linux-kernel - Re: [PATCH] Revert "cpufreq: Fix possible race in cpufreq online error path"

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Date:   Mon, 9 May 2022 19:08:44 +0200
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Viresh Kumar <viresh.kumar@...aro.org>
Cc:     Rafael Wysocki <rjw@...ysocki.net>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Schspa Shi <schspa@...il.com>,
        Linux PM <linux-pm@...r.kernel.org>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] Revert "cpufreq: Fix possible race in cpufreq online
 error path"

On Mon, May 9, 2022 at 5:57 AM Viresh Kumar <viresh.kumar@...aro.org> wrote:
>
> This reverts commit f346e96267cd76175d6c201b40f770c0116a8a04.
>
> The commit tried to fix a possible real bug but it made it even worse.
> The fix was simply buggy as now an error out to out_offline_policy or
> out_exit_policy will try to release a semaphore which was never taken in
> the first place. This works fine only if we failed late, i.e. via
> out_destroy_policy.
>
> Fixes: f346e96267cd ("cpufreq: Fix possible race in cpufreq online error path")
> Signed-off-by: Viresh Kumar <viresh.kumar@...aro.org>

Applied, thanks!

I should have caught the breakage in this patch, sorry about missing it.

> ---
>  drivers/cpufreq/cpufreq.c | 5 ++---
>  1 file changed, 2 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
> index 233e8af48848..fbaa8e6c7d23 100644
> --- a/drivers/cpufreq/cpufreq.c
> +++ b/drivers/cpufreq/cpufreq.c
> @@ -1534,6 +1534,8 @@ static int cpufreq_online(unsigned int cpu)
>         for_each_cpu(j, policy->real_cpus)
>                 remove_cpu_dev_symlink(policy, get_cpu_device(j));
>
> +       up_write(&policy->rwsem);
> +
>  out_offline_policy:
>         if (cpufreq_driver->offline)
>                 cpufreq_driver->offline(policy);
> @@ -1542,9 +1544,6 @@ static int cpufreq_online(unsigned int cpu)
>         if (cpufreq_driver->exit)
>                 cpufreq_driver->exit(policy);
>
> -       cpumask_clear(policy->cpus);
> -       up_write(&policy->rwsem);
> -
>  out_free_policy:
>         cpufreq_policy_free(policy);
>         return ret;
> --
> 2.31.1.272.g89b43f80a514
>