepoint(cld->metaspace_lock());
+  while (next == NULL) {
+    cld = cld->next();
+    if (cld == NULL) {
+      break;
+    }
+    next = cld->_klasses;
+  }
+
+  return next;
+}
+
+Klass* ClassLoaderDataGraphKlassIteratorAtomic::next_klass() {
+  Klass* head = _next_klass;
+
+  while (head != NULL) {
+    Klass* next = next_klass_in_cldg(head);
+
+    Klass* old_head = (Klass*)Atomic::cmpxchg_ptr(next, &_next_klass, head);
+
+    if (old_head == head) {
+      return head; // Won the CAS.
+    }
+
+    head = old_head;
+  }
+
+  // Nothing more for the iterator to hand out.
+  assert(head == NULL, "head is " PTR_FORMAT ", expected not null:", p2i(head));
+  return NULL;
+}
+
+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);
+}
+#endif // PRODUCT
+
+void ClassLoaderData::print_value_on(outputStream* out) const {
+  if (class_loader() == NULL) {
+    out->print("NULL class loader");
+  } else {
+    out->print("class loader " INTPTR_FORMAT " ", p2i(this));
+    class_loader()->print_value_on(out);
+  }
+}
+
+void ClassLoaderData::print_on(outputStream* out) const {
+  if (class_loader() == NULL) {
+    out->print("NULL class loader");
+  } else {
+    out->print("class loader " INTPTR_FORMAT " ", p2i(this));
+    class_loader()->print_on(out);
+  }
+}
+
+#if INCLUDE_TRACE
+
+Ticks ClassLoaderDataGraph::_class_unload_time;
+
+void ClassLoaderDataGraph::class_unload_event(Klass* const k) {
+  assert(k != NULL, "invariant");
+
+  // post class unload event
+  EventClassUnload event(UNTIMED);
+  event.set_endtime(_class_unload_time);
+  event.set_unloadedClass(k);
+  event.set_definingClassLoader(k->class_loader_data());
+  event.commit();
+}
+
+#endif // INCLUDE_TRACE