linux-kernel - Re: [PATCH v2 01/10] devm-helpers: introduce devm_mutex

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Date:   Mon, 4 Dec 2023 23:05:25 +0000
From:   Christophe Leroy <christophe.leroy@...roup.eu>
To:     George Stark <gnstark@...utedevices.com>,
        "pavel@....cz" <pavel@....cz>, "lee@...nel.org" <lee@...nel.org>,
        "vadimp@...dia.com" <vadimp@...dia.com>,
        "mpe@...erman.id.au" <mpe@...erman.id.au>,
        "npiggin@...il.com" <npiggin@...il.com>,
        "hdegoede@...hat.com" <hdegoede@...hat.com>,
        "mazziesaccount@...il.com" <mazziesaccount@...il.com>,
        "andy.shevchenko@...il.com" <andy.shevchenko@...il.com>,
        "jic23@...nel.org" <jic23@...nel.org>
CC:     "linux-leds@...r.kernel.org" <linux-leds@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>,
        "kernel@...utedevices.com" <kernel@...utedevices.com>
Subject: Re: [PATCH v2 01/10] devm-helpers: introduce devm_mutex_init



Le 04/12/2023 à 19:05, George Stark a écrit :
> Using of devm API leads to 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() is
> extended so introduce devm_mutex_init().

This is not needed for patch 2. Should patch 2 go first ?

> 
> Signed-off-by: George Stark <gnstark@...utedevices.com>
> ---
>   include/linux/devm-helpers.h | 18 ++++++++++++++++++
>   1 file changed, 18 insertions(+)
> 
> diff --git a/include/linux/devm-helpers.h b/include/linux/devm-helpers.h
> index 74891802200d..2f56e476776f 100644
> --- a/include/linux/devm-helpers.h
> +++ b/include/linux/devm-helpers.h
> @@ -76,4 +76,22 @@ static inline int devm_work_autocancel(struct device *dev,
>   	return devm_add_action(dev, devm_work_drop, w);
>   }
>   
> +static inline void devm_mutex_release(void *res)
> +{
> +	mutex_destroy(res);
> +}
> +
> +/**
> + * devm_mutex_init - Resource-managed mutex initialization
> + * @dev:	Device which lifetime work is bound to
> + * @lock:	Pointer to a mutex
> + *
> + * Initialize mutex which is automatically destroyed when driver is detached.
> + */
> +static inline int devm_mutex_init(struct device *dev, struct mutex *lock)
> +{
> +	mutex_init(lock);
> +	return devm_add_action_or_reset(dev, devm_mutex_release, lock);
> +}
> +
>   #endif