linux-kernel - Re: [PATCH 11/23] sched,spi: Convert to sched_set

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Date:   Wed, 22 Apr 2020 14:56:28 +0100
From:   Mark Brown <broonie@...nel.org>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     mingo@...nel.org, linux-kernel@...r.kernel.org, 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,
        Douglas Anderson <dianders@...omium.org>,
        Guenter Roeck <groeck@...omium.org>
Subject: Re: [PATCH 11/23] sched,spi: Convert to sched_set_fifo*()

On Wed, Apr 22, 2020 at 01:27:30PM +0200, 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.
> 
> No effective change.

Copying Doug who did this change and Guenter who reviewed it.  This
looks fine to me but I've no particular involvement with the code or
platforms that are affected here.

> Cc: broonie@...nel.org
> Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
> Reviewed-by: Ingo Molnar <mingo@...nel.org>
> ---
>  drivers/platform/chrome/cros_ec_spi.c |    6 +-----
>  1 file changed, 1 insertion(+), 5 deletions(-)
> 
> --- a/drivers/platform/chrome/cros_ec_spi.c
> +++ b/drivers/platform/chrome/cros_ec_spi.c
> @@ -709,9 +709,6 @@ static void cros_ec_spi_high_pri_release
>  static int cros_ec_spi_devm_high_pri_alloc(struct device *dev,
>  					   struct cros_ec_spi *ec_spi)
>  {
> -	struct sched_param sched_priority = {
> -		.sched_priority = MAX_RT_PRIO / 2,
> -	};
>  	int err;
>  
>  	ec_spi->high_pri_worker =
> @@ -728,8 +725,7 @@ static int cros_ec_spi_devm_high_pri_all
>  	if (err)
>  		return err;
>  
> -	err = sched_setscheduler_nocheck(ec_spi->high_pri_worker->task,
> -					 SCHED_FIFO, &sched_priority);
> +	err = sched_set_fifo(ec_spi->high_pri_worker->task);
>  	if (err)
>  		dev_err(dev, "Can't set cros_ec high pri priority: %d\n", err);
>  	return err;
> --- a/drivers/spi/spi.c
> +++ b/drivers/spi/spi.c
> @@ -1589,11 +1589,9 @@ EXPORT_SYMBOL_GPL(spi_take_timestamp_pos
>   */
>  static void spi_set_thread_rt(struct spi_controller *ctlr)
>  {
> -	struct sched_param param = { .sched_priority = MAX_RT_PRIO / 2 };
> -
>  	dev_info(&ctlr->dev,
>  		"will run message pump with realtime priority\n");
> -	sched_setscheduler(ctlr->kworker_task, SCHED_FIFO, &param);
> +	sched_set_fifo(ctlr->kworker_task);
>  }
>  
>  static int spi_init_queue(struct spi_controller *ctlr)
> 
> 

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