Martijn M. H. P. van den Heuvel

Integrating Cache-Related Pre-Emption Delays into Analysis of Fixed Priority Scheduling with Pre-Emption Thresholds

Cache-related pre-emption delays (CRPD) have been integrated into the schedulability analysis of sporadic tasks with constrained deadlines for fixed-priority pre-emptive scheduling (FPPS). This paper generalizes that work by integrating CRPD into the schedulability analysis of tasks with arbitrary deadlines for fixed-priority pre-emption threshold scheduling (FPTS). The analysis is complemented by an optimal threshold assignment algorithm that minimizes CRPD. The paper includes a comparative evaluation of the schedulability ratios of FPPS and FPTS, for constrained-deadline tasks, taking CRPD into account.

Dynamic resource allocation for real-time priority processing applications

Flexible signal processing on programmable platforms are increasingly important for consumer electronic applications and others. Scalable video algorithms (SVAs) using novel priority processing can guarantee real-time performance on programmable platforms even with limited resources. Dynamic resource allocation is required to maximize the overall output quality of independent, competing priority processing algorithms that are executed on a shared platform. In this paper, we describe basic mechanisms for dynamic resource allocation and compare the performance of different implementations on a general purpose platform.

Limited preemptive scheduling of mixed time-triggered and event-triggered tasks

Many embedded systems have complex timing constraints and, at the same time, have flexibility requirements which prohibit offline planning of the entire system. To support a mixture of time-triggered and event-triggered tasks, some industrial systems deploy a table-driven dispatcher for time-triggered tasks complemented with a preemptive scheduler to allocate the free time slots to event-driven tasks. Contrary to fully preemptive scheduling, limiting the preemptions of tasks to fixed preemptions points may reduce memory requirements and it alleviates the preemption costs in the system. We revisit slotshifting, which at run time mixes time-triggered and event-triggered tasks in a preemptive EDF schedule. In this paper, we extend slotshifting with limited-preemptive execution of event-triggered tasks. We present a synchronization protocol to arbitrate the executions of non-preemptive regions, so that time-triggered tasks keep meeting their timing constraints implicitly. Furthermore, we investigate how to disable preemptions of event-triggered tasks during the execution of the offline-scheduled time-triggered tasks, while keeping the feature of slotshifting to reallocate their slots of execution dynamically at run time.

RTOS Support for Mixed Time-triggered and Event-triggered Task Sets

Many embedded systems have complex timing constraints and, at the same time, have flexibility requirements which prohibit offline planning of the entire system. To support a mixture of time-triggered and event-triggered tasks, some industrial systems deploy an RTOS with a table-driven dispatcher complemented with a preemptive scheduler to allocate the free time slots to event-driven tasks. Rather than allocating dedicated time-slots to time-triggered tasks, in this work we provide RTOS support to dynamically re-allocate time-slots of time-triggered tasks within pre-computed time ranges to maximize the availability of the processing capacity for event-triggered tasks. Although the concept - called slot shifting - is not new, we are the first to extend a commercial RTOS with such support. In addition, we extend slot shifting with a run-time mechanism to reclaim resources of time-triggered tasks when their reserved capacities are unused. This mechanism eliminates over-provisioning of capacities to tasks that have been converted into periodic tasks to resolve interdependencies during off-line synthesis, but by nature are event-triggered. This allows, for example, for a resource-efficient implementation of a polling task. After implementing our unique RTOS extensions, we investigate the run-time overheads for the corresponding scheduling mechanisms. Measurements show that the increase in terms of absolute run-time overhead is minor compared to an off-the-shelf micro-kernel with a fixed-priority scheduler.

Dependable partitioning for autonomous agents in adaptive lighting environments

Adaptive lighting environments (ALEs) are becoming increasingly important to regulate lighting conditions for our daily activities due to its promises to increase user comfort and decrease power consumption compared to static lighting. We propose a service to synchronize lighting scenarios over a partition of autonomous light agents. To the best of our knowledge, we are the first to present an ALE with decentralized dynamic scenario management.

Towards RTOS support for mixed time-triggered and event-triggered task sets

Many embedded systems have complex timing constraints and, at the same time, have flexibility requirements which prohibit offline planning of the entire system. To support a mixture of time-triggered and event-triggered tasks, some industrial systems deploy a real-time operating system (RTOS) with a table-driven dispatcher complemented with a preemptive scheduler to allocate free time slots to event-driven tasks. Rather than allocating dedicated time-slots to time-triggered tasks, we propose to dynamically re-allocate time-slots of time-triggered tasks within a pre-computed time range to maximize the available processing capacity for event-triggered tasks. Although the concept — called slotshifting — is not new, we are unaware of a commercial RTOS with such support. After identifying the mechanisms for an RTOS implementation of slotshifting, we discuss the run-time overheads for admitting aperiodic requests into the system1.

An Approach for Systematic In-the-Loop Simulations for Development and Test of a Complex Mechatronic Embedded System

Simulations are widely used in the engineering workflow of complex mechatronic embedded systems in various domains, such as healthcare, railway, automotive and aerospace, for analyzing, testing and validating purposes. This paper focuses on the development and test of the control software of complex mechatronic embedded systems from the perspective of software interfaces (e.g., driver APIs) and presents a systematic approach for testing the control software during the various stages of an engineering process. Since we assume that the physical (hardware) components of an under-control plant could be replaced with simulation models, various kinds of in-the-loop simulations, ranging from MiL to HiL, can be consequently acquired. Additionally, we present a mathematical model of MESes required to formally describe the approach and also a healthcare case study to which our approach was applied.

Composing and synchronizing real-time software through virtual platforms in vehicular systems

This paper gives an overview of the challenges we faced when integrating software components on an electronic control unit (ECU) embedded in a car. The results show management of scarce ECU resources and a demonstration of temporal isolation between components in an industrial case study.

Guidelines and challenges for composing and synchronizing real-time software components through virtual platforms in vehicular systems

This work investigates the composition of interdependent software components on a shared platform from a timing perspective. Because we consider software components for vehicular systems, which are often sensitive to timing, the individual components and the composed system require timing analysis. In order to support independent development of components, the real-time systems community proposed hierarchical scheduling frameworks (HSFs). HSFs in essence provide a virtual platform to individual components, including well-defined protocols for their synchronization. In this paper, we give an overview of recent research for applying HSFs into in-vehicle technology standards and we look ahead to some future challenges regarding the safety certification of such systems.

Towards an interoperable framework for mixed real-time simulations of industrial embedded systems

Simulations are often used to improve the development and test time of industrial embedded systems in different domains, such as healthcare, railway, automobile and aerospace. This paper introduces a general framework capable of simulating real components simultaneously with simulated ones, in real-time, and with a low impact on the performance of the overall system. Our framework is loosely dependent on the application and the domain where the application is developed in. More importantly, it enhances interoperability and reuse, because it paves the way to reuse existing simulating tools and models and to integrate separately developed models from earlier stages in the design into a single coherent simulation.