Re: [PATCH v9 2/7] cgroup/cpuset: Allow no-task partition to have empty cpuset.cpus.effective

On Sun, Dec 05, 2021 at 01:32:15PM -0500, Waiman Long wrote:

adding = deleting = false; old_prs = new_prs = cpuset->partition_root_state; if (cmd == partcmd_enable) {

• /*
  

•  * Enabling partition root is not allowed if not all the CPUs
  

•  * can be granted from parent's effective_cpus.
  

•  */
  

• if (!cpumask_subset(cpuset->cpus_allowed, parent->effective_cpus))
  

• 	return -EINVAL;
  

• /*
  

•  * A parent can be left with no CPU as long as there is no
  

•  * task directly associated with the parent partition. For
  

•  * such a parent, no new task can be moved into it.
  

•  */
  

• if (partition_is_populated(parent, cpuset) &&
  

•     cpumask_equal(cpuset->cpus_allowed, parent->effective_cpus))
  

• 	return -EINVAL;
  

So, given that this only happens with threaded domains, can we just not allow partitions within threaded domains? The combination doesn't make whole lot of sense to me anyway.

• /*

• * On default hierarchy, task cannot be moved to a cpuset with empty
  

• * effective cpus.
  

• */
  

• if (is_in_v2_mode() && cpumask_empty(cs->effective_cpus))

• goto out_unlock;
  

And then we can avoid this extra restriction too, right?

Thanks.