OperatingSystem
Version2.122.May2000
Thisdocumentisanofficialreleaseandreplacesallpreviouslydistributeddocuments.TheOSEKgroupretainstherightto
makechangestothisdocumentwithoutnoticeanddoesnotacceptanyliabilityforerrors.
Allrightsreserved.Nopartofthisdocumentmaybereproduced,inanyformorbyanymeans,withoutpermissionin
writingfromtheOSEK/VDXsteeringcommittee.
OSEKOS2.1©byOSEKDocument:Os21
OSEK/VDXWhatisOSEK/VDX?
OperatingSystemSpecification2.1OSEK/VDXisajointprojectoftheautomotiveindustry.Itaimsatanindustrystandardforanopen-endedarchitecturefordistributedcontrolunitsinvehicles.
Areal-timeoperatingsystem,softwareinterfacesandfunctionsforcommunicationandnetworkmanagementtasksarethusjointlyspecified.
ThetermOSEKmeans”OffeneSystemeundderenSchnittstellenfürdieElektronikimKraftfahrzeug”(Opensystemsandthecorrespondinginterfacesforautomotiveelectronics).ThetermVDXmeans„VehicleDistributedeXecutive“.ThefunctionalityofOSEKoperatingsystemwasharmonisedwithVDX.ForsimplicityOSEKwillbeusedinsteadofOSEK/VDXinthedocument.
OSEK/VDXpartners
ThefollowingcompaniesattendedandcontributedtotheOSEK/VDXTechnicalCommittee:AcceleratedTechnologyInc.,ACTIA,
AdamOpelAG,AFTGmbH,
ATMComputerGmbH,Blaupunkt,BMWAG,
BorgInstrumentsGmbH,CambridgeConsultants,ContinentalTeves,
CumminsEngineCompany,DaimlerChryslerAG,DelcoElectronics,Denso,
EpsilonGmbH,
ETASGmbH&CoKG,FIAT-CentroRicerche,FZI,
GMEuropeGmbH,HellaKG,
HewlettPackardFrance,
HitachiMicroSystemsEuropeLtd.,Hitex,
IBMDeutschlandEntwicklungGmbH,IIIT-UniversityofKarlsruhe,Infineon,INRIA,
IntegratedSystemsInc.,IRISA,
LucasVarity,MagnetiMarelli,
Mecel,Motorola,
NationalSemiconductor,NECElectronicsGmbH,NRTA,
PhilipsCarSystems,PorscheAG,PSA,Renault,
RobertBoschGmbH,
SagemElectronicDivision,SiemensAutomotive,SoftingGmbH,
STMircroelectronics,StenkilSystemsAB,
SysgoReal-TimeSolutionsGmbH,TECSI,
TelelogicGmbH,TEMIC,
TexasInstruments,Thomson-CSFDetexis,Trialog,
UTA-UnitedTechnologiesAutomotive,VDOAdolfSchindlingGmbH,VectorInformatik,Visteon,
VolkswagenAG,
VolvoCarCorporation,WindRiverSystems,3SoftGmbH.
2©byOSEKOSEKOS2.1
OSEK/VDXOperatingSystemSpecification2.1Motivation• High,recurringexpensesinthedevelopmentandvariantmanagementofnon-application
relatedaspectsofcontrolunitsoftware.• Incompatibilityofcontrolunitsmadebydifferentmanufacturersduetodifferent
interfacesandprotocols.Goal
Supportoftheportabilityandreusabilityoftheapplicationsoftwareby:• Specificationofinterfaceswhichareabstractandasapplication-independentaspossible,
inthefollowingareas:real-timeoperatingsystem,communicationandnetworkmanagement.• Specificationofauserinterfaceindependentofhardwareandnetwork.• Efficientdesignofarchitecture:Thefunctionalityshallbeconfigurableandscaleable,to
enableoptimaladjustmentofthearchitecturetotheapplicationinquestion.• Verificationoffunctionalityandimplementationofprototypesinselectedpilotprojects.Advantages• Clearsavingsincostsanddevelopmenttime.• Enhancedqualityofthesoftwareofcontrolunitsofvariouscompanies.• Standardisedinterfacingfeaturesforcontrolunitswithdifferentarchitecturaldesigns.• Sequencedutilisationoftheintelligence(existingresources)distributedinthevehicle,to
enhancetheperformanceoftheoverallsystemwithoutrequiringadditionalhardware.• Providesindependencewithregardstoindividualimplementation,asthespecification
doesnotprescribeimplementationaspects.
Remarksbytheauthors
Thisdocumentdescribestheconceptofareal-timeoperatingsystem,capableofmultitasking,whichcanbeusedformotorvehicles.Itisnotaproductdescriptionwhichrelatestoaspecificimplementation.
ThisdocumentalsospecifiestheOSEKoperatingsystem-ApplicationProgramInterface.Generalconventions,explanationsoftermsandabbreviationshavebeencompiledintheadditionalinter-project\"OSEKOverallGlossary\".
Regardingimplementationandsystemgenerationaspectspleaserefertothe\"OSEKImplementationLanguage\"(OIL)specification.
OSEKOS2.1©byOSEK3
OSEK/VDXTableofContents
OperatingSystemSpecification2.11Introduction......................................................................................................................81.1Systemphilosophy....................................................................................................81.2Purposeofthisdocument.......................................................................................101.3Structureofthisdocument......................................................................................112Summary........................................................................................................................133ArchitectureoftheOSEKoperatingsystem....................................................................143.1Processinglevels.....................................................................................................143.2Conformanceclasses...............................................................................................1Taskmanagement...........................................................................................................174.1Taskconcept..........................................................................................................174.2Taskstatemodel.....................................................................................................174.2.1Extendedtasks..............................................................................................174.2.2Basictasks....................................................................................................184.2.3Comparisonofthetasktypes.........................................................................194.3Activatingatask.....................................................................................................204.4Taskswitchingmechanism......................................................................................204.5Taskpriority...........................................................................................................204.6Schedulingpolicy...................................................................................................214.6.1Nonpre-emptivescheduling..........................................................................214.6.2Fullpre-emptivescheduling...........................................................................224.6.3Mixedpre-emptivescheduling.......................................................................234.6.4Selectingtheschedulingpolicy......................................................................244.7Terminationoftasks...............................................................................................244.8Applicationmodes..................................................................................................244.8.1Startupperformance.....................................................................................2.8.2Supportofexclusiveapplications...................................................................2.8.3Supportedbyallconformanceclasses............................................................255Interruptprocessing........................................................................................................266Eventmechanism............................................................................................................297Resourcemanagement....................................................................................................317.1Behaviourduringaccesstooccupiedresources.......................................................317.2Restrictionswhenusingresources...........................................................................317.3Schedulerasaresource..........................................................................................327.4Generalproblemswithsynchronisationmechanisms................................................327.4.1Explanationofpriorityinversion....................................................................327.4.2Deadlocks.....................................................................................................337.5OSEKPriorityCeilingProtocol..............................................................................337.6OSEKPriorityCeilingProtocolwithextensionsforinterruptlevels........................348Alarms............................................................................................................................378.1Counters.................................................................................................................378.2Alarmmanagement.................................................................................................379Messages........................................................................................................................3910Errorhandling,tracinganddebugging.............................................................................40
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OSEKOS2.1
OSEK/VDX10.110.210.310.410.5
OperatingSystemSpecification2.1Hookroutines.........................................................................................................40Errorhandling.........................................................................................................41Systemstart-up.......................................................................................................42Systemshutdown....................................................................................................43Debugging...............................................................................................................44
11Descriptionofsystemservices.........................................................................................4511.1Definitionofsystemobjects.....................................................................................4511.2Conventions............................................................................................................4511.2.1Typeofcalls...................................................................................................4511.2.2Legitimacyofcalls..........................................................................................4511.2.3Errorcharacteristics.......................................................................................4512Specificationofoperatingsystemservices........................................................................4712.1Commondatatypes..................................................................................................4712.2Taskmanagement....................................................................................................4812.2.1Datatypes......................................................................................................4812.2.2Constructionalelements..................................................................................49
12.2.2.1DeclareTask............................................................................................................49
12.2.3Systemservices..............................................................................................49
12.2.3.112.2.3.212.2.3.312.2.3.412.2.3.512.2.3.6
ActivateTask...........................................................................................................49TerminateTask........................................................................................................50ChainTask...............................................................................................................50Schedule..................................................................................................................51GetTaskID...............................................................................................................51GetTaskState...........................................................................................................52
12.2.4Constants.......................................................................................................5212.2.5Namingconvention.........................................................................................5312.3Interrupthandling....................................................................................................5312.3.1Datatypes......................................................................................................5312.3.2Systemservices..............................................................................................53
12.3.2.112.3.2.212.3.2.312.3.2.412.3.2.512.3.2.612.3.2.712.3.2.812.3.2.9
EnterISR.................................................................................................................53LeaveISR.................................................................................................................EnableInterrupt.......................................................................................................DisableInterrupt......................................................................................................55GetInterruptDescriptor............................................................................................55EnableAllInterrupts.................................................................................................56DisableAllInterrupts................................................................................................56ResumeOSInterrupts...............................................................................................57SuspendOSInterrupts...............................................................................................57
12.3.3Constants.......................................................................................................5812.3.4Namingconvention.........................................................................................5812.4Resourcemanagement.............................................................................................5812.4.1Datatypes......................................................................................................5812.4.2Constructionalelements..................................................................................58
12.4.2.1DeclareResource......................................................................................................58
12.4.3Systemservices..............................................................................................59
12.4.3.1GetResource............................................................................................................5912.4.3.2ReleaseResource......................................................................................................59
12.4.4Constants.......................................................................................................6012.5Eventcontrol...........................................................................................................6012.5.1Datatypes......................................................................................................6012.5.2Constructionalelements..................................................................................60
12.5.2.1DeclareEvent...........................................................................................................60
OSEKOS2.1
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OSEK/VDX12.5.3
12.5.3.112.5.3.212.5.3.312.5.3.4
OperatingSystemSpecification2.1Systemservices.............................................................................................60
SetEvent.................................................................................................................60ClearEvent..............................................................................................................61GetEvent.................................................................................................................61WaitEvent...............................................................................................................62
12.6Alarms....................................................................................................................6212.6.1Datatypes.....................................................................................................6212.6.2Constructionalelements.................................................................................63
12.6.2.1DeclareAlarm.........................................................................................................63
12.6.3Systemservices.............................................................................................63
12.6.3.112.6.3.212.6.3.312.6.3.412.6.3.5
GetAlarmBase.........................................................................................................63GetAlarm................................................................................................................SetRelAlarm...........................................................................................................SetAbsAlarm..........................................................................................................65CancelAlarm...........................................................................................................66
12.6.4Constants......................................................................................................6612.7Operatingsystemexecutioncontrol........................................................................6612.7.1Datatypes.....................................................................................................6612.7.2Systemservices.............................................................................................67
12.7.2.1GetActiveApplicationMode.....................................................................................6712.7.2.2StartOS...................................................................................................................6712.7.2.3ShutdownOS...........................................................................................................67
12.7.3Constants......................................................................................................6812.8Hookroutines.........................................................................................................6812.8.1ErrorHook....................................................................................................6812.8.2PreTaskHook................................................................................................6812.8.3PostTaskHook...............................................................................................6812.8.4StartupHook.................................................................................................6912.8.5ShutdownHook.............................................................................................6913Implementationandapplicationspecifictopics................................................................7013.1Implementationhints..............................................................................................7013.1.1Aspectsofimplementation.............................................................................7013.1.2Parametersofimplementation........................................................................70
13.1.2.113.1.2.213.1.2.313.1.2.4
Functionality...........................................................................................................70Hardwareresources.................................................................................................71Performance............................................................................................................71Configurationofruntimecontext...........................................................................71
13.2Applicationdesignhints..........................................................................................7213.2.1Resourcemanagement...................................................................................72
13.2.1.1OccupationinLIFOorder.......................................................................................7213.2.1.2CalllevelofAPI-services........................................................................................7213.2.1.3Resourcesstilloccupiedattasktermination.............................................................73
13.2.213.2.3PlacementofAPIcalls...................................................................................73Interruptserviceroutines...............................................................................73
13.2.3.1LocalvariablesinISRsofcategory3.......................................................................7313.2.3.2Nestedinterruptsofdifferentcategories..................................................................7413.2.3.3Directmanipulationofinterruptlevels....................................................................75
13.2.4Priorityandpre-emption................................................................................7513.2.5ParametertopasstoShutdownOS.................................................................7513.2.6Errorhandling...............................................................................................7513.2.7Errorsandwarnings......................................................................................7613.3Implementationspecifictools..................................................................................76
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OSEKOS2.1
OSEK/VDXOperatingSystemSpecification2.114Changesfromspecification1.0to2.1..............................................................................7814.1Changesfromspecification1.0to2.0r1...................................................................7814.1.1Conceptualchanges........................................................................................78
14.1.1.114.1.1.214.1.1.314.1.1.414.1.1.514.1.1.614.1.1.7
Conformanceclasses...............................................................................................78Messages.................................................................................................................78Multiplerequestingoftaskactivation......................................................................78Applicationmodes...................................................................................................78Counters..................................................................................................................78Hookroutines..........................................................................................................79OSexecutioncontrol...............................................................................................79Schedulingofnonpre-emptivetasks.......................................................................79Servicesavailableonwhichlevel.............................................................................79Interruptprocessing.................................................................................................79Priorityceiling........................................................................................................79Typesandconstants................................................................................................79Namingconventions................................................................................................79
14.1.2Clarifications..................................................................................................79
14.1.2.114.1.2.214.1.2.314.1.2.414.1.2.514.1.2.6
14.1.3Changesofthedocumentation........................................................................80
14.1.3.1Documentstructure.................................................................................................8014.1.3.2Newchapters...........................................................................................................8014.1.3.3Removedchapters...................................................................................................80
14.2Changesfromspecification2.0r1to2.1...................................................................8014.2.1BehaviourofChainTask/TerminateTaskwithallocatedresourcesis
undefined.......................................................................................................80
14.2.2GetTaskIDisallowedinISRs.........................................................................8014.2.3Interrupthandlinghasbeenclarifiedandextended..........................................8114.2.4ErrorcheckingofGetResource/ReleaseResourcehavebeenmodified.............8114.2.5AddedconstantOSTICKSPERBASE.............................................................8114.2.6ShutdownOSisallowedinISRsandcertainhookroutines.............................8114.2.7BehaviourofShutdownOSafterShutdownHookreturnsis
implementationdefined...................................................................................81
14.2.8AddedconstantOSDEFAULTAPPMODE.....................................................8114.2.9ErrorHookisnevercalledrecursively.............................................................8114.2.10LocalMessagesaddedtospecification............................................................8115Index...............................................................................................................................8215.1Listoffigures..........................................................................................................8316History............................................................................................................................84
OSEKOS2.1©byOSEK7
OSEK/VDX1Introduction
OperatingSystemSpecification2.1ThespecificationoftheOSEKoperatingsystemistorepresentauniformenvironmentwhichsupportsefficientutilisationofresourcesforautomotivecontrolunitapplicationsoftware.TheOSEKoperatingsystemisasingleprocessoroperatingsystemmeantfordistributedembeddedcontrolunits.
1.1Systemphilosophy
Automotiveapplicationsarecharacterisedbystringentreal-timerequirements.ThereforetheOSEKoperatingsystemoffersthenecessaryfunctionalitytosupporteventdrivencontrolsystems.
Thespecifiedoperatingsystemservicesconstituteabasistoenabletheintegrationofsoftwaremodulesmadebyvariousmanufacturers.Tobeabletoreacttothespecificfeaturesoftheindividualcontrolunitsasdeterminedbytheirperformanceandtherequirementsofaminimumconsumptionofresources,theprimefocuswasnottoachieve100%compatibilitybetweentheapplicationmodules,buttheirdirectportability.
Astheoperatingsystemisintendedforuseinanytypeofcontrolunits,itmustsupporttime-criticalapplicationsonawiderangeofhardware.Ahighdegreeofmodularityandabilityforflexibleconfigurationareprerequisitestomaketheoperatingsystemsuitableforlow-endmicroprocessorsandcomplexcontrolunitsalike.Theserequirementshavebeensupportedbydefinitionof\"conformanceclasses\"(seechapter3.2,Conformanceclasses)andacertaincapabilityforapplicationspecificadaptations.
Fortime-criticalapplicationsdynamicgenerationofsystemobjectswasleftout.Instead,generationofsystemobjectswasassignedtothesystemgenerationphase.Errorinquirieswithintheoperatingsystemareobviatedtoalargeextent,soasnottoaffectthespeedoftheoverallsystemunnecessarily.Ontheotherhand,asystemversionwithextendederrorinquirieshasbeendefined.Itisintendedforthetestphaseandforlesstime-criticalapplications.Evenatthatstagedefineduniformsystemappearanceisensured.Standardisedinterfaces
Theinterfacebetweentheapplicationsoftwareandtheoperatingsystemisdefinedbysystemservices.Theinterfaceisidenticalforallimplementationsoftheoperatingsystemonvariousprocessorfamilies.
SystemservicesarespecifiedinanISO/ANSI-C-likesyntax,howevertheimplementationlanguageofthesystemservicesisnotspecified.Scaleability
Differentconformanceclasses,variousschedulingmechanismsandtheconfigurationfeaturesmaketheOSEKoperatingsystemfeasibleforabroadspectrumofapplicationsandhardware.TheOSEKoperatingsystemisdesignedtorequireonlyaminimumofhardwareresources(RAM,ROM,CPUtime)andthereforerunsevenon8bitmicrocontrollers.Errorchecking
TheOSEKoperatingsystemofferstwolevelsoferrorchecking,extendedstatusfordevelopmentphaseandstandardstatusforproductionphase.
OSEKOS2.1©byOSEK8
OSEK/VDXOperatingSystemSpecification2.1Theextendedstatusallowsforenhancedplausibilitychecksoncallingoperatingsystemservices.Duetotheadditionalerrorcheckingitrequiresmoreexecutiontimeandmemoryspacethanthestandardversion.However,manyerrorscanbefoundinatestphase.Afterallerrorshavebeeneliminated,thesystemcanberecompiledwiththestandardversion.Portabilityofapplicationsoftware
OneofthegoalsofOSEKistosupporttheportabilityandre-usabilityofapplicationsoftware.Thereforetheinterfacebetweentheapplicationsoftwareandtheoperationsystemisdefinedbystandardisedsystemserviceswithwell-definedfunctionality.Useofstandardisedsystemservicesreducestheefforttomaintainandtoportapplicationsoftwareanddevelopmentcost.PortabilitymeanstheabilitytotransferanapplicationsoftwaremodulefromoneECUtoanotherECUwithoutbiggerchangesinsidetheapplication.
Theapplicationsoftwareliesontheoperatingsystemandinparallelonaapplication-specificInput/OutputSysteminterfacewhichisnotstandardisedintheOSEKspecification.Theapplicationsoftwaremodulecanhaveseveralinterfaces.Thereareinterfacestotheoperatingsystemforrealtimecontrolandresourcemanagement,butalsointerfacestoothersoftwaremodulestorepresentacompletefunctionalityinasystemandatleasttothehardware,iftheapplicationhastoworkdirectlywithmicrocontrollermodules.
Forbetterportabilityofapplicationsoftware,theOSEKdefinesalanguageforastandardisedconfigurationinformation.Thislanguage\"OIL\"(OSEKImplementationLanguage)supportsaportabledescriptionofallOSEKspecificobjectssuchas\"tasks\"and\"alarms\"etc.
module1module2module3modulenapplicationsoftwareOSEKoperationsystemInput/OutputSystemµControllerFigure1-1
SoftwareinterfacesinsideECU1
DuringtheprocesstoportapplicationsoftwarefromoneECUtoanotherECUitisnecessarytoconsidercharacteristicsofthesoftwaredevelopmentprocess,thedevelopmentenvironment,andthehardwarearchitectureoftheECU,forexample:
1
OSEKOSallowsdirectinterfacingbetweenapplicationandthehardware.
