linux-kernel - Re: [PATCH v5 02/14] sched/debug: Stop and start server based on if it was active

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Message-ID: <aFm2NSeFE9LJS_BU@slm.duckdns.org>
Date: Mon, 23 Jun 2025 10:16:53 -1000
From: Tejun Heo <tj@...nel.org>
To: Joel Fernandes <joelagnelf@...dia.com>
Cc: linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Juri Lelli <juri.lelli@...hat.com>,
	Vincent Guittot <vincent.guittot@...aro.org>,
	Dietmar Eggemann <dietmar.eggemann@....com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Ben Segall <bsegall@...gle.com>, Mel Gorman <mgorman@...e.de>,
	Valentin Schneider <vschneid@...hat.com>,
	David Vernet <void@...ifault.com>, Andrea Righi <arighi@...dia.com>,
	Changwoo Min <changwoo@...lia.com>
Subject: Re: [PATCH v5 02/14] sched/debug: Stop and start server based on if
 it was active

On Fri, Jun 20, 2025 at 04:32:17PM -0400, Joel Fernandes wrote:
> @@ -381,7 +382,8 @@ static ssize_t sched_fair_server_write(struct file *filp, const char __user *ubu
>  			return  -EINVAL;
>  		}
>  
> -		if (rq->cfs.h_nr_queued) {
> +		if (dl_server_active(&rq->fair_server)) {
> +			was_active = true;
>  			update_rq_clock(rq);
>  			dl_server_stop(&rq->fair_server);
>  		}
> @@ -392,7 +394,7 @@ static ssize_t sched_fair_server_write(struct file *filp, const char __user *ubu
>  			printk_deferred("Fair server disabled in CPU %d, system may crash due to starvation.\n",
>  					cpu_of(rq));
>  
> -		if (rq->cfs.h_nr_queued)
> +		if (was_active)

This is minor but the style looks a bit odd to me. Would it make more sense
to put was_active in the scoped_guard block and do something like:

        is_active = dl_server_active(&rq->fair_server);
        if (is_active) {
                ...
        }
        ...
        if (is_active)
                dl_server_start(&rq->fair_server);

Other than that,

Acked-by: Tejun Heo <tj@...nel.org>

Thanks.

-- 
tejun