Re: [PATCH] sched/deadline: Check SCHED_DEADLINE affinity under the rq lock

[Sebastian Andrzej Siewior]

On 2026-11-05 17:48:43 [+0100], Andrea Parri wrote:
> __sched_setaffinity() calls dl_task_check_affinity() before
> __set_cpus_allowed_ptr() takes task_rq_lock(), whereas
> __sched_setscheduler() runs its admission test and switches the policy
> under a single task_rq_lock(). So both calls can pass their checks:
…

This looks fine to me. You do the check under the RQ lock so everything
that you checked can not change later on.
If you race with cpuset then you try to revert and drop that check-flag.
I can't comment on that. It looks wrong to set it to CPUs mask which not
part of the domain but you made a comment why it needs to happen. So
stay out here ;)

You could keep the check in __sched_setaffinity() so it bails out early
if it is not possible right away. The check under the RQ ist just due to
the race window that we have. But I don't have a strong opinion on that.

Anyway. The reported problem looks solved to me:
Reviewed-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>

Sebastian