RTSJ Extensions: Event Manager and Feasibility Analyzer

International audienceWe present in this paper our experience on the implementation with RTSJ of advanced algorithms to handle aperiodic traffic. We have adapted existing algorithms in order to take into account some constraints brought about by the use of Java language, and our aim which is to propose a portable mechanism. To circumscribe some difficulties, we had to use some programming ruses which could be better integrated into the specification. From these experiences resulted a set of modifications to the specification which we propose to submit to the community in this paper, in addition to a unified event manager framework

On the compatibility of exact schedulability tests for global fixed priority pre-emptive scheduling with Audsley’s optimal priority assignment algorithm

Audsley's optimal priority assignment (OPA) algorithm can be applied to multiprocessor scheduling provided that three conditions hold with respect to the schedulability tests used. In this short paper, we prove that no exact test for global fixed priority pre-emptive scheduling of sporadic tasks can be compatible with Audsley's algorithm, and hence the OPA algorithm cannot be used to obtain an optimal priority assignment for such systems

(m,k)-firm constraints and DBP scheduling: impact of the initial k-sequence and exact schedulability test

In this paper we study the scheduling of (m,k)-firm synchronous periodic task systems using the Distance Based Priority (DBP) scheduler. We first show three phenomena: (i) choosing, for each task, the initial k-sequence 1^k is not optimal, (ii) we can even start the scheduling from a (fictive) error state (in regard to the initial k-sequence) and (iii) the period of feasible DBP-schedules is not necessarily the task hyper-period. We then show that any feasible DBP-schedule is periodic and we upper-bound the length of that period. Lastly, based on our periodicity result we provide an exact schedulability test

A Few Results on Non-Preemptive Real Time Scheduling

In this paper, we investigate the non-preemptive scheduling problem as it arises in single processor systems. We focus on non-idling scheduling, the idling scheduling is briefly introduced in the last section. We extend some previous published results concerning preemptive and non-preemptive scheduling over a single processor. The main issue that we study in this article is the applicability and/or adaptation of results obtained in preemptive scheduling. In a first part we embark on revisiting aperiodic non idling non preemptive scheduling. We review complexity results and investigate conditions under which Earliest Deadline First is optimal in non preemptive scheduling. In a second part, we scrutinize periodic non idling non preemptive scheduling and we show that for non preemptive scheduling feasibility must be checked on a time interval of duration r+2P (r denotes the maximum of the release times and P the smallest common multiple of the task periods). We also show that a well established result concerning feasibility of task sets under non preemptive scheduling (no overload on any given time intervals) has no equivalence in non preemptive scheduling even if one takes into account the blocking factor. The third part is a very quick introduction to scheduling problems in an idling and non preemptive context

Advanced flight control system study

The architecture, requirements, and system elements of an ultrareliable, advanced flight control system are described. The basic criteria are functional reliability of 10 to the minus 10 power/hour of flight and only 6 month scheduled maintenance. A distributed system architecture is described, including a multiplexed communication system, reliable bus controller, the use of skewed sensor arrays, and actuator interfaces. Test bed and flight evaluation program are proposed