linux-kernel - Re: [PATCH 10/23] sched,mmc: Convert to sched_set

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Message-ID: <CAPDyKFo+qCZU=snj==4CFRfL9R0KLcG2RMYeFW_BMX=-Mo5rtg@mail.gmail.com>
Date:   Wed, 22 Apr 2020 18:59:35 +0200
From:   Ulf Hansson <ulf.hansson@...aro.org>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Ingo Molnar <mingo@...nel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Steven Rostedt <rostedt@...dmis.org>, qais.yousef@....com,
        Juri Lelli <juri.lelli@...hat.com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        bsegall@...gle.com, mgorman@...e.de
Subject: Re: [PATCH 10/23] sched,mmc: Convert to sched_set_fifo*()

On Wed, 22 Apr 2020 at 13:29, Peter Zijlstra <peterz@...radead.org> 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.
>
> In this case, use fifo_low, because it only cares about being above
> SCHED_NORMAL. Effectively no change in behaviour.
>
> Cc: ulf.hansson@...aro.org
> Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
> Reviewed-by: Ingo Molnar <mingo@...nel.org>

Acked-by: Ulf Hansson <ulf.hansson@...aro.org>

FYI: I am slowly moving towards removing the entire kthread for the
sdio_irq_thread(). It shouldn't be too far off to be posted, one or
two kernel releases or so.

Kind regards
Uffe

> ---
>  drivers/mmc/core/sdio_irq.c |    3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
>
> --- a/drivers/mmc/core/sdio_irq.c
> +++ b/drivers/mmc/core/sdio_irq.c
> @@ -139,11 +139,10 @@ EXPORT_SYMBOL_GPL(sdio_signal_irq);
>  static int sdio_irq_thread(void *_host)
>  {
>         struct mmc_host *host = _host;
> -       struct sched_param param = { .sched_priority = 1 };
>         unsigned long period, idle_period;
>         int ret;
>
> -       sched_setscheduler(current, SCHED_FIFO, &param);
> +       sched_set_fifo_low(current);
>
>         /*
>          * We want to allow for SDIO cards to work even on non SDIO
>
>