Nachos的线程管理模块升级。扩充了线程数据结构。扩展了现现有的线程状态。修改了线程调度算法。增加了全局性的线程管理机制。 -Nachos thread management module upgrade. Expansion of the thread data structure. Extend the currently existing state of the thread. Modify the thread scheduling algorithm. Global threa