void JvmtiDeferredEventQueue::enqueue(const JvmtiDeferredEvent& event) {

  {- -------------------------------------------
  (1) (assert)
      ---------------------------------------- -}

      assert(Service_lock->owned_by_self(), "Must own Service_lock");

  {- -------------------------------------------
  (1) 
      ---------------------------------------- -}

      process_pending_events();

  {- -------------------------------------------
  (1) 新しい QueueNode オブジェクトを作成し, 
      _queue_tail の先頭に追加する.

      (なお _queue_tail が空の場合は, _queue_tail だけでなく
       _queue_head も新しい QueueNode オブジェクトを指すようにする)
      ---------------------------------------- -}

      // Events get added to the end of the queue (and are pulled off the front).
      QueueNode* node = new QueueNode(event);
      if (_queue_tail == NULL) {
        _queue_tail = _queue_head = node;
      } else {
        assert(_queue_tail->next() == NULL, "Must be the last element in the list");
        _queue_tail->set_next(node);
        _queue_tail = node;
      }

  {- -------------------------------------------
  (1) Service_lock に対して Monitor::notify_all() を呼び出して, ServiceThread を起床させる.
      ---------------------------------------- -}

      Service_lock->notify_all();

  {- -------------------------------------------
  (1) (assert)
      ---------------------------------------- -}

      assert((_queue_head == NULL) == (_queue_tail == NULL),
             "Inconsistent queue markers");
    }