linux-kernel - Re: [PATCH] workqueue: Restrict kworker in the offline CPU pool running on housekeeping CPUs

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Message-ID: <CAJhGHyCCg_ttPwW6HX8qUJiOVaSYMbKKYsxT3myJczvZWO7H-w@mail.gmail.com>
Date:   Thu, 31 Mar 2022 12:22:28 +0800
From:   Lai Jiangshan <jiangshanlai@...il.com>
To:     Zqiang <qiang1.zhang@...el.com>
Cc:     Tejun Heo <tj@...nel.org>, LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] workqueue: Restrict kworker in the offline CPU pool
 running on housekeeping CPUs

Acked-by: Lai Jiangshan <jiangshanlai@...il.com>

I don't think the patch can be applied to the wq tree due to
the change
https://lore.kernel.org/lkml/164512420798.16921.1042432342597886877.tip-bot2@tip-bot2/
which did the rename of HK_TYPE_WQ has not been merged into Linus's tree.

On Tue, Mar 29, 2022 at 1:16 PM Zqiang <qiang1.zhang@...el.com> wrote:
>
> When CPU going offline, all workers in this CPU pool will lose
> affinity to this CPU, and may run to isolated CPU. like kworker
> in unbound pool, set CPU affinity of these kworker is housekeeping
> cpumask.
>
> Signed-off-by: Zqiang <qiang1.zhang@...el.com>
> ---
>  kernel/workqueue.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/kernel/workqueue.c b/kernel/workqueue.c
> index abcc9a2ac319..c509ce73a783 100644
> --- a/kernel/workqueue.c
> +++ b/kernel/workqueue.c
> @@ -5023,7 +5023,8 @@ static void unbind_workers(int cpu)
>
>                 for_each_pool_worker(worker, pool) {
>                         kthread_set_per_cpu(worker->task, -1);
> -                       WARN_ON_ONCE(set_cpus_allowed_ptr(worker->task, cpu_possible_mask) < 0);
> +                       WARN_ON_ONCE(set_cpus_allowed_ptr(worker->task,
> +                                               housekeeping_cpumask(HK_TYPE_WQ)) < 0);
>                 }
>
>                 mutex_unlock(&wq_pool_attach_mutex);
> --
> 2.25.1
>