The researchers have proposed always-on data-race exceptions as a way to avoid the ill effects of data races, but slow performance of accurate dynamic data-race detection remains a barrier to the adoption of always-on data-race exceptions. Proposals for accurate low-level (e.g., hardware) data-race detection have the potential to reduce this performance barrier. This paper explains why low-level data-race detectors are wrong for programs written in high-level languages: they miss true data races and report false data races in these programs.