On Thu, Sep 04, 2025 at 06:55:14AM +0100, Al Viro wrote: > Bugger... Either I've got false 'good' at several points, or it's something > brought in by commit 2004cef11ea0 "Merge tag 'sched-core-2024-09-19' of > git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip" - bisection has > converged to something within the first 48 commits of the branch in question. > > Which is not impossible, but then the underlying race could've been there > for years before that, only to be exposed by timing changes ;-/ > > Anyway, I'll get the bisection to the end, but it looks like the end result > won't be particularly useful... It's definitely within that branch; breakage reproduce on dae4320b29f0 "sched: Fixup set_next_task() implementations" and does *not* reproduce on 8e2e13ac6122 "sched/fair: Cleanup pick_task_fair() vs throttle" Trying to bisect it further runs into a bisect hazard left there - commit 54a58a787791 "sched/fair: Implement DELAY_ZERO" has +SCHED_FEAT(DELAY_ZERO, true) and 2e0199df252a "sched/fair: Prepare exit/cleanup paths for delayed_dequeue" - + if (sched_feat(DELAY_ZERO) && p->se.vlag > 0) 6 commits before the definition. I'm not going to try and reorder that branch into something bisectable - I do not know that area anywhere near well enough for that. In any case, I doubt that it's a scheduler bug; something exposed by the timings change, but that's about it...
