Abstract—In real-time systems, there are two distinct trends for
scheduling task sets on unicore systems: non-preemptive and preemptive
scheduling. Non-preemptive scheduling is obviously not subject
to any preemption delay but its schedulability may be quite poor,
whereas fully preemptive scheduling is subject to preemption delay,
but benefits from a higher flexibility in the scheduling decisions.
The time-delay involved by task preemptions is a major source
of pessimism in the analysis of the task Worst-Case Execution
Time (WCET) in real-time systems. Preemptive scheduling policies
including non-preemptive regions are a hybrid solution between
non-preemptive and fully preemptive scheduling paradigms, which
enables to conjugate both world’s benefits. In this paper, we exploit
the connection between the progression of a task in its operations,
and the knowledge of the preemption delays as a function of its
progression. The pessimism in the preemption delay estimation is
then reduced in comparison to state of the art methods, due to the
increase in information available in the analysis.