End-to-End Analysis of Event Chains under the QNX Adaptive Partitioning Scheduler

Modern autonomous cars run classic AUTOSAR applications alongside advanced driving assistance systems on a single-vehicle computer. Ensuring safety and predictability in such a complex system is challenging and requires temporal isolation between the various components. A promising solution is the POSIX-compliant QNX operating system: it meets the automotive standards for functional safety at the highest level (ISO 26262 ASIL-D) and provides temporal isolation through the Adaptive Partitioning Scheduler (APS), a resource reservation algorithm that guarantees processor bandwidth to groups of threads. These guarantees make it an ideal platform for composing diverse and complex applications on centralized vehicle computers. However, so far, there is no precise description or analysis of the APS reservation mechanism in real-time literature. In this paper, we provide the first description of the behavior of the APS from a real-time point of view and validate the results by running experiments on a real QNX platform. Based on the derived scheduler rules, we develop a response-time analysis to bound the end-to-end latency of event chains under APS. Finally, we evaluate different design strategies on a case study based on a real autonomous construction vehicle.