https://ojs.dagstuhl.de/index.php/lites/issue/feed Leibniz Transactions on Embedded Systems 2019-05-14T15:39:50+02:00 Michael Wagner (LITES Editorial Office) lites-office@dagstuhl.de Open Journal Systems <span>LITES publishes original articles on all aspects of embedded computer systems according to the principles of OpenAccess.</span> https://ojs.dagstuhl.de/index.php/lites/article/view/LITES-v006-i001-a001 Local Planning Semantics: A Semantics for Distributed Real-Time Systems 2019-05-14T15:32:20+02:00 Mahieddine Dellabani mahieddine.dellabani@univ-grenoble-alpes.fr Jacques Combaz jacques.combaz@univ-grenoble-alpes.fr Saddek Bensalem saddek.bensalem@univ-grenoble-alpes.fr Marius Bozga marius.bozga@univ-grenoble-alpes.fr Design, implementation and verification of distributed real-time systems are acknowledged to be very hard tasks. Such systems are prone to different kinds of delay, such as execution time of actions or communication delays implied by distributed platforms. The latter increase considerably the complexity of coordinating the parallel activities of running components. Scheduling such systems must cope with those delays by proposing execution strategies ensuring global consistency while satisfying the imposed timing constraints. In this paper, we investigate a formal model for such systems as compositions of timed automata subject to multiparty interactions, and propose a semantics aiming to overcome the communication delays problem through anticipating the execution of interactions. To be effective in a distributed context, scheduling an interaction should rely on (as much as possible) local information only, namely the state of its participating components. However, as shown in this paper these information is not always sufficient and does not guarantee a safe execution of the system as it may introduce deadlocks. Moreover, delays may also affect the satisfaction of timing constraints, which also corresponds to deadlocks in the former model. Thus, we also explore methods for analyzing such deadlock situations and for computing deadlock-free scheduling strategies when possible. 2019-02-18T00:00:00+01:00 Copyright (c) 2019 Mahieddine Dellabani, Jacques Combaz, Saddek Bensalem, and Marius Bozga https://ojs.dagstuhl.de/index.php/lites/article/view/LITES-v006-i001-a002 Improving WCET Evaluation using Linear Relation Analysis 2019-05-14T15:32:20+02:00 Pascal Raymond Pascal.Raymond@univ-grenoble-alpes.fr Claire Maiza Claire.Maiza@univ-grenoble-alpes.fr Catherine Parent-Vigouroux catherine.vigouroux@univ-grenoble-alpes.fr Erwan Jahier Erwan.Jahier@univ-grenoble-alpes.fr Nicolas Halbwachs nicolas.halbwachs@univ-grenoble-alpes.fr Fabienne Carrier Fabienne.Carrier@univ-grenoble-alpes.fr Mihail Asavoae mihail.asavoae@gmail.com Rémy Boutonnet remy.boutonnet@imag.fr The precision of a worst case execution time (WCET) evaluation tool on a given program is highly dependent on how the tool is able to detect and discard semantically infeasible executions of the program. In this paper, we propose to use the classical abstract interpretation-based method of linear relation analysis to discover and exploit relations between execution paths. For this purpose, we add auxiliary variables (counters) to the program to trace its execution paths. The results are easily incorporated in the classical workflow of a WCET evaluator, when the evaluator is based on the popular implicit path enumeration technique. We use existing tools - a WCET evaluator and a linear relation analyzer - to build and experiment a prototype implementation of this idea. 2019-02-18T00:00:00+01:00 Copyright (c) 2018 Pascal Raymond, Claire Maiza, Catherine Parent-Vigouroux, Erwan Jahier, Nicolas Halbwachs, Fabienne Carrier, Mihail Asavoae, and Rémy Boutonnet https://ojs.dagstuhl.de/index.php/lites/article/view/LITES-v006-i001-a003 A Survey of Probabilistic Timing Analysis Techniques for Real-Time Systems 2019-05-14T15:39:49+02:00 Robert I. Davis rob.davis@york.ac.uk Liliana Cucu-Grosjean liliana.cucu@inria.fr <p>This survey covers probabilistic timing analysis techniques for real-time systems. It reviews and critiques the key results in the field from its origins in 2000 to the latest research published up to the end of August 2018. The survey provides a taxonomy of the different methods used, and a classification of existing research. A detailed review is provided covering the main subject areas: static probabilistic timing analysis, measurement-based probabilistic timing analysis, and hybrid methods. In addition, research on supporting mechanisms and techniques, case studies, and evaluations is also reviewed. The survey concludes by identifying open issues, key challenges and possible directions for future research.</p> 2019-05-14T00:00:00+02:00 Copyright (c) 2019 Robert I. Davis and Liliana Cucu-Grosjean https://ojs.dagstuhl.de/index.php/lites/article/view/LITES-v006-i001-a004 A Survey of Probabilistic Schedulability Analysis Techniques for Real-Time Systems 2019-05-14T15:39:50+02:00 Robert I. Davis rob.davis@york.ac.uk Liliana Cucu-Grosjean liliana.cucu@inria.fr <p>This survey covers schedulability analysis techniques for probabilistic real-time systems. It reviews the key results in the field from its origins in the late 1980s to the latest research published up to the end of August 2018. The survey outlines<br />fundamental concepts and highlights key issues. It provides a taxonomy of the different methods used, and a classification of existing research. A detailed review is provided covering the main subject areas as well as research on supporting techniques. The survey concludes by identifying open issues, key challenges and possible directions for future research.</p> 2019-05-14T00:00:00+02:00 Copyright (c) 2019 Robert I. Davis and Liliana Cucu-Grosjean https://ojs.dagstuhl.de/index.php/lites/article/view/LITES-v006-i001-a005 Elastic Scheduling for Parallel Real-Time Systems 2019-05-14T15:39:50+02:00 James Orr james.orr@wustl.edu Chris Gill cdgill@wustl.edu Kunal Agrawal kunal@wustl.edu Jing Li jingli@njit.edu Sanjoy Baruah baruah@wustl.edu <p class="p1">The elastic task model was introduced by Buttazzo et al.~in order to represent recurrent real-time workloads executing upon uniprocessor platforms that are somewhat flexible with regards to timing constraints. In this work, we propose an extension of this model and apply it to represent recurrent real-time workloads that exhibit internal parallelism and are executed on multiprocessor platforms. In our proposed extension, the elasticity coefficient - the quantitative measure of a task's elasticity that was introduced in the model proposed by Buttazzo et al. - is interpreted in the same manner as in the original (sequential) model. Hence, system developers who are familiar with the elastic task model in the uniprocessor context may use our more general model as they had previously done, now for real-time tasks whose computational demands require them to utilize more than one processor. </p> 2019-05-14T00:00:00+02:00 Copyright (c) 2019 James Orr, Chris Gill, Kunal Agrawal, Jing Li, and Sanjoy Baruah