Is This Still Normal? Putting Definitions of Timing Anomalies to the Test

Correctness is an important concern during the development of real-time systems. In addition to the functional correctness, the timing behavior is often formally verified in order to ensure that correct results are delivered in-time for all possible execution conditions. The timing behavior of real-time software is thus often validated through a rigorous timing analysis that aims at determining the worst-case execution time.Timing anomalies present a major obstacle during the validation of timing properties on modern computer platforms. Out-of-order execution and concurrent accesses to shared resources may sometimes lead to – at first sight – surprising timing behavior. Several (semi-)formal definitions have been proposed in the literature in order to capture such situations. However, as we present in this work, none of the existing definitions appears to be precise enough to be systematically used for detecting timing anomalies in modern processors with out-of-order execution.