write_first

说明：  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 priority of the additional restrictions : If an application for readers read operation has already been written in another waiting for access to a shared resource, the reader must wait until the person was not waiting for the after the state can begin to read operation.)