On Tue, Aug 01, 2023 at 10:32:45AM -0700, Guenter Roeck wrote: > On 7/31/23 14:15, Peter Zijlstra wrote: > > On Mon, Jul 31, 2023 at 09:34:29AM -0700, Guenter Roeck wrote: > > > > Ha!, I was poking around the same thing. My hack below seems to (so far, > > > > <20 boots) help things. > > > > > > > > > > So, dumb question: > > > How comes this bisects to "sched/fair: Remove sched_feat(START_DEBIT)" ? > > > > That commit changes the timings of things; dumb luck otherwise. > > Kind of scary. So I only experienced the problem because the START_DEBIT patch > happened to be queued roughly at the same time, and it might otherwise have > found its way unnoticed into the upstream kernel. That makes me wonder if this > or other similar patches may uncover similar problems elsewhere in the kernel > (i.e., either hide new or existing race conditions or expose existing ones). > > This in turn makes me wonder if it would be possible to define a test which > would uncover such problems without the START_DEBIT patch. Any idea ? IIRC some of the thread sanitizers use breakpoints to inject random sleeps, specifically to tickle races.
