Temporal and Spatial Partitioning of a Time-Triggered Operating System Based on Real-Time Linux

Real-time Linux variants are becoming prominent solutions for the development of embedded systems. Compared to traditional real-time operating systems, embedded system engineers can leverage solutions and knowhow from the Linux development community (e.g., development tools, applications, drivers). Due to the availability of implementations of Internet protocols and network drivers, Linux also facilitates the implementation of embedded systems connected to the Internet. The goal of this paper is to evaluate experimentally the capabilities of the Real-time Linux variant RTAI/LXRT with respect to partitioning between different application software modules. Partitioning ensures that a failure caused by a design fault in one application software module cannot propagate to cause a failure in other application software modules, e.g., by blocking access to the CPU or by overwriting memory. Partitioning is important when building mixed-criticality systems comprising both non safety-critical software modules and safety-related ones. Even at the same level of criticality, partitioning improves the robustness of an embedded system. The experimental results described in this paper point out several limitations of RTAI/LXRT Linux concerning fault isolation. Based on these results, we propose modifications to improve the partitioning with respect to temporal and spatial interference.