/*

 * Copyright (c) 2018, 2019, 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.

 *

 */

#include "precompiled.hpp"

#include "classfile/classLoaderDataGraph.inline.hpp"

#include "classfile/dictionary.hpp"

#include "classfile/javaClasses.hpp"

#include "classfile/metadataOnStackMark.hpp"

#include "classfile/moduleEntry.hpp"

#include "classfile/packageEntry.hpp"

#include "code/dependencyContext.hpp"

#include "logging/log.hpp"

#include "logging/logStream.hpp"

#include "memory/allocation.inline.hpp"

#include "memory/metaspace.hpp"

#include "memory/resourceArea.hpp"

#include "runtime/atomic.hpp"

#include "runtime/handles.inline.hpp"

#include "runtime/mutex.hpp"

#include "runtime/safepoint.hpp"

#include "runtime/safepointVerifiers.hpp"

#include "utilities/growableArray.hpp"

#include "utilities/macros.hpp"

#include "utilities/ostream.hpp"

volatile size_t ClassLoaderDataGraph::_num_array_classes = 0;

volatile size_t ClassLoaderDataGraph::_num_instance_classes = 0;

void ClassLoaderDataGraph::clear_claimed_marks() {

  // The claimed marks of the CLDs in the ClassLoaderDataGraph are cleared

  // outside a safepoint and without locking the ClassLoaderDataGraph_lock.

  // This is required to avoid a deadlock between concurrent GC threads and safepointing.

  //

  // We need to make sure that the CLD contents are fully visible to the

  // reader thread. This is accomplished by acquire/release of the _head,

  // and is sufficient.

  //

  // Any ClassLoaderData added after or during walking the list are prepended to

  // _head. Their claim mark need not be handled here.

  for (ClassLoaderData* cld = Atomic::load_acquire(&_head); cld != NULL; cld = cld->next()) {

    cld->clear_claim();

  }

}

void ClassLoaderDataGraph::clear_claimed_marks(int claim) {

 for (ClassLoaderData* cld = Atomic::load_acquire(&_head); cld != NULL; cld = cld->next()) {

    cld->clear_claim(claim);

  }

}

// 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");

    size_t max_classes = ClassLoaderDataGraph::num_instance_classes();

    assert(max_classes > 0, "should not be called with no instance classes");

    for (size_t 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() {

  assert(SafepointSynchronize::is_at_safepoint(), "only called at safepoint");

  return static_klass_iterator.try_get_next_class();

}

void ClassLoaderDataGraph::adjust_saved_class(ClassLoaderData* cld) {

  return static_klass_iterator.adjust_saved_class(cld);

}

void ClassLoaderDataGraph::adjust_saved_class(Klass* klass) {

  return static_klass_iterator.adjust_saved_class(klass);

}

void ClassLoaderDataGraph::clean_deallocate_lists(bool walk_previous_versions) {

  assert(SafepointSynchronize::is_at_safepoint(), "must only be called at safepoint");

  uint loaders_processed = 0;

  for (ClassLoaderData* cld = _head; cld != NULL; cld = cld->next()) {

    // is_alive check will be necessary for concurrent class unloading.

    if (cld->is_alive()) {

      // clean metaspace

      if (walk_previous_versions) {

        cld->classes_do(InstanceKlass::purge_previous_versions);

      }

      cld->free_deallocate_list();

      loaders_processed++;

    }

  }

  log_debug(class, loader, data)("clean_deallocate_lists: loaders processed %u %s",

                                 loaders_processed, walk_previous_versions ? "walk_previous_versions" : "");

}

void ClassLoaderDataGraph::walk_metadata_and_clean_metaspaces() {

  assert(SafepointSynchronize::is_at_safepoint(), "must only be called at safepoint");

  _should_clean_deallocate_lists = false; // assume everything gets cleaned

  // Mark metadata seen on the stack so we can delete unreferenced entries.

  // Walk all metadata, including the expensive code cache walk, only for class redefinition.

  // The MetadataOnStackMark walk during redefinition saves previous versions if it finds old methods

  // on the stack or in the code cache, so we only have to repeat the full walk if

  // they were found at that time.

  // TODO: have redefinition clean old methods out of the code cache.  They still exist in some places.

  bool walk_all_metadata = InstanceKlass::has_previous_versions_and_reset();

  MetadataOnStackMark md_on_stack(walk_all_metadata, /*redefinition_walk*/false);

  clean_deallocate_lists(walk_all_metadata);

}

// GC root of class loader data created.

