On Sun, 6 Dec 2020 at 00:47, Thomas Gleixner <tglx@xxxxxxxxxxxxx> wrote: > On Sat, Dec 05 2020 at 19:18, Thomas Gleixner wrote: > > On Fri, Dec 04 2020 at 20:53, Marco Elver wrote: > > It might be useful to find the actual variable, data member or whatever > > which is involved in the various reports and if there is a match then > > the reports could be aggregated. The 3 patterns here are not even the > > complete possible picture. > > > > So if you sum them up: 58 + 148 + 205 instances then their weight > > becomes more significant as well. > > I just looked into the moderation queue and picked stuff which I'm > familiar with from the subject line. We managed to push (almost) everything that was still in private moderation to public moderation, so now there's even more to look at: https://syzkaller.appspot.com/upstream?manager=ci2-upstream-kcsan-gce :-) > There are quite some reports which have a different trigger scenario, > but are all related to the same issue. > > https://syzkaller.appspot.com/bug?id=f5a5ed5b2b6c3e92bc1a9dadc934c44ee3ba4ec5 > https://syzkaller.appspot.com/bug?id=36fc4ad4cac8b8fc8a40713f38818488faa9e9f4 > > are just variations of the same problem timer_base->running_timer being > set to NULL without holding the base lock. Safe, but insanely hard to > explain why :) > > Next: > > https://syzkaller.appspot.com/bug?id=e613fc2458de1c8a544738baf46286a99e8e7460 > https://syzkaller.appspot.com/bug?id=55bc81ed3b2f620f64fa6209000f40ace4469bc0 > https://syzkaller.appspot.com/bug?id=972894de81731fc8f62b8220e7cd5153d3e0d383 > ..... > > That's just the ones which caught my eye and all are related to > task->flags usage. There are tons more judging from the subject > lines. > > So you really want to look at them as classes of problems and not as > individual scenarios. Regarding auto-dedup: as you suggest, it'd make this straightforward if we had the variable name -- it turns out that's not so trivial. I think we need compiler support for that, or is there some existing infrastructure that can just tell us the canonical variable name if it points into a struct or global? For globals it's fine, but for arbitrary pointers that point into structs, I don't see how we could do it without compiler support e.g. mapping PC->variable name (we need to map instructions back to the variable names they access). Any precedence for this? [+Cc linux-toolchains@xxxxxxxxxxxxxxx] Thanks, -- Marco
