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, use global variables to achieve the thread blocking.