Mode Change Protocols for Real-Time Systems: A Survey and a New Proposal

This paper contains both a survey of mode change protocols for single-processor, fixed-priority, preemptively scheduled real-time systems, and a proposal of several new protocols along with their corresponding schedulability analysis and configuration methods. First, a classification of the protocols found in the literature is given and a set of requirements is proposed for their evaluation. Then, the new protocols are introduced and discussed in the light of the stated requirements. A number of mode change protocols are based on delaying the initiation of the new mode by applying an offset to the initial release of tasks in the destination mode. We tackle the problem of how to obtain these offsets for the proposed protocols. The issue of consistently sharing resources during the mode change by means of a priority inheritance protocol is also dealt with.

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