操作系统设计原理课后答案：Stallings第五版英文PDF

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"操作系统_精髓与设计原理(第五版)课后答案(英文版).pdf" 这份资源是威廉·斯托林斯（William Stallings）所著的《操作系统：内部结构与设计原理》第五版的课后答案，以PDF格式提供。这本书深入探讨了操作系统的核心概念和设计原则，是学习操作系统理论和技术的重要教材。作者保留了所有版权，未经书面许可，不得复制或在互联网上发布。答案手册包含了书中每一章的复习问题和作业问题的解答，涵盖了以下章节： 1. 计算机系统概览：这部分内容可能包括计算机硬件、指令集架构、计算机性能指标以及操作系统在计算机系统中的角色等基础知识。 2. 操作系统概述：讨论操作系统的基本功能、类型和历史，可能涵盖批处理系统、分时系统、实时系统以及网络和分布式操作系统。 3. 进程描述与控制：涉及进程的创建、撤销、状态转换、同步与通信，以及进程调度算法等内容。 4. 线程、对称多处理器（SMP）和微内核：线程的优缺点、SMP系统的设计与性能优化，以及微内核架构的特性。 5. 并发：互斥与同步：介绍信号量、管程、条件变量等并发控制机制，解决资源争用问题。 6. 并发：死锁与饥饿：分析死锁的产生、预防、检测和恢复策略，以及避免饥饿的方法。 7. 内存管理：讲解内存分配、回收、虚拟地址空间、页面替换算法等内存管理技术。 8. 虚拟内存：包括分页和分段系统、虚拟内存的工作原理、页面错误（缺页）处理等。 9. 单处理器系统：可能探讨单处理器环境下的操作系统设计挑战和优化策略。通过这些章节的答案，读者可以更好地理解书中的概念，并检验自己对操作系统的理解和应用能力。如果发现答案中的错误或问题，可以通过电子邮件向作者ws@shore.net反馈，以便更新错误解答表。错误解答表可以在ftp://shell.shore.net/members/w/s/ws/S/WS.S.找到，如有需要的话。

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NSWERS TO

UESTIONS

3.1 An instruction trace for a program is the sequence of instructions that execute for

that process.

3.2 New batch job; interactive logon; created by OS to provide a service; spawned by

existing process. See Table 3.1 for details.

3.3 Running: The process that is currently being executed. Ready: A process that is

prepared to execute when given the opportunity. Blocked: A process that cannot

execute until some event occurs, such as the completion of an I/O operation. New:

A process that has just been created but has not yet been admitted to the pool of

executable processes by the operating system. Exit: A process that has been released

from the pool of executable processes by the operating system, either because it

halted or because it aborted for some reason.

3.4 Process preemption occurs when an executing process is interrupted by the

processor so that another process can be executed.

3.5 Swapping involves moving part or all of a process from main memory to disk.

When none of the processes in main memory is in the Ready state, the operating

system swaps one of the blocked processes out onto disk into a suspend queue, so

that another process may be brought into main memory to execute.

3.6 There are two independent concepts: whether a process is waiting on an event

(blocked or not), and whether a process has been swapped out of main memory

(suspended or not). To accommodate this 2 × 2 combination, we need two Ready

states and two Blocked states.

3.7 1. The process is not immediately available for execution. 2. The process may or

may not be waiting on an event. If it is, this blocked condition is independent of the

suspend condition, and occurrence of the blocking event does not enable the

process to be executed. 3. The process was placed in a suspended state by an agent;

either itself, a parent process, or the operating system, for the purpose of

preventing its execution. 4. The process may not be removed from this state until

the agent explicitly orders the removal.

3.8 The OS maintains tables for entities related to memory, I/O, files, and processes.

See Table 3.10 for details.

3.9 Process identification, processor state information, and process control information.

3.10 The user mode has restrictions on the instructions that can be executed and the

memory areas that can be accessed. This is to protect the operating system from

CHAPTER 3

PROCESS DESCRIPTION AND CONTROL

-15-

damage or alteration. In kernel mode, the operating system does not have these

restrictions, so that it can perform its tasks.

3.11 1. Assign a unique process identifier to the new process. 2. Allocate space for the

process. 3. Initialize the process control block. 4. Set the appropriate linkages. 5.

Create or expand other data structures.

3.12 An interrupt is due to some sort of event that is external to and independent of the

currently running process, such as the completion of an I/O operation. A trap

relates to an error or exception condition generated within the currently running

process, such as an illegal file access attempt.

3.13 Clock interrupt, I/O interrupt, memory fault.

3.14 A mode switch may occur without changing the state of the process that is

currently in the Running state. A process switch involves taking the currently

executing process out of the Running state in favor of another process. The process

switch involves saving more state information.

NSWERS TO

ROBLEMS

3.1 •Creation and deletion of both user and system processes. The processes in the

system can execute concurrently for information sharing, computation speedup,

modularity, and convenience. Concurrent execution requires a mechanism for

process creation and deletion. The required resources are given to the process

when it is created, or allocated to it while it is running. When the process

terminates, the OS needs to reclaim any reusable resources.

