Re: [PATCH v6 0/8] cgroup/cpuset: Fix partition related locking issues

[Frederic Weisbecker <frederic@kernel.org>]

On Mon, Feb 23, 2026 at 10:57:24AM -1000, Tejun Heo wrote:
> Hello,
> 
> > Waiman Long (8):
> >   cgroup/cpuset: Fix incorrect change to effective_xcpus in partition_xcpus_del()
> >   cgroup/cpuset: Fix incorrect use of cpuset_update_tasks_cpumask() in update_cpumasks_hier()
> >   cgroup/cpuset: Clarify exclusion rules for cpuset internal variables
> >   cgroup/cpuset: Set isolated_cpus_updating only if isolated_cpus is changed
> >   kselftest/cgroup: Simplify test_cpuset_prs.sh by removing "S+" command
> >   cgroup/cpuset: Move housekeeping_update()/rebuild_sched_domains() together
> >   cgroup/cpuset: Defer housekeeping_update() calls from CPU hotplug to workqueue
> >   cgroup/cpuset: Call housekeeping_update() without holding cpus_read_lock
> 
> Applied 1-8 to cgroup/for-7.0-fixes with the following minor fixups:
> 
> - 5/8: Removed a duplicate test entry that resulted from the "S+"
>   removal (two previously-different lines becoming identical).
> 
> - 8/8: Fixed typos in commit message ("essentally" -> "essentially",
>   "beforce" -> "before") and code comment ("top_cpuset_mutex" ->
>   "cpuset_top_mutex").
> 
> This has gone through more than enough iterations. We can resolve further
> issues if there's any incrementally.

We really need to check the fact that the workqueue is not flushed at any
relevant point in hotplug such that:

- offline CPU might now appear in the live topology, quite dangerous.

- CPUs might not be timely (un)isolated when they are expected to.

Thanks.

> 
> Thanks.
> 
> --
> tejun