Wang Yi, Uppsala University
The Cause-Effect Latency Problem in Real-Time Systems with Non-Blocking Communication


In real-time embedded systems, a system functionality is often implemented using a data-flow chain over a set of communicating tasks. A critical requirement in such systems is to restrict the amount of time, i.e. cause-effect latency, for an input data to impact its corresponding output. The problem of estimating the worst case cause-effect latency is well-studied in the context of blocking intertask communication. In a recent work, we show that non-blocking communication preserving functional semantics is critical for the design of dynamically updatable systems. In this paper, we study non-blocking protocols for intertask communication and the cause-effect latency problem in this setting. We present an algorithm to compute the exact worst-case delay in a data-flow task chain between the releases of the first job for sampling of input data and the final job for actuation based on the corresponding output.