《操作系统教学资料》答案Operating System Review Problems.docxVIP

Operating System Review ProblemsWhat is a process？ Please draw a process state transition diagram with nine states in Unix SVR4?进程是一个正在执行的程序（a program in execution）；九状态转换图如下所示： fork 返回用户模式 存储器空间足够 存储器空间不足 抢占 换出 返回 重新调度进程 换入 系统调用，中断 唤醒 唤醒 退出 睡眠中断，中断返回 换出Illustrated some scenarios（场景）where process switch（进程切换）occur?时钟中断②i/0中断③内存失效④陷阱⑤系统调用Suppose there are threeprocesses running in an operating system with multithreading as following:Process IDThreadsAT11, T12BT21, T22CT31, T32If the multithreading is supported by user-level（用户级） implementation(实现) and thread T11 is blocked, which thread may be scheduled to run next?（one of T21,T22,T31,T32）If the multithreading is supported by kernel-level（核心级）implementation, which thread may be scheduled to run next? （one of T12,T21,T22,T31,T32）原因：核心级的实现，os才知道A中有T124. What is race condition?答：竞争条件是在当多个进程或线程访问共享资源时，其最终结果依赖于多个进程的指令执行顺序。Give a program implementation to demonstrate（演示，展示） the mutual exclusion enforced by Test and Set (or exchange) instruction or by semaphore?用信号量实现互斥：semaphore mutex;mutex=1;…semwait(mutex);…Semsignal(mutex);…TS实现互斥：Lock DB 0…entercritical:TS reg,lock CMP reg,o JNZ entercritical…exitcritical:MOV lock,0exchange实现互斥：Lock DB 0…entercritical:MOV reg,!0Xchg lock,reg CMP reg,0 JNZ entercritical…exitcritical:MOV lock,05.Consider the following program:boolean blocked[2];int turn;void P(int id){ while (true) { blocked[id] = true; while (turn != id){ while (blocked[1-id]) /* do nothing */; turn = id; }//循环结束，则某一进程进入临界区 /* critical section */临界区代码 blocked[id] = false; /* remai