实时操作系统入门讲座

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1、RTOSissuesforsafetransportapplicationsCorporateoverviewDrKenTindellCEOnorthernreal-timeapplicationscontents1WhyuseanRTOS?2RequirementsforusinganRTOS3PerspectiveonRTOSusetoday2costpressures1Productioncost(e.g.automotive)¾Savingjust5¢onacommoncomponentcansavea

2、milliondollarsayear(whichbecomesanextramilliondollarsofprofit)2Developmentcost(e.g.aerospace)¾Highabsolutecosts(typically$1B)andahighfractionoftotallife-cyclecosts¾Certificationisamajorpartofdevelopmentcosts3theneedfordesigncorrectness1Astrongdemandforcorrec

3、tness¾Inaerospacesystemshundredsofpeoplecanbeinjuredinasingleeventcausedbyadesignfailure¾Automotivesystemsrackupbillionsofflyinghourssothenumberofeventsistypicallymuchlarger2Designcorrectnessisvital¾“Ifitcangowrong,thenwhenrunningitforbillionhoursitwillgowro

4、ng”4thereal-timecontrolissue1Wideuseofreal-timecontrolfunctions¾..withcontrolfunctionsbecomingdistributedacrossseveralcontrolunits2Needtobesureeverythingrunsontime,everytime¾E.g.timeoutsforfaultdetectionimposeaharddeadlinefornormaloperation¾Wecallthesesystem

5、s‘hardreal-time’5hardreal-time1Achievehardreal-timebyup-frontdesigneffort¾Needtoknowup-frontthatalldeadlineswillbemet¾Nogoodfindingoutafterdeploymentthattherearetimingfaults2Mustnotrelyontestingtodetecttimingfaults¾Testingregimesimplycannotobtaincoverageclos

6、etothebillionsofhoursofoperationinreallife¾Mustusedesignanalysistobesureofcorrecttimingbehavior6hardreal-timeprocessing1Threestagesintheevolutionofhardreal-timeprocessing¾fromsimplecyclicscheduling..¾..tomajor/minorcyclicscheduling..¾..topre-emptiveRTOSsched

7、uling7InterrupttimeFreetimevoidmain(void){do_init();while(1){do_task_1();do_task_2();do_task_3();do_task_4();do_task_5();busy_wait_cycle();}}cyclicscheduling1Asimpletechnique..¾Easytoseewhattheworst-casetimingbehaviorisgoingtobe¾Easytoimplement2..butnotverye

8、fficient¾Everythinghastorunatthesame(fast)rate¾Can’thandlesporadiceventsverywell(mustpollforthematahighrate)101msInterrupttime2ms01234ms4ms4msFreetimevoidmain(void){do_init();while(1){do_task_1(