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It can still debug multi-threaded programs, but if your bug relies on multi-core interactions it won't appear under rr (you can still catch a lot of race condit

It can still debug multi-threaded programs, but if your bug relies on multi-core interactions it won't appear under rr (you can still catch a lot of race conditions though, and it has a 'chaos mode' which generate irregular scheduling intended to increase the likelyhood of such bugs appearing). It's been used to debug race conditions as well as other bugs in firefox, for example.

menaerus 4y ago
That's what I thought as well, limited to the single-core race conditions era. Thanks for the evidence.
- pm215 4y ago
  It's still much better than the alternative, which is not having any kind of way to reproduce race conditions :-) QEMU's a pretty complex multithreaded program and my experience with chaos mode has been that it's quite good at tripping up the races (and you only need to catch the race once).
- ghusbands 4y ago
  It's not limited to any era - it's a general-purpose tool that can perfectly reproduce bugs, even most race conditions. The lack of multi-threading will mostly just slow things down. Being able to perfectly reproduce a bug is immensely valuable.
  - menaerus 4y ago
    I didn't say anything about the usefulness of rr other than in the context of concurrency bugs so I don't quite understand a defending attitude of yours.