From: Christophe Leroy <christophe.leroy@csgroup.eu>
To: George Stark <gnstark@salutedevices.com>,
"andy.shevchenko@gmail.com" <andy.shevchenko@gmail.com>,
"pavel@ucw.cz" <pavel@ucw.cz>, "lee@kernel.org" <lee@kernel.org>,
"vadimp@nvidia.com" <vadimp@nvidia.com>,
"mpe@ellerman.id.au" <mpe@ellerman.id.au>,
"npiggin@gmail.com" <npiggin@gmail.com>,
"hdegoede@redhat.com" <hdegoede@redhat.com>,
"mazziesaccount@gmail.com" <mazziesaccount@gmail.com>,
"peterz@infradead.org" <peterz@infradead.org>,
"mingo@redhat.com" <mingo@redhat.com>,
"will@kernel.org" <will@kernel.org>,
"longman@redhat.com" <longman@redhat.com>,
"boqun.feng@gmail.com" <boqun.feng@gmail.com>,
"nikitos.tr@gmail.com" <nikitos.tr@gmail.com>
Cc: "linux-leds@vger.kernel.org" <linux-leds@vger.kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"linuxppc-dev@lists.ozlabs.org" <linuxppc-dev@lists.ozlabs.org>,
"kernel@salutedevices.com" <kernel@salutedevices.com>
Subject: Re: [PATCH v4 02/10] locking: introduce devm_mutex_init
Date: Thu, 14 Dec 2023 19:47:20 +0000 [thread overview]
Message-ID: <27479d7f-fe9a-4ae7-8490-2f070fa7a16d@csgroup.eu> (raw)
In-Reply-To: <20231214173614.2820929-3-gnstark@salutedevices.com>
Le 14/12/2023 à 18:36, George Stark a écrit :
> [Vous ne recevez pas souvent de courriers de gnstark@salutedevices.com. Découvrez pourquoi ceci est important à https://aka.ms/LearnAboutSenderIdentification ]
>
> 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()
>
> Signed-off-by: George Stark <gnstark@salutedevices.com>
> ---
> include/linux/mutex.h | 23 +++++++++++++++++++++++
> kernel/locking/mutex-debug.c | 22 ++++++++++++++++++++++
> 2 files changed, 45 insertions(+)
>
> diff --git a/include/linux/mutex.h b/include/linux/mutex.h
> index a33aa9eb9fc3..ebd03ff1ef66 100644
> --- a/include/linux/mutex.h
> +++ b/include/linux/mutex.h
> @@ -21,6 +21,8 @@
> #include <linux/debug_locks.h>
> #include <linux/cleanup.h>
>
> +struct device;
> +
> #ifdef CONFIG_DEBUG_LOCK_ALLOC
> # define __DEP_MAP_MUTEX_INITIALIZER(lockname) \
> , .dep_map = { \
> @@ -127,6 +129,20 @@ extern void __mutex_init(struct mutex *lock, const char *name,
> */
> extern bool mutex_is_locked(struct mutex *lock);
>
> +#ifdef CONFIG_DEBUG_MUTEXES
> +
> +int devm_mutex_init(struct device *dev, struct mutex *lock);
> +
> +#else
> +
> +static inline int devm_mutex_init(struct device *dev, struct mutex *lock)
> +{
> + mutex_init(lock);
> + return 0;
> +}
> +
> +#endif
> +
> #else /* !CONFIG_PREEMPT_RT */
> /*
> * Preempt-RT variant based on rtmutexes.
> @@ -169,6 +185,13 @@ do { \
> \
> __mutex_init((mutex), #mutex, &__key); \
> } while (0)
> +
> +static inline int devm_mutex_init(struct device *dev, struct mutex *lock)
> +{
> + mutex_init(lock);
> + return 0;
> +}
> +
> #endif /* CONFIG_PREEMPT_RT */
>
> /*
> diff --git a/kernel/locking/mutex-debug.c b/kernel/locking/mutex-debug.c
> index bc8abb8549d2..c9efab1a8026 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"
>
> @@ -104,3 +105,24 @@ void mutex_destroy(struct mutex *lock)
> }
>
> EXPORT_SYMBOL_GPL(mutex_destroy);
> +
> +static void devm_mutex_release(void *res)
> +{
> + mutex_destroy(res);
> +}
> +
> +/**
> + * devm_mutex_init - Resource-managed mutex initialization
> + * @dev: Device which lifetime mutex is bound to
> + * @lock: Pointer to a mutex
> + *
> + * Initialize mutex which is automatically destroyed when the driver is detached.
> + *
> + * Returns: 0 on success or a negative error code on failure.
