cgroup/cpuset: Fix incorrect use of cpuset_update_tasks_cpumask() in update_cpumasks_hier()

[ Upstream commit 68230aac8b ]

Commit e2ffe502ba ("cgroup/cpuset: Add cpuset.cpus.exclusive for v2")
incorrectly changed the 2nd parameter of cpuset_update_tasks_cpumask()
from tmp->new_cpus to cp->effective_cpus. This second parameter is just
a temporary cpumask for internal use. The cpuset_update_tasks_cpumask()
function was originally called update_tasks_cpumask() before commit
381b53c3b5 ("cgroup/cpuset: rename functions shared between v1
and v2").

This mistake can incorrectly change the effective_cpus of the
cpuset when it is the top_cpuset or in arm64 architecture where
task_cpu_possible_mask() may differ from cpu_possible_mask.  So far
top_cpuset hasn't been passed to update_cpumasks_hier() yet, but arm64
arch can still be impacted. Fix it by reverting the incorrect change.

Fixes: e2ffe502ba ("cgroup/cpuset: Add cpuset.cpus.exclusive for v2")
Signed-off-by: Waiman Long <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Waiman Long 2026-02-21 13:54:12 -05:00 • committed by Greg Kroah-Hartman
commit 6e4f700343