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’sSolutionSynchronizationHardwareTestAndSetInstructionSwapInstructionSemaphores小结和作业......allowframebreaksBackgroundITheprocessesarecooperatingwitheachotherdirectlyorindirectly.IIndependentprocesscannotaffectorbeaffectedbytheexecutionofanotherprocessICooperatingprocesscanaffectorbeaffectedbytheexecutionofanotherprocessIConcurrentaccesstoshareddatamayresultindatainconsistencyIforexample:printer,sharedvariables/tables/listsIMaintainingdataconsistencyrequiresmechanismstoensuretheorderlyexecutionofcooperatingprocesses......Producer-ConsumerProblemIParadigmforcooperatingprocesses,producerprocessproducesinformationthatisconsumedbyaconsumerprocessIunbounded-bufferplacesnopracticalplimitonthesizeofthebufferIbounded-bufferassumesthatthereisafixedbuffersize......Bounded-Buffer–Shared-MemorySolutionIISolutioniscorrect,butcanonlyuseBUFFERSIZE-1elementsIShareddata#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-Buffer–Shared-MemorySolutionIIIIRemove()Methodwhile(true)fwhile(in==out);//donothing–nothingtoconsume//removeanitemfromthebufferitem=buffer[out];out=(out+1)%BUFFERSIZE;returnitem;g......anothersolutionusingcountingvalueIISupposethatwewantedtoprovideasolutiontotheproducer-consumerproblemthatfillsallthebuffers(notBUFFERSIZE-1).Iusinganintegercountthatkeepstrackofthenumberoffullbuffers.IInitially,countissetto0.IincrementedbytheproducerafteritproducesanewbufferIan