On reducing busy waiting in autosar via task-release-delta-based runnable reordering

The increasing amount of innovative software technologies in the automotive domain comes with challenges regarding inevitable distributed multi-core and many-core methodologies. Approaches for general purpose solutions have been studied over decades but do not completely meet the specific constraints (e. g. timing, safety, reliability, affinity, etc.) for Autosar compliant applications. Autosar utilizes a spinlock mechanism in combination with the priority ceiling protocol in order to provide mutually exclusive access to shared resources. The essential disadvantages of spinlocks are unpredictable task response times on the one hand and wasted computation time caused by busy waiting periods on the other hand. In this paper, we propose a concept of task-release-delta-based runnable reordering for the purpose of sequentializing parallel accesses to shared resources, resulting in reduced task response times, improved timing predictability, and increased parallel efficiency respectively. To achieve this, runnables that represent smallest executable program parts in Autosar are reordered based on precedence constraints. Our experiments among industrial use cases show that task response times can be reduced by up to 18,2%.