Re: [PATCH] cgroup/cpuset: Properly disable partition when partition state switching fails

[Waiman Long <longman@redhat.com>]

On 9/29/26 12:42 PM, Tejun Heo wrote:
> Hello,
>
> On Tue, Sep 29, 2026 at 03:40:27PM +0800, Guopeng Zhang wrote:
>> However, after the parent is created, the ownership of full housekeeping
>> CPUs can still change, so passing the check at creation time doesn't seem
>> to guarantee that returning CPUs later is still safe.
> I think any CPU under an isolated partition should count as isolated when
> testing whether the system has a housekeeping CPU left, whether child
> partitions carved some out or not. Those CPUs go back to the isolated
> parent whenever the child partition is disabled or invalidated, so they
> can't be counted on for housekeeping. In your example, making C isolated
> would then fail.

I am now thinking about treating the whole user defined exclusive CPUs 
(exclusive_cpus or cpus) as wholly owned by the cpuset in question from 
the housekeeping check perspective.  That will require reworking the 
current housekeeping checking code and will require more extensive 
changes. So it will take some time before a patchset will be ready for 
review. This will prevent housekeeping check failure when a child 
partition is disabled and its CPU are moved back to its parent.

Cheers,
Longman