Towards a Predictable Component-Based Run-Time System
Sammanfattning: In this thesis we propose a technique to preserve the temporal properties of realtime components during their integration and reuse. We propose a new concept of runnable virtual node which is a coarse-grained real-time component that provides functional and temporal isolation with respect to its environment. A virtual node’s interaction with the environment is bounded by both a functional and a temporal interface, and the validity of its internal temporal behaviour is preserved when integrated with other components or when reused in a new environment. The first major contribution of this thesis is the implementation of a Hierarchical Scheduling Framework (HSF) on an open source real-time operating system (FreeRTOS) with the emphasis of doing minimal changes to the underlying FreeRTOS kernel and keeping its API intact to support the temporal isolation between a numbers of applications, on a single processor. Temporal isolation between the components during runtime prevents failure propagation between different components. The second contribution of the thesis is with respect to the integration of components, where we first illustrate how the concept of the runnable virtual node can be integrated in several component technologies and, secondly, we perform a proof-of-concept case study for the ProCom component technology where we demonstrate the runnable virtual node’s real-time properties for temporal isolations and reusability. We have performed experimental evaluations on EVK1100 AVR based 32-bit micro-controller and have checked the system behaviour during heavy-load and over-load situations by visualizing execution traces in both hierarchical scheduling and virtual node contexts. The results for the case study demonstrate temporal error containment within a runnable virtual node as well as reuse of the node in a new environment without altering its temporal behaviour.
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