[scott_s]

Very cool stuff! And yes, I took a look at the paper, as I noted in my edit. But I think there's still two classes of race conditions outside of its scope: ones that require simultaneous execution (where you can get surprising interleavings) and lock-free algorithms where correct use of the memory model is paramount. In my personal experience, these are the hardest problems to debug.

[codehog]

Even those are probably not 100% outside of its scope. I forget the details of chaos mode, but that kind of induced thread-switching can cause just the kind of interleaving you seem to be talking about.

What rr cannot capture is a very small subclass of race conditions involving things like cache line misses - I think that's what you're alluding to by "correct use of the memory model is paramount" but it's a subclass even of those. Yes, those are hugely difficult to diagnose and it would be fantastic if tools like rr or UndoDB could capture them. But there's a vast swathe of also very difficult race conditions that this recording tech can and does help with today.