[PATCH/for-next v4 0/4] cgroup/cpuset: Fix partition related locking issues

[Waiman Long <longman@redhat.com>]

 v4:
  - Fix various issues as reported by Chen Ridong.

 v3:
  - Add a new patch to clarify the locking rules for internal variables
  - Defer all housekeeping_update() calls with associated
    rebuild_sched_domains*() calls to either workqueue or task_work.

 v2:
  - Change patch 1 to use workqueue instead of task run as it is a
    per-cpu kthread that performs the cpuset shutdown and bringup work.
  - Simplify and streamline some of the code.

After booting the latest cgroup for-next debug kernel with the latest
cgroup changes as well as Federic's "cpuset/isolation: Honour kthreads
preferred affinity" patch series [1] merged on top and running the
test-cpuset-prs.sh test, a circular locking dependency lockdep splat
was reported. See patch 2 for details.

To fix this issue, a new top level cpuset_top_mutex is added and the
call to housekeeping_update() is deferred to either a task_work or to
a workqueue.

With these changes in place, the cpuset test ran to completion with no
failure and no lockdep splat.

[1] https://lore.kernel.org/lkml/20260125224541.50226-1-frederic@kernel.org/

Waiman Long (4):
  cgroup/cpuset: Clarify exclusion rules for cpuset internal variables
  cgroup/cpuset: Defer housekeeping_update() calls from CPU hotplug to
    workqueue
  cgroup/cpuset: Call housekeeping_update() without holding
    cpus_read_lock
  cgroup/cpuset: Eliminate some duplicated rebuild_sched_domains() calls

 kernel/cgroup/cpuset.c                        | 241 +++++++++++++-----
 kernel/sched/isolation.c                      |   4 +-
 kernel/time/timer_migration.c                 |   4 +-
 .../selftests/cgroup/test_cpuset_prs.sh       |  13 +-
 4 files changed, 196 insertions(+), 66 deletions(-)

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2.52.0