Jukka Mäki-Turja

The Rubus component model for resource constrained real-time systems

In this paper we present a component model for development of distributed real-time systems. The model is developed to support development of embedded control systems for ground vehicles. The model aims at supporting three important activities in real-time development, (i) design, (ii) analysis and (iii) synthesis. These activities emphasise different and sometimes conflicting requirements that need to be balanced. For example, developers desire freedom in designing to solve complex tasks, analysis tools require the design to be formal enough for analysis and synthesis need to be efficient for low run-time footprint. We have considered industrial requirements for these activities and developed the RubusCMv3 component model. The model has been developed in close cooperation with industrial partners and it is currently being evaluated on real systems.

Support for hierarchical scheduling in FreeRTOS

This paper presents the implementation of a Hierarchical Scheduling Framework (HSF) on an open source real-time operating system (FreeRTOS) to support the temporal isolation between a number of applications, on a single processor. The goal is to achieve predictable integration and reusability of independently developed components or applications. We present the initial results of the HSF implementation by running it on an AVR 32-bit board EVK1100. The paper addresses the fixed-priority preemptive scheduling at both global and local scheduling levels. It describes the detailed design of HSF with the emphasis of doing minimal changes to the underlying FreeRTOS kernel and keeping its API intact. Finally it provides (and compares) the results for the performance measures of idling and deferrable servers with respect to the overhead of the implementation.

Worst-case response-time analysis for mixed messages with offsets in Controller Area Network

The existing response-time analysis for Controller Area Network (CAN) does not support mixed messages that are scheduled with offsets. Mixed messages are implemented by several high-level protocols for CAN that are used in the automotive industry. We extend the existing offset-based analysis which is applicable to any high-level protocol for CAN that uses periodic, sporadic and mixed transmission of messages. Moreover, we implement the extended analysis as a standalone simulator that will be integrated as a plug-in with the existing industrial tool suite (Rubus-ICE). The experiments, that we performed, indicate that it is possible to achieve up to 4.48% improvement in schedulability when mixed messages are scheduled with offsets.

Support for End-to-End Response-Time and Delay Analysis in the Industrial Tool Suite: Implementation Issues, Experiences and a Case Study

In this paper we discuss the implementation of the state-of-the-art end-to-end response-time and delay analysis as two individual plug-ins for the existing industrial tool suite Rubus-ICE. The tool ...

Deployment Modelling and Synthesis in a Component Model for Distributed Embedded Systems

We present an approach to combine model-driven and component-based software engineering of distributed embedded systems. Specifically, we describe how deployment modelling is performed in two steps, and present an incremental synthesis of runnable representations of model entities on various abstraction levels. Our approach allows for flexible reuse opportunities, in that entities at different levels of granularity and abstraction can be reused. It also permits detailed analysis, e.g., with respect to timing, of units smaller than a whole physical node. We present a concept, virtual nodes, which preserves real-time properties across reuse and integration in different contexts.

Fast and tight response-times for tasks with offsets

In previous work, we presented a tight approximate response-time analysis for tasks with offsets. While providing a tight bound on response times, the tight analysis exhibits similarly long execution times as does the traditional methods for calculating response-times for tasks with offsets. The existing method for fast analysis of tasks with offsets is not applicable to the tight analysis. In this paper we extend the fast analysis to handle the distinguishing trait of the tight analysis; continuously increasing interference functions. Furthermore, we provide another speedup; by introducing pessimism in the modelling of interference at certain points, we speed up the convergence of the numerical solving for response-times without increasing the pessimism of the resulting response-times. The presented fast-and-tight analysis is guaranteed to calculate the same response-times as the tight analysis, and in a simulation study we obtain speedups of more than two orders of magnitude for realistically sized tasks sets compared to the tight analysis. We also demonstrate that the fast-and-tight analysis has comparable execution time to that of the fast analysis. Hence, we conclude that the fast-and-tight analysis is the preferred analysis technique when tight estimates of response-times are needed, and that we do not need to sacrifice tightness for analysis speed; both are obtained with the fast-and-tight analysis.

Communications-oriented development of component-based vehicular distributed real-time embedded systems

We propose a novel model- and component-based technique to support communications-oriented development of software for vehicular distributed real-time embedded systems. The proposed technique supports modeling of legacy nodes and communication protocols by encapsulating and abstracting the internal implementation details and protocols. It also allows modeling and performing timing analysis of the applications that contain network traffic originating from outside of the system such as vehicle-to-vehicle, vehicle-to-infrastructure, and cloud-based applications. Furthermore, we present a method to extract end-to-end timing models to support end-to-end timing analysis. We also discuss and solve the issues involved during the extraction of these models. As a proof of concept, we implement our technique in the Rubus Component Model which is used for the development of software for vehicular embedded systems by several international companies. We also conduct an application-case study to validate our approach.

Response-time analysis of mixed messages in Controller Area Network with priority- and FIFO-queued nodes

The Controller Area Network (CAN) is a widely used real-time network in automotive domain. We identify that the existing response-time analysis for messages in CAN with some of the connected nodes implementing priority queues while others implementing FIFO queues does not support the analysis of mixed messages. The existing analysis assumes that a message is queued for transmission either periodically or sporadically. However, a message can also be queued both periodically and sporadically using a mixed transmission mode implemented by several high-level protocols for CAN used in the industry today. We extend the existing analysis which is generally applicable to any high-level protocol for CAN (with priority-and FIFO-queued nodes) that uses periodic, sporadic, and mixed transmission of messages.

Analyzable Modeling of Legacy Communication in Component-Based Distributed Embedded Systems

We present extensions to the existing industrial component model Rubus Component Model (RCM). By introducing special purpose components to encapsulate and abstract the communication protocols in distributed embedded systems we allow use of legacy nodes and legacy protocols in a component-based and model-based software engineering environment. With the addition of these components, RCM will be able to support state-of-the-practice development processes of distributed embedded systems where communication rules are defined early in the development process. The proposed extension also allows model-based and component-based development of new nodes that are deployed in the legacy systems that use predefined communication rules. We also demonstrate how an end-to-end timing model can be extracted from a distributed embedded system modeled with extended RCM. The extracted model is then used to perform an end-to-end timing analysis that we implemented in the Rubus Analysis Framework.

Determining Maximum Stack Usage in Preemptive Shared Stack Systems

This paper presents a novel method to determine the maximum stack memory used in preemptive, shared stack, real-time systems. We provide a general and exact problem formulation applicable for any preemptive system model based on dynamic (run-time) properties. We also show how to safely approximate the exact stack usage by using static (compile time) information about the system model and the underlying run-time system on a relevant and commercially available system model: a hybrid, statically and dynamically, scheduled system. Comprehensive evaluations show that our technique significantly reduces the amount of stack memory needed compared to existing analysis techniques. For typical task sets a decrease in the order of 70% is typical