/*

 * Copyright (c) 2016, 2018, 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 "jfr/recorder/checkpoint/jfrCheckpointWriter.hpp"

#include "jfr/recorder/checkpoint/types/jfrThreadGroup.hpp"

#include "jfr/utilities/jfrResourceManager.hpp"

#include "jfr/utilities/jfrTypes.hpp"

#include "runtime/handles.inline.hpp"

#include "runtime/jniHandles.inline.hpp"

#include "runtime/safepoint.hpp"

#include "runtime/semaphore.hpp"

#include "utilities/growableArray.hpp"

class ThreadGroupExclusiveAccess : public StackObj {

 private:

  static Semaphore _mutex_semaphore;

 public:

  ThreadGroupExclusiveAccess() { _mutex_semaphore.wait(); }

  ~ThreadGroupExclusiveAccess() { _mutex_semaphore.signal(); }

};

Semaphore ThreadGroupExclusiveAccess::_mutex_semaphore(1);

JfrThreadGroup* JfrThreadGroup::_instance = NULL;

class JfrThreadGroupPointers : public ResourceObj {

 private:

  const Handle _thread_group_handle;

  jweak _thread_group_weak_ref;

 public:

  JfrThreadGroupPointers(Handle thread_group_handle, jweak thread_group_weak_ref);

  Handle thread_group_handle() const;

  jweak thread_group_weak_ref() const;

  oopDesc* const thread_group_oop() const;

  jweak transfer_weak_global_handle_ownership();

  void clear_weak_ref();

};

JfrThreadGroupPointers::JfrThreadGroupPointers(Handle thread_group_handle, jweak thread_group_weak_ref) :

  _thread_group_handle(thread_group_handle),

  _thread_group_weak_ref(thread_group_weak_ref) {}

Handle JfrThreadGroupPointers::thread_group_handle() const {

  return _thread_group_handle;

}

jweak JfrThreadGroupPointers::thread_group_weak_ref() const {

  return _thread_group_weak_ref;

}

oopDesc* const JfrThreadGroupPointers::thread_group_oop() const {

  assert(_thread_group_weak_ref == NULL ||

         JNIHandles::resolve_non_null(_thread_group_weak_ref) == _thread_group_handle(), "invariant");

  return _thread_group_handle();

}

jweak JfrThreadGroupPointers::transfer_weak_global_handle_ownership() {

  jweak temp = _thread_group_weak_ref;

  _thread_group_weak_ref = NULL;

  return temp;

}

void JfrThreadGroupPointers::clear_weak_ref() {

  if (NULL != _thread_group_weak_ref) {

    JNIHandles::destroy_weak_global(_thread_group_weak_ref);

  }

}

class JfrThreadGroupsHelper : public ResourceObj {

 private:

  static const int invalid_iterator_pos = -1;

  GrowableArray<JfrThreadGroupPointers*>* _thread_group_hierarchy;

  int _current_iterator_pos;

  int populate_thread_group_hierarchy(const JavaThread* jt, Thread* current);

  JfrThreadGroupPointers& at(int index);

 public:

  JfrThreadGroupsHelper(const JavaThread* jt, Thread* current);

  ~JfrThreadGroupsHelper();

  JfrThreadGroupPointers& next();

  bool is_valid() const;

  bool has_next() const;

};

JfrThreadGroupsHelper::JfrThreadGroupsHelper(const JavaThread* jt, Thread* current) {

  _thread_group_hierarchy = new GrowableArray<JfrThreadGroupPointers*>(10, false, mtTracing);

  _current_iterator_pos = populate_thread_group_hierarchy(jt, current) - 1;

}

JfrThreadGroupsHelper::~JfrThreadGroupsHelper() {

  assert(_current_iterator_pos == invalid_iterator_pos, "invariant");

  for (int i = 0; i < _thread_group_hierarchy->length(); ++i) {

    _thread_group_hierarchy->at(i)->clear_weak_ref();

  }

}

JfrThreadGroupPointers& JfrThreadGroupsHelper::at(int index) {

  assert(_thread_group_hierarchy != NULL, "invariant");

  assert(index > invalid_iterator_pos && index < _thread_group_hierarchy->length(), "invariant");

  return *(_thread_group_hierarchy->at(index));

