Policy-independent real-time operating system mechanisms for timing error detection, handling and monitoring

Most research focusing on timing errors deals with scheduling policies that avoid the errors. Since many of the policies are based on estimated worst case execution times for each task, reliability is a function of the accuracy of the estimates. As a result, many hard real time systems are implemented with the dangerous assumption that due to correct design and testing, a missed deadline will never occur. We have designed novel policy independent mechanisms for detecting and handling timing errors, and for monitoring real time tasks. The detection and handling requires less than 1 microsecond overhead per reschedule operation, and has a latency approximately the length of one context switch for handling an error. The monitoring mechanism uses 6 microsecond per context switch, and requires only 1 Kbyte of memory per 32 processes in the system