SMT-Based Repairing Real-Time Task Specifications

When addressing timing issues in real-time systems, approaches for systematic timing debugging and repair have been missing due to (i) Lack of available feedback: most timing analysis techniques, being closed-form analytical techniques, are unable to provide root cause information when a timing property is violated, which is critical for identifying an appropriate repair, and (ii) Pessimism in the analysis: existing schedulability analysis techniques tend to make worst case assumptions in the presence of non-determinism introduced by real-world factors such as release jitter, or sporadic tasks. To address this gap, we propose an SMT encoding of task runs for exact debugging of timing violations, and a procedure to iteratively repair a given task specification. We demonstrate the utility of this procedure by repairing example task sets scheduled under global non-preemptive earliest-deadline-first scheduling, a common choice for many safety-critical systems.