Scheduling Randomization Protocol to Improve Schedule Entropy for Multiprocessor Real-Time Systems

Because most tasks on real-time systems are conducted periodically, its execution pattern is highly predictable. While such a property of real-time systems allows developing the strong schedulability analysis tools providing high analytical capability, it also leads that security attackers could analyze the predictable execution patterns of real-time systems and use them as attack surfaces. Among the few approaches to foil such a timing-inference security attack, TaskShuffler as a schedule randomization protocol received considerable attention owing to its simplicity and applicability. However, the existing TaskShuffler is only applicable to uniprocessor platforms, where the task execution pattern is quite simple to analyze when compared to multiprocessor platforms. In this study, we propose a new schedule randomization protocol for real-time systems on symmetry multiprocessor platforms where all processors are composed of the same architecture, which extends the existing TaskShuffler initially designed for uniprocessor platforms.

An N-Modular Redundancy Framework Incorporating Response-Time Analysis on Multiprocessor Platforms

A timing constraint and a high level of reliability are the fundamental requirements for designing hard real-time systems. To support both requirements, the N modular redundancy (NMR) technique as a fault-tolerant real-time scheduling has been proposed, which executes identical copies for each task simultaneously on multiprocessor platforms, and a single correct one is voted on, if any. However, this technique can compromise the schedulability of the target system during improving reliability because it produces N identical copies of each job that execute in parallel on multiprocessor platforms, and some tasks may miss their deadlines due to the enlarged computing power required for completing their executions. In this paper, we propose task-level N modular redundancy (TL-NMR), which improves the system reliability of the target system of which tasks are scheduled by any fixed-priority (FP) scheduling without schedulability loss. Based on experimental results, we demonstrate that TL-NMR maintains the schedulability, while significantly improving average system safety compared to the existing NMR.