用软件方法解决临界区问题,用软件的流程控制方式实现两个线程的协作与互斥控制,读懂sm6.cpp，并修改为目标代码 ,用全局变量实现线程阻塞。 -With software solutions to critical problems, software flow control method to achieve two threads collaboration and exclusive control, read sm6.cpp, and modify the object code,