acpi-cpufreq: Skip cleanup if initialization didn't occur

Message ID 20210604170500.46875-1-kyle.meyer@hpe.com
State New
Headers show
Series
  • acpi-cpufreq: Skip cleanup if initialization didn't occur
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Commit Message

Kyle Meyer June 4, 2021, 5:05 p.m.
From: Kyle Meyer <kyle.meyer@hpe.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@suse.com>
Signed-off-by: Kyle Meyer <kyle.meyer@hpe.com>
---
 drivers/cpufreq/acpi-cpufreq.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

Comments

Viresh Kumar June 7, 2021, 3:25 a.m. | #1
On 04-06-21, 12:05, kyle.meyer@hpe.com wrote:
> From: Kyle Meyer <kyle.meyer@hpe.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@suse.com>
> Signed-off-by: Kyle Meyer <kyle.meyer@hpe.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 Kumar June 7, 2021, 7:26 a.m. | #2
On 07-06-21, 09:13, Takashi Iwai wrote:
> The missing key information is that it's a fix for the recent change

> for 5.14, i.e. 

> Fixes: c1d6d2fd2f64 ("cpufreq: acpi-cpufreq: Skip initialization if cpufreq driver is present")

> 

> The change made the module left even if it exits before registering

> the cpufreq driver object.


The original patch looks buggy to me, I was never able to review it :(

I have replied on the original thread instead.

-- 
viresh

Patch

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);