Section: New Results

Uniprocessor Real-Time Scheduling

Participants : Mamadou Diallo, Yves Sorel, Walid Talaboulma, Robert Davis.

In the context of the master internship of Mamadou Diallo we implemented the offline time trigger scheduler proposed in his PhD thesis by Falou Ndoye on a development board based on an ARM Cortex M4. We used this ARM version since it is better suited to embedded systems, since more predictable, than the ARM 7 we used last year. Especially, it allows to determine more accurately the cost of the scheduler and of the preemptions we use in our offline schedulability analysis. We remind that the schedulability analysis provides a scheduling table which is exploited by the scheduler during the real-time execution of the tasks. This approach allows a low and fixed cost for the scheduler and the preemptions whereas these costs are variable in the case of classical online schedulers. For several task sets we compared the timing diagrams predicted by the schedulability analysis with the real-time timing diagrams measured on the ARM Cortex M4. It turns out that those timings are very close, as expected.

A new direction opened with the arrival of Rob Davis was to consider by studying the impact of the non-preemptivity constraints on the optimality of the schedulers [37] , or by considering fixed priorities while scheduling messages in the context of Control Area Networks [36] .