四川大学操作系统课件.ppt

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1、Chapter6Concurrency:Deadlock(死锁)andStarvation(饥饿)OperatingSystems16.1PrinciplesofDeadlock6.1PrinciplesofDeadlock6.2DeadlockPrevention6.3DeadlockAvoidance6.4DeadlockDetection6.5AnIntegratedDeadlockStrategy6.6DiningPhilosophersProblem6.7Summary2DeadlockPermanentblo

2、ckingofasetofprocessesthateithercompeteforsystemresourcesorcommunicatewitheachotherNoefficientsolutioninthegeneralcaseAlldeadlockinvolveconflictingneedsforresourcesbytwoormoreprocesses(死锁源于两个或者多个进程的资源需求冲突).Acommonexampleisthetrafficdeadlock(交通死锁)3456ResourcesCate

3、gories(资源的分类)ReusableResources(可重用资源)ConsumableResources(可消费资源)76.1PrinciplesofDeadlock6.1.1ReusableResources6.1.2ConsumableResources6.1.3ResourceAllocationGraphs6.1.4TheConditionsforDeadlock8ReusableResources(可重用资源)Usedbyonlyoneprocessatatimeandnotdepleted(耗尽)by

4、thatuseProcessesobtainresourcesthattheylaterreleaseforreusebyotherprocessesExamplesincludeprocessors,I/Ochannels,mainandsecondarymemory,devices,anddatastructuressuchasfiles,databases9DeadlockExampleofReusableResourcesInterleavestheexecution:p0p1q0q1p2q210AnotherD

5、eadlockExampleofReusableResourcesSpaceisavailableforallocationof200Kbytes,andthefollowingsequenceofeventsoccurDeadlockoccursifbothprocessesprogresstotheirsecondrequestP1......Request80Kbytes;Request60Kbytes;P2......Request70Kbytes;Request80Kbytes;116.1Principleso

6、fDeadlock6.1.1ReusableResources6.1.2ConsumableResources6.1.3ResourceAllocationGraphs6.1.4TheConditionsforDeadlock12ConsumableResources(可消费资源)Maybecreated(produced)anddestroyed(consumed)byprocessesExamplesincludeinterrupts,signals,messages,andinformationinI/Obuffe

7、rs13DeadlockExampleofConsumableResourcesDeadlockoccursifreceiveisblockingP1......Receive(P2);Send(P2,M1);P2......Receive(P1);Send(P1,M2);146.1PrinciplesofDeadlock6.1.1ReusableResources6.1.2ConsumableResources6.1.3ResourceAllocationGraphs6.1.4TheConditionsforDeadl

8、ock15ResourceAllocationGraphs(资源分配图)Directedgraph(有向图)thatdepicts(表述)astateofthesystemofresourcesandprocesses16ResourceAllocationGraphs176.1PrinciplesofDeadloc