©byOSEK
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OSEKOS2.1
OSEK/VDX• • • • • • •
OperatingSystemSpecification2.1SoftwaredevelopmentguidelinesFilemanagementsystem
DataallocationandstackusageofthecompilerMemoryarchitectureoftheECUTimingbehaviouroftheECU
Differentmicrocontrollerspecificinterfacese.g.ports,A/Dconverter,serialcommunicationandwatchdogtimerPlacementoftheAPIcalls
ThismeansthattheOSEKspecificationsarenotenoughtodescribeanOSEKimplementationcompletely.Theimplementationhastosupplyspecificdocumentation.SupportofPortability
Thecertificationprocessensurestheconformanceofdifferentimplementationstothespecification.Chapter13ofthisspecificationcollectsimplementationspecificdetailswhichhavetoberegardedtoincreaseportabilityofanapplicationbetweenvariousOSEKimplementations.Hereinonlytheoperatingsysteminterfacetotheapplicationisconsidered.Specialsupportforautomotiverequirements
SpecificrequirementsforanOSEKoperatingsystemariseintheapplicationcontextofsoftwaredevelopmentforautomotivecontrolunits.Requirementssuchasreliability,real-timecapability,andcostsensitivityareaddressedbythefollowingfeatures:• TheOSEKoperatingsystemisconfiguredandscaledstatically.Thenumberoftasks,
resources,andservicesrequiredisstaticallyspecifiedbytheuser.• ThespecificationoftheOSEKoperatingsystemsupportsimplementationscapableof
runningonROM,i.e.thecodecouldbeexecutedfromRead-Only-Memory.• TheOSEKoperatingsystemsupportsportabilityofapplicationtasks.• ThespecificationoftheOSEKoperatingsystemprovidesapredictableanddocumented
behaviourtoenableoperatingsystemimplementations,whichmeetautomotivereal-timerequirements.• ThespecificationoftheOSEKoperatingsystemallowstheimplementationof
predictableperformanceparameters.
1.2Purposeofthisdocument
ThefollowingdescriptionistoberegardedasagenericdescriptionwhichismandatoryforanyimplementationoftheOSEKoperatingsystem.Thisconcernsthegeneraldescriptionofstrategyandfunctionality,theinterfaceofthecalls,themeaninganddeclarationoftheparametersandthepossibleerrorcodes.
Thespecificationleavesacertainamountofflexibility.Ontheonehand,thedescriptionisgenericenoughforfutureupgrades,ontheotherhand,thereissomeexplicitlyspecifiedimplementation-specificscopeinthedescription.
Anyimplementationdefinesallimplementationspecificissues.Theconformanceclassessupportedbytheimplementationmustbeindicatedprecisely,andtheissuesidentifiedasimplementation-specificmustbedocumented.
ItisassumedthatthedescriptionoftheOSEKoperatingsystemistobeupdatedinthefuture,andwillbeadaptedtoextendedrequirements.Therefore,eachimplementationmustspecify
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OSEKOS2.1
OSEK/VDXOperatingSystemSpecification2.1whichofficiallyauthorisedversionoftheOSEKdescriptionhasbeenusedasareferencedescription.OfficiallyauthorisedversionsoftheOSEKoperatingsystemdescriptionarenamedx.y.Thisdocumentrepresents”Version2.1”.
Becausethisdescriptionismandatory,definitionshaveonlybeenmadewherethegeneralsystemstrategyisconcerned.Inallotherrespects,itisuptothesystemimplementationtodeterminetheoptimaladaptationtoaspecifichardwaretype.
1.3Structureofthisdocument
Inthefollowingtext,thespecificationchaptersaredescribedbriefly:Chapter2,Summary
ThischapterprovidesabriefintroductiontotheOSEKoperatingsystemconcept.Chapter3,ArchitectureoftheOSEKoperatingsystem
ThischaptergivesasurveyaboutthedesignprinciplesandthearchitectureoftheOSEKoperatingsystem.
Chapter4,Taskmanagement
ThischapterexplainstheOSEKtaskmanagementwiththedifferenttasktypesandschedulingmechanisms.
Chapter5,Interruptprocessing
ThischapterprovidesinformationabouttheOSEKinterruptstrategyandthedifferenttypesofinterruptserviceroutines.Chapter6,Eventmechanism
Thischapterexplainstheeventmechanismandthedifferentbehaviourdependingonthescheduling.
Chapter7,Resourcemanagement
ThischapterdescribestheOSEKresourcemanagementanddiscussesthebenefitsandimplementationoftheOSEKpriorityceilingprotocol.Chapter8,Alarms
Thischapterdescribesthetwo-stageconcepttosupporttime-basedevents(e.g.hardware-timer)aswellasnon-time-basedevents(e.g.anglemeasurement).Chapter9,Messages
ThemessagehandlingforintraprocessorcommunicationwillbeaddedtotheOSspecification.FullmessagehandlingisdescribedintheOSEKCOMspecification.Theexactsubsettobeimplementedisyettobedefined.Chapter10,Errorhandling,tracinganddebugging
Descriptionofthemechanismstoachievecentralisederror-handling.Thischapteralsodescribestheservicestoinitialiseandshutdownthesystem.Chapter11,Descriptionofsystemservices
Thischapterdescribestheconventionsusedfordescription.
OSEKOS2.1©byOSEK11
OSEK/VDXChapter12,Specificationofoperatingsystemservices
OperatingSystemSpecification2.1Thischapterdescribesalloperatingsystemservicesmadeavailabletotheuser.Structureofthedescriptionisidenticalforanyservice;itcontainsalltheinformationtheserviceuserrequires.Chapter13,Implementationandapplicationspecifictopics,
Thischapterprovidesalistofalloperatingsystemspecifictopics,includingservices,datatypes,andconstants.
Chapter14,Changesfromspecification1.0to2.1
Thischapterprovidesasurveyofmajorchangesintheoperatingsystemspecificationfromversion1.0toversion2.1.Chapter15,Index
Listofalloperatingsystemservicesandfigures.Chapter16,HistoryListofallofficialreleases.
12©byOSEKOSEKOS2.1
OSEK/VDX2Summary
OperatingSystemSpecification2.1TheOSEKoperatingsystemprovidesapoolofdifferentservicesandprocessingmechanisms.TheOSEKoperatingsystemisbuiltaccordingtotheuser'sconfigurationinstructionsatsystemgenerationtime.
FourconformanceclassesareavailabletosatisfydifferentrequirementsconcerningfunctionalityandcapabilityoftheOSEKoperatingsystem.Thus,theusercanadapttheoperatingsystemtothecontroltaskandthetargethardware.Theoperatingsystemcannotbemodifiedlateratexecutiontime.
ApplicationswhichhavebeenwrittenforacertainconformanceclasshavetobeportabletoOSEKimplementationsofthesameclass.Thisisensuredbyadefinitionoftheservices,theirscopeofcapabilities,andthebehaviourofeachconformanceclass.Onlyifalltheservicesofaconformanceclassareofferedwiththedeterminedscopeofcapabilities,theoperatingsystemimplementationconformstoOSEK.
Theservicegroupsarestructuredintermsoffunctionalities.Taskmanagement• Activationandterminationoftasks• Managementoftaskstates,taskswitchingSynchronisation
Theoperatingsystemsupportstwomeansofsynchronisationeffectiveontasks:• Resourcemanagement
Accesscontrolforinseparableoperationstojointlyused(logic)resourcesordevices,orforcontrolofaprogramflow.• Eventcontrol
Eventmanagementfortasksynchronisation.Interruptmanagement• ServicesforinterruptprocessingAlarms• RelativeandabsolutealarmsIntraprocessormessagehandling• Servicesforexchangeofdata
Errortreatment• Mechanismssupportingtheuserincaseofvariouserrors
OSEKOS2.1©byOSEK13
OSEK/VDXOperatingSystemSpecification2.13ArchitectureoftheOSEKoperatingsystem
3.1Processinglevels
TheOSEKoperatingsystemservesasabasisforapplicationprogramswhichareindependentofeachother,andprovidestheirenvironmentonaprocessor.TheOSEKoperatingsystemenablesacontrolledreal-timeexecutionofseveralprocesseswhichappeartoruninparallel.TheOSEKoperatingsystemprovidesadefinedsetofinterfacesfortheuser.TheseinterfacesareusedbyentitieswhicharecompetingfortheCPU.Therearetwotypesofentities:• Interruptserviceroutinesmanagedbytheoperatingsystem• Tasks(basictasksandextendedtasks)Thehardwareresourcesofacontrolunitcanbemanagedbyoperatingsystemservices.Theseoperatingsystemservicesarecalledbyauniqueinterface,eitherbytheapplicationprogramorinternallywithintheoperatingsystem.OSEKdefinesthreeprocessinglevels:• Interruptlevel
• Logicallevelforscheduler• Tasklevel
Withinthetaskleveltasksarescheduled(non,fullormixedpre-emptive)accordingtotheiruserassignedpriority.Theruntimecontextisoccupiedatthebeginningofexecutiontimeandisreleasedagainoncethetaskisfinished.
interruptlevel
withoutOS-services
priority
high
withOS-services
logicallevelforschedulingactivities
tasklevel
waiting:yes/no
n321
tasks
preemption:non/full
low
OSEKoperatingsystem
runtimecontext
Figure3-1ProcessinglevelsoftheOSEKoperatingsystem
Thefollowingpriorityruleshavebeenestablished:• Interruptshaveprecedenceovertasks• Theinterruptprocessinglevelconsistsofoneormoreinterruptprioritylevels• Interruptserviceroutineshaveastaticallyassignedinterruptprioritylevel
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OSEKOS2.1
OSEK/VDX•
OperatingSystemSpecification2.1Assignmentofinterruptserviceroutinestointerruptprioritylevelsisdependentonimplementationandhardwarearchitecture• Fortaskprioritiesandresourceceiling-prioritiesbiggernumbersrefertohigher
priorities.• Thetask’spriorityisstaticallyassignedbytheuser(themeaningoftaskprioritiesis
describedinchapter4.5)
Processinglevelsaredefinedforthehandlingoftasksandinterruptroutinesasarangeofconsecutivevalues.
Processinglevels
k...mj0...i
Figure3-2
Processedinstance
InterruptSchedulerTask
ProcessinglevelsoftheOSEKoperatingsystem
Thefollowingruleappliesfortheprocessinglevel:
0<=i 3.2Conformanceclasses Variousrequirementsoftheapplicationsoftwareforthesystem,andvariouscapabilitiesofaspecificsystem(e.g.processor,memory)demanddifferentfeaturesoftheoperatingsystem.Inthefollowingdescription,theseoperatingsystemfeaturesaredescribedas\"conformanceclasses\"(CC). Conformanceclassesexisttosupportthefollowingobjectives: • ToprovideconvenientgroupsofoperatingsystemfeaturesforeasierunderstandinganddiscussionoftheOSEKoperatingsystem. • Toallowpartialimplementationsalongpre-definedlines.ThesepartialimplementationsmaybecertifiedasOSEKcompliant. • TocreateanupgradepathfromclassesoflesserfunctionalitytoclassesofhigherfunctionalitywithnochangestotheapplicationusingOSEKrelatedfeatures.Thecompleteconformanceclassmustbeimplementedtobecertified.However,systemgenerationneedsonlytolinkthosesystemservicesthatarerequiredforaspecificapplication.Conformanceclassescannotbechangedduringexecution.Conformanceclassesaredeterminedbythefollowingattributes:• Multiplerequestingoftaskactivation,asdescribedinchapter4.3• Tasktypes,asdescribedinchapter4.2• Numberoftasksperpriority AllotherOSEKfeaturesaremandatoryifnotexplicitlystatedotherwise. OSEKOS2.1©byOSEK15 OSEK/VDXBTonlyOperatingSystemSpecification2.1BTandET1task/prioritynomultipleactivationsBCC1ECC1>1task/prioritymultipleactivationsforbasictasksonlyBCC2ECC2Figure3-3Restrictedupwardcompatibilityforconformanceclasses Thefollowingconformanceclassesaredefined:• BCC1(onlybasictasks,limitedtooneactivationrequestpertaskandonetaskper priority,whilealltaskshavedifferentpriorities)• BCC2(likeBCC1,plusmorethanonetaskperprioritypossibleandmultiplerequesting oftaskactivationallowed)• ECC1(likeBCC1,plusextendedtasks)• ECC2(likeECC1,plusmorethanonetaskperprioritypossibleandmultiplerequesting oftaskactivationallowedforbasictasks)Theportabilityofapplicationscanonlybeassumediftheminimumrequirementsarenotexceeded.TheminimumrequirementsforConformanceClassesareshownintheFigure3-4. BCC1 MultiplerequestingoftaskactivationNumberoftaskswhicharenotinthesuspendedstateMorethanonetaskperpriorityNumberofeventspertaskNumberoftaskprioritiesResourcesAlarm ApplicationMode Figure3-4 RES_SCHEDULER BCC2yes 8 ECC1BT2:noET:no ECC2BT:yesET:no no 16 (anycombinationofBT/ET) yes no (bothBT/ET) 8 8 8(includingRES_SCHEDULER) 11 yes (bothBT/ET) no — TheminimumrequirementsforConformanceClasses 2 BT=BasicTask,ET=ExtendedTask ©byOSEK OSEKOS2.1 16 OSEK/VDX4Taskmanagement 4.1Taskconcept OperatingSystemSpecification2.1Complexcontrolsoftwarecanconvenientlybesubdividedinpartsexecutedaccordingtotheirreal-timerequirements.Thesepartscanbeimplementedbythemeansoftasks.Ataskprovidestheframeworkfortheexecutionoffunctions.Theoperatingsystemprovidesconcurrentandasynchronousexecutionoftasks.Theschedulerorganisesthesequenceoftaskexecution.TheOSEKoperatingsystemprovidesataskswitchingmechanism(scheduler),includinganidlemechanism.(seechapter4.4,Taskswitchingmechanism).TwodifferenttaskconceptsareprovidedbytheOSEKoperatingsystem:• basictasks• extendedtasksBasicTasks Basictasksonlyreleasetheprocessor,if• • • theyterminate, theOSEKoperatingsystemswitchestoahigher-prioritytask,or interruptoccurswhichcausetheprocessortoswitchtoaninterruptserviceroutine(ISR). ExtendedTasks ExtendedtasksaredistinguishedfrombasictasksbybeingallowedtousetheoperatingsystemcallWaitEvent,whichmayresultinawaitingstate(seechapter6,Eventmechanism,andchapter12.5.3.4,WaitEvent).Thewaitingstateallowstheprocessortobereleasedandtobereassignedtoalower-prioritytaskwithouttheneedtoterminatetherunningextendedtask.Inviewoftheoperatingsystem,managementofextendedtasksis,inprinciple,morecomplexthanmanagementofbasictasksandrequiresmoresystemresources. 4.2Taskstatemodel Thefollowingtextdescribesthetaskstatesandthetransitionsbetweenthestatesforbothtasktypes. Ataskmustbeabletochangebetweenseveralstates,astheprocessorcanonlyexecuteoneinstructionofataskatanytime,whileseveraltasksmaybecompetingfortheprocessoratthesametime.TheOSEKoperatingsystemisresponsibleforsavingandrestoringtaskcontextinconjunctionwithtaskstatetransitionswhenevernecessary.4.2.1Extendedtasks Extendedtaskshavefourtaskstates:runningIntherunningstate,theCPUisassignedtothetask,sothatitsinstructions canbeexecuted.Onlyonetaskcanbeinthisstateatanypointintime,whilealltheotherstatescanbeadoptedsimultaneouslybyseveraltasks.ready Allfunctionalprerequisitesforatransitionintotherunningstateexist,andthetaskonlywaitsforallocationoftheprocessor.Theschedulerdecideswhichreadytaskisexecutednext. ©byOSEK 17 OSEKOS2.1 OSEK/VDXwaitingsuspended OperatingSystemSpecification2.1Ataskcannotcontinueexecutionbecauseithastowaitforatleastoneevent(seechapter6,Eventmechanism). Inthesuspendedstatethetaskispassiveandcanbeactivated. runningwaitterminatewaitingpreemptstartsuspendedreleasereadyactivateFigure4-1Transitionactivate Extendedtaskstatemodel Newstateready Description Anewtaskissetintothereadystatebyasystemservice.TheOSEKoperatingsystemensuresthattheexecutionofthetaskwillstartwiththefirstinstruction. Areadytaskselectedbytheschedulerisexecuted.Thetransitionintothewaitingstateiscausedbyasystemservice.Tobeabletocontinueoperation,thewaitingtaskrequiresanevent. Atleastoneeventhasoccurredwhichataskhaswaitedfor. Theschedulerdecidestostartanothertask.Therun-ningtaskisputintothereadystate.Therunningtaskcausesitstransitionintothesuspendedstatebyasystemservice. Formerstatesuspended startwait readyrunning runningwaiting releasepreemptterminate waitingrunningrunning readyreadysuspended Figure4-2Statesandstatustransitionsforextendedtasks Terminationofataskisonlypossibleifthetaskterminatesitself(\"self-termination\").Thisrestrictionreducescomplexityofanoperatingsystem.Thereisnoprovisionforadirecttransitionfromthesuspendedstateintothewaitingstate.Thistransitionisredundantandwouldaddtothecomplexityofthescheduler.4.2.2Basictasks Thestatemodelofbasictasksisnearlyidenticaltotheextendedtasksstatemodel.Theonlyexceptionisthatbasictasksdonothaveawaitingstate. 18©byOSEKOSEKOS2.1 OSEK/VDXrunning OperatingSystemSpecification2.1Intherunningstate,theCPUisassignedtothetask,sothatitsinstructionscanbeexecuted.Onlyonetaskcanbeinthisstateatanypointintime,whilealltheotherstatescanbeadoptedsimultaneouslybyseveraltasks.Allfunctionalprerequisitesforatransitionintotherunningstateexist,andthetaskonlywaitsforallocationoftheprocessor.Theschedulerdecideswhichreadytaskisexecutednext. Inthesuspendedstatethetaskispassiveandcanbeactivated. ready suspended runningterminatepreemptstartsuspendedactivatereadyFigure4-3Transitionactivate Basictaskstatemodel Newstateready3 Description Anewtaskissetintothereadystatebyasystemservice.TheOSEKoperatingsystemensuresthattheexecutionofthetaskwillstartwiththefirstinstruction. Areadytaskselectedbytheschedulerisexecuted.Theschedulerdecidestostartanothertask.Therunningtaskisputintothereadystate.Therunningtaskcausesitstransitionintothesuspendedstatebyasystemservice. Formerstatesuspended startpreemptterminate readyrunningrunning runningreadysuspended Figure4-4Statesandstatustransitionsforbasictasks 4.2.3Comparisonofthetasktypes Basictaskshavenowaitingstate,andthusonlycomprisesynchronisationpointsatthebeginningandtheendofthetask.Partsofapplicationwithinternalsynchronisationpoints,havetobeimplementedbymorethanonebasictasks.Anadvantageofbasictasksistheirmoderaterequirementregardingruntimecontext(RAM). Anadvantageofextendedtasksisthattheycanhandleacoherentjobinasingletask,nomatterwhichsynchronisationrequestsareactive.Whenevercurrentinformationforfurtherprocessingismissing,theextendedtaskswitchesoverintothewaitingstate.Itexitsthisstate Taskactivationwillnotimmediatelychangethestateofthetaskincaseofmultipleactivationrequests.Ifthetaskisnotsuspended,theactivationwillonlyberecordedandperformedlater.OSEKOS2.1 ©byOSEK 19 3 OSEK/VDXOperatingSystemSpecification2.1whenevercorrespondingeventssignalthereceiptortheupdateofthedesireddataorevents.Extendedtasksalsocomprisemoresynchronisationpointsthanbasictasks. 4.3Activatingatask TaskactivationsareperformedusingtheoperatingsystemservicesActivateTaskorChainTask.Afteractivationthetaskisreadytoexecutefromthefirststatement. TheOSEKoperatingsystemdoesnotsupportC-likeparameterpassingwhenstartingatask.Thoseparametersshouldbepassedbymessagecommunication(see“Messages”)orbyglobalvariables. Multiplerequestingoftaskactivation Dependingontheconformanceclassabasictaskcanbeactivatedonceormultipletimes.\"Multiplerequestingoftaskactivation\"meansthattheOSEKoperatingsystemreceivesandrecordsparallelactivationsofabasictaskalreadyactivated. Thenumberofmultiplerequestsinparallelisdefinedinabasictaskspecificattributeduringsystemgeneration.Ifthemaximumnumberofmultiplerequestshasnotbeenreached,therequestisqueued.Therequestsofbasictaskactivationsarequeuedperpriorityinactivationorder. 