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References: <20231214173614.2820929-3-gnstark@salutedevices.com> <c16599b23afa853a44d13b906af5683027959a26.1702621174.git.christophe.leroy@csgroup.eu>
In-Reply-To: <c16599b23afa853a44d13b906af5683027959a26.1702621174.git.christophe.leroy@csgroup.eu>
From: Andy Shevchenko <andy.shevchenko@gmail.com>
Date: Fri, 15 Dec 2023 17:58:44 +0200
Message-ID: <CAHp75VfBcmTBXXtU6o1x0Ea24wG-_Qb46opkS0EXKQ1Ynh0Mcw@mail.gmail.com>
Subject: Re: [PATCH RFC v4-bis] locking: introduce devm_mutex_init
To: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: pavel@ucw.cz, lee@kernel.org, vadimp@nvidia.com, mpe@ellerman.id.au, 
	npiggin@gmail.com, hdegoede@redhat.com, mazziesaccount@gmail.com, 
	peterz@infradead.org, mingo@redhat.com, will@kernel.org, longman@redhat.com, 
	boqun.feng@gmail.com, nikitos.tr@gmail.com, 
	George Stark <gnstark@salutedevices.com>, kernel@salutedevices.com, 
	linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org, 
	linux-leds@vger.kernel.org
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On Fri, Dec 15, 2023 at 8:23=E2=80=AFAM Christophe Leroy
<christophe.leroy@csgroup.eu> wrote:
>
> From: George Stark <gnstark@salutedevices.com>
>
> Using of devm API leads to a certain order of releasing resources.
> So all dependent resources which are not devm-wrapped should be deleted
> with respect to devm-release order. Mutex is one of such objects that
> often is bound to other resources and has no own devm wrapping.
> Since mutex_destroy() actually does nothing in non-debug builds
> frequently calling mutex_destroy() is just ignored which is safe for now
> but wrong formally and can lead to a problem if mutex_destroy() will be
> extended so introduce devm_mutex_init()

Missing period.

...

>  } while (0)
>  #endif /* CONFIG_PREEMPT_RT */

^^^ (1)

> +struct device;
> +
> +/*
> + * devm_mutex_init() registers a function that calls mutex_destroy()
> + * when the ressource is released.
> + *
> + * When mutex_destroy() is a not, there is no need to register that
> + * function.
> + */
> +#ifdef CONFIG_DEBUG_MUTEXES

Shouldn't this be

#if defined(CONFIG_DEBUG_MUTEXES) && !defined(CONFIG_PREEMPT_RT)

(see (1) as well)?

> +void mutex_destroy(struct mutex *lock);
> +int devm_mutex_init(struct device *dev, struct mutex *lock);
> +#else
> +static inline void mutex_destroy(struct mutex *lock) {}
> +
> +static inline int devm_mutex_init(struct device *dev, struct mutex *lock=
)
> +{
> +       mutex_init(lock);
> +       return 0;
> +}
> +#endif

--=20
With Best Regards,
Andy Shevchenko