Feasibility conditions with kernel overheads for mixed preemptive FP/FIFO Scheduling with priority ceiling protocol on an event driven OSEK system

Abstract

In this paper, we propose to extend real-time feasibility conditions taking into account kernel overheads for mixed preemptive periodic tasks with shared resources when tasks are scheduled with fixed priority FP/FIFO scheduling, where FIFO is used to arbitrate tasks having the same fixed priority. The kernel considered in this paper is an event driven OSEK kernel which uses the priority ceiling protocol to avoid deadlocks. The overheads are due to context switching, task activations and terminations, and task rescheduling. Periodic timers used to create the time base to implement periodic tasks and to the OSEK's services used to request and release resources also introduce kernel overheads. We compare the theoretical worst case response time obtained with kernel overheads to the response time obtained on a real event driven OSEK implementation.