信号量也称为信号锁，主要应用于进程间的同步和互斥，在用于互斥时，通常作为资源锁。信号量通常通过两个原子操作wait(P)和signal(V)来访问。wait操作使信号量的值+1，signal操作使信号量的值-1。本程序模拟了操作系统的pv操作-Semaphore is also known as signal lock, mainly used in inter-process synchronization and mutual exclusion, are used in mutually