linux-kernel - Re: [PATCH v5 02/10] locking/mutex: introduce devm_mutex

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Date: Tue, 12 Mar 2024 11:51:43 +0000
From: Christophe Leroy <christophe.leroy@...roup.eu>
To: George Stark <gnstark@...utedevices.com>, Marek Behún
	<marek.behun@....cz>, Waiman Long <longman@...hat.com>
CC: "andy.shevchenko@...il.com" <andy.shevchenko@...il.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>,
	"peterz@...radead.org" <peterz@...radead.org>, "mingo@...hat.com"
	<mingo@...hat.com>, "will@...nel.org" <will@...nel.org>,
	"boqun.feng@...il.com" <boqun.feng@...il.com>, "nikitos.tr@...il.com"
	<nikitos.tr@...il.com>, "kabel@...nel.org" <kabel@...nel.org>,
	"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 v5 02/10] locking/mutex: introduce devm_mutex_init



Le 12/03/2024 à 12:39, George Stark a écrit :
> [Vous ne recevez pas souvent de courriers de gnstark@...utedevices.com. 
> Découvrez pourquoi ceci est important à 
> https://aka.ms/LearnAboutSenderIdentification ]
> 
> Hello Christophe
> 
> Thanks for the review
> You were right about typecheck - it was meant to check errors even if
> CONFIG_DEBUG_MUTEXES was off.

Yes that's current practice in order to catch problems as soon as possible.

> 
> Here's new version based on the comments:
> 
> diff --git a/include/linux/mutex.h b/include/linux/mutex.h
> index 67edc4ca2bee..9193b163038f 100644
> --- a/include/linux/mutex.h
> +++ b/include/linux/mutex.h
> @@ -22,6 +22,8 @@
>   #include <linux/cleanup.h>
>   #include <linux/mutex_types.h>
> 
> +struct device;
> +
>   #ifdef CONFIG_DEBUG_LOCK_ALLOC
>   # define __DEP_MAP_MUTEX_INITIALIZER(lockname)                        \
>                 , .dep_map = {                                  \
> @@ -117,6 +119,34 @@ do 
> {                                                       \
>   } while (0)
>   #endif /* CONFIG_PREEMPT_RT */
> 
> +#ifdef CONFIG_DEBUG_MUTEXES
> +
> +int debug_devm_mutex_init(struct device *dev, struct mutex *lock);
> +
> +static inline int __devm_mutex_init(struct device *dev, struct mutex 
> *lock)
> +{
> +       return debug_devm_mutex_init(dev, lock);
> +}

You don't need that inline function, just change debug_devm_mutex_init() 
to __devm_mutex_init().

> +
> +#else
> +
> +static inline int __devm_mutex_init(struct device *dev, struct mutex 
> *lock)
> +{
> +       /*
> +       * When CONFIG_DEBUG_MUTEXES is off mutex_destroy is just a nop so
> +       * no really need to register it in devm subsystem.
> +       */

Don't know if it is because tabs are replaced by blanks in you email, 
but the stars should be aligned

/* ...
  * ...
  */

> +       return 0;
> +}
> +
> +#endif
> +
> +#define devm_mutex_init(dev, mutex)                    \
> +({                                                     \
> +       mutex_init(mutex);                              \
> +       __devm_mutex_init(dev, mutex);                  \
> +})
> +
>   /*
>    * See kernel/locking/mutex.c for detailed documentation of these APIs.
>    * Also see Documentation/locking/mutex-design.rst.
> diff --git a/kernel/locking/mutex-debug.c b/kernel/locking/mutex-debug.c
> index bc8abb8549d2..967a5367c79a 100644
> --- a/kernel/locking/mutex-debug.c
> +++ b/kernel/locking/mutex-debug.c
> @@ -19,6 +19,7 @@
>   #include <linux/kallsyms.h>
>   #include <linux/interrupt.h>
>   #include <linux/debug_locks.h>
> +#include <linux/device.h>
> 
>   #include "mutex.h"
> 
> @@ -89,6 +90,16 @@ void debug_mutex_init(struct mutex *lock, const char
> *name,
>         lock->magic = lock;
>   }
> 
> +static void devm_mutex_release(void *res)
> +{
> +       mutex_destroy(res);
> +}
> +
> +int debug_devm_mutex_init(struct device *dev, struct mutex *lock)

Rename __devm_mutex_init();

It makes it more clear that nobody is expected to call it directly.

> +{
> +       return devm_add_action_or_reset(dev, devm_mutex_release, lock);
> +}
> +
>   /***
>    * mutex_destroy - mark a mutex unusable
>    * @lock: the mutex to be destroyed
> -- 
> 2.25.1
> 
>