举例说明P、V操作为什么要求设计成原语(即对同一信号量上的操作必须互斥)。P(S)操作: S.value--; If(S.value<0) { Add this process to S.L; Block( ); } V(S)操作 S.value++; If(S.value<=0) { Remove a process P from S.L; Wakeup(P); }
【判断题】When checking ID certificates, examine whether the ID certificates are authentic and the key information such as gender, age, photo carried in valid certificates should match with guests.