On Wed, Dec 01, 2021 at 09:56:21AM -0500, Waiman Long wrote:

Right, I shouldn't say corner cases. Having task in an intermediate
partition is possible depending on event sequence. I am aware that there are
code in the cpuset code to prevent that, but it didn't block all cases.

quoted

quoted

A valid parent partition may distribute out all its CPUs to
  its child partitions as long as there is no task associated with it.

Assuming there's always at least one kernel thread in the root cgroup
that can't be migrated anyway.]

I am aware of that. That is why I said root cgroup must have at least one
cpu in its "cpuset.cpus.effective".

In that case, let's explicitly describe that condition.

Thanks.

-- 
tejun