4.4Taskswitchingmechanism Unlikeconventionalsequentialprogramming,theprincipleofmultitaskingallowstheoperatingsystemtoexecutevarioustasksconcurrently.Thereforetheschedulingpolicyhasclearlytobedefined(seechapter4.6,Schedulingpolicy). TheentitydecidingwhichtaskhastobestartedandthetriggeringofallnecessaryOSEKoperatingsysteminternalactivitiesiscalledscheduler.Theschedulerisactivatedwheneverataskswitchispossibleaccordingtotheimplementedschedulingpolicy.Theschedulercanbeconsideredasaresourcewhichcanbeoccupiedandreleasedbytasks.Thus,ataskcanreservetheschedulertoavoidataskswitchuntilitisreleased.Forfurtherdetails,pleaserefertochapter7.3,Schedulerasaresource. 4.5Taskpriority Theschedulerdecidesonthebasisofthetaskpriority(precedence)whichisthenextofthereadytaskstobetransferredintotherunningstate. Thevalue0isdefinedasthelowestpriorityofatask.Accordinglybiggernumbersdefinehigherpriorities. Toenhanceefficiency,adynamicprioritymanagementisnotsupported.Accordinglythepriorityofataskisdefinedstatically,i.e.itcannotbechangedbytheuseratthetimeofexecution.However,inparticularcasestheoperatingsystemcantreatataskwithadefinedhigherpriority.Inthiscontext,pleaserefertochapter7.5,OSEKPriorityCeilingProtocol.TasksofidenticalpriorityaresupportedintheconformanceclassesBCC2andECC2,seechapter3.2,Conformanceclasses. Tasksonthesameprioritylevelarestarteddependingontheirorderofactivation,wherebyextendedtasksinthewaitingstatedonotblockthestartofsubsequenttasksofidenticalpriority. Apre-emptedtaskisconsideredtobethefirsttaskinthereadylistofitscurrentpriority. 20 ©byOSEK OSEKOS2.1 OSEK/VDXOperatingSystemSpecification2.1Ataskbeingreleasedfromthewaitingstateistreatedlikethenewesttaskinthereadyqueueofitspriority. Figure4-5showsanexampleimplementationoftheschedulerusingforeachprioritylevel.Severaltasksofdifferentprioritiesareinthereadystate;i.e.threetasksofpriority3,oneofpriority2andoneofpriority1,plustwotasksofpriority0.Thetaskwhichhaswaitedthelongesttime,dependingonitsorderofrequesting,isshownatthebottomofeachqueue.Theprocessorhasjustprocessedandterminatedatask.Theschedulerselectsthenexttasktobeprocessed(priority3,firstqueue).Beforepriority2taskscanbeprocessed,alltasksofhigherprioritymusthavelefttherunningandreadystate,i.e.startedandthenremovedfromthequeueeitherduetoterminationorduetotransitionintowaitingstate. nexttasktobeprocessedn3210FIFOqueuetaskpriorityhighschedulerlowprocessoractuallyprocessedandterminatedtaskFigure4-5Scheduler:orderofevents Thefollowingfundamentalstepsarenecessarytodeterminethenexttasktobeprocessed:• Theschedulersearchesforalltasksintheready/runningstate.• Fromthesetoftasksintheready/runningstate,theschedulerdeterminesthesetoftasks withthehighestpriority.• Withinthesetoftasksintheready/runningstateandofhighestpriority,thescheduler findstheoldesttask. 4.6Schedulingpolicy 4.6.1Nonpre-emptivescheduling Theschedulingpolicyisdescribedasnonpre-emptive,iftaskswitchingisonlyperformedviaoneofaselectionofexplicitlydefinedsystemservices(explicitpointsofrescheduling).Nonpre-emptiveschedulingimposesparticularconstraintsonthepossibletimingrequirementsoftasks.Specificallythenonpre-emptablesectionofarunningtaskwithlowerprioritydelaysthestartofataskwithhigherpriorityuptothenextpointofrescheduling. InFigure4-6,taskT2withthelowerprioritydelaystaskT1withhigherpriorityuptothenextpointofrescheduling(inthiscaseterminationoftaskT2). OSEKOS2.1©byOSEK21 OSEK/VDXactivationoftaskT1OperatingSystemSpecification2.1latencytimefortaskT1TaskT1suspendedTaskT2runningreadyrunningsuspendedterminationoftaskT2Figure4-6Nonpre-emptivescheduling Pointsofrescheduling Inthecaseofanonpre-emptivetask,reschedulingwilltakeplaceexactlyinthefollowing cases:• Successfulterminationofatask(systemserviceTerminateTask,seechapter12.2.3.2).• Successfulterminationofataskwithexplicitactivationofasuccessortask(system serviceChainTask,seechapter12.2.3.3).• Explicitcallofscheduler(systemserviceSchedule,seechapter12.2.3.4).• Atransitionintothewaitingstatetakesplace(systemserviceWaitEvent,seechapter 12.5.3.4)4.Implementationsofnonpre-emptivesystemsmayprescribethatoperatingsystemserviceswhichcausereschedulingmayonlybecalledatthehighesttaskprogramlevel(notintasksubfunctions).Consequently,ataskswitchatthesepointsofschedulingonlyrequiressavingminimumtaskcontext(nostack,onlyfewregisterse.g.programcounterand/orprocessorstatus). 4.6.2Fullpre-emptivescheduling Fullpre-emptiveschedulingmeansthatataskwhichispresentlyrunningmayberescheduledatanyinstructionbytheoccurrenceoftriggerconditionspre-setbytheoperatingsystem.Fullpre-emptiveschedulingwillputtherunningtaskintothereadystate,assoonasahigher-prioritytaskhasgotready.Thetaskcontextissavedsothatthepre-emptedtaskcanbecontinuedatthelocationwhereitwaspre-empted. Withfullpre-emptiveschedulingthelatencytimeisindependentoftheruntimeoflowerprioritytasks.Certainrestrictionsarerelatedtotheincreased(RAM-)memoryspacerequiredforsavingthecontext,andtheenhancedcomplexityoffeaturesnecessaryforsynchronisationbetweentasks.Aseachtaskcantheoreticallyberescheduledatanylocation,accesstodatawhichareusedjointlywithothertasksmustbesynchronised. InFigure4-7,taskT2withthelowerprioritydoesnotdelaytheschedulingoftaskT1withhigherpriority. 4 ThecallofWaitEventdoesnotleadtoawaitingstateifoneoftheeventspassedintheeventmasktoWaitEventisalreadyset.InthiscaseWaitEventdoesnotleadtoarescheduling. ©byOSEK OSEKOS2.1 22 OSEK/VDXactivationoftaskT1 OperatingSystemSpecification2.1terminationoftaskT1 TaskT1suspendedTaskT2running dyarerunning suspendedrunning ready Figure4-7Fullpre-emptivescheduling Inthecaseofafullpre-emptivesystem,theusermustconstantlyexpectpre-emptionoftherunningtask.Ifataskfragmentmustnotbepre-empted,thiscanbeachievedbyblockingtheschedulertemporarilyviathesystemserviceGetResource. Summarised,reschedulingisperformedinallofthefollowingcases:• Successfulterminationofatask(systemserviceTerminateTask,seechapter12.2.3.2).• Successfulterminationofataskwithexplicitactivatingofasuccessortask(system serviceChainTask,seechapter12.2.3.3).• Activatingataskattasklevel(e.g.systemserviceActivateTask,seechapter12.2.3.1,messagenotificationmechanism,alarmexpiration,iftaskactivationisdefined,seechapter8.2). Explicitwaitcall,ifatransitionintothewaitingstatetakesplace(extendedtasksonly,systemserviceWaitEvent,seechapter12.5.3.4). Settinganeventtoawaitingtaskattasklevel(e.g.systemserviceSetEvent,seechapter12.5.3.1,messagenotificationmechanism,alarmexpiration,ifeventsettingdefined,seechapter8.2). Releaseofresourceattasklevel(systemserviceReleaseResource,seechapter11.3.3.2)Returnfrominterruptleveltotasklevel • • • • Duringinterruptserviceroutinesnoreschedulingisperformed(seefigure3-1). Toenableportableapplicationstobewritteninspiteofthedifferentschedulingpolicies,theusercanenforceareschedulingviathesystemserviceScheduleatlocationswhereheassumesacorrectassignmentoftheCPU. 4.6.3Mixedpre-emptivescheduling Iffullpre-emptiveandnonpre-emptivetasksaremixedonthesamesystem,theresulting policyiscalled\"mixedpre-emptive\"scheduling.Inthiscaseschedulingpolicydependsonpre-emptionpropertiesofrunningtask.Iftherunningtaskisnonpre-emptive,thennonpre-emptiveschedulingisperformed.Iftherunningtaskispre-emptive,thenpre-emptiveschedulingisperformed. Thedefinitionofanonpre-emptivetaskmakessenseinafullpre-emptiveoperatingsystem,• iftheexecutiontimeofthetaskisinthesamemagnitudeofthetimeofataskswitch,• ifRAMistobeusedeconomicallytoprovidespaceforsavingthetaskcontext,or• ifthetaskmustnotbepre-empted.Manyapplicationscompriseonlyfewparalleltaskswithalongexecutiontime,forwhichafullpre-emptiveoperatingsystemwouldbeconvenient,andmanyshorttaskswithadefinedexecutiontimewherenonpre-emptiveschedulingwouldbemoreefficient.Forthisconfigura-OSEKOS2.1 ©byOSEK 23 OSEK/VDXOperatingSystemSpecification2.1tion,themixedpre-emptiveschedulingpolicywasdevelopedasacompromise(seealsothedesignhintinchapter13.2.4). 4.6.4Selectingtheschedulingpolicy Thesoftwaredeveloperorthesystemintegratordeterminesthetaskexecutionsequencebyconfiguringthetaskprioritiesandassigningthepre-emptibilityasataskattribute. Wewouldliketopointoutexpresslythatthepre-emptibilityofthesystemdependsneitherontheconformanceclass,noronthetasktype.Aboveall,afullpre-emptivesystemmaythereforecontainbasictasks,andanonpre-emptivesystemextendedtasks. Ifanoperatingsystemserviceisrunning,pre-emptionandcontextswitchmightbedelayeduntilthecompletionoftheservice. 4.7Terminationoftasks IntheOSEKoperatingsystem,ataskcanonlyterminateitself(\"self-termination\"). TheOSEKoperatingsystemprovidestheserviceChainTasktoensurethatadedicatedtaskactivationisperformedjustaftertheterminationoftherunningtask.Chainingitselfputsthetaskintothelastelementofthepriorityqueue. Eachtaskhastoterminateitselfattheendofit’scode.EndingthetaskwithoutacalltoTerminateTaskorChainTaskisstrictlyforbidden! 4.8Applicationmodes ApplicationmodesaredesignedtoallowanOSEKoperatingsystemtocomeupunderdifferentmodesofoperation.Theminimumnumberofsupportedapplicationmodesisone.Itisintendedonlyformodesofoperationthataretotallymutuallyexclusive.Anexampleoftwoexclusivemodesofoperationwouldbeend-of-lineprogrammingandnormaloperation.Oncetheoperatingsystemhasbeenstarted,itisnotallowedtochangetheapplicationmode.Thecharacteristicsofapplicationmodesare:• startupperformance• supportofexclusiveapplications• supportedbyallconformanceclassesScopeofapplicationmodes ManyECUsmayexecutecompletelyindependentapplicationsase.g.factorytest,Flashpro-grammingornormaloperation.TheapplicationmodeisameanstostructurethesoftwarerunningintheECUaccordingtothosedifferentconditions.Typicallyeachapplicationmodeconsistsofanownsetoftasks,ISRsandtimingconditions,althoughthereisnolimitationtohavingataskorISRrunningindifferentmodes.Sharingatask/ISRbetweendifferentmodesisrecommendedifthesamefunctionalityisneededagain,becausecheckingthecurrentapplicationmodeinsidethetask/ISRatruntimeisveryinefficient. Havingsystemgenerationandoptimisationinmind,applicationmodesarehelpfultoreducethenumberofOSobjectstakenintoconsideration. Switchingbetweenapplicationmodesatruntimeisnotastrongrequestfromapplications.Itcouldbehelpfule.g.ifend-of-fabrication-testisdesignedasaseparatemode.Onereasonwhymodeswitchingatruntimeisnotallowedisthatnormallytimingconstrainshavetobemet 24©byOSEKOSEKOS2.1 OSEK/VDXOperatingSystemSpecification2.1throughouttheoperationasforexamplethestill-alive-protocolbetweenmainandsupervisorprocessors. 4.8.1Startupperformance ThestartupperformanceisasafetycriticalissueforECUsinautomotiveapplicationssinceresetconditionsmayoccurduringnormaloperation.Asaresultthecodeusedtodeterminetheapplicationmodeshouldbeveryquick.Itisrecommendedthatonlypinstates,orsimilarlyeasytoassessconditionsbeusedtodeterminethemode.Themodewillbedeterminedbeforethekernelisstartedandtheresultingcodeisnon-portable.Itisclearthatalengthyorcomplicatedstartingprocedureshouldbeavoided.4.8.2Supportofexclusiveapplications Applicationmodesallowindependentdevelopmentoftotallyseparatesystems. Forsystemsthatarecompletelyexclusive,thisfeaturewillallowaverycleanmechanismforindependentsystemdevelopment. 4.8.3Supportedbyallconformanceclasses Becausetheoverheadofmodedetectionisminimal,thereisnoreasontorestrictthefeatureofapplicationmodestoasubsetofconformanceclasses.Itisrequiredforallclasses.Atstartup,theusercodeusingnosystemservices(seeFigure10-2),willdeterminethemodeandpassitasaparametertotheAPI-serviceStartOS.Thiswillallowtheoperatingsystemtoloadthecorrectcontexts,andotherOSinformationtoallowtheexecutionofthecorrectapplications.Thereisnoimpactontheshutdownfunctionality. OSEKOS2.1©byOSEK25 OSEK/VDX5Interruptprocessing OperatingSystemSpecification2.1Thefunctionsforprocessinganinterrupt(InterruptServiceRoutine:ISR)aresubdividedintothreeISRcategories: ISRcategory1TheISRdoesnotuseanoperatingsystemservice.AftertheISRisfinished, processingcontinuesexactlyattheinstructionwheretheinterrupthasoccurred,i.e.theinterrupthasnoinfluenceontaskmanagement.ISRsofthiscategoryhavetheleastoverhead.ISRcategory2TheOSEKoperatingsystemprovidesanISR-frametopreparearun-time environmentforadedicateduserroutine.Duringsystemgenerationtheuserroutineisassignedtotheinterrupt.Fromtheapplications'pointofview,thiscategoryisthemostcomfortableone. Withinaninterruptserviceroutineofcategory2,usageofOSEKoperatingsystemservicesisrestrictedaccordingtoFigure5-2.ISRcategory3SuchISRscanbeusedlikecategory1ISRs.However,iftheuserneedsto callsystemservices,hehasfirsttocallEnterISR.AfterEnterISR,theISRactslikeanISRofcategory2.IfEnterISRwascalled,aLeaveISRcallisneededtoreturnfromtheISR.Thiscategoryisthemostflexibleone.TheservicesEnterISRandLeaveISRareprovidedasapartoftheAPI. BetweenEnterISRandLeaveISRrestrictionsonOSEKoperatingsystemservicesareequaltocategory2.Concerningtheuseofstack,registersandlocalvariablesoutsideandbetweenEnterISRandLeaveISRimplementationspecificrestrictionsmightapply.LeaveISRmustbethelaststatementexecutedintheISR.TheimplementationofISRcategories1and2ismandatory,whereasISRcategory3isoptional. Category1{codewithoutanyAPIcalls}}}Category2ISR(isr_name){codewithAPIcalls{Category3codewithoutanyAPIcallsEnterISR();codewithAPIcallsLeaveISR();Figure5-1ISRcategoriesoftheOSEKoperatingsystem InsidetheISRnoreschedulingwilltakeplace.ReschedulingtakesplaceonterminationoftheISRcategory2or3ifapre-emptivetaskhasbeeninterruptedandifnootherinterruptisactive. TheimplementationensuresthattasksareexecutedaccordingtotheOSEKschedulingpoints(seechapter4.6.2Fullpre-emptivescheduling).ToachievethistheimplementationmayprescriberestrictionsconcerninginterruptprioritylevelsforISRsofallcategoriesand/orperformchecksatconfigurationtime(seechapter13.2.3.2,Nestedinterruptsofdifferentcategories). 26 ©byOSEK OSEKOS2.1 OSEK/VDXOperatingSystemSpecification2.1Themaximumnumberofinterruptprioritiesdependsonthecontrollerusedaswellasontheimplementation.TheschedulingofinterruptsishardwaredependentandnotspecifiedinOSEK.Interruptsarescheduledbyhardwarewhiletasksarescheduledbythescheduler.Regardingtheinterruptprioritylevelstheremayberestrictionsasdescribedin13.2.3.2.Interruptscaninterrupttasks(nonandfullpre-emptivetasks).Ifataskisactivatedfromaninterruptroutinethetaskisscheduledaftertheendofallactiveinterruptroutines. IninterruptserviceroutinesthefollowingservicesoftheOSEKoperatingsystemcanbeused: ServiceActivateTaskTerminateTaskChainTaskScheduleGetTaskIDGetTaskStateEnterISRLeaveISREnableInterruptDisableInterruptGetInterruptDescriptorDisableAllInterruptsEnableAllInterruptsSuspendOSInterruptsResumeOSInterruptsGetResourceReleaseResourceSetEventClearEventGetEventWaitEventGetAlarmBaseGetAlarmSetRelAlarmSetAbsAlarmCancelAlarm GetActiveApplicationModeStartOSShutdownOS calledbyTaskallowedallowedallowedallowedallowedallowed----allowedallowedallowedallowedallowedallowedallowedallowedallowedallowedallowedallowedallowedallowedallowedallowedallowedallowedallowed--allowed calledbyISRcategory2and3 allowed------allowedallowedallowedallowed 55 allowedallowedallowedallowedallowedallowedallowedallowedallowedallowed--allowed--allowedallowedallowedallowedallowedallowed--allowed Figure5-2APIservicesallowedtobecalledbytasksandISRs 5 ThisserviceisallowedinISRcategory3only. ©byOSEK 27 OSEKOS2.1 OSEK/VDXSourcerelatedDisable/EnableinterruptAPI OperatingSystemSpecification2.1Operatingsystemserviceshavebeenprovidedtoenableanddisableselectedinterruptsources.Aninterruptsourcewhichhasbeendisabledwillstaydisableduntilitisre-enabledbytheapplication. Hint:Duetonormalschedulingalgorithms,interruptsorhigherprioritytasksmaydelaythetimeuntilaninterruptsourceisenabled.Tokeepthedelayshort,interruptsandtaskscanbeblockedoutusingresourcemanagement.FastDisable/EnableAPI-functions OSEKoffersfastfunctionstodisableallinterrupts(seechapter12.3.2.6,EnableAllInterruptsand12.3.2.7,DisableAllInterrupts),andtodisableallinterruptsofcategory2and3(seechapter12.3.2.8,ResumeOSInterruptsand12.3.2.9,SuspendOSInterrupts).Typicalusageistoprotectshortcriticalsections.Operatingsystemservicecallsarenotallowedbetweendisableandenablepairs.Exception:SuspendOSInterruptsandResumeOSInterruptsareallowedtobenested. 