Exact worst-case response times of real-time tasks under fixed-priority scheduling with deferred preemption

In this paper, we present equations to determine the exact worst-case response times of periodic tasks under fixedpriority scheduling with deferred preemption (FPDS) and arbitrary phasing. We show that the worst-case response time analysis is not uniform for all tasks. Our exact analysis is based on a dedicated conjecture for an ε-critical instant, and uses the notion of worst-case occupied time.