Response-Time Analysis for Task Chains with Complex Precedence and Blocking Relations

Abstract

For the development of complex software systems, we often resort to component-based approaches that separate the different concerns, enhance verifiability and reusability, and for which microkernel-based implementations are a good fit to enforce these concepts. Composing such a system of several interacting software components will, however, lead to complex precedence and blocking relations, which must be taken into account when performing latency analysis. When modelling these systems by classical task graphs, some of these effects are obfuscated and tend to render such an analysis either overly pessimistic or even optimistic. We therefore firstly present a novel task (meta-)model that is more expressive and accurate w.r.t. these (functional) precedence and mutual blocking relations. Secondly, we apply the busy-window approach and formulate a modular response-time analysis on task-chain level suitable but not restricted to static-priority scheduled systems. We show that the conjunction of both concepts allows the calculation of reasonably tight latency bounds for scenarios not adequately covered by related work