28©byOSEKOSEKOS2.1 OSEK/VDX6Eventmechanism Theeventmechanism• isameansofsynchronisation• • OperatingSystemSpecification2.1isonlyprovidedforextendedtasks initiatesstatetransitionsoftaskstoandfromthewaitingstate. Eventsareobjectsmanagedbytheoperatingsystem.Theyarenotindependentobjects,butassignedtoextendedtasks.Eachextendedtaskhasadefinitenumberofevents.Thistaskiscalledtheowneroftheseevents.Anindividualeventisidentifiedbyitsowneranditsname(ormask).Whenactivatinganextendedtask,theseeventsareclearedbytheoperatingsystem.Eventscanbeusedtocommunicatebinaryinformationtotheextendedtasktowhichtheyareassigned.Themeaningofeventsisdefinedbytheapplication,e.g.signallingofanexpiringtimer,theavailabilityofaresource,thereceptionofamessage,etc. Variousoptionsareavailabletomanipulateevents,dependingonwhetherthededicatedtaskistheowneroftheeventoranothertaskwhichdoesnotnecessarilyhavetobeanextendedtask.Alltaskscansetanyeventsofanyextendedtask.Onlytheownerisabletoclearitseventsandtowaitforthereception(=setting)ofitsevents. Eventsarethecriteriaforthetransitionofextendedtasksfromthewaitingstateintothereadystate.Theoperatingsystemprovidesservicesforsetting,clearingandinterrogationofevents,andforwaitingforeventstooccur. AnytaskorISRcansetaneventforanextendedtask,andthusinformtheextendedtaskaboutanystatuschangeviathisevent. Thereceiverofaneventisanextendedtaskinanycase.Consequently,itisnotpossibleforaninterruptserviceroutineorabasictasktowaitforanevent.Aneventcanonlybeclearedbythetaskwhichistheowneroftheevent.Extendedtasksmayonlycleareventstheyown,whereasbasictasksmustnotusetheoperatingsystemserviceforclearingevents. Anextendedtaskinthewaitingstateisreleasedtothereadystateifatleastoneeventforwhichthetaskiswaitinghasoccurred.Ifarunningextendedtasktriestowaitforaneventandthiseventhasalreadyoccurred,thetaskremainsintherunningstate. OSEKOS2.1©byOSEK29 OSEK/VDXOperatingSystemSpecification2.1Figure6-1explainssynchronisationofextendedtasksbysettingeventsincaseoffullpre-emptivescheduling,whereextendedtaskT1hasthehigherpriority. schedulereventofclearextendedtaskT1setclearextendedtaskT1waitingextendedtaskT2runningdyarerunningcleareventwaitforeventwaitingrunningrunningseteventreadyFigure6-1Fullpre-emptivesynchronisationofextendedtasks Figure6-1illustratestheprocedureswhichareeffectedbysettinganevent:TaskT1waitsfor anevent.TaskT2setsthiseventforT1.Theschedulerisactivated.Subsequently,T1istransferredfromthewaitingstateintothereadystate.DuetothehigherpriorityofT1thisresultsinataskswitch,T2beingpre-emptedbyT1.T1resetstheevent.ThereafterT1waitsforthiseventagainandtheschedulercontinuesexecutionofT2. Ifnonpre-emptiveschedulingissupposed,reschedulingdoesnottakeplaceimmediatelyaftertheeventhasbeenset(seeFigure6-2,whereextendedtaskT1isofhigherpriority) schedulereventofclearextendedtaskT1setclearextendedtaskT1waitingextendedtaskT2runningreadycleareventrunningreadywaitforeventwaitingrunningseteventreschedulingFigure6-2Nonpre-emptivesynchronisationofextendedtasks 30©byOSEKOSEKOS2.1 OSEK/VDX7Resourcemanagement OperatingSystemSpecification2.1Theresourcemanagementisusedtoco-ordinateconcurrentaccessesofseveraltaskswithdifferentprioritiestosharedresources,e.g.managemententities(scheduler),programsequences,memoryorhardwareareas. Theresourcemanagementismandatoryforallconformanceclasses. Theresourcemanagementcanoptionallybeextendedtoco-ordinateconcurrentaccessesoftasksandinterruptroutines. Resourcemanagementensuresthat• twotaskscannotoccupythesameresourceatthesametime.• priorityinversioncannotoccur.• deadlocksdonotoccurbyuseoftheseresources.• accesstoresourcesneverresultsinawaitingstate. Iftheresourcemanagementisextendedtotheinterruptlevelitassuresinadditionthat• twotasksorinterruptroutinescannotoccupythesameresourceatthesametime.Thefunctionalityofresourcemanagementisonlyrequiredinthefollowingcases:• fullpre-emptivetasks• nonpre-emptivetasks,ifresourcesarealsotoremainoccupiedbeyondascheduling point• nonpre-emptivetasks,iftheuserintendstohavetheapplicationcodeexecutedunder otherschedulingpolicies,too• resourcesharingbetweentasksandinterruptserviceroutines• resourcesharingbetweeninterruptserviceroutinesIftheuserrequiresprotectionagainstinterruptionsnotonlycausedbytasks,butalsocausedbyinterrupts,hecanalsousetheoperatingsystemservicestosetandresetinterruptmasks.Resettinginterruptmasksdoesnotcauserescheduling.(Seechapter5,Interruptprocessing,andchapter12.3,Interrupthandling). 7.1Behaviourduringaccesstooccupiedresources OSEKOSprescribestheOSEKpriorityceilingprotocol(seechapter7.5)Consequently,nosituationoccursinwhichataskoraninterrupttriestoaccessanoccupiedresource. Iftheresourceconceptisusedfortask-andinterrupt-coordinationtheOSEKoperatingsystemensuresalsothataninterruptserviceroutineisonlyprocessedifallresourceswhichmightbeoccupiedbythatinterruptserviceroutineduringitsexecutionhavebeenreleased.Additionally,OSEKstrictlyforbidsnestedaccesstothesameresource! 7.2Restrictionswhenusingresources NeitherTerminateTask,ChainTasknorWaitEventmustbecalledwhilearesourceisoccupied.Interruptserviceroutinemustnotbecompletedwitharesourceoccupied. Incaseofmultipleresourceoccupationwithinonetask,theuserhastorequestandreleaseresourcesfollowingtheLIFOprinciple(stack). OSEKOS2.1 ©byOSEK 31 OSEK/VDX7.3Schedulerasaresource OperatingSystemSpecification2.1Ifataskhastoprotectitselfagainstpre-emptionsbyothertasks,itcanlockthescheduler.Thescheduleristreatedlikearesourcewhichisaccessibletoalltasks.ThereforearesourcewithapredefinednameRES_SCHEDULERisgenerated. Interruptsarereceivedandprocessedindependentofthestateoftheresourcescheduler.However,itpreventsthereschedulingoftasks. 7.4Generalproblemswithsynchronisationmechanisms 7.4.1Explanationofpriorityinversion Atypicalproblemofcommonsynchronisationmechanisms-e.g.theuseofsemaphores-istheproblemrelatingtopriorityinversion. Thismeansthatalower-prioritytaskdelaystheexecutionofhigher-prioritytask.OnesolutiontoavoidpriorityinversionistousetheOSEKPriorityCeilingProtocol(seechapter7.5).Figure7-1illustratessequencingofthecommonaccessoftwotaskstoasemaphore(inafullpre-emptivesystem,taskT1hasthehighestpriority) TaskT4whichhasalowpriority,occupiesthesemaphoreS1.T1pre-emptsT4andrequeststhesamesemaphore.AsthesemaphoreS1isalreadyoccupied,T1entersthewaitingstate.Nowthelow-priorityT4isinterruptedandpre-emptedbytaskswithaprioritybetweenthoseofT1andT4.T1canonlybeexecutedafteralllower-prioritytaskshavebeenterminated,andthesemaphoreS1hasbeenreleasedagain.AlthoughT2andT3donotusesemaphoreS1,theydelayT1withtheirruntime. adreyaccesstosemaphoreS1denied waiting running running running runningsuspendedsuspended ready taskT1taskT2taskT3taskT4 suspendedsuspendedsuspendedrunning runningreadyreadyready semaphoreS1occupiedsemaphoreS1released Figure7-1Priorityinversiononoccupyingsemaphores 32©byOSEKOSEKOS2.1 OSEK/VDX7.4.2Deadlocks OperatingSystemSpecification2.1Anothertypicalproblemofcommonsynchronisationmechanisms,suchastheuseofsema-phores,istheproblemofdeadlocks.Inthiscasedeadlockmeanstheimpossibilityoftaskexecutionduetoinfinitewaitingformutuallylockedresources. Thefollowingscenarioresultsinadeadlock(seeFigure7-2): TaskT1occupiesthesemaphoreS1andsubsequentlycannotcontinuerunning,e.g.becauseitiswaitingforanevent.Thus,thelower-prioritytaskT2istransferredintotherunningstate.ItoccupiesthesemaphoreS2.IfT1getsreadyagainandtriestooccupysemaphoreS2,itentersthewaitingstateagain.IfnowT2triestooccupysemaphoreS1,thisresultsinadeadlock. e.gwaitaccessto semaphoreS1foreventtaskT1taskT2 runningready waitingrunning eventaccesstosemaphoreS2happeneddenied yadrerunning waiting Deadlock! ready running waiting accessto semaphoreS2accessto semaphoreS1denied Figure7-2Deadlocksituationusingsemaphores 7.5OSEKPriorityCeilingProtocol ToavoidtheproblemsofpriorityinversionanddeadlockstheOSEKoperatingsystemrequiresfollowingbehaviour: • Atthesystemgeneration,toeachresourceitsownceilingprioritywillbeassigned.Theceilingprioritywillbesetatleasttothehighestpriorityofalltasksthataccessaresource.Theceilingprioritymustbelowerthanthelowestpriorityofalltasksthatdonotaccesstheresource,andwhichhaveprioritieshigherthanthehighestpriorityofalltasksthataccesstheresource.• Ifataskrequiresaresource,anditscurrentpriorityislowerthantheceilingpriorityoftheresource,thepriorityofthetaskwillberaisedtotheceilingpriorityoftheresource.• Ifthetaskreleasestheresource,thepriorityofthistaskwillberesettotheprioritybeforerequiringthatresource.Priorityceilingresultsinapossibletimedelayfortaskswithprioritiesequalorbelowtheresourcepriority.Thisdelayislimitedbythemaximumtimetheresourceisoccupiedbyanylowerprioritytask. Taskswhichmightoccupythesameresourceastherunningtaskdonotentertherunningstate,duetotheirlowerorequalprioritythantherunningtask.Ifaresourceoccupiedbyataskisreleased,othertaskwhichmightoccupytheresourcecanentertherunningstate.Forpre-emptivetasksthisisapointofrescheduling. OSEKOS2.1©byOSEK33 OSEK/VDXtaskT0ceilingprioritysuspendedrunningsuspendedOperatingSystemSpecification2.1releaseresourcereleaseresourcerunningreadysuspendedsuspendedsuspendedrunningreadyrunningreadyreadyreadyrunningrunningsuspendedrunningsuspendedrunningrunningtaskT1taskT2taskT3taskT4requestresourcerequestresourceFigure7-3Resourceassignmentwithpriorityceilingbetweenpre-emptivetasks. TheexampleshowninFigure7-3illustratesthemechanismofthepriorityceiling.TaskT0hasthehighest,andtaskT4thelowestpriority.TaskT1andtaskT4wanttoaccessthesameresource.Thesystemshowsclearlythatnounboundedpriorityinversionisentailed.Thehigh-prioritytaskT1waitsforashortertimethanthemaximumdurationofresourceoccupationbyT4. 7.6OSEKPriorityCeilingProtocolwithextensionsforinterruptlevels Theextensionofresourcemanagementtointerruptlevelisoptional. Todeterminetheceilingpriorityofresourceswhichareusedininterrupts,virtualprioritieshigherthanalltasksprioritiesareassignedtointerrupts.Thecalculatedceilingprioritymeansforaresourcewhichisonlyoccupiedbytasksadifferenthandlingthanforaresourceoccupiedbytasksandinterruptroutines.Themanipulationofsoftwareprioritiesandofhardwareinterruptlevelsisuptotheimplementation. • Atthesystemgeneration,toeachresourceitsownceilingprioritywillbeassigned.Theceilingprioritywillbesetatleasttothehighestpriorityofalltasksandinterruptroutinesthataccessaresource.Theceilingprioritymustbelowerthanthelowestpriorityofalltasksorinterruptroutinesthatdonotaccesstheresource,andwhichhaveatthesametimehigherprioritiesthanthehighestpriorityofalltasksorinterruptroutinesthataccesstheresource.• Ifataskorinterruptroutinerequiresaresource,anditscurrentpriorityislowerthantheceilingpriorityoftheresource,thepriorityofthetaskorinterruptwillberaisedtotheceilingpriorityoftheresource.• Ifthetaskorinterruptroutinereleasestheresource,thepriorityofthistaskorinterruptwillberesettotheprioritybeforerequiringthatresource.Tasksorinterruptroutineswhichmightoccupythesameresourceastherunningtaskorinterruptroutinehasoccupieddonotrun,duetotheirlowerorequalprioritythantherunningtaskorinterruptroutine.Ifaresourceoccupiedbyataskisreleased,anothertaskorinterruptroutineswhichmightoccupytheresourcecouldrun.Forpre-emptivetasksthisisapointofrescheduling. 34©byOSEKOSEKOS2.1 OSEK/VDXinterruptoccursisrINT2ceilingpriorityexecutionOperatingSystemSpecification2.1releaseresourcerunninginterruptedpendingexecutionisrINT1interruptoccurstaskT3taskT2taskT1suspendedsuspendedrunningreadyreadyrunningsuspendedrunningsuspendedrunningreadyrequestresourceFigure7-4 Resourceassignmentwithpriorityceilingbetweenpre-emptivetasksandinterruptservicesroutines. Theexampleshowninfigure7-4describesthefollowingscenario: Thepre-emptivetaskT1isrunningandrequestsaresourcesharedwiththeinterruptserviceroutineINT1.ThetaskT1activatesthehigherpriortasksT2andT3.BecauseofOSEK PriorityCeilingProtocolthetaskT1isstillrunning.InterruptINT1occurs.BecauseofOSEKPriorityCeilingProtocolthetaskT1isstillrunning,theinterruptINT1ispending.InterruptINT2occurs.TheinterruptserviceroutineINT2interruptsthetaskT1anditisexecuted.AfterINT2isdonethetaskT1iscontinued.ThetaskT1releasestheresource.TheinterruptserviceroutineINT1isexecuted,thetaskT1isinterrupted.AfterINT1isdonetheTask3isrunning.AfterterminationoftaskT3thetaskT2isrunning.AfterterminationoftaskT2thetaskT1iscontinued. Theexamplebelowshowninfigure7-5describesthefollowingscenario: Thepre-emptivetaskT1isrunning.TheinterruptINT1occurs.ThetaskT1isinterruptedandtheinterruptserviceroutineINT1isexecuted..TheINT1requestsaresourcesharedwiththeinterruptserviceroutineINT2.ThehigherpriorinterruptINT2occurs.BecauseofOSEKPriorityCeilingProtocoltheINT1isstillexecuted,theINT2ispending.TheinterruptINT3occurs.BecauseofhigherprioritythantheINT1,theINT3interruptsthisinterruptserviceroutineandisexecuted.TheINT3activatesthetaskT2.AftertheINT3isdonetheINT1iscontinued.AftertheINT1releasestherequestedresourcetheINT2isexecutedbecauseofhigherprioritythantheINT1.AftertheINT2isdonetheINT1iscontinued.AftertheINT1isdonethetaskT2isrunningbecauseofhigherprioritythanthetaskT1,thetaskT1isready.AfterthetaskT2isterminatedthetaskT1iscontinued. OSEKOS2.1©byOSEK35 OSEK/VDXinterruptoccursisrINT3ceilingpriorityexecutionOperatingSystemSpecification2.1releaseresourceexecutioninterruptedinterruptoccursisrINT2pendingexecutionisrINT1interruptoccursexecutioninterruptedrequestresourcetaskT2taskT1runningsuspendedreadyreadyrunningsuspendedrunningFigure7-5 Resourceassignmentwithpriorityceilingbetweeninterruptservicesroutines 36©byOSEKOSEKOS2.1 OSEK/VDX8Alarms OperatingSystemSpecification2.1TheOSEKoperatingsystemprovidesservicesforprocessingrecurringevents.Sucheventsmaybeforexampletimerswhichprovideaninterruptatregularintervals,orencodersataxleswhichgenerateaninterruptincaseofaconstantchangeofa(camshaftorcrankshaft)angle,orotherregularapplicationspecifictriggers. TheOSEKoperatingsystemprovidesatwo-stageconcepttoprocesssuchevents.Therecurringevents(sources)areregisteredbyimplementationspecificcounters.Basedoncounters,theOSEKoperatingsystemsoftwareoffersalarmmechanismstotheapplicationsoftware. 8.1Counters Acounterisrepresentedbyacountervalue,measuredin”ticks”,andsomecounterspecificconstants. TheOSEKoperatingsystemdoesnotprovideastandardisedAPItomanipulatecountersdirectly. TheOSEKoperatingsystemtakescareofthenecessaryactionsofmanagingalarmswhenacounterisadvancedandhowthecounterisadvanced. TheOSEKoperatingsystemoffersatleastonecounterwhichisderivedfroma(hardwareorsoftware)timer.Theusercanassumetheexistenceofthiscounter. 8.2Alarmmanagement TheOSEKoperatingsystemprovidesservicestoactivatetasksorseteventswhenanalarmexpires.Analarmwillexpirewhenapredefinedcountervalueisreached.Thiscountervaluecanbedefinedrelativetotheactualcountervalue(ðrelativealarm)orasanabsolutevalue(ðabsolutealarm).Alarmscanbedefinedtobeeithersinglealarmsorcyclicalarms.Alarmsmaybeforexamplethereceiptofanumberoftimerinterrupts,aspecificangularposition,orreceivingamessage.InadditiontheOSprovidesservicestocancelalarmsandtogetthecurrentstateofanalarm. Morethanonealarmcanbeattachedtoacounter. Analarmisstaticallyassignedatsystemgenerationtimeto:• onecounter• onetask Dependingonconfigurationthistaskwillbeactivated,oraneventwillbesetforthistask whenthealarmexpires.Taskactivationandeventsettingwhenanalarmexpireshavethesamepropertiesasnormaltaskactivationandeventsetting. OSEKOS2.1©byOSEK37 OSEK/VDXsourceforcounterOperatingSystemSpecification2.1implementationOSinternalapplicationviewcounteralarmsFigure8-1Layeredmodelofalarmmanagement Countersandalarmsaredefinedstatically.Theassignmentofalarmstocounters,aswellastheactiontobeperformedwhenanalarmexpires,aredefinedstatically,too. Dynamicparametersarethecountervaluewhenanalarmhastoexpire,andtheperiodforcyclicalarms. 38©byOSEKOSEKOS2.1 OSEK/VDX9Messages OperatingSystemSpecification2.1ForanOSEKimplementationtobecompliant,messagehandlingforintraprocessor communicationhastobeoffered.TheminimumfunctionalityrequiredisCCCAasdescribedintheOSEKCOMspecification.CCCAdescribesacommunicationconformanceclass specificallytailoredtotheneedsofintraprocessorcommunicationwhichsupportsunqueuedmessages.CCCBdefinesanextensionwhichaddsqueuedmessages. IfanimplementationoffersevenmorefunctionalitywhichisspecifiedinotherconformanceclassesdescribedintheOSEKCOMspecification,theimplementationmuststicktosyntaxandsemanticoftherespectiveOSEKCOMfunctionality. PleasenotethatformessagestherulesstatedintheOSEKCOMspecificationarevalid.Forexample,OSEKCOMsysteminterfacesdonotcallErrorHook.However,iftheOSEKCOMfunctionalityinternallycallsOSsystemfunctionlikeActivateTask,ErrorHookwillbecalledifnecessaryfromActivateTask.Formoredetails,refertotheOSEKCOMspecification. OSEKOS2.1©byOSEK39 OSEK/VDXOperatingSystemSpecification2.110Errorhandling,tracinganddebugging 10.1Hookroutines TheOSEKoperatingsystemprovidessystemspecifichookroutinestoallowuser-definedactionswithintheOSinternalprocessing.ThefirstparameterisfixedforallimplementationsofOSEKoperatingsystems,additionalparametersareoptionalandimplementationdependent.Thosehookroutinesare• calledbytheoperatingsystem,inaspecialcontextdependingontheimplementationof theoperatingsystem• higherpriorthanalltasks• notinterruptedbycategory2and3interruptroutines• usinganimplementationdependentcallinginterface.• partoftheoperatingsystem• implementedbytheuserwithuserdefinedfunctionality• standardisedininterfaceperOSEKOSimplementation,butnotstandardisedin functionality(environmentandbehaviourofthehookroutineitself),thereforeusuallyhookroutinesarenotportable• areonlyallowedtouseasubsetofAPIfunctions• optional(theimplementationshouldomitcallstohookroutineswhichdonotexist)IntheOSEKoperatingsystemhookroutinesmaybeusedfor:• systemstart-up(seechapter10.3,Systemstart-up). Thecorrespondinghookroutine(StartupHook)iscalledaftertheoperatingsystemstart-upandbeforetheschedulerisrunning.• systemshutdown(seechapter10.4,Systemshutdown). Thecorrespondinghookroutine(ShutdownHook)iscalledwhenasystemshutdownisrequestedbytheapplicationorbytheoperatingsystemincaseofasevereerror.• tracingorapplicationdependentdebuggingpurposesaswellasuserdefinedextensions ofthecontextswitch(seechapter10.5,Debugging).• errorhandling. EachimplementationofOSEKhastodescribetheinterfacesandconventionsforthehookroutines. IftheapplicationcallsanotallowedAPIserviceinhookroutinesthebehaviourisnotdefined.Ifanerrorisraised,theimplementationshouldreturnanimplementationspecificerrorcode. 40©byOSEKOSEKOS2.1 OSEK/VDXService ActivateTaskTerminateTaskChainTaskScheduleGetTaskIDGetTaskStateEnterISRLeaveISREnableInterruptDisableInterruptGetInterruptDescriptorDisableAllInterruptsEnableAllInterruptsSuspendOSInterruptsResumeOSInterruptsGetResourceReleaseResourceSetEventClearEventGetEventWaitEventGetAlarmBaseGetAlarmSetRelAlarmSetAbsAlarmCancelAlarm GetActiveApplicationModeStartOSShutdownOS OperatingSystemSpecification2.1PostTaskHook --------allowedallowed--------allowed----------------allowed--allowedallowed------allowed---- ErrorHook --------allowed--------allowed----------------allowed--allowedallowed------allowed--allowed 6 PreTaskHook --------allowedallowed--------allowed----------------allowed--allowedallowed------allowed---- StartupHook allowed--------------------------------------------------allowed--allowed ShutdownHook ----------------------------------------------------allowed---- allowed Figure10-1APIservicesforhookroutines Mostoperatingsystemservicesarenotallowedforhookroutines.Thisrestrictionisnecessarytoreducesystemcomplexity. 