linux-kernel - Re: [PATCH 1/2] sched/deadline: use online cpus for validating runtime

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Message-ID: <Z8lc79prs3OdUXtB@jlelli-thinkpadt14gen4.remote.csb>
Date: Thu, 6 Mar 2025 08:29:35 +0000
From: Juri Lelli <juri.lelli@...hat.com>
To: Shrikanth Hegde <sshegde@...ux.ibm.com>
Cc: linux-kernel@...r.kernel.org, mingo@...nel.org, peterz@...radead.org,
	vincent.guittot@...aro.org, dietmar.eggemann@....com,
	rostedt@...dmis.org, bsegall@...gle.com, mgorman@...e.de,
	vschneid@...hat.com, hbathini@...ux.ibm.com, joelagnelf@...dia.com
Subject: Re: [PATCH 1/2] sched/deadline: use online cpus for validating
 runtime

Hi!

On 06/03/25 10:59, Shrikanth Hegde wrote:
> ftrace selftest reported failure since writing -1 to sched_rt_runtime_us
> return -EBUSY. This happens when the possible CPUs is different than
> the active CPUS.
> 
> Active CPUs are part of one root domain, while remaining CPUs are part
> of def_root_domain. Since active cpumask is being used, this results in
> cpus=0 when a non active CPUs is used in the loop.
> 
> Fix it by looping over the online CPUs instead for validation the
> bandwidth calculations.
> 
> Signed-off-by: Shrikanth Hegde <sshegde@...ux.ibm.com>
> ---
>  kernel/sched/deadline.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
> index 2d0f571f95e9..7ea9c040c72f 100644
> --- a/kernel/sched/deadline.c
> +++ b/kernel/sched/deadline.c
> @@ -3187,7 +3187,7 @@ int sched_dl_global_validate(void)
>  	 * value smaller than the currently allocated bandwidth in
>  	 * any of the root_domains.
>  	 */
> -	for_each_possible_cpu(cpu) {
> +	for_each_online_cpu(cpu) {
>  		rcu_read_lock_sched();
>  
>  		if (dl_bw_visited(cpu, gen))
> -- 

Makes sense to me.

Acked-by: Juri Lelli <juri.lelli@...hat.com>

Thanks,
Juri