linux-kernel - Re: [PATCH 3/4] workqueue: Tag bound workers with KTHREAD_IS_PER

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Date:   Tue, 12 Jan 2021 17:57:23 +0000
From:   Valentin Schneider <valentin.schneider@....com>
To:     Peter Zijlstra <peterz@...radead.org>, mingo@...nel.org,
        tglx@...utronix.de
Cc:     linux-kernel@...r.kernel.org, jiangshanlai@...il.com,
        cai@...hat.com, vincent.donnefort@....com, decui@...rosoft.com,
        paulmck@...nel.org, vincent.guittot@...aro.org,
        rostedt@...dmis.org, tj@...nel.org, peterz@...radead.org
Subject: Re: [PATCH 3/4] workqueue: Tag bound workers with KTHREAD_IS_PER_CPU

On 12/01/21 15:43, Peter Zijlstra wrote:
> @@ -4919,8 +4922,10 @@ static void unbind_workers(int cpu)
>
>               raw_spin_unlock_irq(&pool->lock);
>
> -		for_each_pool_worker(worker, pool)
> +		for_each_pool_worker(worker, pool) {
> +			kthread_set_per_cpu(worker->task, false);
>                       WARN_ON_ONCE(set_cpus_allowed_ptr(worker->task, cpu_possible_mask) < 0);
> +		}

Doesn't this supersede patch 1? With patch 4 on top, the BALANCE_PUSH
stuff should start resetting the affinity of the kworkers for which we
are removing the IS_PER_CPU flag.

It's the only nit I have, the rest looks good to me so:

Reviewed-by: Valentin Schneider <valentin.schneider@....com>

I'll go frob that sched_cpu_dying() warning.