Resumen
Design and analysis of real-time systems is heavily based on knowing worst-case execution times of periodic threads and periodic servers. However, there has been little research into detecting and handling timing errors. These types of errors, which occur in real-time systems, are failures to meet the timing specifications of the system. Much research in real-time systems focuses on developing scheduling policies that can be used to guarantee that timing errors will not occur. The most common timing error is the missed deadline, where a real-time thread fails to complete its execution on time. Another timing error, which is perhaps just as common but not necessarily as obvious, is the incorrect estimate of execution time. Timing errors are detected jointly by the scheduler and the microkernel. An obvious use of the timing error detection and handling mechanism is to implement soft real-time threads. For example, one scheduling policy may be for a thread that misses deadlines to continue to execute, but to use up the time from its next cycle as wel