linux-kernel - Re: [PATCH v2 5/7] sched: Implement shared runqueue in CFS

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Message-ID: <20230713075809.GA24959@ziqianlu-dell>
Date:   Thu, 13 Jul 2023 15:58:09 +0800
From:   Aaron Lu <aaron.lu@...el.com>
To:     David Vernet <void@...ifault.com>
CC:     <linux-kernel@...r.kernel.org>, <mingo@...hat.com>,
        <peterz@...radead.org>, <juri.lelli@...hat.com>,
        <vincent.guittot@...aro.org>, <dietmar.eggemann@....com>,
        <rostedt@...dmis.org>, <bsegall@...gle.com>, <mgorman@...e.de>,
        <bristot@...hat.com>, <vschneid@...hat.com>,
        <gautham.shenoy@....com>, <kprateek.nayak@....com>, <clm@...a.com>,
        <tj@...nel.org>, <roman.gushchin@...ux.dev>, <kernel-team@...a.com>
Subject: Re: [PATCH v2 5/7] sched: Implement shared runqueue in CFS

On Mon, Jul 10, 2023 at 03:03:40PM -0500, David Vernet wrote:
>  static void shared_runq_dequeue_task(struct task_struct *p)
> -{}
> +{
> +	unsigned long flags;
> +	struct shared_runq *shared_runq;
> +
> +	if (!list_empty(&p->shared_runq_node)) {
> +		shared_runq = rq_shared_runq(task_rq(p));
> +		spin_lock_irqsave(&shared_runq->lock, flags);

After taking the lock, p may have been poped by another newidle cpu.
Running list_del_init() doesn't seem hurt, but is this intended?

> +		list_del_init(&p->shared_runq_node);
> +		spin_unlock_irqrestore(&shared_runq->lock, flags);
> +	}
> +}