/*

 * Copyright (c) 2012, 2016, 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/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 "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.inline.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_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(NULL), _deallocate_list(NULL),

  _next(NULL), _dependencies(dependencies), _shared_class_loader_id(-1),

  _metaspace_lock(new Mutex(Monitor::leaf+1, "Metaspace allocation lock", true,

                            Monitor::_safepoint_check_never)) {

    // empty

}

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);

}

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() {

  assert(_keep_alive >= 0, "Invalid keep alive count");

  _keep_alive++;

}

void ClassLoaderData::dec_keep_alive() {

  assert(_keep_alive > 0, "Invalid keep alive 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)) {

  assert_locked_or_safepoint(_metaspace_lock);

  for (Klass* k = _klasses; k != NULL; k = k->next_link()) {

    f(k);

  }

}

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)->methods_do(f);

    }

  }

}

void ClassLoaderData::loaded_classes_do(KlassClosure* klass_closure) {

  // Lock to avoid classes being modified/added/removed during iteration

  MutexLockerEx ml(metaspace_lock(),  Mutex::_no_safepoint_check_flag);

  for (Klass* k = _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 (_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*)) {

  // Lock-free access requires load_ptr_acquire

  PackageEntryTable* packages = load_ptr_acquire(&_packages);

  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());

  }

}

// 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");

  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);

  if (log_is_enabled(Debug, class, loader, data)) {

    ResourceMark rm;

    outputStream* log = Log(class, loader, data)::debug_stream();

    log->print(": unload loader data " INTPTR_FORMAT, p2i(this));

    log->print(" for instance " INTPTR_FORMAT " of %s", p2i((void *)class_loader()),

               loader_name());

    if (is_anonymous()) {

      log->print(" for anonymous class  " INTPTR_FORMAT " ", p2i(_klasses));

    }

    log->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();

}

PackageEntryTable* ClassLoaderData::packages() {

  // Lazily create the package entry table at first request.

  // Lock-free access requires load_ptr_acquire.

  PackageEntryTable* packages = load_ptr_acquire(&_packages);

  if (packages == NULL) {

    MutexLockerEx m1(metaspace_lock(), Mutex::_no_safepoint_check_flag);

    // Check if _packages got allocated while we were waiting for this lock.

    if ((packages = _packages) == NULL) {

      packages = new PackageEntryTable(PackageEntryTable::_packagetable_entry_size);

      // Ensure _packages is stable, since it is examined without a lock

      OrderAccess::release_store_ptr(&_packages, packages);

    }

  }

  return packages;

}

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);

      // Each loader has one unnamed module entry. Create it before

      // any classes, loaded by this loader, are defined in case

      // they end up being defined in loader's unnamed module.

      modules->create_unnamed_module(this);

      {

        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;

}

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 the metaspace

  Metaspace *m = _metaspace;

  if (m != NULL) {

    _metaspace = NULL;

    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