四川大学操作系统课件.ppt

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1、Chapter5MutualExclusion(互斥)andSynchronization(同步)OperatingSystems1Agenda5.1PrinciplesofConcurrency5.2MutualExclusion:HardwareSupport5.3Semaphores5.4Monitors5.5MessagePassing5.6Readers/WritersProblem5.7Summary2ConcurrencyConcurrencyarisesinthreedifferentcontexts:Multipleapplications(多应用程序)Multipro

2、grammingStructuredapplication(结构化应用程序)SomeapplicationcanbedesignedasasetofconcurrentprocessesOperating-systemstructure(操作系统结构)Operatingsystemisasetofprocessesorthreads3Concurrency临界区死锁活锁互斥竞争条件饥饿45.1PrinciplesofConcurrency5.1.1ASimpleExample5.1.2RaceCondition5.1.3OperatingSystemConcerns5.1.4Proces

3、sInteraction5.1.5RequirementsforMutualExclusion5DifficultiesofConcurrencySharingofglobalresourcesOperatingsystemmanagingtheallocationofresourcesoptimallyDifficulttolocateprogrammingerrors6ASimpleExamplecharchin,chout;voidecho(){chin=getchar();chout=chin;putchar(chout);}7ASimpleExample(Uniprocesso

4、r)ProcessP1ProcessP2..chin=getchar();.chout=chin;.chin=getchar();chout=chin;putchar(chout);putchar(chout);...8ASimpleExample(Multiprocessor)ProcessP1ProcessP2..chin=getchar();..chin=getchar();chout=chin;chout=chin;putchar(chout);..putchar(chout);..95.1PrinciplesofConcurrency5.1.1ASimpleExample5.1

5、.2RaceCondition5.1.3OperatingSystemConcerns5.1.4ProcessInteraction5.1.5RequirementsforMutualExclusion10RaceCondition(竞争条件)Araceconditionoccurswhenmultipleprocessesorthreadsreadandwritedataitemssothatthefinalresultdependsontheorderofexecutionofinstructionsinthemultipleprocessesorthread.(竞争条件发生在当多个

6、进程或者线程在读写数据时，其最终结果依赖于多个进程或者线程的指令执行顺序)115.1PrinciplesofConcurrency5.1.1ASimpleExample5.1.2RaceCondition5.1.3OperatingSystemConcerns5.1.4ProcessInteraction5.1.5RequirementsforMutualExclusion12OperatingSystemConcernsKeeptrackofvariousprocesses(throughPCB)AllocateanddeallocateresourcesProcessortimeMe

7、moryFilesI/OdevicesProtectdataandresourcesOutputofprocessmustbeindependentofthespeedofexecutionofotherconcurrentprocesses135.1PrinciplesofConcurrency5.1.1ASimpleExample5.1.2RaceCondition5.1.3OperatingSystemConcerns5.1.