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ISO/IEC PDTR 24772 Section 6.47, "REU Termination strategy" says:
When a fault is detected, there are many ways in which a system can react. The quickest and most noticeable way is to fail hard, also known as fail fast or fail stop. The reaction to a detected fault is to immediately halt the system. Alternatively, the reaction to a detected fault could be to fail soft. The system would keep working with the faults present, but the performance of the system would be degraded. Systems used in a high availability environment such as telephone switching centers, e-commerce, etc. would likely use a fail soft approach. What is actually done in a fail soft approach can vary depending on whether the system is used for safety critical or security critical purposes. For fail safe systems, such as flight controllers, traffic signals, or medical monitoring systems, there would be no effort to meet normal operational requirements, but rather to limit the damage or danger caused by the fault. A system that fails securely, such as cryptologic systems, would maintain maximum security when a fault is detected, possibly through a denial of service.
ISO/IEC PDTR 24772 Section 6.47, "REU Termination strategy" also says:
The reaction to a fault in a system can depend on the criticality of the part in which the fault originates. When a program consists of several tasks, the tasks each may be critical, or not. If a task is critical, it may or may not be restartable by the rest of the program. Ideally, a task which detects a fault within itself should be able to halt leaving its resources available for use by the rest of the program, halt clearing away its resources, or halt the entire program. The latency of any such communication, and whether other tasks can ignore such a communication, should be clearly specified. Having inconsistent reactions to a fault, such as the fault reaction to a crypto fault, can potentially be a vulnerability.
ISO/IEC PDTR 24772 Section 6.47, "REU Termination strategy" describes the following mitigation strategies:
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