}

bool JfrThreadGroupsHelper::has_next() const {

  return _current_iterator_pos > invalid_iterator_pos;

}

bool JfrThreadGroupsHelper::is_valid() const {

  return (_thread_group_hierarchy != NULL && _thread_group_hierarchy->length() > 0);

}

JfrThreadGroupPointers& JfrThreadGroupsHelper::next() {

  assert(is_valid(), "invariant");

  return at(_current_iterator_pos--);

}

/*

 * If not at a safepoint, we create global weak references for

 * all reachable threadgroups for this thread.

 * If we are at a safepoint, the caller is the VMThread during

 * JFR checkpointing. It can use naked oops, because nothing

 * will move before the list of threadgroups is cleared and

 * mutator threads restarted. The threadgroup list is cleared

 * later by the VMThread as one of the final steps in JFR checkpointing

 * (not here).

 */

int JfrThreadGroupsHelper::populate_thread_group_hierarchy(const JavaThread* jt, Thread* current) {

  assert(jt != NULL && jt->is_Java_thread(), "invariant");

  assert(current != NULL, "invariant");

  assert(_thread_group_hierarchy != NULL, "invariant");

  // immediate thread group

  Handle thread_group_handle(current, java_lang_Thread::threadGroup(jt->threadObj()));

  if (thread_group_handle == NULL) {

    return 0;

  }

  const bool use_weak_handles = !SafepointSynchronize::is_at_safepoint();

  jweak thread_group_weak_ref = use_weak_handles ? JNIHandles::make_weak_global(thread_group_handle) : NULL;

  JfrThreadGroupPointers* thread_group_pointers = new JfrThreadGroupPointers(thread_group_handle, thread_group_weak_ref);

  _thread_group_hierarchy->append(thread_group_pointers);

  // immediate parent thread group

  oop parent_thread_group_obj = java_lang_ThreadGroup::parent(thread_group_handle());

  Handle parent_thread_group_handle(current, parent_thread_group_obj);

  // and check parents parents...

  while (!(parent_thread_group_handle == NULL)) {

    const jweak parent_group_weak_ref = use_weak_handles ? JNIHandles::make_weak_global(parent_thread_group_handle) : NULL;

    thread_group_pointers = new JfrThreadGroupPointers(parent_thread_group_handle, parent_group_weak_ref);

    _thread_group_hierarchy->append(thread_group_pointers);

    parent_thread_group_obj = java_lang_ThreadGroup::parent(parent_thread_group_handle());

    parent_thread_group_handle = Handle(current, parent_thread_group_obj);

  }

  return _thread_group_hierarchy->length();

}

static traceid next_id() {

  static traceid _current_threadgroup_id = 0;

  return ++_current_threadgroup_id;

}

class JfrThreadGroup::JfrThreadGroupEntry : public JfrCHeapObj {

  friend class JfrThreadGroup;

 private:

  traceid _thread_group_id;

  traceid _parent_group_id;

  char* _thread_group_name; // utf8 format

  // If an entry is created during a safepoint, the

  // _thread_group_oop contains a direct oop to

  // the java.lang.ThreadGroup object.

  // If an entry is created on javathread exit time (not at safepoint),

  // _thread_group_weak_ref contains a JNI weak global handle

  // indirection to the java.lang.ThreadGroup object.

  // Note: we cannot use a union here since CHECK_UNHANDLED_OOPS makes oop have

  //       a ctor which isn't allowed in a union by the SunStudio compiler

  oop _thread_group_oop;

  jweak _thread_group_weak_ref;

  JfrThreadGroupEntry(const char* tgstr, JfrThreadGroupPointers& ptrs);

  ~JfrThreadGroupEntry();

  traceid thread_group_id() const { return _thread_group_id; }

  void set_thread_group_id(traceid tgid) { _thread_group_id = tgid; }

  const char* const thread_group_name() const { return _thread_group_name; }

  void set_thread_group_name(const char* tgname);

  traceid parent_group_id() const { return _parent_group_id; }

  void set_parent_group_id(traceid pgid) { _parent_group_id = pgid; }

  void set_thread_group(JfrThreadGroupPointers& ptrs);

  bool is_equal(const JfrThreadGroupPointers& ptrs) const;

  const oop thread_group() const;

