Pthread本来是一套用户级线程库, 但在Linux上实现时, 却使用了内核级线程 来完成, 这样的好处是, 可以充分的提高程序的并发性, 线程也可以象以前一样调用 read这样的函数, 而不必担心会由于阻赛影响其它的线程的运行. -Pthread have is a set of user-level thread library, but in Linux to achieve, they use a kernel-level thread to complete, so the advantage may be sufficient to improve the complicated procedures, the thread can also be the same as before read such a function call without having to worry about race as a result of the impact resistance of other threads running.