> + */
> +int devm_mutex_init(struct device *dev, struct mutex *lock)
> +{
> + mutex_init(lock);
> + return devm_add_action_or_reset(dev, devm_mutex_release, lock);
> +}
> +EXPORT_SYMBOL_GPL(devm_mutex_init);
> --
> 2.25.1
>
I think it would make sense to keep mutex_destroy() and
devm_mutex_init() together, see exemple below:
diff --git a/include/linux/mutex.h b/include/linux/mutex.h
index ebd03ff1ef66..c620759ff85b 100644
--- a/include/linux/mutex.h
+++ b/include/linux/mutex.h
@@ -83,14 +83,10 @@ struct mutex {
#define __DEBUG_MUTEX_INITIALIZER(lockname) \
, .magic = &lockname
-extern void mutex_destroy(struct mutex *lock);
-
#else
# define __DEBUG_MUTEX_INITIALIZER(lockname)
-static inline void mutex_destroy(struct mutex *lock) {}
-
#endif
/**
@@ -131,10 +127,13 @@ extern bool mutex_is_locked(struct mutex *lock);
#ifdef CONFIG_DEBUG_MUTEXES
+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);
@@ -169,8 +168,6 @@ extern void __mutex_rt_init(struct mutex *lock,
const char *name,
struct lock_class_key *key);
extern int mutex_trylock(struct mutex *lock);
-static inline void mutex_destroy(struct mutex *lock) { }
-
#define mutex_is_locked(l) rt_mutex_base_is_locked(&(l)->rtmutex)
#define __mutex_init(mutex, name, key) \
@@ -186,6 +183,8 @@ do { \
__mutex_init((mutex), #mutex, &__key); \
} while (0)
+static inline void mutex_destroy(struct mutex *lock) { }
+
static inline int devm_mutex_init(struct device *dev, struct mutex *lock)
{
mutex_init(lock);
---
Would also be nice to have a comment explaining that when
mutex_destroy() is a nop, devm_mutext_init() doesn't need to register a
release function.
Either way,
Reviewed-by: christophe.leroy@csgroup.eu
next prev parent reply other threads:[~2023-12-14 19:47 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-12-14 17:36 [PATCH v4 00/10] devm_led_classdev_register() usage problem George Stark
2023-12-14 17:36 ` [PATCH v4 01/10] leds: aw2013: unlock mutex before destroying it George Stark
2024-02-23 15:07 ` (subset) " Lee Jones
2023-12-14 17:36 ` [PATCH v4 02/10] locking: introduce devm_mutex_init George Stark
2023-12-14 18:48 ` Waiman Long
2023-12-14 19:53 ` Christophe Leroy
2023-12-14 21:48 ` Waiman Long
2023-12-15 5:46 ` Christophe Leroy
2023-12-17 1:05 ` George Stark
2023-12-17 9:31 ` Christophe Leroy
2023-12-18 13:26 ` George Stark
2023-12-14 19:47 ` Christophe Leroy [this message]
2023-12-15 6:22 ` [PATCH RFC v4-bis] " Christophe Leroy
2023-12-15 15:58 ` Andy Shevchenko
2023-12-15 17:51 ` Christophe Leroy
2023-12-16 1:30 ` Waiman Long
2023-12-14 17:36 ` [PATCH v4 03/10] leds: aw2013: use devm API to cleanup module's resources George Stark
2023-12-14 17:36 ` [PATCH v4 04/10] leds: aw200xx: " George Stark
2023-12-14 17:36 ` [PATCH v4 05/10] leds: lp3952: " George Stark
2023-12-14 17:36 ` [PATCH v4 06/10] leds: lm3532: " George Stark
2023-12-14 17:36 ` [PATCH v4 07/10] leds: nic78bx: " George Stark
2023-12-14 17:36 ` [PATCH v4 08/10] leds: mlxreg: use devm_mutex_init for mutex initializtion George Stark
2023-12-14 17:36 ` [PATCH v4 09/10] leds: an30259a: use devm_mutext_init for mutext initialization George Stark
2023-12-14 17:36 ` [PATCH v4 10/10] leds: powernv: use LED_RETAIN_AT_SHUTDOWN flag for leds George Stark
2023-12-21 15:11 ` [PATCH v4 00/10] devm_led_classdev_register() usage problem Lee Jones
2024-02-09 17:11 ` Andy Shevchenko
2024-02-11 23:52 ` [DMARC error][SPF error] " George Stark
2024-02-12 9:53 ` Andy Shevchenko
2024-02-13 0:14 ` George Stark
2024-02-13 10:55 ` Andy Shevchenko
2024-02-13 23:56 ` George Stark
2024-02-09 17:17 ` Andy Shevchenko
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