linux-kernel - Re: 答复: Re: [RFC PATCH V5 5/5] workqueue: introduce a way to setworkqueue's scheduler

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Message-ID: <1517207502.7290.53.camel@gmx.de>
Date:   Mon, 29 Jan 2018 07:31:42 +0100
From:   Mike Galbraith <efault@....de>
To:     wen.yang99@....com.cn
Cc:     tj@...nel.org, zhong.weidong@....com.cn, jiang.biao2@....com.cn,
        tan.hu@....com.cn, jiangshanlai@...il.com, xiaolong.ye@...el.com,
        linux-kernel@...r.kernel.org
Subject: Re: 答复: Re: [RFC PATCH V5 5/5]
 workqueue: introduce a way to setworkqueue's scheduler

On Mon, 2018-01-29 at 13:50 +0800, wen.yang99@....com.cn wrote:
> 
> > What happens when a new kworker needs to be spawned?
> create_worker -> worker_attach_to_pool, in the function
> worker_attach_to_pool，  we add this chunk:
> 
> --- a/kernel/workqueue.c
> +++ b/kernel/workqueue.c
> @@ -1699,6 +1699,7 @@ static void worker_attach_to_pool(struct worker *worker,
>          * online CPUs.  It'll be re-applied when any of the CPUs come up.
>          */
>         set_cpus_allowed_ptr(worker->task, pool->attrs->cpumask);
> +       sched_setattr(worker->task, &pool->attrs->sched_attr);
>  
>         /*
>          * The pool->attach_mutex ensures %POOL_DISASSOCIATED remains
> 		 
> pool->attach_mutex may guarante it, add  sched_setattr may apply the
> wq's sched_attr to the spawned kworer.

That doesn't help kthreadd get to a CPU in a box being saturated by RT.

As long as you are careful, it's not a problem, I just mentioned it
because it's a hole.

	-Mike