cgroup/cpuset: Release invalid isolated CPUs with a shrunk root partition parent

It is also reported by sashiko that there may be leakages of isolated
CPUs when a root partition parent shrinks its effective_xcpus with
isolated partition children. Leakage here means that isolated_cpus may
contain extra CPUs that are not in any isolated partitions and not boot
time isolated. Those CPUs cannot be used in any isolated partitions
anymore.

There are 2 different cases here. The effective_xcpus becomes empty and
the isolated partition should be invalidated in this case. Alternatively
some of its effective_xcpus are not in parent's effective xcpus but
still have some valid effective_xcpus left. The isolated partition can
remain valid. In both cases, the invalid isolated CPUs will have to be
released from isolated_cpus if appropriate.

Fix that by calling isolated_cpus_release() to release those isolated
CPUs from isolated_cpus.

New test cases are added to test_cpuset_prs.sh to test this.

Fixes: 11e5f407b64a ("cgroup/cpuset: Keep track of CPUs in isolated partitions")
Signed-off-by: Waiman Long <longman@redhat.com>
Reviewed-by: Guopeng Zhang <zhangguopeng@kylinos.cn>
Tested-by: Guopeng Zhang <zhangguopeng@kylinos.cn>
Signed-off-by: Tejun Heo <tj@kernel.org>

0 files changed, 0 insertions, 0 deletions