# Restart-Based Fault-Tolerance: System Design and Schedulability Analysis

## TL;DR

This paper presents a fault-tolerance system design for embedded safety-critical systems using restart-based recovery and schedulability analysis to ensure timing constraints despite faults.

## Contribution

It introduces a restart-based fault-tolerance approach with schedulability analysis for safety-critical embedded systems, enabling fault recovery without full software verification.

## Key findings

- Schedulability results for four restart-tolerant task models.
- Simulation shows effective fault recovery with minimal timing disruption.
- System design ensures safety-critical task deadlines are met during faults.

## Abstract

Embedded systems in safety-critical environments are continuously required to deliver more performance and functionality, while expected to provide verified safety guarantees. Nonetheless, platform-wide software verification (required for safety) is often expensive. Therefore, design methods that enable utilization of components such as real-time operating systems (RTOS), without requiring their correctness to guarantee safety, is necessary. In this paper, we propose a design approach to deploy safe-by-design embedded systems. To attain this goal, we rely on a small core of verified software to handle faults in applications and RTOS and recover from them while ensuring that timing constraints of safety-critical tasks are always satisfied. Faults are detected by monitoring the application timing and fault-recovery is achieved via full platform restart and software reload, enabled by the short restart time of embedded systems. Schedulability analysis is used to ensure that the timing constraints of critical plant control tasks are always satisfied in spite of faults and consequent restarts. We derive schedulability results for four restart-tolerant task models. We use a simulator to evaluate and compare the performance of the considered scheduling models.