std::mutex config_mutex;
std::vector<interruptible_thread> background_threads;

void
background_thread(int disk_id)
{
  while (true) {
    interruption_point();
    fs_change fsc = get_fs_changes(disk_id);
    if (fsc.has_changes()) {
      update_index(fsc);
    }
  }
}

void
start_background_processing()
{
  background_threads.push_back(interruptible_thread(background_thread, disk_1));
  background_threads.push_back(interruptible_thread(background_thread, disk_2));
}

int
main()
{
  start_background_processing();
  process_gui_until_exit();
  std::unique_lock<std::mutex> lk(config_mutex);
  for (unsigned i = 0; i < background_threads.size(); ++i) {
    background_threads[i].interrupt();
  }
  for (unsigned i = 0; i < background_threads.size(); ++i) {
    background_threads[i].join();
  }
}