linux-kernel - Re: [PATCH 5/8] ACPI: platform_profile: Use guard(mutex) for register/unregister

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Message-ID: <3bd91a7f-f9d4-fa00-f254-5caaddbbe18a@linux.intel.com>
Date: Tue, 29 Oct 2024 12:02:23 +0200 (EET)
From: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
To: Mario Limonciello <mario.limonciello@....com>
cc: Hans de Goede <hdegoede@...hat.com>, 
    "Rafael J . Wysocki" <rafael@...nel.org>, Len Brown <lenb@...nel.org>, 
    Maximilian Luz <luzmaximilian@...il.com>, Lee Chun-Yi <jlee@...e.com>, 
    Shyam Sundar S K <Shyam-sundar.S-k@....com>, 
    Corentin Chary <corentin.chary@...il.com>, 
    "Luke D . Jones" <luke@...nes.dev>, Ike Panhc <ike.pan@...onical.com>, 
    Henrique de Moraes Holschuh <hmh@....eng.br>, 
    Alexis Belmonte <alexbelm48@...il.com>, 
    Uwe Kleine-König <u.kleine-koenig@...gutronix.de>, 
    Ai Chao <aichao@...inos.cn>, Gergo Koteles <soyer@....hu>, 
    open list <linux-kernel@...r.kernel.org>, 
    "open list:ACPI" <linux-acpi@...r.kernel.org>, 
    "open list:MICROSOFT SURFACE PLATFORM PROFILE DRIVER" <platform-driver-x86@...r.kernel.org>, 
    "open list:THINKPAD ACPI EXTRAS DRIVER" <ibm-acpi-devel@...ts.sourceforge.net>, 
    Mark Pearson <mpearson-lenovo@...ebb.ca>, 
    Matthew Schwartz <matthew.schwartz@...ux.dev>
Subject: Re: [PATCH 5/8] ACPI: platform_profile: Use guard(mutex) for
 register/unregister

On Fri, 25 Oct 2024, Mario Limonciello wrote:

> guard(mutex) can be used to automatically release mutexes when going
> out of scope.
> 
> Tested-by: Matthew Schwartz <matthew.schwartz@...ux.dev>
> Signed-off-by: Mario Limonciello <mario.limonciello@....com>
> ---
>  drivers/acpi/platform_profile.c | 19 ++++++-------------
>  1 file changed, 6 insertions(+), 13 deletions(-)
> 
> diff --git a/drivers/acpi/platform_profile.c b/drivers/acpi/platform_profile.c
> index 0c60fc970b6e8..81928adccfade 100644
> --- a/drivers/acpi/platform_profile.c
> +++ b/drivers/acpi/platform_profile.c
> @@ -180,41 +180,34 @@ int platform_profile_register(struct platform_profile_handler *pprof)
>  {
>  	int err;
>  
> -	mutex_lock(&profile_lock);
> +	guard(mutex)(&profile_lock);
>  	/* We can only have one active profile */
> -	if (cur_profile) {
> -		mutex_unlock(&profile_lock);
> +	if (cur_profile)
>  		return -EEXIST;
> -	}
>  
>  	/* Sanity check the profile handler field are set */
>  	if (!pprof || bitmap_empty(pprof->choices, PLATFORM_PROFILE_LAST) ||
> -		!pprof->profile_set || !pprof->profile_get) {
> -		mutex_unlock(&profile_lock);
> +		!pprof->profile_set || !pprof->profile_get)

Could you please also correct the misleading indentation here while 
touching the line.

>  		return -EINVAL;
> -	}
>  
>  	err = sysfs_create_group(acpi_kobj, &platform_profile_group);
> -	if (err) {
> -		mutex_unlock(&profile_lock);
> +	if (err)
>  		return err;
> -	}
>  	list_add_tail(&pprof->list, &platform_profile_handler_list);
>  
>  	cur_profile = pprof;
> -	mutex_unlock(&profile_lock);
>  	return 0;
>  }
>  EXPORT_SYMBOL_GPL(platform_profile_register);
>  
>  int platform_profile_remove(struct platform_profile_handler *pprof)
>  {
> +	guard(mutex)(&profile_lock);
> +
>  	list_del(&pprof->list);
>  
>  	sysfs_remove_group(acpi_kobj, &platform_profile_group);
> -	mutex_lock(&profile_lock);

Now this something I don't want to sneak in with a transformation change 
like this. What is a clear extension of the critical section should be in 
own patch with proper justification given.

If that was not intentional, you can sill place guard() where the original 
mutex_lock() was, it doesn't have to be on the first line of a function.

>  	cur_profile = NULL;
> -	mutex_unlock(&profile_lock);
>  	return 0;
>  }
>  EXPORT_SYMBOL_GPL(platform_profile_remove);
> 

-- 
 i.