Re: [PATCH] sched: fix warning in sched_setaffinity

[Josh Don]

On Thu, Aug 29, 2024 at 3:04 PM Josh Don <joshdon@xxxxxxxxxx> wrote:
>
> Commit 8f9ea86fdf99b added some logic to sched_setaffinity that included
> a WARN when a per-task affinity assignment races with a cpuset update.
>
> Specifically, we can have a race where a cpuset update results in the
> task affinity no longer being a subset of the cpuset. That's fine; we
> have a fallback to instead use the cpuset mask. However, we have a WARN
> set up that will trigger if the cpuset mask has no overlap at all with
> the requested task affinity. This shouldn't be a warning condition; its
> trivial to create this condition.
>
> Reproduced the warning by the following setup:
>
> - $PID inside a cpuset cgroup
> - another thread repeatedly switching the cpuset cpus from 1-2 to just 1
> - another thread repeatedly setting the $PID affinity (via taskset) to 2
>
> Fixes: 8f9ea86fdf99b ("sched: Always preserve the user requested cpumask")
> Signed-off-by: Josh Don <joshdon@xxxxxxxxxx>

Gentle ping to bump this in case it got lost.

I've also collected the following:

Acked-by: Waiman Long <longman@xxxxxxxxxx>
Tested-by: Madadi Vineeth Reddy <vineethr@xxxxxxxxxxxxx>

Best,
Josh