linux-kernel - [PATCH-wq v3 0/4] workqueue: Enable unbound cpumask update on ordered workqueues

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Date: Mon,  5 Feb 2024 14:45:58 -0500
From: Waiman Long <longman@...hat.com>
To: Tejun Heo <tj@...nel.org>,
	Lai Jiangshan <jiangshanlai@...il.com>
Cc: linux-kernel@...r.kernel.org,
	Juri Lelli <juri.lelli@...hat.com>,
	Cestmir Kalina <ckalina@...hat.com>,
	Alex Gladkov <agladkov@...hat.com>,
	Phil Auld <pauld@...hat.com>,
	Costa Shulyupin <cshulyup@...hat.com>,
	Waiman Long <longman@...hat.com>
Subject: [PATCH-wq v3 0/4] workqueue: Enable unbound cpumask update on ordered workqueues

 v3:
  - [v2] https://lore.kernel.org/lkml/20240203154334.791910-1-longman@redhat.com/
  - Drop patch 1 as it has been merged into the for-6.9 branch.
  - Use rcu_access_pointer() to access wq->dfl_pwq.
  - Use RCU protection instead of acquiring wq->mutex in
    apply_wqattrs_cleanup().

 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 (3):
  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 | 127 ++++++++++++++++++++++++++++++++++++++++-----
 1 file changed, 113 insertions(+), 14 deletions(-)

-- 
2.39.3