ClassLoaderData* volatile ClassLoaderDataGraph::_head = NULL;

ClassLoaderData* ClassLoaderDataGraph::_unloading = NULL;

bool ClassLoaderDataGraph::_should_clean_deallocate_lists = false;

bool ClassLoaderDataGraph::_safepoint_cleanup_needed = 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_to_graph(Handle loader, bool is_unsafe_anonymous) {

  assert_lock_strong(ClassLoaderDataGraph_lock);

  ClassLoaderData* cld;

  // First check if another thread beat us to creating the CLD and installing

  // it into the loader while we were waiting for the lock.

  if (!is_unsafe_anonymous && loader.not_null()) {

    cld = java_lang_ClassLoader::loader_data_acquire(loader());

    if (cld != NULL) {

      return cld;

    }

  }

  // We mustn't GC until we've installed the ClassLoaderData in the Graph since the CLD

  // contains oops in _handles that must be walked.  GC doesn't walk CLD from the

  // loader oop in all collections, particularly young collections.

  NoSafepointVerifier no_safepoints;

  cld = new ClassLoaderData(loader, is_unsafe_anonymous);

  // First install the new CLD to the Graph.

  cld->set_next(_head);

  Atomic::release_store(&_head, cld);

  // Next associate with the class_loader.

  if (!is_unsafe_anonymous) {

    // Use OrderAccess, since readers need to get the loader_data only after

    // it's added to the Graph

    java_lang_ClassLoader::release_set_loader_data(loader(), cld);

  }

  // Lastly log, if requested

  LogTarget(Trace, class, loader, data) lt;

  if (lt.is_enabled()) {

    ResourceMark rm;

    LogStream ls(lt);

    ls.print("create ");

    cld->print_value_on(&ls);

    ls.cr();

  }

  return cld;

}

ClassLoaderData* ClassLoaderDataGraph::add(Handle loader, bool is_unsafe_anonymous) {

  MutexLocker ml(ClassLoaderDataGraph_lock);

  ClassLoaderData* loader_data = add_to_graph(loader, is_unsafe_anonymous);

  return loader_data;

}

void ClassLoaderDataGraph::cld_unloading_do(CLDClosure* cl) {

  assert_locked_or_safepoint_weak(ClassLoaderDataGraph_lock);

  for (ClassLoaderData* cld = _unloading; cld != NULL; cld = cld->next()) {

    assert(cld->is_unloading(), "invariant");

    cl->do_cld(cld);

  }

}

// These are functions called by the GC, which require all of the CLDs, including the

// unloading ones.

void ClassLoaderDataGraph::cld_do(CLDClosure* cl) {

  assert_locked_or_safepoint_weak(ClassLoaderDataGraph_lock);

  for (ClassLoaderData* cld = _head;  cld != NULL; cld = cld->_next) {

    cl->do_cld(cld);

  }

}

void ClassLoaderDataGraph::roots_cld_do(CLDClosure* strong, CLDClosure* weak) {

  assert_locked_or_safepoint_weak(ClassLoaderDataGraph_lock);

  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::always_strong_cld_do(CLDClosure* cl) {

  assert_locked_or_safepoint_weak(ClassLoaderDataGraph_lock);

  if (ClassUnloading) {

    roots_cld_do(cl, NULL);

  } else {

    cld_do(cl);

  }

}

// Closure for locking and iterating through classes. Only lock outside of safepoint.

LockedClassesDo::LockedClassesDo(classes_do_func_t f) : _function(f),

  _do_lock(!SafepointSynchronize::is_at_safepoint()) {

  if (_do_lock) {

    ClassLoaderDataGraph_lock->lock();

  }

}

LockedClassesDo::LockedClassesDo() : _function(NULL),

  _do_lock(!SafepointSynchronize::is_at_safepoint()) {

  // callers provide their own do_klass

  if (_do_lock) {

    ClassLoaderDataGraph_lock->lock();

  }

}

LockedClassesDo::~LockedClassesDo() {

  if (_do_lock) {

    ClassLoaderDataGraph_lock->unlock();

  }

}

// Iterating over the CLDG needs to be locked because

// unloading can remove entries concurrently soon.

class ClassLoaderDataGraphIterator : public StackObj {

  ClassLoaderData* _next;

  HandleMark       _hm;  // clean up handles when this is done.

  Handle           _holder;

  Thread*          _thread;

  NoSafepointVerifier _nsv; // No safepoints allowed in this scope

                            // unless verifying at a safepoint.

public:

  ClassLoaderDataGraphIterator() : _next(ClassLoaderDataGraph::_head) {

    _thread = Thread::current();

    assert_locked_or_safepoint(ClassLoaderDataGraph_lock);

  }

  ClassLoaderData* get_next() {

    ClassLoaderData* cld = _next;

    // Skip already unloaded CLD for concurrent unloading.

    while (cld != NULL && !cld->is_alive()) {

      cld = cld->next();

    }

    if (cld != NULL) {

      // Keep cld that is being returned alive.

