Re: [PATCH v5] cgroup: split cgroup_destroy_wq into 3 workqueues

[Chen Ridong <chenridong@huaweicloud.com>]

On 2025/8/18 14:14, Chen Ridong wrote:

> 
> diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c
> index 312c6a8b55bb..679dc216e3ed 100644
> --- a/kernel/cgroup/cgroup.c
> +++ b/kernel/cgroup/cgroup.c
> @@ -126,8 +126,22 @@ DEFINE_PERCPU_RWSEM(cgroup_threadgroup_rwsem);
>   * of concurrent destructions.  Use a separate workqueue so that cgroup
>   * destruction work items don't end up filling up max_active of system_wq
>   * which may lead to deadlock.
> + *
> + * A cgroup destruction should enqueue work sequentially to:
> + * cgroup_offline_wq: use for css offline work
> + * cgroup_release_wq: use for css release work
> + * cgroup_free_wq: use for free work
> + *
> + * Rationale for using separate workqueues:
> + * The cgroup root free work may depend on completion of other css offline
> + * operations. If all tasks were enqueued to a single workqueue, this could
> + * create a deadlock scenario where:
> + * - Free work waits for other css offline work to complete.
> + * - But other css offline work is queued after free work in the same queue.
>   */

More comments are added to clarify why we split the destroy work into 3 workqueues in v5.

-- 
Best regards,
Ridong