写者优先问题。操作限制：1）写-写互斥；2）读-写互斥；3）读-读允许；写者优先的附加限制：如果一个读者申请进行读操作时已有另一写者在等待访问共享资源，则该读者必须等到没有写者处于等待状态后才能开始读操作。-wrote priority issues. Operating restrictions : a) write-write contradict; 2) read-write mutually exclusive; 3) Reading-Reading allowed; Write pri

读者与写者的实现，是n个线程之间的信号量的互斥问题 -The reader and the realization of writing is the thread between the n-the Mutex Semaphore problem