Re: [PATCH] sched/deadline: Fix stale dl_defer_running in update_dl_entity() if-branch

[John Stultz]

On Fri, Apr 3, 2026 at 3:51 PM John Stultz <jstultz@xxxxxxxxxx> wrote:
>
> On Fri, Apr 3, 2026 at 3:46 PM Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote:
> > On Fri, Apr 03, 2026 at 12:31:19PM -0700, John Stultz wrote:
> > > I haven't really diagnosed the issue, but it feels a little like the
> > > dl_server is boosting until the fair rq is empty but then giving up
> > > the rest of its time, so if a fair task runs repeatedly but for a very
> > > short period of time, it won't get to run again until the next
> > > dl_server period? Causing this rate-limiting one-task-per-second
> > > effect for thread spawning? I still need to stare at the dl_server
> > > logic some more.
> >
> > I'm getting a sense of deja-vu here. Didn't we cure this once before?
>
> Oh yeah:
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=4ae8d9aa9f9dc7137ea5e564d79c5aa5af1bc45c

Oops, sorry, that was the other one. This was the previous fix for a
similar issue with the same test:
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=a3a70caf7906708bf9bbc80018752a6b36543808

thanks
-john