操作系统作业3

第三章作业

3.1

题目：Using the program shown in Figure 3.30, explain what the output will be at Line A.

 

回答：

• 结果为：PARENT: value = 5。子进程改变的是子进程的value值，当控制权给回父进程之后，他的值保持为5。

 

 

3.2

题目：Including the initial parent process, how many processes are created by the program shown in Figure 3.31?

 

回答：

8个：2的三次方

 

 

3.5

题目：When a process creates a new process using the fork() operation, which of the following state is shared between the parent process and the child process?

a. Stack 

b. Heap

c. Shared memory segments

 

回答：

堆和栈不被共享，而子进程可以从父进程那里获得资源子集。子进程继承了父进程的权限，调度属性以及某些资源。

a. Stack 

b. Heap

c. Shared memory segments只有c被共享，a和b由子进程新建。

 

 

3.7

题目：Assume that a distributed system is susceptible to server failure. What mechanisms would be required to guarantee the “exactly once” semantic for execution of RPCs?

 

回答：

首先，需要消除服务器从未收到请求的风险。服务器必须要向客户确认RPC调用已经收到并且已经执行。客户机应该周期性的重发每个RPC调用直到它接收到对该调用的ACK。