Safety-Aware Implementation of Control Tasks via Scheduling with Period Boosting and Compressing

A crucial requirement for control tasks in safety-critical systems like automotive is that all deadlines be met. This is becoming increasingly difficult when several tasks share common resources. One main reason for this lies in obtaining tight WCET estimations, especially as software and processor architectures continue to become more complex. Using safe but not necessarily tight WCET estimates and meeting all deadlines come at the expense of very pessimistic and inefficient implementations. In this paper, we show that by focusing on 'higher-level' properties like control safety, instead of trying to meet all deadlines, it is possible to achieve more efficient implementations of control tasks on shared resources. This has considerable benefits in cost-sensitive domains like automotive. The core of our technique follows the AUTOSAR paradigm where groups of control computations with the same period constitute units of scheduling. Towards this, we suitably increase (boost) or decrease (compress) the sampling periods of control tasks and schedule them in a manner that is cognizant of their high-level safety constraints, but does not necessarily meet all deadlines. Our results for several standard controllers from the automotive domain illustrate the benefits of our approach.