10.2Errorhandling AnerrorserviceisprovidedtohandletemporarilyandpermanentlyoccurringerrorswithintheOSEKoperatingsystem.Itsbasicframeworkispredefinedandhastobecompletedbytheuser.Thisgivestheuserachoiceofefficientcentralisedordecentralisederrorhandling. 6 Itmayhappenthatcurrentlynotaskisrunning.InthiscasetheservicereturnsthetaskIDINVALID_TASK(seechapter12.2.3.5GetTaskID). ©byOSEK 41 OSEKOS2.1 OSEK/VDXOperatingSystemSpecification2.1Twodifferentkindsoferrorsaredistinguished:• Applicationerrors Theoperatingsystemcouldnotexecutetherequestedservicecorrectly,butassumesthecorrectnessofitsinternaldata. Inthiscase,centralisederrortreatmentiscalled.Additionallytheoperatingsystemreturnstheerrorbythestatusinformationfordecentralisederrortreatment.Itisuptotheusertodecidewhattododependingonwhicherrorhasoccured.• Fatalerrors Theoperatingsystemcannolongerassumecorrectnessofitsinternaldata.Inthiscasetheoperatingsystemcallsthecentralisedsystemshutdown.Allthoseerrorservicesareassignedwithaparameterthatspecifiestheerror. ThereturnvalueoftheOSEKAPI-serviceshasprecedenceovertheoutputparameters.IfanAPIservicereturnsanerror,thevaluesoftheoutputparametersareundefined. Thecorrespondinghookroutine(ErrorHook)iscalledifasystemservicereturnsaStatusTypevaluenotequaltoE_OK.ThehookroutineErrorHookisnotcalledifasystemserviceiscalledfromtheErrorHookitself(i.e.,arecursivecalloferrorhookneveroccurs).AnypossiblyoccuringerrorbycallingsystemservicesfromtheErrorHookcanonlybedetectedbyevaluatingthereturnvalue. ErrorHookalsoiscalledifanerrorisdetectedduringtaskactivationoreventsetting,forexampleuponalarmexpirationormessagearrival. Ifataskisactivatedintheversionwithstandardstatus,only\"E_OK\"isreturned.Moreover,inaversionwithextendedstatus,theadditionalreturnvalues\"Taskisinvalid\"or\"Toomanytaskactivations\etc.canbereturned.Theseextendedreturnvaluesmustnolongeroccurinthetargetapplicationatthetimeofexecution,i.e.thecorrespondingerrorsarenotinterceptedintheruntimeversionoftheoperatingsystem. 10.3Systemstart-up Initialisationafteraprocessorresetisuptotheimplementation,butOSEKOSofferssupportforastandardisedwayofinitialisation. Interfacesforinitialisationofhardware,operatingsystemandapplicationhavetobeclearlydefinedbytheimplementation. OSEKOSdoesnotforcetheapplicationtodefinespecialtaskswhichhavetobestartedaftertheoperatingsysteminitialisation,butitallowstheusertospecifyautostart-tasksduringsystemgeneration. AfteraresetoftheCPU,hardware-specificapplicationsoftwareisexecuted(nooperatingsystemcontext).Thenon-portablesectionendswiththedetectionoftheapplicationmode.Forsafetyreasonsthisdetectionshouldnotrelyonsystemhistory. Theportablesectionoftheapplicationstartswiththecalltoafunctionwhichstartsuptheoperatingsystem,i.e.StartOSwiththeapplicationmodeasaparameter.Aftertheoperatingsystemisinitialised(schedulerisnotrunning),itcallsthehookroutineStartupHook,wheretheusercanplacetheinitialisationcodeforallhisoperatingsystemdependentinitialisation.InordertostructuretheinitialisationcodeinStartupHookaccordingtothestartedapplicationmode,theserviceGetActiveApplicationModeisprovided.Afterthereturnfromthathookroutinetheoperatingsystemsenablestheinterruptsaccordingtothe 42©byOSEKOSEKOS2.1 OSEK/VDXOperatingSystemSpecification2.1INITIAL_INTERRUPT_DESCRIPTOR7,andstartsthescheduler.Afterthatthesystemisrunningandexecutesusertasks. (Re-)Starthardware-specificcalltoinitializationcodeStartOS12OSexecutesoperatingsysteminitializationcode3OSexecutesStartupHook4OSkernelisrunning5firstusertaskisrunningDuringStartupHookalluserinterruptsaredisabledFigure10-2Systemstart-up (1)Afterareset,theuserisfreetoexecute(non-portable)hardwarespecificcode.Interruptsofcategory2and3arenotallowedtorununtilthephase5.Thenon-portablesectionendsbydetectionoftheapplicationmode. (2)CallStartOSwiththeapplicationmodeasaparameter.Thiscallstartstheoperatingsystem. (3)Theoperatingsystemperformsinternalstart-upfunctionsand (4)callsthehookroutineStartupHook,wheretheusermayplaceinitialisationprocedures.Duringthishookroutine,alluserinterruptsaredisabled.(5)TheoperatingsystemenablesuserinterruptsaccordingtotheINITIAL_INTERRUPT_DESCRIPTOR,andstartstheschedulingactivity.TheINITIAL_INTERRUPT_DESCRIPTORisstaticallyassignedbytheuser. 10.4Systemshutdown TheOSEKOSspecificationdefinesaservicetoshutdowntheoperatingsystem,ShutdownOSThisservicecanberequestedbytheapplicationorbytheoperatingsystemduetoafatalerror.WhenShutdownOSiscalledtheoperatingsystemwillcallthehookroutineShutdownHookandshutdownafterwards. TheuserisfreetodefineanysystembehaviourinShutdownHooke.g.nottoreturnfromtheroutine.(Seechapter12.7.2.3,ShutdownOS). 7 ThevalueoftheINITIAL_INTERRUPT_DESCRIPTORisdefinedbytheuserorbytheimplementation. ©byOSEK 43 OSEKOS2.1 OSEK/VDX10.5Debugging OperatingSystemSpecification2.1Twohookroutines(PreTaskHookandPostTaskHook)arecalledontaskcontextswitches.Thesetwohookroutinesmaybeusedfordebuggingortimemeasurement(includingcontextswitchtime).ThereforePostTaskHookiscalledafterleavingthecontextoftheoldtask,PreTaskHookiscalledbeforeenteringthecontextofanewtask. PostTaskHookOSinternalactivitiesPreTaskHooktaskT1taskT2runningsuspendedreadyrunningFigure10-3PreTaskHookandPostTaskHook WhenShutdownOSiscalledwhileataskisrunningShutdownOSmayormaynotcallPostTaskHook.IfPostTaskHookiscalleditisundefinedifitiscalledbeforeorafterShutdownHook. 44©byOSEKOSEKOS2.1 OSEK/VDX11Descriptionofsystemservices 11.1Definitionofsystemobjects OperatingSystemSpecification2.1WithintheOSEKoperatingsystemallsystemobjectshavetobedeterminedstaticallybytheuser.Thedefinitionoftheoperatingsystemobjectsisprovidedbytheoperatingsystemsupplier.Theactualcreationoftheobjects(uniquenamesandspecificcharacteristics)isdoneduringthesystemgenerationphase.Thedeclarationsdoneintheapplicationsourceareexternalreferencestothoseoperatingsystemobjects.Therearenosystemservicesavailabletodynamicallycreatesystemobjects.Declarationsprovideinformationthatasystemobjectistobeusedwhichhasbeencreatedatanotherlocation.Thenamesareusedasidentificationswithinthesystemservices. UsuallythescopeofthosenamesislikeanexternalvariableinC-language. Thecreationofsystemobjectswithinthesourceshouldbeconsideredasanexception,duetolossofportability. Internalrepresentationofsystemobjectsisimplementationspecific.Therearevariousalternativesforimplementationofsystemobjects.Forexample,aTaskTypecouldbeimplementedeitherasapointertothedatastructureofthetaskorasanindextothecorrespondinglistelement.Applicationprogrammerscannotassumeaspecificrepresentation.Thecreationofsystemobjectsmayrequireadditionaltools.Theyenabletheusertoaddortomodifyvalueswhichhavebeenspecifiedindefinitions.Consequently,thesystemgenerationandthetoolsusedtothiseffectarealsoimplementation-specific. 11.2Conventions 11.2.1Typeofcalls ThesystemserviceinterfaceisISO/ANSI-C.Itsimplementationisnormallyafunctioncall,butmayalsobesolveddifferently,asrequiredbytheimplementation-forexamplebymacrosoftheCpre-processor.Aspecifictypeofimplementationcannotbeassumed.11.2.2Legitimacyofcalls Systemservicesarecalledfromtasks,interruptserviceroutines,andhookroutines.Dependingonthesystemservice,theremayberestrictionsregardingtheavailability.Furtherrestrictionsareimposedbytheconformanceclasses.11.2.3Errorcharacteristics Tokeepthesystemefficientandfast,theOSEKoperatingsystemdoesnottestallerrors.Iftheapplicationusesoperatingsystemservicesincorrectly,undefinedsystembehaviourmayresult. Mostsystemservicesreturnastatustotheuser.ThereturnstatusisE_OKifitwaspossibletoexecutethesystemservicewithoutanyrestrictions.Ifthesystemrecognisesanexceptionalconditionwhichrestrictsexecutionofthesystemservice,adifferentstatusisreturned.AstatusotherthanE_OKmaybeinformationwhichisnotconsideredtobeanerror(\"warning\").AnexampleisthereturnstatusofthesystemserviceCancelAlarm,whichinformsthatthealarmtobecancelledhasalreadyexpired.Auserprogramisthusinformedthate.g.a OSEKOS2.1 ©byOSEK 45 OSEK/VDXOperatingSystemSpecification2.1taskactivationhastakenplacewhichwasnotwanted.Thedetectionofmilderrors(warnings)ispartofthesystemservices. Ifitispossibletoexcludeerrorsbeforeruntime,theruntimeversionmayomitcheckingoftheseerrors.IftheonlypossiblereturnstatusisE_OK,theimplementationisfreenottoreturnastatus. Allreturnvaluesofasystemservicearelistedundertheindividualdescriptions.Thereturnstatusdistinguishesbetweenthe”standard”and”extended”status.The”standard”versionfulfilstherequirementsofadebuggedapplicationsystemasdescribedbefore.The\"extended\"versionisconsideredtosupporttestingofnotyetfullydebuggedapplications.Itcomprisesextendederrorcheckingcomparedtothestandardversion. Thesequenceoferrorcheckingwithintheoperatingsystemisnotspecified.Whenevermultipleerrorsoccur,itisimplementationdependentwhichstatusisreturnedtotheapplication. Incaseofapplicationerrors,theOSEKoperatingsystemwillcallthehookroutineErrorHookifdefined.ThepurposeofErrorHookistotreatstatusinformationcentralised. Incaseoffatalerrors,thesystemservicedoesnotreturntotheapplication,butactivatesShutdownOS.Anexampleisanon-detectedincorrectparameterofasystemservicewhichgeneratesaninconsistencyinthesystem.TheparameterpassedtoShutdownOSisanimplementationdependentsystemerrorcode.Systemerrorcodesoccupyarangeofnumbersoftheirownanddonotconflictwiththestatesoftheoperatingsystemservices. ThefunctionalityofShutdownOSisimplementation-specific.Possibleimplementationsaretostoptheapplicationortoissueanassertion.TheapplicationitselfcanaccessShutdownOStoshutdowntheoperatingsysteminacontrolledfashion. CallingofShutdownOSisalsorecommendedwhenprocessingnon-assignableerrors,forexample\"illegalinstructioncode\".Thisisnotrequiredbecausethismustbesupportedbythehardware,whichcannotbetakenforgranted. 46©byOSEKOSEKOS2.1 OSEK/VDXOperatingSystemSpecification2.112Specificationofoperatingsystemservices Structureofthedescription Operatingsystemservicesarearrangedinlogicalgroups.Acoherentdescriptionisprovidedforallservicesofthetaskmanagement,theinterruptmanagement,etc. Thedescriptionofeachlogicalgroupstartswithdatatypedefinitions.Adescriptionofthegroup-specificconstructionalelementsandsystemservicesfollows.Thelastitemsareadescriptionofconstants,andofanyadditionalconventions.Constructionalelements Thedescriptionofconstructionalelementscontainsthefollowingfields:Syntax:InterfaceinC-likesyntax.Parameter(In):Listofallinputparameters.Description:Explanationoftheconstructionalelement.Particularities:Explanationofrestrictionsrelatingtotheutilisation.Conformance:Specifiestheconformanceclasseswheretheconstructional elementisprovided.Servicedescription Aservicedescriptioncontainsthefollowingfields:Syntax:InterfaceinC-likesyntax.Parameter(In):Listofallinputparameters.Parameter(Out):Listofalloutputparameters.Description:Explanationofthefunctionalityoftheoperatingsystemservice.Particularities:Explanationofrestrictionsrelatingtotheutilisationoftheop-eratingsystemservice.Status:Listofpossiblereturnvalues. Standard:•Listofreturnvaluesprovidedintheoperatingsystem'sstan-dardversion.Specialcase:Servicedoesnotreturn. Extended:•Listofadditionalreturnvaluesintheoperatingsystem'sex-tendedversion. Conformance:Specifiestheconformanceclasseswheretheoperatingsystem serviceisprovided.Thespecificationofoperatingsystemservicesusesthefollowingnamingconventionsfordatatypes:...Type:...RefType: describesthevaluesofindividualdata(includingpointers).describesapointertothe...Type(forcallbyreference). 12.1Commondatatypes StatusType ThisdatatypeisusedforallstatusinformationtheAPIservicesoffer.Namingconvention:allerrorsforAPIservicesstartwithE_.ThosereservedfortheoperatingsystemwillbeginwithE_OS_. OSEKOS2.1 ©byOSEK 47 OSEK/VDXThefollowingerrorvaluesaredefined: OperatingSystemSpecification2.1ThenormalreturnvalueisE_OKwhichisassociatedwiththevalue0. AllerrorsofAPIservices:• E_OS_ACCESS=1,• E_OS_CALLEVEL=2,• E_OS_ID=3,• E_OS_LIMIT=4,• E_OS_NOFUNC=5,• E_OS_RESOURCE=6,• E_OS_STATE=7,• E_OS_VALUE=8 IftheonlypossiblereturnstatusisE_OK,theimplementationisfreenottoreturnastatus,thisisnotseparatelystatedinthedescriptionoftheindividualservices.Internalerrorsoftheoperatingsystem: Theseerrorsareimplementationspecificandnotpartoftheportablesection.Theerrornamesresideinthesamename-spaceastheerrorsforAPIservicesmentionedabove,i.e.therangeofnumbersmustnotoverlap. Toshowthedifferenceinuse,thenamesinternalerrorsmuststartwithE_OS_SYS_Examples:• E_OS_SYS_STACK• E_OS_SYS_PARITY• ...andotherimplementation-specificerrors,whichhavetobedescribedinthevendor-specificdocument.ThenamesandrangeofnumbersoftheinternalerrorsoftheOSEKoperatingsystemdonotoverlapthenamesandrangeofnumbersofotherOSEKservices(i.e.communicationandnetworkmanagement)ortherangeofnumbersoftheAPIerrorvalues. 12.2Taskmanagement 12.2.1DatatypesTaskType Thisdatatypeidentifiesatask. TaskRefType ThisdatatypepointstoavariableofTaskType.TaskStateType Thisdatatypeidentifiesthestateofatask. TaskStateRefType ThisdatatypepointstoavariableofthedatatypeTaskStateType. 48©byOSEKOSEKOS2.1 OSEK/VDX12.2.2Constructionalelements OperatingSystemSpecification2.112.2.2.1DeclareTaskSyntax:DeclareTask(TaskIdentifier)Parameter(In): -Taskidentifier(C-identifier) Description:DeclareTaskservesasanexternaldeclarationofatask.The functionanduseofthisservicearesimilartothatoftheexter-naldeclarationofvariables. Particularities:-Conformance:BCC1,BCC2,ECC1,ECC212.2.3Systemservices 12.2.3.1ActivateTaskSyntax:StatusTypeActivateTask(TaskType TaskIDTaskreferenceParameter(Out):noneDescription:Thetask 8 thereadystate.Theoperatingsystemensuresthatthetaskcodeisbeingexecutedfromthefirststatement. Particularities:Theservicemaybecalledfrominterruptlevel,fromtasklevel andthehookroutineStartupHook(seeFigure10-1). ReschedulingafterthecalltoActivateTaskdependsontheplaceitiscalledfrom(ISR,non-preemptivetask,preemptivetask). IfE_OS_LIMITisreturnedtheactivationisignored. Whenanextendedtaskistransferredfromsuspendedstateintoreadystateallitseventsarecleared. Status: Standard:•Noerror,E_OK Extended:•Task •Toomanytaskactivationsof Conformance:BCC1,BCC2,ECC1,ECC2 ActivateTaskwillnotimmediatelychangethestateofthetaskincaseofmultipleactivationrequests.Ifthetaskisnotsuspended,theactivationwillonlyberecordedandperformedlater.OSEKOS2.1 ©byOSEK 49 8 OSEK/VDXOperatingSystemSpecification2.112.2.3.2TerminateTaskSyntax:StatusTypeTerminateTask(void)Parameter(In):noneParameter(Out):noneDescription:Thisservicecausestheterminationofthecallingtask.The callingtaskistransferredfromtherunningstateintothesuspendedstate9. Particularities:Theresourcesoccupiedbythetaskmusthavebeenreleased beforethecalltoTerminateTask.Iftheresourceisstilloccupiedinstandardstatusthebehaviourisundefined. Ifthecallwassuccessful,TerminateTaskdoesnotreturntothecalllevelandthestatuscannotbeevaluated. Iftheversionwithextendedstatusisused,theservicereturnsincaseoferror,andprovidesastatuswhichcanbeevaluatedintheapplication. IftheserviceTerminateTaskiscalledsuccessfully,itenforcesarescheduling. EndingataskfunctionwithoutcalltoTerminateTaskorChainTaskisstrictlyforbiddenandmayleavethesysteminanundefinedstate. Status: Standard:Noreturntocalllevel Extended:•Taskstilloccupiesresources,E_OS_RESOURCE •Callatinterruptlevel,E_OS_CALLEVEL Conformance:BCC1,BCC2,ECC1,ECC212.2.3.3ChainTaskSyntax:StatusTypeChainTask(TaskType TaskIDReferencetothesequentialsucceedingtasktobeactivated.Parameter(Out):noneDescription:Thisservicecausestheterminationofthecallingtask.After terminationofthecallingtaskasucceedingtask Particularities:Ifthesucceedingtaskisidenticalwiththecurrenttask,this doesnotresultinmultiplerequests.Thetaskisnottransferedtothesuspendedstate. TheresourcesoccupiedbythecallingtaskmusthavebeenreleasedbeforeChainTaskiscalled.Iftheresourceisstilloccupiedinstandardstatusthebehaviourisundefined. Incaseoftaskswithmultipleactivationrequests,terminatingthecurrentinstanceofthetaskautomaticallyputsthenextinstanceofthesametaskintothereadystate.50 ©byOSEK OSEKOS2.1 9 OSEK/VDXOperatingSystemSpecification2.1Ifcalledsuccessfully,ChainTaskdoesnotreturntothecalllevelandthestatuscannotbeevaluated. Iftheversionwithextendedstatusisused,theservicereturnsincaseoferrortothecallingtask,andprovidesastatuswhichcanthenbeevaluatedintheapplication. IftheserviceChainTaskiscalledsuccessfully,thisenforcesarescheduling. EndingataskfunctionwithoutcalltoTerminateTaskorChainTaskisstrictlyforbiddenandmayleavethesysteminanundefinedstate. IfE_OS_LIMITisreturnedtheactivationisignored. Whenanextendedtaskistransferredfromsuspendedstateintoreadystateallitseventsarecleared. Status: Standard:Extended: ••••• Noreturntocalllevel Task Toomanytaskactivationsof Conformance:12.2.3.4ScheduleSyntax: Parameter(In):Parameter(Out):Description: Particularities: StatusTypeSchedule(void)nonenone Ifahigher-prioritytaskisready,thecurrenttaskisputintothereadystate,itscontextissavedandthehigher-prioritytaskisexecuted.Otherwisethecallingtaskiscontinued. Innonpre-emptivetasksScheduleenablesaprocessorassignmenttoothertasksinapplication-specificlocations.Thisservicehasnoinfluenceonfullpre-emptivetasks. Status: Standard:Extended:Conformance: •Noerror,E_OK •Callatinterruptlevel,E_OS_CALLEVELBCC1,BCC2,ECC1,ECC2 12.2.3.5GetTaskIDSyntax:StatusTypeGetTaskID(TaskRefType TaskIDReferencetothetaskwhichiscurrentlyrunningDescription:GetTaskIDreturnstheinformationabouttheTaskIDofthetask whichiscurrentlyrunning. OSEKOS2.1©byOSEK51 OSEK/VDXParticularities: OperatingSystemSpecification2.1Allowedontasklevel,ISRlevelandinseveralhookroutines(seeFigure10-1). Thisserviceisintendedtobeusedbylibraryfunctionsandhookroutines. If BCC1,BCC2,ECC1,ECC2 Status: Standard:Extended:Conformance: 12.2.3.6GetTaskStateSyntax:StatusTypeGetTaskState(TaskType TaskStateRefType Parameter(In): TaskIDTaskreferenceParameter(Out): StateReferencetothestateofthetask atthetimeofcallingGetTaskState. Particularities:Theservicemaybecalledfrominterruptserviceroutines,task level,andsomehookroutines(seeFigure10-1). Withinafullpre-emptivesystem,callingthisoperatingsystemserviceonlyprovidesameaningfulresultifthetaskrunsinaninterruptdisablingstateatthetimeofcalling. Whenacallismadefromataskinafullpre-emptivesystem,theresultmayalreadybeincorrectatthetimeofevaluation.Whentheserviceiscalledforatask,whichismultiplyactivated,thestateissettorunningifanyinstanceofthetaskisrunning. Status: Standard:•Noerror,E_OK Extended:•Task SUSPENDEDINVALID_TASK •ConstantofdatatypeTaskStateTypefortaskstatewaiting.