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

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Message-ID: <9e13fd46-b05b-4fc2-abb6-c6c96dd576ee@salutedevices.com>
Date: Tue, 12 Mar 2024 14:39:13 +0300
From: George Stark <gnstark@...utedevices.com>
To: Christophe Leroy <christophe.leroy@...roup.eu>,
	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"
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Subject: Re: [PATCH v5 02/10] locking/mutex: introduce devm_mutex_init

Hello Christophe

Thanks for the review
You were right about typecheck - it was meant to check errors even if 
CONFIG_DEBUG_MUTEXES was off.

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);
+}
+
+#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.
+	*/
+	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)
+{
+	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



On 3/12/24 09:04, Christophe Leroy wrote:

..

> 
> I think it would be preferable to minimise the number of macros.
> 
> If I were you I would keep your devm_mutex_init() as is but rename it
> __devm_mutex_init() and just remove the mutex_init() from it, then add
> only one macro that works independant of CONFIG_DEBUG_MUTEXES:
> 
> #define devm_mutex_init(dev, mutex)	\
> ({					\
> 	mutex_init(mutex);		\
> 	__devm_mutex_init(dev, mutex);	\
> })
> 
> With that, no need of a second version of the macro and no need for the
> typecheck either.
> 
> Note the __ which is a clear indication that allthough that function is
> declared in public mutex.h, it is not meant to be used outside of it.
> 
> 
> 


-- 
Best regards
George