      _holder = Handle(_thread, cld->holder_phantom());

      _next = cld->next();

    } else {

      _next = NULL;

    }

    return cld;

  }

};

void ClassLoaderDataGraph::loaded_cld_do(CLDClosure* cl) {

  ClassLoaderDataGraphIterator iter;

  while (ClassLoaderData* cld = iter.get_next()) {

    cl->do_cld(cld);

  }

}

// These functions assume that the caller has locked the ClassLoaderDataGraph_lock

// if they are not calling the function from a safepoint.

void ClassLoaderDataGraph::classes_do(KlassClosure* klass_closure) {

  ClassLoaderDataGraphIterator iter;

  while (ClassLoaderData* cld = iter.get_next()) {

    cld->classes_do(klass_closure);

  }

}

void ClassLoaderDataGraph::classes_do(void f(Klass* const)) {

  ClassLoaderDataGraphIterator iter;

  while (ClassLoaderData* cld = iter.get_next()) {

    cld->classes_do(f);

  }

}

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

  ClassLoaderDataGraphIterator iter;

  while (ClassLoaderData* cld = iter.get_next()) {

    cld->methods_do(f);

  }

}

void ClassLoaderDataGraph::modules_do(void f(ModuleEntry*)) {

  assert_locked_or_safepoint(Module_lock);

  ClassLoaderDataGraphIterator iter;

  while (ClassLoaderData* cld = iter.get_next()) {

    cld->modules_do(f);

  }

}

void ClassLoaderDataGraph::modules_unloading_do(void f(ModuleEntry*)) {

  assert_locked_or_safepoint(ClassLoaderDataGraph_lock);

  for (ClassLoaderData* cld = _unloading; cld != NULL; 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);

  ClassLoaderDataGraphIterator iter;

  while (ClassLoaderData* cld = iter.get_next()) {

    cld->packages_do(f);

  }

}

void ClassLoaderDataGraph::packages_unloading_do(void f(PackageEntry*)) {

  assert_locked_or_safepoint(ClassLoaderDataGraph_lock);

  for (ClassLoaderData* cld = _unloading; cld != NULL; cld = cld->next()) {

    assert(cld->is_unloading(), "invariant");

    cld->packages_do(f);

  }

}

void ClassLoaderDataGraph::loaded_classes_do(KlassClosure* klass_closure) {

  ClassLoaderDataGraphIterator iter;

  while (ClassLoaderData* cld = iter.get_next()) {

    cld->loaded_classes_do(klass_closure);

  }

}

// This case can block but cannot do unloading (called from CDS)

void ClassLoaderDataGraph::unlocked_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_locked_or_safepoint(ClassLoaderDataGraph_lock);

  for (ClassLoaderData* cld = _unloading; cld != NULL; cld = cld->next()) {

    assert(cld->is_unloading(), "invariant");

    cld->classes_do(f);

  }

}

#define FOR_ALL_DICTIONARY(X)   ClassLoaderDataGraphIterator iter; \

                                while (ClassLoaderData* X = iter.get_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);

  }

}

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_table_statistics(outputStream* st) {

  FOR_ALL_DICTIONARY(cld) {

    ResourceMark rm;

    stringStream tempst;

    tempst.print("System Dictionary for %s class loader", cld->loader_name_and_id());

    cld->dictionary()->print_table_statistics(st, tempst.as_string());

  }

}

#ifndef PRODUCT

bool ClassLoaderDataGraph::contains_loader_data(ClassLoaderData* loader_data) {

  assert_locked_or_safepoint(ClassLoaderDataGraph_lock);

  for (ClassLoaderData* data = _head; data != NULL; data = data->next()) {

    if (loader_data == data) {

      return true;

    }

  }

  return false;

}

#endif // PRODUCT

bool ClassLoaderDataGraph::is_valid(ClassLoaderData* loader_data) {

  DEBUG_ONLY( if (!VMError::is_error_reported()) { assert_locked_or_safepoint(ClassLoaderDataGraph_lock); } )

  if (loader_data != NULL) {

    if (loader_data == ClassLoaderData::the_null_class_loader_data()) {

      return true;

    }

    for (ClassLoaderData* data = _head; data != NULL; data = data->next()) {

      if (loader_data == data) {

        return true;

      }

    }

  }

  return false;

}

// Move class loader data from main list to the unloaded list for unloading

// and deallocation later.

bool ClassLoaderDataGraph::do_unloading() {

  assert_locked_or_safepoint(ClassLoaderDataGraph_lock);

  // Indicate whether safepoint cleanup is needed.

  _safepoint_cleanup_needed = true;

  ClassLoaderData* data = _head;

  ClassLoaderData* prev = NULL;

  bool seen_dead_loader = false;

  uint loaders_processed = 0;

  uint loaders_removed = 0;

  data = _head;

  while (data != NULL) {

    if (data->is_alive()) {

      prev = data;

      data = data->next();

      loaders_processed++;

      continue;

    }

    seen_dead_loader = true;