都写者模拟程序 思路：对一个CPU时间段处理，用一个STATE标志来做互斥，对写者来说一般处理它的第一个，读者是重点出来第一个，再以读者可以重入的思想， 处理相应的后面的读者-Those who have written simulation program ideas: CPU time for a deal, with a sign to do STATE mutex for write who generally deal with it first, the reader is