linux-kernel - Re: [PATCH 2/2][v3] PM / s2idle: Code cleanup to make s2idle consistent with normal idle path

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Message-ID: <CAJZ5v0jD__jK_tkNHk_ZqKEfdGiDa_afL5f65k3=z-8ZSq_UFQ@mail.gmail.com>
Date:   Thu, 25 Jun 2020 12:49:02 +0200
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Chen Yu <yu.c.chen@...el.com>
Cc:     "Rafael J. Wysocki" <rjw@...ysocki.net>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        Len Brown <len.brown@...el.com>,
        Linux PM <linux-pm@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Len Brown <lenb@...nel.org>
Subject: Re: [PATCH 2/2][v3] PM / s2idle: Code cleanup to make s2idle
 consistent with normal idle path

On Thu, Jun 25, 2020 at 7:14 AM Chen Yu <yu.c.chen@...el.com> wrote:
>
> Hi Rafael,
> On Tue, Jun 23, 2020 at 07:57:59PM +0200, Rafael J. Wysocki wrote:
> > From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> > Subject: [PATCH] cpuidle: Rearrange s2idle-specific idle state entry code
> >
> > Implement call_cpuidle_s2idle() in analogy with call_cpuidle()
> > for the s2idle-specific idle state entry and invoke it from
> > cpuidle_idle_call() to make the s2idle-specific idle entry code
> > path look more similar to the "regular" idle entry one.
> >
> > No intentional functional impact.
> >
> > Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> > ---
> >  drivers/cpuidle/cpuidle.c |    6 +++---
> >  kernel/sched/idle.c       |   15 +++++++++++----
> >  2 files changed, 14 insertions(+), 7 deletions(-)
> >
> > Index: linux-pm/kernel/sched/idle.c
> > ===================================================================
> > --- linux-pm.orig/kernel/sched/idle.c
> > +++ linux-pm/kernel/sched/idle.c
> > @@ -96,6 +96,15 @@ void __cpuidle default_idle_call(void)
> >       }
> >  }
> >
> > +static int call_cpuidle_s2idle(struct cpuidle_driver *drv,
> > +                            struct cpuidle_device *dev)
> > +{
> > +     if (current_clr_polling_and_test())
> > +             return -EBUSY;
> > +
> > +     return cpuidle_enter_s2idle(drv, dev);
> > +}
> > +
> >  static int call_cpuidle(struct cpuidle_driver *drv, struct cpuidle_device *dev,
> >                     int next_state)
> >  {
> > @@ -171,11 +180,9 @@ static void cpuidle_idle_call(void)
> >               if (idle_should_enter_s2idle()) {
> >                       rcu_idle_enter();
> >
> > -                     entered_state = cpuidle_enter_s2idle(drv, dev);
> > -                     if (entered_state > 0) {
> > -                             local_irq_enable();
> > +                     entered_state = call_cpuidle_s2idle(drv, dev);
> I guess this changes the context a little bit that(comparing to [1/2 patch],
> after this modification, when we found that TIF_NEED_RESCHED is set we can have
> a second chance in the following call_cpuidle to do a second s2idle try. However
> in [1/2 patch], it might exit the s2idle phase directly once when we see
> TIF_NEED_RESCHED is set(because entered_state is postive we treat it as a successful
> s2idle). In summary I think the change (patch [2/2]) is more robust.

Yeah, good point.

> Acked-by: Chen Yu <yu.c.chen@...el.com>

OK, thanks!

I'll queue up this one too along with the [1/2] for -rc4 then.

Thanks!