linux-kernel - Re: [PATCH] locking/mutex: annotate __devm_mutex_init() with __must

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Message-ID: <20250407091438-557fe081-0c03-40d9-9b1e-9331c5181e31@linutronix.de>
Date: Mon, 7 Apr 2025 09:21:48 +0200
From: Thomas Weißschuh <thomas.weissschuh@...utronix.de>
To: Bartosz Golaszewski <brgl@...ev.pl>
Cc: Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>, 
	Will Deacon <will@...nel.org>, Boqun Feng <boqun.feng@...il.com>, 
	Waiman Long <longman@...hat.com>, linux-kernel@...r.kernel.org, 
	Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
Subject: Re: [PATCH] locking/mutex: annotate __devm_mutex_init() with
 __must_check

On Mon, Apr 07, 2025 at 09:03:46AM +0200, Bartosz Golaszewski wrote:
> From: Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
> 
> Unlike the non-managed mutex_init(), devm_mutex_init() can fail (for
> instance: on OOM). Now that we've fixed all instances of users not
> checking the return value, annotate it with __must_check to avoid this
> problem in the future.
> 
> Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
> ---
>  include/linux/mutex.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/include/linux/mutex.h b/include/linux/mutex.h
> index 2143d05116be..e194f8c22d72 100644
> --- a/include/linux/mutex.h
> +++ b/include/linux/mutex.h
> @@ -126,7 +126,7 @@ do {							\
>  
>  #ifdef CONFIG_DEBUG_MUTEXES
>  
> -int __devm_mutex_init(struct device *dev, struct mutex *lock);
> +int __must_check __devm_mutex_init(struct device *dev, struct mutex *lock);

This didn't work for me, see [0].

	"Unfortunately __must_check/warn_unused_result don't propagate through
	statement expression."

Also it is missing the !CONFIG_DEBUG_MUTEXES case.
I'll resend my patch once more.


[0] https://lore.kernel.org/lkml/20250208-must_check-devm_mutex_init-v3-2-245e417dcc9e@weissschuh.net/

>  
>  #else
>  
> 
> ---
> base-commit: 0af2f6be1b4281385b618cb86ad946eded089ac8
> change-id: 20250326-devm-mutex-must-check-8c1b94ae151f
> 
> Best regards,
> -- 
> Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
>