操作系统设计原理详解及答案第五版

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《操作系统操作精髓与设计原理》第五版是由威廉·斯托林斯所著的一本深入探讨操作系统内部结构和设计原则的专业教材。该书提供了丰富的理论知识和实践案例，旨在帮助读者理解计算机系统的工作原理、操作系统的基本概念、进程管理和控制、多线程与SMP架构、并发中的互斥与同步、死锁与饥饿现象，以及内存管理，特别是虚拟内存的概念。第一章"计算机系统概述"为读者介绍了计算机系统的构成及其各个组件的功能，包括处理器、存储器、输入/输出设备等，强调了它们在操作系统中的作用和交互。第二章"操作系统概述"涵盖了操作系统的主要类别（如批处理、实时、分时和网络操作系统）以及它们的核心功能，如任务调度、文件管理、设备管理等，帮助读者建立起对操作系统整体架构的理解。第三章"进程描述与控制"详细解析了进程的生命周期、状态转换，以及操作系统如何通过进程控制原语实现对进程的管理和通信。第四章"线程、SMP与微内核"讨论了并发计算中的线程模型，解释了多线程的优势，以及在Symmetric Multi-Processor (SMP) 系统中如何利用多个处理器执行多个并发任务。同时，微内核架构的特点和优势也在此处得以介绍。第五章和第六章重点研究并发控制，第五章阐述了互斥（Mutual Exclusion）和同步（Synchronization）在并发环境中的重要性，而第六章则深入探讨了死锁（Deadlock）和饥饿（Starvation）问题的预防和解决策略。第七章"内存管理"涵盖了物理内存分配、虚拟内存的使用，以及内存保护机制，确保程序运行的安全性和资源的有效利用。第八章"虚拟内存"详细解释了虚拟地址空间的概念，以及虚拟内存管理系统如何将物理内存抽象为连续的虚拟地址，提高内存利用率。第九章"单处理器系统"可能讨论了在资源有限的环境中，操作系统如何优化资源分配和调度，尤其是在没有多核支持的情况下。作为学习或教学参考书籍，本书提供了大量习题的解决方案，鼓励读者通过实践来巩固理论知识。同时，作者还强调了解决过程中可能出现的错误和反馈的重要性，以便持续更新和完善教材内容。总体而言，《操作系统操作精髓与设计原理》第五版是一本深度解析操作系统设计与实现的经典之作。

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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

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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

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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

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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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