linux-kernel - Re: [PATCH] acpi-cpufreq: Skip cleanup if initialization didn't occur

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Date:   Mon, 7 Jun 2021 08:55:50 +0530
From:   Viresh Kumar <viresh.kumar@...aro.org>
To:     kyle.meyer@....com
Cc:     rjw@...ysocki.net, linux-kernel@...r.kernel.org,
        linux-pm@...r.kernel.org, linux-acpi@...r.kernel.org,
        Takashi Iwai <tiwai@...e.com>
Subject: Re: [PATCH] acpi-cpufreq: Skip cleanup if initialization didn't occur

On 04-06-21, 12:05, kyle.meyer@....com wrote:
> From: Kyle Meyer <kyle.meyer@....com>
> 
> acpi-cpufreq is loaded without performing initialization when a cpufreq
> driver exists.
> 
> If initialization didn't occur then skip cleanup in acpi_cpufreq_exit().
> This prevents unnecessary freeing and unregistering when the module is
> unloaded.
> 
> Reported-by: Takashi Iwai <tiwai@...e.com>
> Signed-off-by: Kyle Meyer <kyle.meyer@....com>
> ---
>  drivers/cpufreq/acpi-cpufreq.c | 11 +++++++++++
>  1 file changed, 11 insertions(+)
> 
> diff --git a/drivers/cpufreq/acpi-cpufreq.c b/drivers/cpufreq/acpi-cpufreq.c
> index 7e7450453714..8d425f14c267 100644
> --- a/drivers/cpufreq/acpi-cpufreq.c
> +++ b/drivers/cpufreq/acpi-cpufreq.c
> @@ -1042,8 +1042,19 @@ static int __init acpi_cpufreq_init(void)
>  
>  static void __exit acpi_cpufreq_exit(void)
>  {
> +	const char *current_driver;
> +
>  	pr_debug("%s\n", __func__);
>  
> +	/*
> +	 * If another cpufreq_driver was loaded, preventing acpi-cpufreq from
> +	 * registering, there's no need to unregister it.
> +	 */
> +	current_driver = cpufreq_get_current_driver();
> +	if (!current_driver ||
> +	    strncmp(current_driver, acpi_cpufreq_driver.name, strlen(acpi_cpufreq_driver.name)))
> +		return;
> +
>  	acpi_cpufreq_boost_exit();
>  
>  	cpufreq_unregister_driver(&acpi_cpufreq_driver);

Looks like some misunderstanding here, this shouldn't happen. If
initialization didn't occur, then exit shall never be called.

-- 
viresh