linux-kernel - Re: [PATCH v5 1/5] soc: qcom: rpmh-rsc: Correctly ignore CPU_CLUSTER

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Date:   Mon, 4 May 2020 10:54:54 -0700
From:   Doug Anderson <dianders@...omium.org>
To:     Maulik Shah <mkshah@...eaurora.org>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
        Andy Gross <agross@...nel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Evan Green <evgreen@...omium.org>,
        Matthias Kaehlcke <mka@...omium.org>,
        Stephen Boyd <swboyd@...omium.org>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v5 1/5] soc: qcom: rpmh-rsc: Correctly ignore
 CPU_CLUSTER_PM notifications

Hi,

On Sun, May 3, 2020 at 10:19 PM Maulik Shah <mkshah@...eaurora.org> wrote:
>
> Hi,
>
> On 4/24/2020 10:16 PM, Douglas Anderson wrote:
> > Our switch statement doesn't have entries for CPU_CLUSTER_PM_ENTER,
> > CPU_CLUSTER_PM_ENTER_FAILED, and CPU_CLUSTER_PM_EXIT and doesn't have
> > a default.  This means that we'll try to do a flush in those cases but
> > we won't necessarily be the last CPU down.  That's not so ideal since
> > our (lack of) locking assumes we're on the last CPU.
> >
> > Luckily this isn't as big a problem as you'd think since (at least on
> > the SoC I tested) we don't get these notifications except on full
> > system suspend.  ...and on full system suspend we get them on the last
> > CPU down.  That means that the worst problem we hit is flushing twice.
> > Still, it's good to make it correct.
> >
> > Fixes: 985427f997b6 ("soc: qcom: rpmh: Invoke rpmh_flush() for dirty caches")
> > Reported-by: Stephen Boyd <swboyd@...omium.org>
> > Signed-off-by: Douglas Anderson <dianders@...omium.org>
> > Reviewed-by: Maulik Shah <mkshah@...eaurora.org>
> > Reviewed-by: Stephen Boyd <swboyd@...omium.org>
> > ---
> >
> > Changes in v5:
> > - Corrently => Correctly
> >
> > Changes in v4:
> > - ("...Corrently ignore CPU_CLUSTER_PM notifications") split out for v4.
> >
> > Changes in v3: None
> > Changes in v2: None
> >
> >   drivers/soc/qcom/rpmh-rsc.c | 2 ++
> >   1 file changed, 2 insertions(+)
> >
> > diff --git a/drivers/soc/qcom/rpmh-rsc.c b/drivers/soc/qcom/rpmh-rsc.c
> > index a9e15699f55f..3571a99fc839 100644
> > --- a/drivers/soc/qcom/rpmh-rsc.c
> > +++ b/drivers/soc/qcom/rpmh-rsc.c
> > @@ -806,6 +806,8 @@ static int rpmh_rsc_cpu_pm_callback(struct notifier_block *nfb,
> >       case CPU_PM_EXIT:
> >               cpumask_clear_cpu(smp_processor_id(), &drv->cpus_entered_pm);
> >               goto exit;
> > +     default:
> > +             return NOTIFY_DONE;
>
> I noticed a bug here,
>
> Either need to unlock and return here.

Dang it!  Thank you very much for noticing.  v6 sent.  I removed both
yours and Stephen's "Reviewed-by" tags.  Please re-review to make sure
I didn't do anything else stuid.


> +       default:
> +               ret = NOTIFY_DONE;
> +               goto exit;
>
> Or
>
> If you move this patch at the end of series, it should will work fine as is.
> Since in patch 5 of this series,  pm_lock is removed, so return
> NOTIFY_DONE; do not any unlock.

Right.  It used to be part of the last patch but Stephen requested I
move the bugfixes first so they could land sooner even if we aren't
ready to land the "remove the pm_lock" patch.


> When i pulled in only first two changes in this series i got spinlock
> recursion during suspend-resume.
> Back when i pull in entire series for validation, the issue do not come
> because last patch removes pm_lock.

OK, v6 is sent out.

-Doug