Re: [PATCH 6.18] sched/fair: Revert 6d71a9c61604 ("sched/fair: Fix EEVDF entity placement bug causing scheduling lag")

[John Stultz]

On Mon, Aug 10, 2026 at 4:32 PM Jose Fernandez (Anthropic)
<jose.fernandez@xxxxxxxxx> wrote:
>
> On Mon, Aug 10, 2026 at 09:38:30AM +0200, Peter Zijlstra wrote:
> > Yeah, this should be fine without 4823725d9d1d.
>
> One heads up, our review tooling caught this after I sent the
> Tested-by. The revert was written after commit 80390ead2080
> ("sched/fair: Separate se->vlag from se->vprot") took vlag and vprot
> out of their union, and 6.18 still has the union. Without that split
> first, the rel_vprot path in the new reweight_entity() scales vlag
> twice and curr's vruntime comes out wrong.

Indeed! I was looking earlier today as I had some foggy memory of an
issue the backport caused in our android17-6.18 tree, but couldn't
find it right off!

Since we were KABI frozen in the android tree, we used the following
patch to work around it: https://r.android.com/4103883

But then reverted that and cherry-picked 80390ead2080 ("UPSTREAM:
sched/fair: Separate se->vlag from se->vprot") for the KABI thaw.

Thanks for noticing and reminding me of this!

thanks
-john