concurrency-in-action/source/listing_7.18.cpp

template <typename T>
class lock_free_queue {
private:
  static void increase_external_count(std::atomic<counted_node_ptr>& counter,
                                      counted_node_ptr& old_counter)
  {
    counted_node_ptr new_counter;
    do {
      new_counter = old_counter;
      ++new_counter.external_count;
    } while (!counter.compare_exchange_strong(old_counter,
                                              new_counter,
                                              std::memory_order_acquire,
                                              std::memory_order_relaxed));
    old_counter.external_count = new_counter.external_count;
  }
};