ERCOS: An Operating System for Automotive Applications

Poledna, Stefan; Mocken, T.; Schiemann, J.; Beck, T.

doi:10.4271/960623

Cited by 22 publications

(13 citation statements)

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“…An experimental implementation of the message operations send and receive has shown an overhead of 0.625 s and 0.750 s, respectively. This implementation has been carried out in the framework of ERCOS [24] under the assumption that the message length is equal to the word length of the processor.…”

Section: Discussionmentioning

confidence: 99%

“…Although conceptually simple, the cyclic executive approach suffers from a number of drawbacks [18]; it uses resources inefficiently, it does not easily cater to sporadic jobs, and it gives poor support to more flexible and adaptive requirements. A more appropriate scheme, using priority-based scheduling of application tasks [4], is currently been used (or evaluated) in a number of application domains, for example, in avionics [2] or automotive electronics [24]. Both preemptive and nonpreemptive (cooperative) methods are under consideration.…”

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confidence: 99%

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Replica determinism and flexible scheduling in hard real-time dependable systems

Poledna¹,

Burns

Wellings

et al. 2000

IEEE Trans. Comput.

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AbstractÐFault-tolerant real-time systems are typically based on active replication where replicated entities are required to deliver their outputs in an identical order within a given time interval. Distributed scheduling of replicated tasks, however, violates this requirement if on-line scheduling, preemptive scheduling, or scheduling of dissimilar replicated task sets is employed. This problem of inconsistent task outputs has been solved previously by coordinating the decisions of the local schedulers such that replicated tasks are executed in an identical order. Global coordination results either in an extremely high communication effort to agree on each schedule decision or in an overly restrictive execution model where on-line scheduling, arbitrary preemptions, and nonidentically replicated task sets are not allowed. To overcome these restrictions, a new method, called timed messages, is introduced. Timed messages guarantee deterministic operation by presenting consistent message versions to the replicated tasks. This approach is based on simulated common knowledge and a sparse time base. Timed messages are very effective since they neither require communication between the local scheduler nor do they restrict usage of on-line flexible scheduling, preemptions and nonidentically replicated task sets.

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Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 99%

Replica determinism and flexible scheduling in hard real-time dependable systems

Poledna¹,

Burns

Wellings

et al. 2000

IEEE Trans. Comput.

Self Cite

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“…For example, a task can be released earlier, execute initial code and then voluntarily suspend itself until the beginning of its LET. This is a form of cooperative scheduling [11]. Taking into account internal task structure has been shown to improve scheduling margins.…”

Section: Conclusion and Related Workmentioning

confidence: 98%

Flexible Static Scheduling of Software with Logical Execution Time Constraints

Derler

Resmerita

2010

2010 10th IEEE International Conference on Computer and Information Technology

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Various programming models for embedded, timetriggered software employ the logical execution time (LET) abstraction in order to achieve time-and value-determinism. In these models, the application software is partitioned into tasks and a LET is associated with every task. In every execution, a task reads input values at the beginning of the LET and writes output values at the end of the LET. To achieve this behavior, existing implementations of LET models impose execution constraints where every physical execution of a task must take place between the corresponding LET bounds. In this paper we investigate a more efficient implementation paradigm in which LET-based execution constraints are relaxed by allowing tasks to execute outside of their LET bounds while preserving their I/O LET behavior. We present a modified runtime operational semantics where scheduling operations are decoupled from data transfer operations. Moreover, we propose a way to statically determine task release times that may precede LET start times, by using information about tasks connectivity (available in the LET model) and about task execution times (required for schedulability analysis). The consequences of using the relaxed constraints on the schedulability of the system are explored. We address sustainability of preemptive scheduling with respect to variations in release times and propose bounds on such variations that preserve schedulability for Fixed Priority (FP) scheduling. Moreover, we describe an application of Dual Priority scheduling which guarantees schedulability for any release time variation of a system that is originally FP-schedulable. Relaxing execution constraints leads to increased processor utilization. Some of the benefits thereof are illustrated on a typical control application. 1

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“…Dabei wird der Cluster mit der kleinsten Deadline oder Periode auf die Task mit der höchsten Priorität abgebildet. Kommunikation zwischen Clustern muss in bestimmten Fällen durch doppelt gepufferte Interprozesskommunikation (IPC) [22] abgesichert werden, um die Semantik des Modells in der Implementierung zu erhalten. Die auf der Implementierungsebene auftretenden Verzögerungen werden dabei auf Modellebene durch die logisch gezeiteten Verzögerungen an den Clustergrenzen abgebildet.…”

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