};

JfrThreadGroup::JfrThreadGroupEntry::JfrThreadGroupEntry(const char* tgname, JfrThreadGroupPointers& ptrs) :

  _thread_group_id(0),

  _parent_group_id(0),

  _thread_group_name(NULL),

  _thread_group_oop(NULL),

  _thread_group_weak_ref(NULL) {

  set_thread_group_name(tgname);

  set_thread_group(ptrs);

}

JfrThreadGroup::JfrThreadGroupEntry::~JfrThreadGroupEntry() {

  if (_thread_group_name != NULL) {

    JfrCHeapObj::free(_thread_group_name, strlen(_thread_group_name) + 1);

  }

  if (_thread_group_weak_ref != NULL) {

    JNIHandles::destroy_weak_global(_thread_group_weak_ref);

  }

}

void JfrThreadGroup::JfrThreadGroupEntry::set_thread_group_name(const char* tgname) {

  assert(_thread_group_name == NULL, "invariant");

  if (tgname != NULL) {

    size_t len = strlen(tgname);

    _thread_group_name = JfrCHeapObj::new_array<char>(len+1);

    strncpy(_thread_group_name, tgname, len);

    _thread_group_name[len] = '\0';

  }

}

const oop JfrThreadGroup::JfrThreadGroupEntry::thread_group() const {

  return _thread_group_weak_ref != NULL ? JNIHandles::resolve(_thread_group_weak_ref) : _thread_group_oop;

}

void JfrThreadGroup::JfrThreadGroupEntry::set_thread_group(JfrThreadGroupPointers& ptrs) {

  _thread_group_weak_ref = ptrs.transfer_weak_global_handle_ownership();

  if (_thread_group_weak_ref == NULL) {

    _thread_group_oop = ptrs.thread_group_oop();

    assert(_thread_group_oop != NULL, "invariant");

  } else {

    _thread_group_oop = NULL;

  }

}

JfrThreadGroup::JfrThreadGroup() : _list(NULL) {

  _list = new (ResourceObj::C_HEAP, mtTracing) GrowableArray<JfrThreadGroupEntry*>(30, true);

}

JfrThreadGroup::~JfrThreadGroup() {

  assert(SafepointSynchronize::is_at_safepoint(), "invariant");

  if (_list != NULL) {

    for (int i = 0; i < _list->length(); i++) {

      JfrThreadGroupEntry* e = _list->at(i);

      delete e;

    }

    delete _list;

  }

}

JfrThreadGroup* JfrThreadGroup::instance() {

  return _instance;

}

void JfrThreadGroup::set_instance(JfrThreadGroup* new_instance) {

  _instance = new_instance;

}

traceid JfrThreadGroup::thread_group_id(const JavaThread* jt, Thread* current) {

  ResourceMark rm(current);

  HandleMark hm(current);

  JfrThreadGroupsHelper helper(jt, current);

  return helper.is_valid() ? thread_group_id_internal(helper) : 0;

}

traceid JfrThreadGroup::thread_group_id(JavaThread* const jt) {

  assert(!JfrStream_lock->owned_by_self(), "holding stream lock but should not hold it here");

  return thread_group_id(jt, jt);

}

traceid JfrThreadGroup::thread_group_id_internal(JfrThreadGroupsHelper& helper) {

  ThreadGroupExclusiveAccess lock;

  JfrThreadGroup* tg_instance = instance();

  if (tg_instance == NULL) {

    tg_instance = new JfrThreadGroup();

    if (tg_instance == NULL) {

      return 0;

    }

    set_instance(tg_instance);

  }

  JfrThreadGroupEntry* tge = NULL;

  int parent_thread_group_id = 0;

  while (helper.has_next()) {

    JfrThreadGroupPointers& ptrs = helper.next();

    tge = tg_instance->find_entry(ptrs);

    if (NULL == tge) {

      tge = tg_instance->new_entry(ptrs);

      assert(tge != NULL, "invariant");

      tge->set_parent_group_id(parent_thread_group_id);

