[PATCH-wq v2 0/5] workqueue: Enable unbound cpumask update on ordered workqueues

[Waiman Long <longman@redhat.com>]

 v2:
  - [v1] https://lore.kernel.org/all/20240130183336.511948-1-longman@redhat.com/
  - Rebased on top of wq's for-v6.9 branch.
  - Use the new pwq_tryinc_nr_active() mechanism to freeze the new
    pwq of an ordered workqueue until the old pwq has been properly
    drained to maintain ordering.
  - Make rescuer follow changes in workqueue unbound cpumask as well
    as its sysfs cpumask, if available.

Ordered workqueues does not currently follow changes made to the
global unbound cpumask because per-pool workqueue changes may break
the ordering guarantee. IOW, a work function in an ordered workqueue
may run on a cpuset isolated CPU.

This series enables ordered workqueues to follow changes made to
the global unbound cpumask by temporaily freeze the newly allocated
pool_workqueue by using the new frozen flag to freeze execution of
newly queued work items until the old pwq has been properly flushed.

The cpumask of the rescuer task of each workqueue is also made to follow
changes in workqueue unbound cpumask as well as its sysfs cpumask,
if available.

Juri Lelli (1):
  kernel/workqueue: Let rescuers follow unbound wq cpumask changes

Waiman Long (4):
  workqueue: Skip __WQ_DESTROYING workqueues when updating global
    unbound cpumask
  workqueue: Enable unbound cpumask update on ordered workqueues
  workqueue: Thaw frozen pwq in workqueue_apply_unbound_cpumask()
  workqueue: Bind unbound workqueue rescuer to wq_unbound_cpumask

 kernel/workqueue.c | 128 +++++++++++++++++++++++++++++++++++++++------
 1 file changed, 113 insertions(+), 15 deletions(-)

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2.39.3