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SubjectRe: [PATCH v4 2/2] sched: Skip priority checks with SCHED_FLAG_KEEP_PARAMS
On Monday 26 Jul 2021 at 14:56:10 (+0100), Quentin Perret wrote:
> On Thursday 22 Jul 2021 at 10:47:33 (+0200), Dietmar Eggemann wrote:
> > (*) This changes the behaviour when setting uclamp values on a DL task.
> >
> > Before uclamp values could be set but now, because of
> >
> > void __getparam_dl(struct task_struct *p, struct sched_attr *attr)
> > ..
> > attr->sched_flags = dl_se->flags
> >
> > SCHED_FLAG_UTIL_CLAMP gets overwritten and __sched_setscheduler() bails in:
> >
> > if (unlikely(policy == p->policy)) {
> > ...
> > retval = 0;
> > goto unlock;
> > }
> > change:
> >
> > I.e. the:
> >
> > if (attr->sched_flags & SCHED_FLAG_UTIL_CLAMP)
> > goto change;
> >
> > can't trigger anymore.
>
> Bah, as you said it doesn't seem to be a big deal, but clearly that was
> unintentional. Let me try and fix this.

While looking at this I found existing bugs in the area. Fixes are here:

https://lore.kernel.org/lkml/20210727101103.2729607-1-qperret@google.com/

And with the above series applied this patch should behave correctly
now.

Thanks,
Quentin

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