    }

    parent_thread_group_id = tge->thread_group_id();

  }

  // the last entry in the hierarchy is the immediate thread group

  return tge->thread_group_id();

}

bool JfrThreadGroup::JfrThreadGroupEntry::is_equal(const JfrThreadGroupPointers& ptrs) const {

  return ptrs.thread_group_oop() == thread_group();

}

JfrThreadGroup::JfrThreadGroupEntry*

JfrThreadGroup::find_entry(const JfrThreadGroupPointers& ptrs) const {

  for (int index = 0; index < _list->length(); ++index) {

    JfrThreadGroupEntry* curtge = _list->at(index);

    if (curtge->is_equal(ptrs)) {

      return curtge;

    }

  }

  return (JfrThreadGroupEntry*) NULL;

}

// Assumes you already searched for the existence

// of a corresponding entry in find_entry().

JfrThreadGroup::JfrThreadGroupEntry*

JfrThreadGroup::new_entry(JfrThreadGroupPointers& ptrs) {

  JfrThreadGroupEntry* const tge = new JfrThreadGroupEntry(java_lang_ThreadGroup::name(ptrs.thread_group_oop()), ptrs);

  add_entry(tge);

  return tge;

}

int JfrThreadGroup::add_entry(JfrThreadGroupEntry* tge) {

  assert(tge != NULL, "attempting to add a null entry!");

  assert(0 == tge->thread_group_id(), "id must be unassigned!");

  tge->set_thread_group_id(next_id());

  return _list->append(tge);

}

void JfrThreadGroup::write_thread_group_entries(JfrCheckpointWriter& writer) const {

  assert(_list != NULL && !_list->is_empty(), "should not need be here!");

  const int number_of_tg_entries = _list->length();

  writer.write_count(number_of_tg_entries);

  for (int index = 0; index < number_of_tg_entries; ++index) {

    const JfrThreadGroupEntry* const curtge = _list->at(index);

    writer.write_key(curtge->thread_group_id());

    writer.write(curtge->parent_group_id());

    writer.write(curtge->thread_group_name());

  }

}

void JfrThreadGroup::write_selective_thread_group(JfrCheckpointWriter* writer, traceid thread_group_id) const {

  assert(writer != NULL, "invariant");

  assert(_list != NULL && !_list->is_empty(), "should not need be here!");

  const int number_of_tg_entries = _list->length();

  // save context

  const JfrCheckpointContext ctx = writer->context();

  writer->write_type(TYPE_THREADGROUP);

  const jlong count_offset = writer->reserve(sizeof(u4)); // Don't know how many yet

  int number_of_entries_written = 0;

  for (int index = number_of_tg_entries - 1; index >= 0; --index) {

    const JfrThreadGroupEntry* const curtge = _list->at(index);

    if (thread_group_id == curtge->thread_group_id()) {

      writer->write_key(curtge->thread_group_id());

      writer->write(curtge->parent_group_id());

      writer->write(curtge->thread_group_name());

      ++number_of_entries_written;

      thread_group_id = curtge->parent_group_id();

    }

  }

  if (number_of_entries_written == 0) {

    // nothing to write, restore context

    writer->set_context(ctx);

    return;

  }

  assert(number_of_entries_written > 0, "invariant");

  writer->write_count(number_of_entries_written, count_offset);

}

// Write out JfrThreadGroup instance and then delete it

void JfrThreadGroup::serialize(JfrCheckpointWriter& writer) {

  ThreadGroupExclusiveAccess lock;

  JfrThreadGroup* tg_instance = instance();

  assert(tg_instance != NULL, "invariant");

  ResourceManager<JfrThreadGroup> tg_handle(tg_instance);

  set_instance(NULL);

  tg_handle->write_thread_group_entries(writer);

}

// for writing a particular thread group

void JfrThreadGroup::serialize(JfrCheckpointWriter* writer, traceid thread_group_id) {

  assert(writer != NULL, "invariant");

  ThreadGroupExclusiveAccess lock;

  JfrThreadGroup* const tg_instance = instance();

  assert(tg_instance != NULL, "invariant");

  tg_instance->write_selective_thread_group(writer, thread_group_id);

}