基于防危核(壳)的安全关键硬实时系统响应时间的分析

基于响应时间的可调度分析是设计硬实时系统的基础.防危核(壳)是安全关键硬实时系统的一种新防危措施,现有的普适响应时间分析方法不能适用于这类系统.本文的贡献在于采用检测点时间冗余容错和优先级提升思想,通过分析内/外错误、隐/显错误,提出了一种合适的响应时间分析方法,从而为这类系统提供有效的离线可调度分析工具,同时也为这类系统设计了一种基于检测点的容错方案.本方法稍作修改也可为其它安全关键系统服务.最后通过仿真实验验证了本方法的有效性和优越性.

Response Time Analysis for Safety-Critical Hard Real-Time Systems Based on Safety Kernel/Shell Scheme

Safety-critical hard real-time systems(in brief,we call them SCHRS below) often operate in harsh environmental conditions that necessitate fault-tolerant computing and safety assurance techniques.Various hardware as well as software safety assurance techniques are employed in these systems among which safety kernel(shell) is a new scheme in application layer and it's correctness can be proofed by formal tool.Appropriate response time analysis schemes(in brief,we call them RTA below) are fundamental to the design of predictable hard realtime systems.However few RTA schemes is suitable to SCHRS based on safety kernel or shell.The main contribution of this paper is twofold.First,we propose an appropriate RTA to improve system fault resilience.Compared with other response time analysis polices,the proposed scheduling analysis takes into account the fact that the recoveries of tasks in safety kernel or shell may be executed at higher priority levels,and there are several kinds of error,such as internal,external,hidden and visible error.This characteristic is very important in SCHRS based on safety kernel or shell.Second,we present a suitable checkpointing fault-tolerant scheme for SCHRS based on safety kernel or shell.The emphasis here is on utilizing this RTA as an off-line design support tool.The effectiveness of the proposed approach is evaluated by simulation.