操作系统精髓与设计原理英文pptcha

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1、Concurrency:DeadlockandStarvationChapter61DeadlockEachprocessinaprocessgroupiswaitingforsomeresourceoccupiedbyanotherprocessofthesamegroup,sothateveryprocessofthegroupisinstarvationPermanentblockingofasetofprocessesthateithercompeteforsystemresourcesorcommunicatewitheachotherNoe

2、fficientsolutionInvolveconflictingneedsforresourcesbytwoormoreprocesses2P1P2P3P43ProcessPProcessQ…………GetAGetB…………GetBGetA…………ReleaseAReleaseB…………ReleaseBReleaseA…………4ProcessPProcessQ…………GetAGetB…………ReleaseAGetA…………GetBReleaseB…………ReleaseBReleaseA…………5ReusableResourcesUsedbyonlyo

3、neprocessatatimeandnotdepletedbythatuseProcessesobtainresourcesthattheylaterreleaseforreusebyotherprocessesProcessors,I/Ochannels,mainandsecondarymemory,devices,anddatastructuressuchasfiles,databases,andsemaphoresDeadlockoccursifeachprocessholdsoneresourceandrequeststheother6Exa

4、mpleofDeadlockDeadlockwouldbehappenedifExecutingsequenceisp0p1q0q1p2q27AnotherExampleofDeadlockSpaceisavailableforallocationof200Kbytes,andthefollowingsequenceofeventsoccurDeadlockoccursifbothprocessesprogresstotheirsecondrequestP1......Request80Kbytes;Request60Kbytes;P2......Re

5、quest70Kbytes;Request80Kbytes;8ConsumableResourcesCreated(produced)anddestroyed(consumed)Interrupts,signals,messages,andinformationinI/ObuffersDeadlockmayoccurifaReceivemessageisblockingMaytakeararecombinationofeventstocausedeadlock9ExampleofDeadlockDeadlockoccursifreceivesarebl

6、ockingP1......Receive(P2);Send(P2,M1);P2......Receive(P1);Send(P1,M2);10ResourceAllocationGraphsDirectedgraphthatdepictsastateofthesystemofresourcesandprocesses11ResourceAllocationGraphs12ConditionsforDeadlockMutualexclusionOnlyoneprocessmayusearesourceatatimeHold-and-waitAproce

7、ssmayholdallocatedresourceswhileawaitingassignmentofothersNopreemptionNoresourcecanbeforciblyremovedfromaprocessholdingit13ConditionsforDeadlockCircularwaitaclosedchainofprocessesexists,suchthateachprocessholdsatleastoneresourceneededbythenextprocessinthechainconsequenceofthefir

8、stthreeconditions1415ConditionsforDeadlockMutua