# 过程中可能需要输入 y 来确认
We know where it broke, but we can’t see why. Was it a race condition? Did a database read return stale data that has since been overwritten? To find the cause, we have to mentally reconstruct the state of the world as it existed milliseconds before the crash. Welcome to debugging hell.
，更多细节参见服务器推荐
free_list[classno] = h->next;
chapter on mastering the eshell (which happens to be free).