Real time systems must respect their temporal constraints both in nominal and degraded conditions. Environment disturbances cause faults which are revealed by errors during task execution. Therefore, schedulers must be fault tolerant to guarantee no missed deadline. Phenomena like electromagnetic fields disturb real-time systems on a extended period of time. It is difficult to forecast faults and their consequences to build efficient faulttolerant systems. The classical fault models deal with pseudo-periodic faults. They are not made for phenomena extended in time. This paper intends to describe electromagnetic disturbances in a new fault model, named fault burst model. In adequation with the fault burst model, we provide error recovery strategies. Finally, we study the effects of strategies on the schedulability analysis to guarantee fault tolerance when fault bursts occur.
The use of real-time systems can differ from their initial design and requirements. New missions may take place in a more agressive environment and cause faults that are not managed by the initial fault tolerance mechanisms. Before attributing a new mission it is interesting to know the limits of a real-time system in order to avoid a new validation process. In this paper we intend to evaluate the fault resilience. We deal with the fault tolerant scheduling analysis under pseudo-periodic faults and fault bursts. We provide methods to compute the features of temporal fault distribution that maximize the Worst Case Response Time of tasks. Thus we are able to evaluate the maximum fault resilience of a task. We also provide the maximum fault resilience of the real-time system.
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