•ConstantofdatatypeTaskStateTypefortaskstateready.•ConstantofdatatypeTaskStateTypefortaskstatesuspended.•ConstantofdatatypeTaskTypeforanotdefinedtask. 52©byOSEKOSEKOS2.1 OSEK/VDX12.2.5Namingconvention OperatingSystemSpecification2.1Theoperationsystemmustbeabletoassigntheentryaddressofthetaskfunctiontothenameofthecorrespondingtaskforidentification.Withtheentryaddresstheoperatingsystemisabletocallthetask. Withintheapplication,ataskisdefinedaccordingtothefollowingpattern: TASK(TaskName){} WiththemacroTASKtheusermayusethesamenamefor\"taskidentification\"and\"nameoftaskfunction\". ThetaskidentificationwillbegeneratedfromtheTaskNameduringsystemgenerationtime.10 12.3Interrupthandling 12.3.1DatatypesIntDescriptorType Datatypeforlogicalinterruptmasks.IntDescriptorRefType Referencetothelogicalinterruptmask,thisdatatypeusuallyisimplementedas\"pointertoIntDescriptorType\".12.3.2Systemservices12.3.2.1EnterISRSyntax: Parameter(In):Parameter(Out):Description: Particularities: voidEnterISR(void)nonenone EnterISRestablishestheconditionsneededtorequestOSservicesinaninterruptserviceroutinecategory3(seeparticularities).InsideEnterISRthefollowingfunctionsareexecutedifneeded: •Registrationoftheswitchingtotheinterruptlevelinsidetheoperatingsystem. •Switchofthecurrentcontext(e.g.totheISRstack). EnterISRestablishesinISRscategory3thepossibilitytouseoperatingsystemservices.ItisnecessarytoplaceEnterISRbeforethefirstcallofanoperatingsystemservice. ThedetailedimplementationofEnterISRdependsonthetargetsystem.Itisexplicitlyallowedtousesystemspecificvariations. Thepre-processorcouldforexamplegeneratethenameofthetaskfunctionbyusingthepre-processorsymbolsequence##toaddastring„Func“tothetaskname: #defineTASK(TaskName)StatusTypeFunc##TaskName(void)Withthismacro,TASK(MyTask)hastheentryfunctionFuncMyTaskOSEKOS2.1 ©byOSEK 53 10 OSEK/VDXOperatingSystemSpecification2.1ThecalltothisserviceisonlyallowedinISRscategory3,butthespecificationdoesnotforceanerrorstatus.Forexamplesomemicrocontrollerscannotperformthetest\"calledoutsidefromISR\".Butasystemanalysistoolmaycheckwhetherthecallisperformedwithintasklevel. ThisserviceisacounterpartofLeaveISRservice(seeChapter5). Status: Standard:Extended:Conformance:12.3.2.2LeaveISRSyntax: Parameter(In):Parameter(Out):Description: nonenone BCC1,BCC2,ECC1,ECC2 Particularities: voidLeaveISR(void)nonenone LeaveISRisthecounterpartofEnterISRandresetstheconditionstorequestoperatingsystemservicesinanISRcategory3.LeaveISRmayonlybecalledafterEnterISRhasbeencalled. ThisfunctiondoesnotimplythereturnfromISRalthoughithastobethelaststatementexecutedintheISR. ThecalltothisserviceisonlyallowedinISRscategory3. ThedetailedimplementationofLeaveISRdependsonthetargetsystem.Itisexplicitlyallowedtousesystemspecificvariations. nonenone BCC1,BCC2,ECC1,ECC2 Status: Standard:Extended:Conformance: 12.3.2.3EnableInterruptSyntax:StatusTypeEnableInterrupt(IntDescriptorType DescriptorHardwaredependentparameterforselectionsofinterrupt sourcestoenable.In Parameter(Out):noneDescription:Thisserviceallowsenablingofseveralinterruptsources simultaneously. Particularities:TheservicemaybecalledfromanISRandfromthetasklevel, butnotfromhookroutines. TosavethecurrentstateofinterruptsourcestheapplicationmustuseGetInterruptDescriptorbefore. Theimplementationhastoadaptthisservicetothetargethardware. ©byOSEK OSEKOS2.1 OSEK/VDXOperatingSystemSpecification2.1Ifnotallrequestedinterruptsourcesaredisabled,thisserviceisneverthelessexecutedforthedisabledinterruptsourcesandreturnsE_OS_NOFUNCinExtendedStatus. Status: Standard:Extended:Conformance: •Noerror,E_OK •Atleastoneoftheinterruptsourceswasnotdisabled,E_OS_NOFUNC BCC1,BCC2,ECC1,ECC2 12.3.2.4DisableInterruptSyntax:StatusTypeDisableInterrupt(IntDescriptorType DescriptorHardwaredependentparameterforselectionsofinterrupt sourcestodisable.In Parameter(Out):noneDescription:Thisserviceallowsdisablingofseveralinterruptsources simultaneously. Particularities:TheservicemaybecalledfromanISRandfromthetasklevel, butnotfromhookroutines. TosavethecurrentstateofinterruptsourcestheapplicationmustuseGetInterruptDescriptorbefore. Theimplementationhastoadaptthisservicetothetargethardware. Ifnotallrequestedinterruptsourcesareenabled,thisserviceisneverthelessexecutedfortheenabledinterruptsourcesandreturnsE_OS_NOFUNCinExtendedStatus. Status: Standard:•Noerror,E_OK Extended:•Atleastoneinterruptsourcewasnotenabled,E_OS_NOFUNCConformanceBCC1,BCC2,ECC1,ECC212.3.2.5GetInterruptDescriptorSyntax:StatusTypeGetInterruptDescriptor(IntDescriptorRefType Parameter(In):noneParameter(Out): DescriptorReferencetocurrentstatusofinterruptsources.In Description:QueryofinterruptstatusParticularities:TheservicemaybecalledfromanISR,tasklevel,andsome hookroutines(seeFigure10-1). Theimplementationhastoadaptthisservicetothetargethardware. OSEKOS2.1©byOSEK55 OSEK/VDXStatus: Standard:Extended:Conformance: •Noerror,E_OK•none BCC1,BCC2,ECC1,ECC2 OperatingSystemSpecification2.112.3.2.6EnableAllInterruptsSyntax:voidEnableAllInterrupts(void)Parameter(In): DescriptornoneParameter(Out):noneDescription:ThisservicerestoresthestatesavedbyDisableAllInterrupts.Particularities:TheservicemaybecalledfromanISRandfromthetasklevel, butnotfromhookroutines. ThisserviceisacounterpartofDisableAllInterruptsservice,anditsaimisthecompletionofthecriticalsectionofcode.NoAPIservicecallsareallowedwithinthiscriticalsection. Theimplementationshouldadaptthisservicetothetargethardwareprovidingaminimumoverhead.Usuallythisserviceenablesrecognitionofinterruptsbythecentralprocessingunit. Status: Standard:•noneExtended:•noneConformance:BCC1,BCC2,ECC1,ECC212.3.2.7DisableAllInterruptsSyntax:voidDisableAllInterrupts(void)Parameter(In): DescriptornoneParameter(Out):noneDescription:Thisserviceallowsdisablingofallinterruptssupportedbythe hardware.ThestatebeforeissavedfortheEnableAllInterruptscall. Particularities:TheservicemaybecalledfromanISRandfromthetasklevel, butnotfromhookroutines. Thisserviceisintendedtostartacriticalsectionofthecode.ThissectionmustbefinishedbycallingtheEnableAllInterruptsservice.NoAPIservicecallsareallowedwithinthiscriticalsection. Theimplementationshouldadaptthisservicetothetargethardwareprovidingaminimumoverhead.Usuallythisservicedisablesrecognitionofinterruptsbythecentralprocessingunit.Notethatthisservicedoesnotsupportnesting.Ifnestingisneededforcriticalsectionse.g.forlibrariesSuspendOSInterruptsandResumeOSInterruptsshouldbeused. 56 ©byOSEK OSEKOS2.1 OSEK/VDXStatus: Standard:Extended:Conformance: •none•none BCC1,BCC2,ECC1,ECC2 OperatingSystemSpecification2.112.3.2.8ResumeOSInterruptsSyntax:voidResumeOSInterrupts(void)Parameter(In): DescriptornoneParameter(Out):noneDescription:Thisservicerestorestherecognitionstatusofinterruptssaved bytheSuspendOSInterruptsservice. Particularities:TheservicemaybecalledfromanISRandfromthetasklevel, butnotfromhookroutines. ThisserviceisthecounterpartofSuspendOSInterruptsservice,anditsaimisthecompletionofthecriticalsectionofcode.NoAPIservicecallsbesideSupendOSInterrupts/ResumeOSInterruptsareallowedwithinthiscriticalsection.Theimplementationshouldadaptthisservicetothetargethardwareprovidingaminimumoverhead. IncaseofnestingpairsofthecallsSuspendOSInterruptsandResumeOSInterruptstheinterruptrecognitionstatussavedbythefirstcallofSuspendOSInterruptsisrestoredbythelastcalloftheResumeOSInterruptsservice. Status: Standard:•noneExtended:•noneConformance:BCC1,BCC2,ECC1,ECC212.3.2.9SuspendOSInterruptsSyntax:voidSuspendOSInterrupts(void)Parameter(In): DescriptornoneParameter(Out):noneDescription:Thisservicesavestherecognitionstatusofinterruptsof categories2and3anddisablestherecognitionoftheseinterrupts. Particularities:TheservicemaybecalledfromanISRandfromthetasklevel, butnotfromhookroutines. Thisserviceisintendedtoprotectacriticalsectionofcode.ThissectionmustbefinishedbycallingtheResumeOSInterruptsservice.NoAPIservicecallsbesideSupendOSInterrupts/ResumeOSInterruptsareallowedwithinthiscriticalsection. OSEKOS2.1©byOSEK57 OSEK/VDXOperatingSystemSpecification2.1Theimplementationshouldadaptthisservicetothetargethardwareprovidingaminimumoverhead. Itisintendedonlytodisableinterruptsofcategory2and3.Howeverifthisisnotpossibleinanefficientwaymoreinterruptsmaybedisabled. Status: Standard:Extended:Conformance: •none•none BCC1,BCC2,ECC1,ECC2 12.3.3Constants INITIAL_INTERRUPT_DESCRIPTOR •ConstantofdatatypeIntDescriptorType(seechapter10.3,Systemstart-up).12.3.4Namingconvention Withintheapplication,aninterruptserviceroutineofcategory2isdefinedaccordingtothefollowingpattern: ISR(FuncName){} ThekeywordISRisevaluatedbythesystemgenerationtoclearlydistinguishbetweenfunc-tionsandinterruptserviceroutinesinthesourcecode. Forcategory1and3interruptserviceroutinesnonamingconventionsareprescribed,theirdefinitionisimplementationspecific. 12.4Resourcemanagement 12.4.1DatatypesResourceTypeDatatypeforaresource. 12.4.2Constructionalelements 12.4.2.1DeclareResourceSyntax:DeclareResource(ResourceIdentifier)Parameter(In): -Resourceidentifier(C-identifier) Description:DeclareResourceservesasanexternaldeclarationofare-source.Thefunctionanduseofthisservicearesimilartothat oftheexternaldeclarationofvariables. Particularities:-Conformance:BCC1,BCC2,ECC1,ECC2 58©byOSEKOSEKOS2.1 OSEK/VDX12.4.3Systemservices OperatingSystemSpecification2.112.4.3.1GetResourceSyntax:StatusTypeGetResource(ResourceType ResIDReferencetoresourceParameter(Out):noneDescription:Thiscallservestoentercriticalsectionsinthecodethatare assignedtotheresourcereferencedby Particularities:TheOSEKpriorityceilingprotocolforresourcemanagementis describedinchapter7.5. Nestedresourceoccupationisonlyallowediftheinnercriticalsectionsarecompletelyexecutedwithinthesurroundingcriticalsection(strictlystacked,seechapter7.2,Restrictionswhenusingresources).Nestedoccupationofoneandthesameresourceisalsoforbidden! CorrespondingcallstoGetResourceandReleaseResourceshouldappearwithinthesamefunctiononthesamefunctionlevel. Serviceswhichputtherunningtaskintothestatesuspendedorwaitingmustnotbeusedincriticalsections(i.e.TerminateTask,ChainTaskandWaitEvent). Generallyspeaking,criticalsectionsshouldbeshort. TheservicemaybecalledfromanISRandfromtasklevel(seeFigure10-1). Status: Standard:•Noerror,E_OK Extended:•Resource •AttempttogetresourcewhichisalreadyoccupiedbyanytaskorISR,ortheassignedpriorityofthecallingtaskorinterruptroutineishigherthanthecalculatedceilingpriority,E_OS_ACCESSConformance: BCC1,BCC2,ECC1,ECC2 12.4.3.2ReleaseResourceSyntax:StatusTypeReleaseResource(ResourceType ResIDReferencetoresourceParameter(Out):noneDescription:ReleaseResourceisthecounterpartofGetResourceand servestoleavecriticalsectionsinthecodethatareassignedtotheresourcereferencedby OSEKOS2.1©byOSEK59 OSEK/VDXParticularities: OperatingSystemSpecification2.1Forinformationonnestingconditions,seeparticularitiesofGetResource. TheservicemaybecalledfromanISRandfromtasklevel(seeFigure10-1). •Noerror,E_OK •Resource •AttempttoreleasearesourcewhichisnotoccupiedbyanytaskorISR,oranotherresourcehastobereleasedbeforeE_OS_NOFUNC •AttempttoreleasearesourcewhichhasalowerceilingprioritythantheassignedpriorityofthecallingtaskorinterruptroutineE_OS_ACCESS BCC1,BCC2,ECC1,ECC2 Status: Standard:Extended: Conformance: 12.4.4Constants RES_SCHEDULER•ConstantofdatatypeResourceType(seechapter7,Resource management). 12.5Eventcontrol 12.5.1DatatypesEventMaskType Datatypeoftheeventmask.EventMaskRefTypeReferencetoaneventmask.12.5.2Constructionalelements 12.5.2.1DeclareEventSyntax:DeclareEvent(EventIdentifier)Parameter(In): Eventidentifier(C-identifier)Description:DeclareEventservesasanexternaldeclarationofanevent. Thefunctionanduseofthisservicearesimilartothatoftheexternaldeclarationofvariables. Particularities:-Conformance:ECC1,ECC212.5.3Systemservices 12.5.3.1SetEventSyntax:StatusTypeSetEvent(TaskType EventMaskType 60©byOSEKOSEKOS2.1 OSEK/VDXParameter(In): TaskIDMask Parameter(Out):Description: OperatingSystemSpecification2.1Particularities:Status: Standard:Extended: Referencetothetaskforwhichoneorseveraleventsaretobeset. Maskoftheeventstobesetnone Theservicemaybecalledfromaninterruptserviceroutineandfromthetasklevel,butnotfromhookroutines. Theeventsoftask Anyeventsnotsetintheeventmaskremainunchanged.•••• Noerror,E_OK Task Referencedtaskisnoextendedtask,E_OS_ACCESSEventscannotbesetasthereferencedtaskisinthesuspendedstate,E_OS_STATEECC1,ECC2 Conformance: 12.5.3.2ClearEventSyntax:StatusTypeClearEvent(EventMaskType MaskMaskoftheeventstobeclearedParameter(Out)noneDescription:TheeventsoftheextendedtaskcallingClearEventarecleared accordingtotheeventmask Particularities:ThesystemserviceClearEventisrestrictedtoextendedtasks whichowntheevent. Status: Standard:•Noerror,E_OK Extended:•Callnotfromextendedtask,E_OS_ACCESS •Callatinterruptlevel,E_OS_CALLEVEL Conformance:ECC1,ECC212.5.3.3GetEventSyntax:StatusTypeGetEvent(TaskType EventMaskRefType Parameter(In): TaskIDTaskwhoseeventmaskistobereturned.Parameter(Out): EventReferencetothememoryofthereturndata.Description:Thisservicereturnsthecurrentstateofalleventbitsofthetask OSEKOS2.1©byOSEK61 OSEK/VDXOperatingSystemSpecification2.1Particularities:Status: Standard:Extended: Theservicemaybecalledfrominterruptserviceroutines,tasklevelandsomehookroutines(seeFigure10-1). Thecurrentstatusoftheeventmaskoftask Thereferencedtaskmustbeanextendedtask.•Noerror,E_OK •Task •Referencedtask •Referencedtask Conformance: 12.5.3.4WaitEventSyntax: Parameter(In): Mask Parameter(Out):Description:Particularities: StatusTypeWaitEvent(EventMaskType Maskoftheeventswaitedfor.none Thestateofthecallingtaskissettowaiting,unlessatleastoneoftheeventsspecifiedin Noerror,E_OK Callingtaskisnotanextendedtask,E_OS_ACCESSCallingtaskoccupiesresources,E_OS_RESOURCECallatinterruptlevel,E_OS_CALLEVELECC1,ECC2 Status: Standard:Extended: •••• Conformance: 12.6Alarms 12.6.1DatatypesTickType Thisdatatyperepresentscountvaluesinticks.TickRefType ThisdatatypepointstothedatatypeTickType.AlarmBaseType Thisdatatyperepresentsastructureforstorageofcountercharacteristics.Theindividualelementsofthestructureare:maxallowedvalue•Maximumpossibleallowedcountvalueinticks 62 ©byOSEK OSEKOS2.1 OSEK/VDXticksperbasemincycle OperatingSystemSpecification2.1•Numberofticksrequiredtoreachacounter-specific(significant)unit. •Smallestallowedvalueforthecycle-parameterof SetRelAlarm/SetAbsAlarm)(onlyforsystemswithextendedstatus). AllelementsofthestructureareofdatatypeTickType.AlarmBaseRefType ThisdatatypepointstothedatatypeAlarmBaseType.AlarmType Thisdatatyperepresentsanalarmobject.12.6.2Constructionalelements 12.6.2.1DeclareAlarmSyntax:DeclareAlarm(AlarmIdentifier)Parameter(In): Alarmidentifier(C-identifier) Description:DeclareAlarmservesasexternaldeclarationofanalarm element. Particularities:Conformance:BCC1,BCC2,ECC1,ECC212.6.3Systemservices 12.6.3.1GetAlarmBaseSyntax:StatusTypeGetAlarmBase(Parameter(In): AlarmIDParameter(Out): InfoDescription: AlarmType AlarmBaseRefType Referencetoalarm Referencetostructurewithconstantsofthealarmbase. ThesystemserviceGetAlarmBasereadsthealarmbasecharacteristics.Thereturnvalue Allowedontasklevel,ISR,andinseveralhookroutines(seeFigure10-1). •Noerror,E_OK •Alarm Particularities:Status: Standard:Extended:Conformance: OSEKOS2.1©byOSEK63 OSEK/VDXOperatingSystemSpecification2.112.6.3.2GetAlarmSyntax:StatusTypeGetAlarm(AlarmType TickRefType Parameter(In): AlarmIDReferencetoanalarmParameter(Out): TickRelativevalueinticksbeforethealarm beforethealarm Particularities:Itisuptotheapplicationtodecidewhetherforexamplea CancelAlarmmaystillbeuseful. If Allowedontasklevel,ISR,andinseveralhookroutines(seeFigure10-1).Status: Standard:•Noerror,E_OK •Alarm Extended:•Alarm TickType Parameter(In): AlarmIDReferencetothealarmelementincrementRelativevalueintickscycleCyclevalueincaseofcyclicalarm.Incaseofsinglealarms, cyclehastobezero. Parameter(Out):noneDescription:Thesystemserviceoccupiesthealarm After Particularities:Thebehaviourof implementation. Iftherelativevalue If Tochangevaluesofalarmsalreadyinusethealarmhastobecancelledfirst. Ifthealarmisalreadyinuse,thiscallwillbeignoredandtheerrorE_OS_STATEisreturned. ©byOSEK OSEKOS2.1 OSEK/VDXStatus: Standard: Extended: •••• OperatingSystemSpecification2.1AllowedontasklevelandinISR,butnotinhookroutines.Noerror,E_OK Alarm Valueof •Valueof Conformance: BCC1,BCC2,ECC1,ECC2;EventsonlyECC1,ECC2 12.6.3.4SetAbsAlarmSyntax:StatusTypeSetAbsAlarm( AlarmType TickType Parameter(In): AlarmIDstartcycleParameter(Out):Description: Particularities: ReferencetothealarmelementAbsolutevalueinticks Cyclevalueincaseofcyclicalarm.Incaseofsinglealarms,cyclehastobe=zero.none Thesystemserviceoccupiesthealarm Iftheabsolutevalue Iftheabsolutevalue If Tochangevaluesofalarmsalreadyinusethealarmhastobecancelledfirst. Ifthealarmisalreadyinuse,thiscallwillbeignoredandtheerrorE_OS_STATEisreturned. AllowedontasklevelandinISR,butnotinhookroutines.