Re: [PATCH] cpuset: Fix multi-source deadline task accounting and bandwidth bypass

[Waiman Long <longman@redhat.com>]

On 5/13/26 7:39 PM, Aaron Tomlin wrote:
> On Wed, May 13, 2026 at 07:19:18PM -0400, Waiman Long wrote:
>> Multiple source or destination cpusets in task migration can only happens
>> when the cpuset controller is enabled or disabled in a cgroup subtree. If
>> there are DL tasks in 2 or more child cgroups, enabling or disabling of the
>> cpuset controller for those child cgroups may lead to incorrect DL task
>> accounting. This patch will probably fix the DL accounting aspect. However,
>> there are also other issues unrelated to DL tasks that need to be addressed
>> as well. So this patch is incomplete in this regard. I am working on a patch
>> series to address these issues. Hopefully I can send it out in a day or 2.
>>
> Hi Longman,
>
> Acknowledged.
>
> Also, the Sashiko AI review reported: "TOCTOU race on dl_task(task) during
> rollback causes state corruption."
>
> A concurrent sched_setscheduler() could alter the scheduling class of a
> task between the initial pass and a rollback. This assertion seems valid to
> me. Currently, neither cgroup_mutex or cpuset_mutex prevents scheduling
> class changes.
>
> Should I let you handle this too?

No, you can handle it if you want. I am more familiar with the cpuset 
code, but scheduler is much more complex. I don't think I have enough 
understanding of the code to handle it correctly.

Cheers,
Longman