linux-kernel - Re: [PATCH V3 1/3] cpufreq: Fix locking issues with governors

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Message-ID: <20200629080511.GB1217385@google.com>
Date:   Mon, 29 Jun 2020 09:05:11 +0100
From:   Quentin Perret <qperret@...gle.com>
To:     Viresh Kumar <viresh.kumar@...aro.org>
Cc:     Rafael Wysocki <rjw@...ysocki.net>, linux-pm@...r.kernel.org,
        Vincent Guittot <vincent.guittot@...aro.org>,
        kernel-team@...roid.com, tkjos@...gle.com, adharmap@...eaurora.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH V3 1/3] cpufreq: Fix locking issues with governors

On Monday 29 Jun 2020 at 07:43:09 (+0530), Viresh Kumar wrote:
> I described why I chose to keep it that way in the other email, but I
> am all for dropping the variable. And so what about this ?
> 
> diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
> index e798a1193bdf..d9e9ae7051bb 100644
> --- a/drivers/cpufreq/cpufreq.c
> +++ b/drivers/cpufreq/cpufreq.c
> @@ -1064,18 +1064,17 @@ static int cpufreq_init_policy(struct cpufreq_policy *policy)
>         struct cpufreq_governor *def_gov = cpufreq_default_governor();
>         struct cpufreq_governor *gov = NULL;
>         unsigned int pol = CPUFREQ_POLICY_UNKNOWN;
> -       bool put_governor = false;
>         int ret;
>  
>         if (has_target()) {
>                 /* Update policy governor to the one used before hotplug. */
>                 gov = get_governor(policy->last_governor);
>                 if (gov) {
> -                       put_governor = true;
>                         pr_debug("Restoring governor %s for cpu %d\n",
>                                  policy->governor->name, policy->cpu);
>                 } else if (def_gov) {
>                         gov = def_gov;
> +                       module_get(gov->owner);
>                 } else {
>                         return -ENODATA;
>                 }
> @@ -1099,7 +1098,7 @@ static int cpufreq_init_policy(struct cpufreq_policy *policy)
>         }
>  
>         ret = cpufreq_set_policy(policy, gov, pol);
> -       if (put_governor)
> +       if (gov)
>                 module_put(gov->owner);
>  
>         return ret;

Right, I guess this is a good trade-off, so that works for me.

Thanks,
Quentin