•Noerror,E_OK •Alarm ©byOSEK 65 Status: Standard: OSEKOS2.1 OSEK/VDXExtended: OperatingSystemSpecification2.1•Alarm •Valueof Conformance:BCC1,BCC2,ECC1,ECC2;EventsonlyECC1,ECC2 12.6.3.5CancelAlarmSyntax:StatusTypeCancelAlarm(AlarmType AlarmIDReferencetoanalarmParameter(Out):noneDescription:Thesystemservicecancelsthealarm Status: Standard:•Noerror,E_OK •Alarm Extended:•Alarm Therealwaysexistsatleastonecounterwhichisatimecounter(systemcounter).Tofacilitateprogrammingofthiscounter,thereturnvaluesofthecallGetAlarmBasearealsodefinedasconstants. OSMAXALLOWEDVALUE•Maximumpossibleallowedvalueofthesystemcounterinticks.OSTICKSPERBASEOSMINCYCLE •Numberofticksrequiredtoreachspecificunitofthesystemcounter. •Minimumallowednumberofticksforacyclicalarm. Additionallythefollowingconstantissupplied:OSTICKDURATION•Durationofatickofthesystemcounterinnanoseconds. 12.7Operatingsystemexecutioncontrol 12.7.1DatatypesAppModeType Thisdatatyperepresentstheapplicationmode. 66©byOSEKOSEKOS2.1 OSEK/VDX12.7.2Systemservices OperatingSystemSpecification2.112.7.2.1GetActiveApplicationModeSyntaxAppModeTypeGetActiveApplicationMode(void)Description:Thisservicereturnsthecurrentapplicationmode.Itmaybe usedtowritemodedependentcode. Particularities:Seechapter4.8forageneraldescriptionofapplicationmodes. Allowedfortask,ISRandallhookroutines. Conformance:BCC1,BCC2,ECC1,ECC212.7.2.2StartOSSyntax Parameter(In): Mode Parameter(Out):Description:Particularities: voidStartOS(AppModeType applicationmodenone Theusercancallthissystemservicetostarttheoperatingsysteminaspecificmode,seechapter4.8,Applicationmodes.Onlyallowedoutsideoftheoperatingsystem,thereforeimplementationspecificrestrictionsmayapply.Seealsochapter10.3,Systemstart-up.Thiscalldoesnotneedtoreturn. BCC1,BCC2,ECC1,ECC2 Conformance: 12.7.2.3ShutdownOSSyntaxvoidShutdownOS(StatusType ErrorerroroccurredParameter(Out):noneDescription:Theusercancallthissystemservicetoaborttheoverall system(e.g.emergencyoff).Theoperatingsystemalsocallsthisfunctioninternally,ifithasreachedanundefinedinternalstateandisnolongerreadytorun. IfaShutdownHookisconfiguredthehookroutineShutdownHookisalwayscalled(with IfShutdownHookreturns,furtherbehaviourofShutdownOSisimplementationspecific. Particularities:Afterthisservicetheoperatingsystemisshutdown. Allowedattasklevel,ISRlevel,inErrorHookandStartupHook,andalsocalledinternallybytheoperatingsystem. IftheoperatingsystemcallsShutdownOSitneverusesE_OKasthepassedparametervalue. Conformance:BCC1,BCC2,ECC1,ECC2 OSEKOS2.1©byOSEK67 OSEK/VDX12.7.3ConstantsOSDEFAULTAPPMODE OperatingSystemSpecification2.1•Defaultapplicationmode,alwaysavalidparametertoStartOS. 12.8Hookroutines Thespecificationallowsforimplementationspecificadditionalparametersinhookroutines.Inthefollowingdescriptiononlymandatoryparametersarelisted.12.8.1ErrorHookSyntax Parameter(In): Error Parameter(Out):Description: voidErrorHook(StatusType erroroccurrednone ThishookroutineiscalledbytheoperatingsystemattheendofasystemservicewhichreturnsStatusTypenotequalE_OK.Itiscalledbeforereturningtothetasklevel. Thishookroutineiscalledwhenanalarmexpiresandanerrorisdetectedduringtaskactivationoreventsetting. TheErrorHookisnotcalled,ifasystemservicecalledfromErrorHookdoesnotreturnE_OKasstatusvalue.AnyerrorbycallingofsystemservicesfromtheErrorHookcanonlybedetectedbyevaluatingthestatusvalue. Seechapter10.1forgeneraldescriptionofhookroutines.BCC1,BCC2,ECC1,ECC2 Particularities:Conformance: 12.8.2PreTaskHookSyntaxvoidPreTaskHook(void)Parameter(In):noneParameter(Out):noneDescription:Thishookroutineiscalledbythetheoperatingsystembefore executinganewtask,butafterthetransitionofthetasktotherunningstate(toallowevaluationoftheTaskIDbyGetTaskID). Particularities:Seechapter10.1forgeneraldescriptionofhookroutines.Conformance:BCC1,BCC2,ECC1,ECC212.8.3PostTaskHookSyntaxvoidPostTaskHook(void)Parameter(In):noneParameter(Out):noneDescription:Thishookroutineiscalledbytheoperatingsystemafter executingthecurrenttask,butbeforeleavingthetask'srunningstate(toallowevaluationoftheTaskIDbyGetTaskID). Particularities:Seechapter10.1forgeneraldescriptionofhookroutines.Conformance:BCC1,BCC2,ECC1,ECC2 68©byOSEKOSEKOS2.1 OSEK/VDXOperatingSystemSpecification2.112.8.4StartupHookSyntaxvoidStartupHook(void)Parameter(In):noneParameter(Out):noneDescription:Thishookroutineiscalledbytheoperatingsystemattheend oftheoperatingsysteminitialisationandbeforetheschedulerisrunning.Atthistimetheapplicationcanstarttasks,initialisedevicedriversetc. Particularities:Seechapter10.1forgeneraldescriptionofhookroutines.Conformance:BCC1,BCC2,ECC1,ECC212.8.5ShutdownHookSyntaxvoidShutdownHook(StatusType ErrorerroroccurredParameter(Out):noneDescription:Thishookroutineiscalledbytheoperatingsystemwhenthe OSserviceShutdownOShasbeencalled.Thisroutineiscalledduringtheoperatingsystemshutdown. Particularities:ShutdownHookisahookroutineforuserdefinedshutdown functionality,seechapter10.4. Conformance:BCC1,BCC2,ECC1,ECC2 OSEKOS2.1©byOSEK69 OSEK/VDXOperatingSystemSpecification2.113Implementationandapplicationspecifictopics Thischapterisnotnormativenormandatory.Itprovidesinformationforimplementersandapplicationprogrammers. 13.1Implementationhints. OSEKspecifiesanoperatingsysteminterfaceanditsfunctionality.Implementationaspectsarenotprescribed.Thereisnorestrictionontheimplementationoftheoperatingsystemaslongastheimplementationcorrespondstoanyofthedefinedconformanceclasses.13.1.1Aspectsofimplementation Therangeofautomotiveapplicationsvariesgreatlysuchthatnoperformancecharacteristicsoftheoperatingsystemimplementationcanbespecified,i.e.astotheexecutiontimeandmemoryspacerequired. Asaresult,• theOSEKoperatingsystemcanbeimplementedwithvariousdegreesofefficiency.• Thelinkerneedsonlytolinkthoseobjectsandservicesoftheoperatingsystemwhich areactuallyused.• theoperatingsystemusedinaproduct(e.g.inacontrolunit'sEPROM)cannotbede-scribedasOSEKoperatingsystem,butasanoperatingsystemwhichconformstoan OSEKoperatingsystemconformanceclass.• thetoolenvironmentoftheoperatingsystemconfigurationandinitialisationisnotpartof theoperatingsystemspecificationandthereforeimplementation-specific.• commercialsystemswhichprovidetheuserwithallOSEKoperatingsystemspecific servicesandtheirfunctionalitiesviaanOSEKadaptationlayer,arealsoOSEKoperatingsystemcompliant.Theyarecompliantirrespectiveoftheiractualsuitabilityforcontrolunitsasregardsthememoryspacetheyrequireandtheirprocessingspeed.Theconformanceclassselectedforanapplicationsoftwareisdeterminedbytheneedsonfunctionalityandflexibility. Thereal-timebehaviouroftheapplicationsoftwareusedwithaspecifichardwareisalsodefinedbythequalityofimplementation. 13.1.2Parametersofimplementation Theoperatingsystemvendorprovidesalistofparametersspecifyingtheimplementation.Detailedinformationisrequiredconcerningthefunctionality,performanceandmemorydemand.Furthermorethebasicconditionstoreproducethemeasurementofthoseparametershavetobementioned,e.g.functionality,targetCPU,clockspeed,busconfiguration,waitstatesetc. 13.1.2.1Functionality • Maximumnumberoftasks • Maximumnumberofnotsuspendedtasks• Maximumnumberofpriorities 70 ©byOSEK OSEKOS2.1 OSEK/VDX• • • • OperatingSystemSpecification2.1Numberoftasksperpriority(forBCC2andECC2) Upperlimitfornumberoftaskactivations(mustbe\"1\"forBCC1andextendedtasks)Maximumnumberofeventspertask Limitsforthenumberofalarmobjects(persystem/pertask) • Limitsforthenumberofnestedresources(persystem/pertask)• LowestprioritylevelusedinternallybytheOS13.1.2.2Hardwareresources • RAMandROMrequirementforeachoftheoperatingsystemcomponents• Sizeforeachlinkablemodule • ApplicationdependentRAMandROMrequirementsforoperatingsystemdata(e.g.bytesRAMpertask,RAMrequiredperalarm,...) • Executioncontextoftheoperatingsystem(e.g.sizeofOSinternaltables)• TimerunitsreservedfortheOS • Interrupts,trapsandotherhardwareresourcesoccupiedbytheoperatingsystem13.1.2.3Performance • Totalexecutiontimeforeachservice11 • OSstart-uptime(beginningofStartOSuntilexecutionoffirsttaskinstandardmode)withoutinvokinghookroutines • Interruptlatency12forISRsofcategory1,2and3• Taskswitchingtimesforalltypesofswitching13• Baseloadofsystemwithoutapplicationsrunning Allperformancefiguresshallbestatedasminimumandmaximum(worstcase)values.13.1.2.4Configurationofruntimecontext Aruntimecontextisassignedtoeachtask.Thisreferstoallmemoryresourcesofthetaskwhichareoccupiedatthebeginningoftheexecutiontime,andwhicharereleasedagainoncethetaskisterminated.Typicallytheruntimecontextconsistsofsomeregisters,ataskcontrolblockandacertainamountofstacktooperate. Dependingonthedesignoftasks(e.g.typeandpre-emptibility)anddependingontheschedulingmechanism(non-,mixed-orfullpre-emptive)theruntimecontextmayhave 11 Thetimeofexecutionmaydependonthecurrentstateofthesystem,e.g.therearedifferentexecutiontimesof\"SetEvent\"dependingonthestateofthetask(waitingorready).Thereforecomparableresultshavetobeextractedfromacommonbenchmarkprocedure. TimebetweeninterruptrequestandexecutionofthefirstinstructionofusercodeinsidetheISR.A comparisonofinterruptlatenciesofISRsfromcategory1toISRsfromcategory2or3specifiestheoperatingsystemoverhead. 12 13 Shouldbemeasuredfromthelastuserinstructionoftheprecedingtasktothefirstuserinstructionofthefollowingtasksothatalloverheadiscovered.Taskswitchingtypesaredifferentfor:normalterminationofatask,terminationforcedbyChainTask(),preemptivetaskswitch,taskactivationwhenOSidletaskisrunning,alarmtriggeredtaskactivationandtaskactivationsfromISRsoftypes2and3. ©byOSEK 71 OSEKOS2.1 OSEK/VDXOperatingSystemSpecification2.1differentsizes.Taskswhichcanneverpre-empteachothermaybeexecutedinthesameruntimecontextinordertoachieveanefficientutilisationoftheavailableRAMspace. Theoperatingsystemvendorshouldprovideinformationabouttheimplementedhandlingoftheruntimecontext(e.g.onecontextpertaskoronecontextperprioritylevel).ConsideringthisinformationtheusermayoptimisethedesignofhisapplicationregardingRAMrequirementsversusruntimeefficiency. 13.2Applicationdesignhints ThepurposeofthischapteristoprovideadditionalinformationaboutpossibleproblemswhichmightarisewhendesigningapplicationsfortheOSEKoperatingsystem.Notalloftheconsequencesforthesystemdesigncanbementionedinthespecificationitself.OtherdesignhintsresultfromtheexperienceofcurrentECUapplications.13.2.1Resourcemanagement Someaspectsarementionedinthischapterinordertoguaranteeaproperhandlingofallresources. 13.2.1.1OccupationinLIFOorder EachaccesstoaresourceshouldbeencapsulatedwithcallstotheservicesGetResourceandReleaseResource.Resourceshavetobereleasedinreversedorderoftheiroccupation.Thefollowingcodesequenceisincorrectbecausefunctionfooisnotallowedtoreleaseresourceres_1. TASK(incorrect){ GetResource(res_1); /*somecodeaccessingresourceres_1*/...foo();... ReleaseResource(res_2);} voidfoo(){ GetResource(res_2); /*codeaccessingresourceres_2*/... ReleaseResource(res_1);} Nestedresourceoccupationsisallowed.TheoccupationofresourceshastobeperformedinstrictLIFOorder(stackprinciple).Ifthecodeaccessingtheresourceasshownaboveispre-emptedbyataskwithhigherpriority(higherthantheceilingpriorityoftheresource),anotherresourcemightberequestedinthattaskleadingtoanestedresourceoccupationwhichconformstotheLIFOorder. 13.2.1.2CalllevelofAPI-services TheOSEKAPI-servicesGetResourceandReleaseResourceshouldbecalledfromthesamefunctionalcalllevel.IffunctionfooiscorrectedconcerningtheLIFOorderofresourceoccupationlike: voidfoo(void){72 ©byOSEK OSEKOS2.1 OSEK/VDXReleaseResource(res_1);GetResource(res_2); /*somecodeaccessingresourceres_2*/... ReleaseResource(res_2);} OperatingSystemSpecification2.1therestillmaybeaproblembecauseReleaseResource(res_1)iscalledonadifferentlevelthanGetResource(res_1).CallingtheAPIservicesfromdifferentcalllevelsmightcauseproblemsinsomeimplementations. 13.2.1.3Resourcesstilloccupiedattasktermination TheaccesstoaresourceshouldbeencapsulateddirectlybythecallsofGetResourceandReleaseResource.Otherwiseonemightmisstoreleasetheresourceandpossiblyterminatethetask. GetResource(res_1);... switch(condition){ caseCASE_1: do_something1(); ReleaseResource(res_1);break;caseCASE_2:/*!!!WRONG:noreleaseof /*resourcehere!!! do_something2();break;default: do_something3(); ReleaseResource(res_1); }... */*/ Ifinstandardstatusoftheoperatingsystemataskterminateswithoutreleasingalloftheoccupiedresourcestheresultingbehaviourisnotdefinedbythespecification.Dependingontheimplementationoftheoperatingsystemtheresourcemaybelockedforeversincefurtheraccessesarerejectedbytheoperatingsystem.13.2.2PlacementofAPIcalls Forthesamereasonsasabovementionedinchapter13.2.1.2theplacementofAPIservicesTerminateTaskandChainTaskiscrucialfortheoperatingsystem.Bothservicesareusedtoterminatetherunningtask.Callingtheseservicesfromasubroutinelevelofthetask,theoperatingsystemisresponsibleforacorrecttreatmentofthestackwhenterminatingthetask.Onesolutioncouldbetostorethepositionofthestackpointerattheentrypointoftherunningtaskandrestorethatvalueafterterminatingthetask.13.2.3Interruptserviceroutines TheuserhastobeawareofsomepossibleerrorcaseswhenusingISRsofcategory1,2and3asdescribedinchapter5. 13.2.3.1LocalvariablesinISRsofcategory3 InISRsofcategory3theuserisallowedtowriteapplicationcodebeforetheoperatingsystemcontextisenteredusingtheserviceEnterISR.IfEnterISRswitchestoadifferentstack,automaticvariablesdefinedintheprecedingapplicationcodemightbenolongeraccessibleintheoperatingsystemcontext. OSEKOS2.1 ©byOSEK 73 OSEK/VDXOperatingSystemSpecification2.1TheapplicationcodeatthebeginningoftheISRmightnotbeportablebetweendifferentcompilerswhenusinglocalvariables.Thisisbecausetheconventionforregisterusageisnotalwaysthesameforcompilersfromdifferentmanufacturers.13.2.3.2Nestedinterruptsofdifferentcategories Sinceallinterruptsareofhigherprioritythanthetasklevels,theprocessingofinterruptshastobeterminatedbeforethesystemreturnstotasklevel.IfanISRofcategory2interruptsanISRofcategory1thesystemwillcontinueprocessingofISR1afterISR2terminates.HavingtasksactivatedoreventssetfrominterruptlevelinISR2theoperatingsystemisnotinvokedafterterminationofISR1inordertoperformarescheduling. Pleasenotethat,inthisrespect,anISR3,beforeEnterISRiscalled,actslikeanISRcategory1,afterwardslikeanISRcategory2. InterruptISRofcategory1{ISRofcategory2{codewithoutcalltoanOSservicecodewithcalltoanOSservicee.g.ActivateTask();SetEvent();NoOScallattheendofISR1Figure13-1Nestedinterrupts BecauseISRsofcategory1(orcategory3beforeEnterISR)donotrunundercontroloftheoperatingsystemtheOShasnopossibilitytoperformareschedulingwhentheISRterminates.ThusanyactivitiescorrespondingtothecallsoftheoperatingsystemintheinterruptingISR2(orISR3afterEnterISR)areunboundeddelayeduntilthenextreschedulingpoint. Asaresultoftheproblemsdiscussedabove,eachsystemshouldsetuprulestoavoidtheseproblems.Theremaybespecificimplementationswhichcanavoidtheseproblems,ortheapplicationmighthavespecificpropertiessuchthattheseproblemscannotoccur(e.g.innonpre-emptivesystems).Therulesmustthereforetakeintoaccountboththespecificimplementationsandtheapplications. However,formaximalapplicationportability,aneasyruleofthumbwhichalwaysworksisthefollowing: • allinterruptsofcategory1havetohaveahigherorequalhardwareprioritycomparedwithinterruptsofcategory2.• allinterruptsofcategory3havetoshareonehardwareprioritynothigherthanthelowestcategory1interruptpriority,andnotlowerthanthehighestcategory2interruptpriority. 74 ©byOSEK OSEKOS2.1 OSEK/VDX13.2.3.3Directmanipulationofinterruptlevels OperatingSystemSpecification2.1Directmanipulationofinterruptlevelsisnotportableandrestrictedbytheimplementation.13.2.4Priorityandpre-emption Tasksarescheduledbytheoperatingsystemaccordingtotheirpriority.Ataskisdeclaredasbeingpre-emptive/nonpre-emptive(seechapter4.6.3).Theapplicationhastotreatthesetwotaskattributesinaconsistentmannertoavoidconflictsintherun-timebehaviourofthesystem.Carehastobetakenbecausenonpre-emptivetasksoflowerprioritydelaytasksofhigherpriority. Typicallythepre-emptionofataskisassignedwhendesigning,whereaspriorityisconfiguredduringsystemintegration.Becausemanypeopleareinvolvedinlargersoftwareprojects,thedevelopmentprocesshastobeco-ordinatedprecisely.Toachieveawell-definedrun-timebehaviourofthesystemthisco-ordinationiscrucial.13.2.5ParametertopasstoShutdownOS TheparameterpassedtoShutdownOSisalsopassedtotheShutdownHook.IftheoperatingsystemcallstheShutdownHook,thepassedparameterisanimplementationdependenterrorvalue.IftheusercallsShutdownOShehastouseoneoftheexistingerrornumbers. Itisrecommendedtousetheerrornumberdescribedintheimplementationdocumentation.IfnospecificerrornumberforShutdownOSisdefined,itispossibletouseE_OKandtodistinguishthiswaybetweenoperatingsystemcallsofShutdownOSandapplicationcalls.13.2.6Errorhandling Errorsintheapplicationsoftwarearetypicallycausedby:• Errorsonhandlingtheoperatingsystem,i.e.incorrectconfiguration/initialisation/ dimensioningoftheoperatingsystemorviolationsofrestrictionsregardingtheoperatingsystemservice.