Efficient and robust dynamic scheduling and synchronization in practical embedded real-time multiprocessor systems

Multiprocessors are on the way to become a standard platform for embedded systems with real-time requirements. For real-time systems, it is crucial that functional and temporal constraints are fulfilled. The focus of this dissertation lies on the aspect of these timing requirements. Within this context, two fundamental questions arise: (1) How to schedule a given task set on the available cores, and (2) How to synchronize tasks without a loss of data consistency and unbounded blocking times. In theory, optimal scheduling algorithms are already known. In this case, optimal means that if there is any option that a task set fulfills all its temporal requirements, the algorithm finds such a schedule. Nevertheless, they are not in practical use (at least in automotive powertrain systems) because these optimal algorithms are accompanied by overheads caused by core migrations, context switches and the need for repeatedly priority calculations. This thesis tries to close the gap between theory and practice by developing a concept for an efficient implementation global scheduler with dynamic priorities that fulfills the requirements of engine control units. Furthermore, there exists no generic optimal multiprocessor real-time synchronization mechanism that is able to handle all types of task allocation and priorities, and supports as well resting of resource requests. Thus, two different locking protocols are provided that outperform existing ones for specific types of task sets for embedded multiprocessor real-time systems. Case studies are presented that evaluate the assumptions of the efiiciency and robustness of the locking protocols.Multi-Prozessor Systeme haben in eingebettete Systeme mit Echtzeit Anforderungen Einzug gehalten. Für Echtzeitsysteme ist entscheidend, dass sowohl funktionale als auch temporale Erfordernisse eingehalten werden. Diese Dissertation beschäftigt sich mit dem Aspekt der zeitlichen Anforderungen an Echtzeitsysteme. In diesem Kontext stehen zwei grundlegende Fragen im Raum, nämlich (1) Wie verteilt man die zur Ausführung bereiten Tasks am besten auf die zur Verfügung stehenden Rechenkerne? (2) Wie synchronisiert man die Tasks ohne dass die Datenkonsistenz beeinträchtigt wird und unnötige oder endlose Blockierzeiten entstehen? Es wurden bereits Scheduling-Algorithmen entwickelt, die theoretisch optimal sind. Optimal bedeutet in diesem Kontext, dass wenn immer es eine Möglichkeit gibt, ein Task-Set ohne Deadline Verletzung auszuführen, der Algorithmus eine solche Möglichkeit auch findet. Diese optimalen Algorithmen haben sich jedoch in der Praxis (z.B. im Antriebsstrang von Automobilen) bisher nicht durchgesetzt, da mit dem Einsatz dieser Scheduling Algorithmen eine Vielzahl an Kern-Migrationen, Kontextwechsel und die Notwendigkeit von Prioritäts-Neuberechnungen einhergehen, die zu Verzögerungen des gesamten Systems führen. Diese Arbeit versucht, die Lücke zwischen Theorie und Praxis ein Stück weit zu schließen. Dafür wurde ein Konzept für einen globalen Scheduling Algorithmus entwickelt, der effizient zu implementieren ist und Prioritätsänderungen während der Laufzeit zulässt. Er enthält außerdem Erweiterungen, die beim Einsatz in Motorsteuergeräten benötigt werden. Im Fall der zweiten Frage stellte sich heraus, dass es kein Synchronisationsprotokoll gibt, das für alle Arten von Task-Sets und Hardwarearchitekturen optimal ist, also so wenig Blockierzeiten wie möglich verursacht. Daher werden im Rahmen dieser Arbeit zwei Synchronisationsprotokolle für Multi-Prozessor Echtzeitsysteme vorgestellt, die bisher entwickelten Protokolle in der Vermeidung von Blockierzeiten für bestimmte Task-sets überlegen sind. Diese Protokolle werden mittles diskreter, event-basierter Simulation im Rahmen einer Fallstudie experimentell evakuiert

An Efficient Partitioning Strategy for Runnables in Weakly Dependent Tasks on Embedded Multi-Core Systems

International audienceWith multi-core controllers entering the area of automotive control ECUs, strategies for parallelizing the control- algorithms come into focus. This paper deals with a special part of automotive powertrain software, called state transitions. Since dependencies between runnables executed there are weak, the transitions provide a good basis for parallelization. We present a strategy of how to distribute efficiently the execution of runnables to different cores while taking care of inner and outer dependencies. The strategy is accompanied by two case studies demonstrating the performance of the concept. The first one is carried out to find the most efficient strategies of parallelize state transitions based on randomly generated, simulated state transitions. In the second one, the developed partitioning strategies are applied to a real software project for an automotive powertrain system

AUTOtech.agil: architecture and technologies for orchestrating automotive agility

Future mobility will be electrified, connected and automated. This opens completely new possibilities for mobility concepts that have the chance to improve not only the quality of life but also road safety for everyone. To achieve this, a transformation of the transportation system as we know it today is necessary. The UNICARagil project, which ran from 2018 to 2023, has produced architectures for driverless vehicles that were demonstrated in four full-scale automated vehicle prototypes for different applications. The AUTOtech.agil project builds upon these results and extends the system boundaries from the vehicles to include the whole intelligent transport system (ITS) comprising, e.g., roadside units, coordinating instances and cloud backends. The consortium was extended mainly by industry partners, including OEMs and tier 1 suppliers with the goal to synchronize the concepts developed in the university-driven UNICARagil project with the automotive industry. Three significant use cases of future mobility motivate the consortium to develop a vision for a Cooperative Intelligent Transport System (C-ITS), in which entities are highly connected and continually learning. The proposed software ecosystem is the foundation for the complex software engineering task that is required to realize such a system. Embedded in this ecosystem, a modular kit of robust service-oriented modules along the effect chain of vehicle automation as well as cooperative and collective functions are developed. The modules shall be deployed in a service-oriented E/E platform. In AUTOtech.agil, standardized interfaces and development tools for such platforms are developed. Additionally, the project focuses on continuous uncertainty consideration expressed as quality vectors. A consistent safety and security concept shall pave the way for the homologation of the researched ITS