function Door:checkForDeadlock()
  -- In an ideal world, deadlocks should not occur, as they indicate errors in
  -- some logic elsewhere. From a practical point of view, we should check for
  -- deadlocks from time to time and attempt to fix them.
  if self.queue and self.reserved_for then
    -- If the door is reserved for someone, then that person should either be
    -- at the front of the queue, or not in any queues at all.
    for _, action in ipairs(self.reserved_for.action_queue) do
      if action.name == "queue" then
        if action.queue ~= self.queue or self.queue[1] ~= self.reserved_for then
          self.reserved_for = nil
          self:getRoom():tryAdvanceQueue()
        end
        break
      end
    end
  end
end