linux-kernel - Re: [PATCH v6 3/7] powercap/drivers/dtpm: Simplify the dtpm table

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Message-ID: <CAJZ5v0hDa4dmEJD0EYnOzfDBNC-GU99DM_d7bsTCCoSaP-o3CA@mail.gmail.com>
Date:   Fri, 26 Nov 2021 20:29:58 +0100
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Doug Smythies <dsmythies@...us.net>
Cc:     "Rafael J. Wysocki" <rafael@...nel.org>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        Linux PM list <linux-pm@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Lukasz Luba <lukasz.luba@....com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: Re: [PATCH v6 3/7] powercap/drivers/dtpm: Simplify the dtpm table

On Fri, Nov 26, 2021 at 8:10 PM Doug Smythies <dsmythies@...us.net> wrote:
>
> On Fri, Nov 26, 2021 at 9:22 AM Rafael J. Wysocki <rafael@...nel.org> wrote:
> >
> > Hi Doug,
> >
> > On Fri, Nov 26, 2021 at 6:08 PM Doug Smythies <dsmythies@...us.net> wrote:
> > >
> > > Hi Daniel,
> > >
> > > This patch introduces a regression, at least on my test system.
> > > I can no longer change CPU frequency scaling drivers, for example
> > > from intel_cpufreq (A.K.A intel_pstate in passive mode) to intel_pstate
> > > (A.K.A. active mode). The task just hangs forever.
> > >
> > > I bisected the kernel and got this commit as the result.
> > > As a double check, I reverted this commit:
> > > 7a89d7eacf8e84f2afb94db5ae9d9f9faa93f01c
> > > on kernel 5.16-rc2 and the issue was resolved.
> > >
> > > While your email is fairly old, I observe that it was only included as of
> > > kernel 5.16-rc1.
> > >
> > > Command Example that never completes:
> > >
> > > $ echo passive | sudo tee /sys/devices/system/cpu/intel_pstate/status
> > >
> > > syslog excerpt attached.
> >
> > This looks like it may be problematic:
> >
> > diff --git a/drivers/powercap/dtpm_cpu.c b/drivers/powercap/dtpm_cpu.c
> > index f6076de39540..98841524a782 100644
> > --- a/drivers/powercap/dtpm_cpu.c
> > +++ b/drivers/powercap/dtpm_cpu.c
> > @@ -204,7 +204,7 @@ static int cpuhp_dtpm_cpu_online(unsigned int cpu)
> >        return ret;
> > }
> >
> > -int dtpm_register_cpu(struct dtpm *parent)
> > +static int __init dtpm_cpu_init(void)
> > {
> >        int ret;
> >
> > so please try to remove the __init annotation from dtpm_cpu_init() and
> > see if that helps.
>
> Hi Rafael,
>
> That did not fix the issue.
> Just to be clear this is what I did, on top of 5.16-rc2:
>
> $ git diff
> diff --git a/drivers/powercap/dtpm_cpu.c b/drivers/powercap/dtpm_cpu.c
> index b740866b228d..26d1a87bdec6 100644
> --- a/drivers/powercap/dtpm_cpu.c
> +++ b/drivers/powercap/dtpm_cpu.c
> @@ -231,7 +231,7 @@ static int cpuhp_dtpm_cpu_online(unsigned int cpu)
>         return ret;
>  }
>
> -static int __init dtpm_cpu_init(void)
> +static int dtpm_cpu_init(void)
>  {
>         int ret;

OK

This needs to be fixed or we'll need to revert commit
7a89d7eacf8e84f2afb94db5ae9d9f9faa93f01c for 5.16.