(Disclaimer: rr maintainer.) As others have said here, in practice rr works very well for debugging a wide range of bugs in multithreaded programs, including r

(Disclaimer: rr maintainer.) As others have said here, in practice rr works very well for debugging a wide range of bugs in multithreaded programs, including race conditions. Where it falls down: * It can only use a single core, so highly parallel programs run very slowly when recorded by rr. * Some race conditions may be difficult or impossible to reproduce under rr recording (but rr's chaos mode helps a lot with this). * rr imposes sequential consistency on the recorded program, so bugs due to weak memory models do not show up under rr. Such bugs are pretty rare on x86 (because x86's memory model is pretty strong); this may be more of an issue on ARM.