/*

 * Copyright (c) 2012, 2015, 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/metadataOnStackMark.hpp"

#include "classfile/systemDictionary.hpp"

#include "code/codeCache.hpp"

#include "gc/shared/gcLocker.hpp"

#include "memory/metadataFactory.hpp"

#include "memory/metaspaceShared.hpp"

#include "memory/oopFactory.hpp"

#include "oops/objArrayOop.inline.hpp"

#include "oops/oop.inline.hpp"

#include "runtime/atomic.inline.hpp"

#include "runtime/jniHandles.hpp"

#include "runtime/mutex.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

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()),

  _metaspace(NULL), _unloading(false), _klasses(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;

}

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) {

  for (Klass* k = _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)) {

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

    f(k);

  }

}

void ClassLoaderData::methods_do(void f(Method*)) {

  for (Klass* k = _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*)) {

  for (Klass* k = _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::record_dependency(Klass* k, TRAPS) {

  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) {

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

  Klass* old_value = _klasses;

  k->set_next_link(old_value);

  // Make sure linked class is stable, since the class list is walked without a lock

  OrderAccess::storestore();

  // link the new item into the list

  _klasses = k;

  if (TraceClassLoaderData && Verbose && k->class_loader_data() != NULL) {

    ResourceMark rm;

    tty->print_cr("[TraceClassLoaderData] 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());

  }

}

// 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;

    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 (TraceClassLoaderData) {

    ResourceMark rm;

    tty->print("[ClassLoaderData: unload loader data " INTPTR_FORMAT, p2i(this));

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

               loader_name());

    if (is_anonymous()) {

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

    }

    tty->print_cr("]");

  }

}

oop ClassLoaderData::keep_alive_object() const {

  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);

  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;

  }

}

/**

 * Returns true if this class loader data is for the extension class loader.

 */

bool ClassLoaderData::is_ext_class_loader_data() const {

  return SystemDictionary::is_ext_class_loader(class_loader());

}

Metaspace* ClassLoaderData::metaspace_non_null() {

  assert(!DumpSharedSpaces, "wrong metaspace!");

  // 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 (this == the_null_class_loader_data()) {

      assert (class_loader() == NULL, "Must be");

      set_metaspace(new Metaspace(_metaspace_lock, Metaspace::BootMetaspaceType));

    } else if (is_anonymous()) {

      if (TraceClassLoaderData && Verbose && class_loader() != NULL) {

        tty->print_cr("is_anonymous: %s", class_loader()->klass()->internal_name());

      }

      set_metaspace(new Metaspace(_metaspace_lock, Metaspace::AnonymousMetaspaceType));

    } else if (class_loader()->is_a(SystemDictionary::reflect_DelegatingClassLoader_klass())) {

      if (TraceClassLoaderData && Verbose && class_loader() != NULL) {

        tty->print_cr("is_reflection: %s", class_loader()->klass()->internal_name());

      }

      set_metaspace(new Metaspace(_metaspace_lock, Metaspace::ReflectionMetaspaceType));

    } else {

      set_metaspace(new Metaspace(_metaspace_lock, Metaspace::StandardMetaspaceType));

    }

  }

  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();

      }

    } 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.

  return ClassLoaderDataGraph::add(loader, 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) {

  ResourceMark rm;

  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->print(" handles " INTPTR_FORMAT, p2i(handles()));

  out->cr();