Re: [PATCH] cgroup/cpuset: Disable cpuset_cpumask_can_shrink() test if not load balancing

[Tejun Heo <tj@kernel.org>]

On Thu, Nov 14, 2024 at 01:19:15PM -0500, Waiman Long wrote:
> With some recent proposed changes [1] in the deadline server code,
> it has caused a test failure in test_cpuset_prs.sh when a change
> is being made to an isolated partition. This is due to failing
> the cpuset_cpumask_can_shrink() check for SCHED_DEADLINE tasks at
> validate_change().
> 
> This is actually a false positive as the failed test case involves an
> isolated partition with load balancing disabled. The deadline check
> is not meaningful in this case and the users should know what they
> are doing.
> 
> Fix this by doing the cpuset_cpumask_can_shrink() check only when loading
> balanced is enabled. Also change its arguments to use effective_cpus
> for the current cpuset and user_xcpus() as an approiximation for the
> target effective_cpus as the real effective_cpus hasn't been fully
> computed yet as this early stage.
> 
> As the check isn't comprehensive, there may be false positives or
> negatives. We may have to revise the code to do a more thorough check
> in the future if this becomes a concern.
> 
> [1] https://lore.kernel.org/lkml/82be06c1-6d6d-4651-86c9-bcc828cbcb80@redhat.com/T/#t
> 
> Signed-off-by: Waiman Long <longman@redhat.com>

Applied to cgroup/for-6.13.

Thanks.

-- 
tejun