SFWRENG 4AA4 Study Guide - Final Guide: Priority Inheritance, Vxworks, Qnx
11 Oct 2016
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Classification of rts: hard rts = failure to meet 1 deadline = complete and catastrophic system failure. Soft rts = performance degraded, not destroyed by failure to meet response-time constraints. Firm rts = missing more than a few may lead to failure. fork(): child gets 0, parent gets pid of child. Rtoss: polled loop, synchronous polled loop, clock driven approach(timer-driven & cyclic executive): off-line calculation of schedule, used at runtime, priority-based: pre-emptive priority, either fixed-priority or dynamic. Overall utilization = sum(i = 1 n, ui). Formats: tn( n, pn, en, dn), where n = phase, pn = period, rn = execution time, dn = deadline. aperiodic tasks:tasks whose release times are not known in advance. Round-robin: each task executes for 1 slice, if not finished, is pre-empted and placed at end of queue. Cyclic executive: scheduling decisions made at regular intervals. f = frame size. Schedule is for largest task aperiodic tasks: scheduled after all hard-deadline jobs are completed.
