中科大操作系统原理与实现课件6_Process_synchronizati.pdf

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1、操作系统原理与设计第6章ProcesseSynchronization1（进程同步1）陈香兰中国科学技术大学计算机学院2009年10月28日......提纲BackgroundTheCritical-SectionProblemPeterson’sSolutionSynchronizationHardwareTestAndSetInstructionSwapInstructionSemaphores小结和作业......OutlineBackgroundTheCritical-SectionProblemPeterson’sSolutionSynchr

2、onizationHardwareTestAndSetInstructionSwapInstructionSemaphores小结和作业......allowframebreaksBackgroundITheprocessesarecooperatingwitheachotherdirectlyorindirectly.IIndependentprocesscannotaffectorbeaffectedbytheexecutionofanotherprocessICooperatingprocesscanaffectorbeaffectedbytheexec

3、utionofanotherprocessIConcurrentaccesstoshareddatamayresultindatainconsistencyIforexample:printer,sharedvariables/tables/listsIMaintainingdataconsistencyrequiresmechanismstoensuretheorderlyexecutionofcooperatingprocesses......Producer-ConsumerProblemIParadigmforcooperatingproces

4、ses,producerprocessproducesinformationthatisconsumedbyaconsumerprocessIunbounded-bufferplacesnopracticallimitonthesizeofthebufferpIbounded-bufferassumesthatthereisafixedbuffersize......Bounded-Buffer–Shared-MemorySolutionIISolutioniscorrect,butcanonlyuseBUFFERSIZE-1elementsIShareddata

5、#defineBUFFERSIZE10typedefstructf...gitem;itembuffer[BUFFERSIZE];intin=0;intout=0;......Bounded-Buffer–Shared-MemorySolutionIIIInsert()Methodwhile(true)f/*Produceanitem*/while(((in+1)%BUFFERSIZE)==out);/*donothing–nofreebuffers*/buffer[in]=item;in=(in+1)%BUFFERSIZE;g......Bounded-Buff

6、er–Shared-MemorySolutionIIIIRemove()Methodwhile(true)fwhile(in==out);//donothing–nothingtoconsume//removeanitemfromthebufferitem=buffer[out];out=(out+1)%BUFFERSIZE;returnitem;g......anothersolutionusingcountingvalueIISupposethatwewantedtoprovideasolutiontotheproducer-consumerprobl

7、emthatfillsallthebuffers(notBUFFERSIZE-1).Iusinganintegercountthatkeepstrackofthenumberoffullbuffers.IInitially,countissetto0.IincrementedbytheproducerafteritproducesanewbufferIandisdecrementedbytheconsumerafteritconsumesabuffer.IProducer......anothersolutionusingcountingvalueIIwhile

8、(true)f/*produceanitemandputinnextProduced*/whi