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Date:   Mon, 8 Jul 2019 12:47:54 +0200
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Viresh Kumar <viresh.kumar@...aro.org>
Cc:     Pavel Machek <pavel@....cz>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Matthias Kaehlcke <mka@...omium.org>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Linux-pm mailing list <linux-pm@...r.kernel.org>,
        kernel list <linux-kernel@...r.kernel.org>,
        Stephen Rothwell <sfr@...b.auug.org.au>
Subject: Re: cpufreq notifiers break suspend -- Re: suspend broken in
 next-20190704 on Thinkpad X60

On Mon, Jul 8, 2019 at 11:28 AM Viresh Kumar <viresh.kumar@...aro.org> wrote:
>
> On 08-07-19, 10:28, Rafael J. Wysocki wrote:
> > Pavel has tested the latest version of the patch series AFAICS.
> >
> > The locking added by the commit in question to
> > refresh_frequency_limits() requires an update of
> > cpufreq_update_policy(), or it will deadlock in there because of the
> > lock acquired by cpufreq_cpu_get() if I haven't missed anything.
>
> Ah, looks quite straight forward.
>
> @Pavel: Can you please try this diff ?
>
> -------------------------8<-------------------------
>
> diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
> index 9f68d0f306b8..4d6043ee7834 100644
> --- a/drivers/cpufreq/cpufreq.c
> +++ b/drivers/cpufreq/cpufreq.c
> @@ -1109,16 +1109,12 @@ void refresh_frequency_limits(struct cpufreq_policy *policy)
>  {
>         struct cpufreq_policy new_policy;
>
> -       down_write(&policy->rwsem);
> -
>         if (!policy_is_inactive(policy)) {
>                 new_policy = *policy;
>                 pr_debug("updating policy for CPU %u\n", policy->cpu);
>
>                 cpufreq_set_policy(policy, &new_policy);
>         }
> -
> -       up_write(&policy->rwsem);
>  }
>  EXPORT_SYMBOL(refresh_frequency_limits);
>
> @@ -1128,7 +1124,9 @@ static void handle_update(struct work_struct *work)
>                 container_of(work, struct cpufreq_policy, update);
>
>         pr_debug("handle_update for cpu %u called\n", policy->cpu);
> +       down_write(&policy->rwsem);
>         refresh_frequency_limits(policy);
> +       up_write(&policy->rwsem);
>  }
>
> -------------------------8<-------------------------
>
> Though it makes me wonder why I didn't hit this thing. I was using the
> cpu_cooling device the other day, which calls cpufreq_update_policy()
> very frequently on heat-up. And I had a hair dryer blowing over my
> board to heat it up. Lemme check that again :)
>
> @Rafael: You want me to send a new diff patch with Fixes tag this time
> if this works out fine ?

I would prefer the original patch to be updated to avoid possible
bisection woes in the future.

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