preemptive scheduling的用法和样例：
例句
- What is the difference between preemptive scheduling and time slicing?
抢先调度与分时调度有何不同？ - Under preemptive scheduling, the highest priority task executes until it enters the waiting or dead states or a higher priority task comes into existence.
采用抢先调度方式时，具有最高优先级的任务先执行直到它进入等待或僵死状态，或者是有更高优先级的任务产生。
