[borodi]

Chaos mode is an option when invoking rr that can expose some concurrency issues. Basically it switches which thread is executing a bunch to try and simulate multiple cores executing. It has found some race conditions for me but it’s of course limited

[dzaima]

Unfortunately that only works for large-scale races, and not, say, one instruction interleaving with another one on another thread without proper synchronization. -fsanitize=thread probably works for that though (and of course you could then combine said sanitizer with rr to some effect probably).

[roca]

One option would be to combine chaos mode with a dynamic race detector to try to focus chaos mode on specific fine-grained races. Someone should try that as a research project. Not really the same thing as rr + TSAN.

There's still the fundamental limitation that rr won't help you with weak memory orderings.

[borodi]

I havent tried Tsan with rr but msan and asan work quite well with it (it’s quite slow when doing this) but seeing the sanitizer trigger then following back what caused it to trigger is very useful.

[bqmjjx0kac]

Yeah, the reason it only works for these coarser race conditions is that RR only has one thread executing at a time. Chaos mode randomizes the durations of time allotted to each thread before it is preempted. This may be out of date. I believe I read it in the Extended Technical Report from 2017: https://arxiv.org/pdf/1705.05937