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Message-ID: <d98bff53-c85f-45c0-acde-8cb4e018af30@redhat.com>
Date: Mon, 11 Mar 2024 21:10:16 -0400
From: Waiman Long <longman@...hat.com>
To: George Stark <gnstark@...utedevices.com>, Marek Behún
<marek.behun@....cz>
Cc: andy.shevchenko@...il.com, pavel@....cz, lee@...nel.org,
vadimp@...dia.com, mpe@...erman.id.au, npiggin@...il.com,
christophe.leroy@...roup.eu, hdegoede@...hat.com, mazziesaccount@...il.com,
peterz@...radead.org, mingo@...hat.com, will@...nel.org,
boqun.feng@...il.com, nikitos.tr@...il.com, kabel@...nel.org,
linux-leds@...r.kernel.org, linux-kernel@...r.kernel.org,
linuxppc-dev@...ts.ozlabs.org, kernel@...utedevices.com
Subject: Re: [PATCH v5 02/10] locking/mutex: introduce devm_mutex_init
On 3/11/24 19:47, George Stark wrote:
> Hello Waiman, Marek
>
> Thanks for the review.
>
> I've never used lockdep for debug but it seems preferable to
> keep that feature working. It could be look like this:
>
> diff --git a/include/linux/mutex.h b/include/linux/mutex.h
> index f7611c092db7..574f6de6084d 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 = { \
> @@ -115,10 +117,31 @@ do { \
>
> #ifdef CONFIG_DEBUG_MUTEXES
>
> +int debug_devm_mutex_init(struct device *dev, struct mutex *lock);
> +
> +#define devm_mutex_init(dev, mutex) \
> +({ \
> + int ret; \
> + mutex_init(mutex); \
> + ret = debug_devm_mutex_init(dev, mutex); \
> + ret; \
> +})
The int ret variable is not needed. The macro can just end with
debug_devm_mutex_init().
> +
> void mutex_destroy(struct mutex *lock);
>
> #else
>
> +/*
> +* When CONFIG_DEBUG_MUTEXES is off mutex_destroy is just a nop so
> +* there's no really need to register it in devm subsystem.
"no really need"?
> +*/
> +#define devm_mutex_init(dev, mutex) \
> +({ \
> + typecheck(struct device *, dev); \
> + mutex_init(mutex); \
> + 0; \
> +})
Do we need a typecheck() here? Compilation will fail with
CONFIG_DEBUG_MUTEXES if dev is not a device pointer.
> +
> static inline void mutex_destroy(struct mutex *lock) {}
>
> #endif
> 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)
> +{
> + return devm_add_action_or_reset(dev, devm_mutex_release, lock);
> +}
> +
> /***
> * mutex_destroy - mark a mutex unusable
> * @lock: the mutex to be destroyed
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