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

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Message-ID: <CAPDyKFo0AX9EycOdxLKQxMbOUsnLri=OqWi3o991feqc6_Q26g@mail.gmail.com>
Date:   Thu, 23 Apr 2020 14:01:05 +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>,
        Benjamin Segall <bsegall@...gle.com>, mgorman@...e.de
Subject: Re: [PATCH 10/23] sched,mmc: Convert to sched_set_fifo*()

On Thu, 23 Apr 2020 at 10:59, Peter Zijlstra <peterz@...radead.org> wrote:
>
> On Wed, Apr 22, 2020 at 06:59:35PM +0200, Ulf Hansson wrote:
> > 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>
>
> Thanks!
>
> > 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.
>
> Moving over to regular threaded interrupts? Anyway, cool, if these
> series collide it's easy enough to drop this patch on the floor if it
> turns out obsolete.

In principle, the only reason for the kthread is that we need it for
polling - for hosts that don't support SDIO irqs. So, I am thinking of
replacing the kthread with a workqueue, as we already have one for
hosts that are using non-threaded IRQs.

Kind regards
Uffe