linux-kernel - Re: [PATCH 09/23] sched,ivtv: Convert to sched_set

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Date:   Fri, 24 Apr 2020 11:58:31 +0200
From:   Hans Verkuil <hverkuil-cisco@...all.nl>
To:     Peter Zijlstra <peterz@...radead.org>, mingo@...nel.org,
        linux-kernel@...r.kernel.org
Cc:     tglx@...utronix.de, rostedt@...dmis.org, qais.yousef@....com,
        juri.lelli@...hat.com, vincent.guittot@...aro.org,
        dietmar.eggemann@....com, bsegall@...gle.com, mgorman@...e.de,
        awalls@...metrocast.net
Subject: Re: [PATCH 09/23] sched,ivtv: Convert to sched_set_fifo*()

On 22/04/2020 13:27, Peter Zijlstra wrote:
> Because SCHED_FIFO is a broken scheduler model (see previous patches)
> take away the priority field, the kernel can't possibly make an
> informed decision.
> 
> Effectively changes from 99 to 50.
> 
> Cc: hverkuil@...all.nl
> Cc: awalls@...metrocast.net
> Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
> Reviewed-by: Ingo Molnar <mingo@...nel.org>

Acked-by: Hans Verkuil <hverkuil-cisco@...all.nl>
Tested-by: Hans Verkuil <hverkuil-cisco@...all.nl>

I didn't see any difference in behavior when I changed the prio from 99 to 50,
so it doesn't seem to be a harmful change :-)

Regards,

	Hans

> ---
>  drivers/media/pci/ivtv/ivtv-driver.c |    4 +---
>  1 file changed, 1 insertion(+), 3 deletions(-)
> 
> --- a/drivers/media/pci/ivtv/ivtv-driver.c
> +++ b/drivers/media/pci/ivtv/ivtv-driver.c
> @@ -737,8 +737,6 @@ static void ivtv_process_options(struct
>   */
>  static int ivtv_init_struct1(struct ivtv *itv)
>  {
> -	struct sched_param param = { .sched_priority = 99 };
> -
>  	itv->base_addr = pci_resource_start(itv->pdev, 0);
>  	itv->enc_mbox.max_mbox = 2; /* the encoder has 3 mailboxes (0-2) */
>  	itv->dec_mbox.max_mbox = 1; /* the decoder has 2 mailboxes (0-1) */
> @@ -758,7 +756,7 @@ static int ivtv_init_struct1(struct ivtv
>  		return -1;
>  	}
>  	/* must use the FIFO scheduler as it is realtime sensitive */
> -	sched_setscheduler(itv->irq_worker_task, SCHED_FIFO, &param);
> +	sched_set_fifo(itv->irq_worker_task);
>  
>  	kthread_init_work(&itv->irq_work, ivtv_irq_work_handler);
>  
> 
>