The cyclic executive model and Ada

Baker, Theodore P.; Shaw, Alan C.

doi:10.1007/bf02341919

Cited by 141 publications

(80 citation statements)

References 9 publications

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“…In an L0 application, when a mission change request arrives, following the semantics in SCJ imply that other PEHs belonging to the current or any other Mode changes in cyclic executives are usually done at the end of a major frame [128,18] therefore in our implementation we perform mission change for L0 applications only at the end of the currently executing major fame. The longest delay before the new-mission PEHs can execute (i.e.…”

Section: New Mission Initializationmentioning

confidence: 99%

Safety‐critical Java for embedded systems

Schoeberl

Dalsgaard

Hansen

et al. 2016

Concurrency and Computation

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Phone +45 4525 3351 compute@compute.dtu.dk www.compute.dtu.dk IMM-PhD-2014-340 Summary (English) Safety-critical systems are real-time systems whose failure can have severe or catastrophic consequences, possibly endangering human life. Many safety-critical systems incorporate embedded computers used to control different tasks. Software running on safety-critical systems needs to be certified before its deployment and the most time-consuming step of this process is the testing and verification phase. Due to the increasing complexity in safety-critical systems there is a need for new technologies that can facilitate testing and verification activities.The safety-critical specification for Java aims at providing a reduced set of the Java programming language that can be used for systems that need to be certified at the highest levels of criticality. Safety-critical Java (SCJ) restricts how a developer can structure an application by providing a specific programming model and by restricting the set of methods and libraries that can be used. Furthermore, its memory model do not use a garbage-collected heap but scoped memories.In this thesis we examine the use of the SCJ specification through an implementation in a time-predictable, FPGA-based Java processor. The specification is now in a mature state and with our implementation we have proved its feasibility in an embedded platform. Moreover, we have explored how simple hardware extensions can reduce the execution time of time-critical operations required by the SCJ specification.The scoped memory model used in SCJ is perhaps one of its most difficult features to use correctly. Therefore, in this work we have also studied practical aspects of its usage by developing scoped memory use patterns and reusable libraries aiming at facilitating the development of complex software systems.ii Summary (Danish)Sikkerhedskritiske systemer er realtidssystemer. Hvis sådanne systemer fejler, kan det have alvorlige eller katastrofale konsekvenser, muligvis livsfarlige konsekvenser. Mange sikkerhedskritiske systemer inkorporerer embeddede computere, som bruges til at kontrollere forskellige opgaver. Software, som kører på sikkerhedskritiske systemer, skal certificeres, før softwaren udrulles, og det mest tidskraevende skridt i denne proces er test-og verifikationsfasen. På grund af den stigende kompleksitet i sikkerhedskritiske systemer er der behov for nye teknologier til at facilitere test-og verifikationsaktiviteter.Den sikkerhedskritiske specifikation for Java har til formål at levere en reduceret udgave af Java-programmeringssproget, som kan bruges til systemer, der skal kunne certificeres på de højeste kritikalitetsniveauer. Safety Critical Java (SCJ) begraenser, hvordan en udvikler kan strukturere en applikation, ved at levere en specifik programmeringsmodel og ved at begraense de metoder og biblioteker, som kan anvendes. Derudover benytter hukommelsesmodellen i SCJ ikke en heap, der er garbage-collected, men afgraensede hukommelser.I denne afhandling undersøger vi brugen a...

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Section: New Mission Initializationmentioning

confidence: 99%

Safety‐critical Java for embedded systems

Schoeberl

Dalsgaard

Hansen

et al. 2016

Concurrency and Computation

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“…Since a sequence of nodes on the Chord overlay network serve a lookup request, each node is required to execute one corresponding job. Our real-time DHT follows a cyclic executive [11], [2] to schedule these jobs on each node. We analyze the response time of these sub-request jobs on each node and aggregate them to bound the end-to-end response time for all requests.…”

Section: Contributionsmentioning

confidence: 99%

A real-time distributed hash table

Qian

Mueller

Xin

2014

2014 IEEE 20th International Conference on Embedded and Real-Time Computing Systems and Applications

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Abstract-Currently, the North American power grid uses a centralized system to monitor and control wide-area power grid states. This centralized architecture is becoming a bottleneck as large numbers of wind and photo-voltaic (PV) generation sources require real-time monitoring and actuation to ensure sustained reliability. We have designed and implemented a distributed storage system, a real-time distributed hash table (DHT), to store and retrieve this monitoring data as a real-time service to an upper layer decentralized control system. Our real-time DHT utilizes the DHT algorithm Chord in a cyclic executive to schedule data-lookup jobs on distributed storage nodes. We formally define the pattern of the workload on our real-time DHT and use queuing theory to stochastically derive the time bound for response times of these lookup requests. We also define the quality of service (QoS) metrics of our real-time DHT as the probability that deadlines of requests can be met. We use the stochastic model to derive the QoS. An experimental evaluation on distributed nodes shows that our model is well suited to provide time bounds for requests following typical workload patterns and that a prioritized extension can increase the probability of meeting deadlines for subsequent requests.

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“…A cyclic executive runs a sequence of non-preemptive tasks, invoking each task in a fixed order throughout the execution history. For an evaluation of cyclic executive models for controller tasks see Baker and Shaw [1988]. Although the advantages of using cyclic executives for computer-controlled systems have been proven, some real limitations have also been identified.…”

Section: Introductionmentioning

confidence: 99%