• Errorinsoftwaredesign,e.g.inappropriatechoiceoftaskpriorities,unprotectedcritical sections,incorrectscalingoftime,inefficientconceptualdesignoftaskorganisationTestofimplementation Breakpoints,tracesandtimestampscanbeintegratedindividuallyintotheapplicationsoftware. Example:Theusercansettimestampsenablinghimtotracetheprogramexecutionatthefollowinglocationsbeforecallingoperatingsystemservices:• Whenactivatingorterminatingtasks.• Whensettingorclearingeventsinthecaseofextendedtasks.• Atexplicitpointsoftheschedule.• AtthebeginningortheendofISRs.• Whenoccupyingandreleasingresourcesoratcriticallocations.Timemonitoring Theoperatingsystemneedsnotincludeatimemonitoringfeaturewhichensuresthateachoronly,e.g.thelowest-prioritytaskhasbeenactivatedinanycaseafteradefinedmaximumtimeperiod. OSEKOS2.1 ©byOSEK 75 OSEK/VDXOperatingSystemSpecification2.1Theusercanoptionallyusehookroutinesorestablishawatchdogtaskthattakes\"one-shotdisplays\"oftheoperatingsystemstatus. Constructionalelements Constructionalelements(e.g.DeclareTask)wereintroducedinOSEKOSasmeanstocreatereferencestosystemobjectsusedintheapplication.Likeexternaldeclarationsconstructorswouldbeplacedatthebeginningofsourcefiles.Withrespecttotheimplementationtheycanbeimplementedasmacros.WiththedefinitionofOILmostimplementationsdonotneedthemanymore.Howevertheyarestillkeptforcompatibility. 13.2.7Errorsandwarnings Mostoftheerrorvaluesofsystemservicespointtoapplicationerrors.However,insomespecialcaseserrorvaluesindicatewarningswhichmightcomeupduringnormaloperation.Thesecasesare: • EnableInterrupt,DisableInterruptE_OS_NOFUNC• GetAlarmE_OS_NOFUNC• SetAbsAlarm,SetRelAlarm• CancelAlarm (standard)E_OS_STATE (standard) (standard)(extended) E_OS_NOFUNC EspeciallywhenimplementingacentralerrorhandlingbyErrorHook,thishastobetakenintoaccount. 13.3Implementationspecifictools Whenbuyingorwritingportablecodeonehastobeawareofthedifferentimplementationtoolsonthemarket.Thishasanimpact,onwhatkindofdocumentationhastogoinparallelwiththecode. VersionAincludeOSEK.xDeclarationsUser-programUser-programVersionBGenerationToolCompilerCompilerLinkerCompilerLinkerExecutableExecutableFigure13-2Implementationspecifictools Theexamplehereshowstwopossibleimplementationsofatoolchain:• VersionA,withalldeclarationsrelatedtotaskpropertiesetc.withinthecode 76 ©byOSEK OSEKOS2.1 OSEK/VDX• OperatingSystemSpecification2.1VersionB,usingaseparategenerationtoolforthesetaskpropertiesetc. FordefinitionswhichshouldbesuppliedwithportablecodepleaseconsulttheOILspecification. OSEKOS2.1©byOSEK77 OSEK/VDXOperatingSystemSpecification2.114Changesfromspecification1.0to2.1 14.1Changesfromspecification1.0to2.0r1 ThischaptermentionsallchangesintheconceptandtheAPIoftheOSEKoperatingsystem,withexplanationforthereasonofchange.14.1.1Conceptualchanges14.1.1.1Conformanceclasses Thischapterreferstochapter3.2Conformanceclasses. TheOSEKOSspecificationversion2.0nowsupportsonlyfourconformanceclassesinsteadoffive(asinversion1.0).AlsotheCCsarerenamed,soforexampleECC1(version1.0)hasotherfeaturesthanECC1(version2.0).Theexperienceofworkingwithversion1.0hasshownthatthefourCCsofversion2.0willbettermeetapplicationrequirements.Changesindetailare: • Multiplerequestingoftaskactivationforextendedtasksisnotsupported.Thatisonlyallowedforbasictasks.• Thenumberofmultiplerequestingoftaskactivationisanattributeofthebasictaskandnorequirementoftheconformanceclass.• Theconformanceclassesofversion2.0arenolongerstrictlyupwardcompatible.14.1.1.2Messages Specificationversion2.0doesnotsupportcommunicationviamessages.AllmessageservicesarepartofthecommunicationspecificationandthereforedescribedintheOSEKCOMspecification. 14.1.1.3MultiplerequestingoftaskactivationThischapterreferstochapter4.3,Activatingatask. Inversion1.0theorderofactivationincaseofmultiplerequestwasnotexplicitlydefinedbutuptotheimplementation.Inversion2.0itisclearlydefinedthattheactivationsarequeuedinaFIFOstructureaccordingtotheorderofrequesting.14.1.1.4Applicationmodes Thischapterreferstochapter4.8,Applicationmodes. Forsomeapplicationsitshouldbeusefultohavedifferentapplicationmodesdependingonexternalconditions.14.1.1.5Counters TheAPIforcountershasbeenremoved(seechapter8.1,Counters).Inversion1.0accesstocounterswasallowedfortheapplication.Thisfeatureisstronglydependingontheunderlyinghardware.ThereforetheAPIservicesforcountersarecancelledinversion2.0.TheAPIservicesforalarmsarestillavailable. 78©byOSEKOSEKOS2.1 OSEK/VDX14.1.1.6Hookroutines Thischapterreferstochapter10.1Hookroutines. OperatingSystemSpecification2.1ThenamingofhookroutineschangedfromOSxxxxtoxxxxHook. Inversion2.0twoadditionalhookroutinesStartupHook(seechapter12.8.4)andShutdownHook(seechapter12.8.5)areintroduced.Thisfeatureoffersthepossibilityofuserdefinedstart-upandshutdown.14.1.1.7OSexecutioncontrol Inversion2.0oftheOSEKOSspecificationtwonewAPIservicesareintroduced,StartOS(seechapter12.7.2.1)andShutdownOS(seechapter12.7.2.3).Withthistwoservices,theusercanstart-upandshutdowntheoverallsystem.14.1.2Clarifications 14.1.2.1Schedulingofnonpre-emptivetasks Whenanonpre-emptivetaskispre-emptedbycallingthescheduler,thetaskcontextissaved.Ifthetaskisassignedtotheprocessoragain,thetaskwillcontinueatthepointofpre-emptionandwillnotberestartedfromthebeginning.14.1.2.2Servicesavailableonwhichlevel Inversion2.0twotablesarespecifyingwhichserviceisavailableoninterruptlevel,ontasklevelandinwhichhookroutine.14.1.2.3Interruptprocessing Inversion2.0theISRcategory3ismandatoryandnotoptionalanymore.14.1.2.4Priorityceiling Thischapterreferstochapter7.5,OSEKPriorityCeilingProtocol. Inversion2.0,theceilingpriorityofaresourceisdefinedexactlyas: a)identicalorhighertothehighesttaskprioritywithaccesstothisresource(e.g.TaskX)and b)lowerthanthepriorityoffallotherofhigherprioritythanthattask(TaskX).14.1.2.5Typesandconstants Inversion2.0thetypeTaskTypeisspecified.Thefollowingtypesaredefined:• TaskType:identifiesatask• TaskRefType:pointstoavariableofTaskType• TaskStateType:identifiesthestateofatask• TaskStateRefType:pointstoavariableofTaskStateType14.1.2.6Namingconventions Inversion2.0themacroTASKhasgotanewmeaning(seechapterFehler!Verweisquellekonntenichtgefundenwerden.).ThischangewasnecessarybecausetheoldversionofTASKhadadrawback;theuserwasforcedtodefineanameforthetaskfunctionhewasnotallowedtouseastaskname OSEKOS2.1 ©byOSEK 79 OSEK/VDXOperatingSystemSpecification2.1TASKTaskFuncName(void) {/*TaskfunctionfortheTask\"TaskName\"*/ /*Thename\"TaskFuncName\"mustNOTbeusedasataskname*/} 14.1.3Changesofthedocumentation14.1.3.1Documentstructure Thespecificationdocumentationofversion1.0consistsoftwodocuments,the\"concept\"andthe\"API\".Inversion2.0thesetwopapersareintegratedintothisone,calledOSEKOSspecification. 14.1.3.2Newchapters Portabilityofapplicationsoftware(paragraphinchapter1.1)ThisnewchapterregardsaspectsofportabilityofOSEKsoftware.Implementationandapplicationspecifictopics(seechapter13)ThisnewchaptergiveshintsforimplementinganOSEKoperatingsystem.14.1.3.3RemovedchaptersChaptermessages ThemessageconceptisdescribedintheOSEKCOMspecification.Thereforethemessagepartsareremoved.Systemgeneration AllquestionsofsystemgenerationaredescribedinanextrapapercalledOILspecification(OIL=OSEKImplementationLanguage).Severalreferencestothatpaperaremadethroughoutthisdocument. 14.2Changesfromspecification2.0r1to2.1 Alotofwordingwithinthedocumenthasbeenchangedforclarificationandtoimprovereadability.Thedocumentstructurewasalsochangedforthesamereason.Thesechangesarenotexplicitlymentionedinthissection,butonlychangesintheconceptandtheAPIoftheOSEKoperatingsystem. 14.2.1BehaviourofChainTask/TerminateTaskwithallocatedresourcesisundefined. In2.0r1thebehaviourwasnotundefinedbutonlytheoccupationoftheresourcewas.Asthisisaclearapplicationerrorresultinginunsafebehaviouritwasnotconsideredusefultodefinepartofthebehaviourincaseofseriouserrors.14.2.2GetTaskIDisallowedinISRs. AsGetTaskStatewasallowedinISRsandhookroutines,andGetTaskIDwasalreadyallowedinhookroutines,itseemedinconsistentandproblematicnottoallowitinISRs. 80©byOSEKOSEKOS2.1 OSEK/VDXOperatingSystemSpecification2.114.2.3Interrupthandlinghasbeenclarifiedandextended.• Supportforinterruptsofcategory3isoptional. • ClarificationthatEnableInterrupt/DisableInterruptmanipulatesinterruptsourcesandthattheInterruptDescriptorisglobal.• AddedfunctionsDisableAllInterrupts/EnableAllInterrupts.• AddedfunctionsSuspendOSInterrupts/ResumeOSInterrupts. • Optionalextensionofresourcestointerrupts(includingtheconceptofinterruptpriorities).14.2.4ErrorcheckingofGetResource/ReleaseResourcehavebeenmodified.Thedefinitionin2.0r1wasincompleteandtheextensionoftheresourceconcepttoISRsrequiredthischange. 14.2.5AddedconstantOSTICKSPERBASE. TherehavebeenconstantsfortwoofthethreevaluesreturnedbyGetAlarmBaseforasinglesystemcounter.Themissingthirdonewasaddedforcompleteness. 14.2.6ShutdownOSisallowedinISRsandcertainhookroutines. ShutdownOSismeanttobecalledbytheapplicationincaseoffatalerrors.AssucherrorsarelikelytobediscoveredinISRsorhooks(e.g.ErrorHook)itwasconsidereddangeroustopreventtheapplicationfromimmediatelyshuttingdowntheoperatingsystem.14.2.7BehaviourofShutdownOSafterShutdownHookreturnsisimplementationdefined. Version2.0r1ofthespecificationwasinconsistentinthispoint.14.2.8AddedconstantOSDEFAULTAPPMODE.Thisconstantwasaddedtoincreaseportabilityofapplications.14.2.9ErrorHookisnevercalledrecursively. RecursivecallingofErrorHookpossiblyleadstounboundedrecursionandwasconsideredtoodangerous. 14.2.10LocalMessagesaddedtospecification. Intraprocessormessagehandling(refertoconformanceclassCCCA/CCABasdefinedintheOSEKCommunicationSpecification)hasbeenadded. OSEKOS2.1©byOSEK81 OSEK/VDX15Index ActivateTask........................................49AlarmBaseRefType..............................63AlarmBaseType....................................62alarms..................................................37AlarmType...........................................63AppModeType.....................................66CancelAlarm........................................66ChainTask............................................50ClearEvent...........................................61counters...............................................37DeclareAlarm.......................................63DeclareEvent.......................................60DeclareResource..................................58DeclareTask.........................................49DisableInterrupt...................................55E_OS_ACCESS...................................48E_OS_CALLEVEL.............................48E_OS_ID.............................................48E_OS_LIMIT......................................48E_OS_NOFUNC.................................48E_OS_RESOURCE.............................48E_OS_STATE.....................................48E_OS_SYS_PARITY..........................48E_OS_SYS_STACK............................48E_OS_VALUE....................................48EnableInterrupt.........................,56,57EnterISR..............................................53ErrorHook...........................................68EventMaskRefType..............................60EventMaskType...................................60GetActiveApplicationMode..................66GetAlarm.............................................63GetAlarmBase......................................63GetEvent..............................................61GetInterruptDescriptor.........................55GetResource........................................59GetTaskID...........................................51GetTaskState.......................................52INITIAL_INTERRUPT_DESCRIPTOR58 OperatingSystemSpecification2.1IntDescriptorRefType...........................53IntDescriptorType................................53ISR.......................................................58LeaveISR.............................................maxallowedvalue..................................62message................................................39mincycle...............................................62multiplerequesting................................20OSMAXALLOWEDVALUE.........66,67OSTICKDURATION...........................66PostTaskHook......................................68PreTaskHook.......................................68READY................................................52ReleaseResource...................................59RES_SCHEDULER.............................60rescheduling....................................22,26ResourceType.......................................58RUNNING...........................................52Schedule...............................................51SetAbsAlarm........................................65SetEvent...............................................60SetRelAlarm.........................................ShutdownHook....................................69ShutdownOS........................................67StartOS................................................66StartupHook.........................................68StatusType...........................................47SUSPENDED......................................52TASK...................................................53TaskRefType........................................48TaskStateRefType................................48TaskType.............................................48TerminateTask......................................50TickRefType.........................................62ticksperbase..........................................62TickType..............................................62WaitEvent............................................62WAITING............................................52 82©byOSEKOSEKOS2.1 OSEK/VDX15.1Listoffigures Figure1-1Figure3-1Figure3-2Figure3-3Figure3-4Figure4-1Figure4-2Figure4-3Figure4-4Figure4-5Figure4-6Figure4-7Figure5-1Figure5-2Figure6-1Figure6-2Figure7-1Figure7-2Figure7-3Figure8-1Figure10-1Figure10-2Figure10-3Figure13-1Figure13-2 OperatingSystemSpecification2.1SoftwareinterfacesinsideECU.......................................................................9ProcessinglevelsoftheOSEKoperatingsystem.............................................14ProcessinglevelsoftheOSEKoperatingsystem.............................................15Restrictedupwardcompatibilityforconformanceclasses................................16TheminimumrequirementsforConformanceClasses.....................................16Extendedtaskstatemodel..............................................................................18Statesandstatustransitionsforextendedtasks...............................................18Basictaskstatemodel....................................................................................19Statesandstatustransitionsforbasictasks.....................................................19Scheduler:orderofevents..............................................................................21Nonpre-emptivescheduling...........................................................................22Fullpre-emptivescheduling............................................................................23ISRcategoriesoftheOSEKoperatingsystem................................................26APIservicesallowedtobecalledbytasksandISRs.......................................27Fullpre-emptivesynchronisationofextendedtasks.........................................30Nonpre-emptivesynchronisationofextendedtasks........................................30Priorityinversiononoccupyingsemaphores....................................................32Deadlocksituationusingsemaphores..............................................................33Resourceassignmentwithpriorityceilingbetweenpre-emptivetasks..............34Layeredmodelofalarmmanagement..............................................................38APIservicesforhookroutines........................................................................41Systemstart-up..............................................................................................43PreTaskHookandPostTaskHook...................................................................44Nestedinterrupts............................................................................................74Implementationspecifictools..........................................................................76 OSEKOS2.1©byOSEK83 OSEK/VDX16History Version1.0 Date 11.Sept.1995 OperatingSystemSpecification2.1RemarksAuthors: ThomasWollstadtWolfgangKremerJochemSpohr StephanSteinhauerThomasThurner KarlJoachimNeumannHelmarKuderFrançoisMosnier DietrichSchäfer-SiebertJürgenSchiemannReinerJohnAuthors: WolfgangKremerSalvatoreParisiAndreeZahir StephanSteinhauerJochemSpohrJanSöderbergPieroMortaraHelmarKuderBobFranceKenjiSuganumaStefanPolednaGerhardGöserGeorgWeilAlainCalvyKarlWesterholzJürgenMeyerAnsgarMaischAuthorsseeversion2.0 AdamOpelAGBMWAG Daimler-BenzAGDaimler-BenzAGDaimler-BenzAG UniversityofKarlsruheMercedes-BenzAGRenaultSA RobertBoschGmbHRobertBoschGmbHSiemensAG BMWAG CentroRicercheFiatETASGmbH&CoKGDaimler-BenzAG ATMComputerGmbHDelco MagnetiMarelliMercedes-BenzAGMotorolaSPS Nippondensoco.,ltdRobertBoschAG SiemensAutomotiveSASiemensAutomotiveSASiemensAutomotiveSASiemensSemiconductorsSoftingGmbH UniversityofKarlsruhe 2.002.June1997 2.0revision12.1 15.October199722.May2000 Authors:ManfredGeischederBMWKlausGresserBMWAdamJankowiakDaimlerChryslerJochemSpohrDaimlerChryslerAndreeZahirETASMarkusSchwabInfineonErikSvenskeMecelMaximTchervinskyMotorolaKenTindellNRTAGerhardGöserSiemensAutomotiveCarstenThiererUniversityofKarlsruheWinfriedJanzVectorInformatikVolkerBarthelmann3Soft ©byOSEK OSEKOS2.1 84 因篇幅问题不能全部显示，请点此查看更多更全内容
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