•Suspension and resumption of processes. In process scheduling, the OS needs to

change the process's state to waiting or ready state when it is waiting for some

resources. When the required resources are available, OS needs to change its

state to running state to resume its execution.

•Provision of mechanism for process synchronization. Cooperating processes

may share data. Concurrent access to shared data may result in data

inconsistency. OS has to provide mechanisms for processes synchronization to

ensure the orderly execution of cooperating processes, so that data consistency is

maintained.

•Provision of mechanism for process communication. The processes executing

under the OS may be either independent processes or cooperating processes.

Cooperating processes must have the means to communicate with each other.

•Provision of mechanisms for deadlock handling. In a multiprogramming

environment, several processes may compete for a finite number of resources. If

a deadlock occurs, all waiting processes will never change their waiting state to

running state again, resources are wasted and jobs will never be completed.

3.2 The following example is used in [PINK89] to clarify their definition of block and

suspend:

Suppose a process has been executing for a while and needs an additional

magnetic tape drive so that it can write out a temporary file. Before it can

initiate a write to tape, it must be given permission to use one of the drives.

When it makes its request, a tape drive may not be available, and if that is the

-16-

case, the process will be placed in the blocked state. At some point, we assume

the system will allocate the tape drive to the process; at that time the process

will be moved back to the active state. When the process is placed into the

execute state again it will request a write operation to its newly acquired tape

drive. At this point, the process will be move to the suspend state, where it

waits for the completion of the current write on the tape drive that it now

owns.

The distinction made between two different reasons for waiting for a device could

be useful to the operating system in organizing its work. However, it is no

substitute for a knowledge of which processes are swapped out and which

processes are swapped in. This latter distinction is a necessity and must be reflected

in some fashion in the process state.

3.3 Figure 9.3 shows the result for a single blocked queue. The figure readily

generalizes to multiple blocked queues.

3.4 Penalize the Ready, suspend processes by some fixed amount, such as one or two

priority levels, so that a Ready, suspend process is chosen next only if it has a

higher priority than the highest-priority Ready process by several levels of priority.

3.5 a. A separate queue is associated with each wait state. The differentiation of

waiting processes into queues reduces the work needed to locate a waiting

process when an event occurs that affects it. For example, when a page fault

completes, the scheduler know that the waiting process can be found on the

Page Fault Wait queue.

b. In each case, it would be less efficient to allow the process to be swapped out

while in this state. For example, on a page fault wait, it makes no sense to swap

out a process when we are waiting to bring in another page so that it can

execute.

c. The state transition diagram can be derived from the following state transition

table:

Next State

Current State

Currently

Executing

Computable

(resident)

Computable

(outswapped)

Variety of wait

states (resident)

Variety of wait

states

(outswapped)

Currently

Executing

Rescheduled

Wait

Computable

(resident)

Scheduled

Outswap

Computable

(outswapped)

Inswap

Variety of wait

states (resident)

Event satisfied

Outswap

Variety of wait

states

(outswapped)

Event satisfied

-17-

3.6 a. The advantage of four modes is that there is more flexibility to control access to

memory, allowing finer tuning of memory protection. The disadvantage is

complexity and processing overhead. For example, procedures running at each

of the access modes require separate stacks with appropriate accessibility.

b. In principle, the more modes, the more flexibility, but it seems difficult to

justify going beyond four.

3.7 a. With j < i, a process running in D

is prevented from accessing objects in D

Thus, if D

contains information that is more privileged or is to be kept more

secure than information in D

, this restriction is appropriate. However, this

security policy can be circumvented in the following way. A process running in

could read data in D

and then copy that data into D

. Subsequently, a

process running in D

could access the information.

b. An approach to dealing with this problem, known as a trusted system, is

discussed in Chapter 16.

3.8 a. A application may be processing data received from another process and

storing the results on disk. If there is data waiting to be taken from the other

process, the application may proceed to get that data and process it. If a

previous disk write has completed and there is processed data to write out, the

application may proceed to write to disk. There may be a point where the

process is waiting both for additional data from the input process and for disk

availability.

b. There are several ways that could be handled. A special type of either/or queue

could be used. Or the process could be put in two separate queues. In either

case, the operating system would have to handle the details of alerting the

process to the occurrence of both events, one after the other.

3.9 This technique is based on the assumption that an interrupted process A will

continue to run after the response to an interrupt. But, in general, an interrupt may

cause the basic monitor to preempt a process A in favor of another process B. It is

now necessary to copy the execution state of process A from the location associated

with the interrupt to the process description associated with A. The machine might

as well have stored them there in the first place. Source: [BRIN73].

3.10 Because there are circumstances under which a process may not be preempted (i.e.,

it is executing in kernel mode), it is impossible for the operating system to respond

rapidly to real-time requirements.

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