linux-kernel - Re: [PATCH] cpufreq: reinitialize new policy min/max when writing scaling_(max|min)

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Message-ID: <CAJZ5v0ih6s9WviSpg9D+kSt2h8T5Vnx-MziOmYuk1H4yZOYLNg@mail.gmail.com>
Date:   Thu, 24 May 2018 09:45:17 +0200
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Kevin Wangtao <kevin.wangtao@...ilicon.com>
Cc:     "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Linux PM <linux-pm@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        gengyanping@...ilicon.com, sunzhaosheng@...ilicon.com
Subject: Re: [PATCH] cpufreq: reinitialize new policy min/max when writing scaling_(max|min)_freq

On Thu, May 24, 2018 at 8:43 AM, Kevin Wangtao
<kevin.wangtao@...ilicon.com> wrote:
> consider such situation, current user_policy.min is 1000000,
> current user_policy.max is 1200000, in cpufreq_set_policy,
> other driver may update policy.min to 1200000, policy.max to
> 1300000. After that, If we input "echo 1300000 > scaling_min_freq",
> then user_policy.min will be 1300000, and user_policy.max is
> still 1200000, because the input value is checked with policy.max
> not user_policy.max. if we get all related cpus offline and
> online again, it will cause cpufreq_init_policy fail because
> user_policy.min is higher than user_policy.max.

How do you reproduce this, exactly?

> The solution is when user space tries to write scaling_(max|min)_freq,
> the min/max of new_policy should be reinitialized with min/max
> of user_policy, like what cpufreq_update_policy does.
>
> Signed-off-by: Kevin Wangtao <kevin.wangtao@...ilicon.com>
> ---
>  drivers/cpufreq/cpufreq.c | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
> index b79c532..8b33e08 100644
> --- a/drivers/cpufreq/cpufreq.c
> +++ b/drivers/cpufreq/cpufreq.c
> @@ -697,6 +697,8 @@ static ssize_t store_##file_name                                    \
>         struct cpufreq_policy new_policy;                               \
>                                                                         \
>         memcpy(&new_policy, policy, sizeof(*policy));                   \
> +       new_policy->min = policy->user_policy.min;                      \
> +       new_policy->max = policy->user_policy.max;                      \

It looks like you haven't even tried to build this, have you?

>                                                                         \
>         ret = sscanf(buf, "%u", &new_policy.object);                    \
>         if (ret != 1)                                                   \
> --
> 2.8.1
>