Re: [PATCH v2 01/10] devm-helpers: introduce devm_mutex_init

[George Stark]

On 12/7/23 15:28, Christophe Leroy wrote:
> Le 07/12/2023 à 13:02, Andy Shevchenko a écrit :
> > On Thu, Dec 7, 2023 at 1:23 AM George Stark <gnstark@xxxxxxxxxxxxxxxxx> wrote:
> > > On 12/7/23 01:37, Christophe Leroy wrote:
> > > > Le 06/12/2023 à 23:14, Christophe Leroy a écrit :
> >
> > ...
> >
> > > > Looking at it closer, I have the feeling that you want to do similar to
> > > > devm_gpio_request() in linux/gpio.h :
> > > >
> > > > In linux/mutex.h, add a prototype for devm_mutex_init() when
> > > > CONFIG_DEBUG_MUTEXES is defined and an empty static inline otherwise.
> > > > Then define devm_mutex_init() in kernel/locking/mutex-debug.c
> > >
> > > Yes, this would be almost perfect decision. BTW just as in linux/gpio.h
> > > we wouldn't have to include whole "linux/device.h" into mutex.h, only
> > > add forward declaration of struct device;
> >
> > In case you place it into a C-file. Otherwise you need a header for
> > the API and that is not acceptable for mutex.h.
>
> Right, that's the reason why I'm suggesting to define devm_mutex_init()
> in kernel/locking/mutex-debug.c.
>
> In linux/mutex.h, you define a stub for when CONFIG_DEBUG_MUTEXES is not
> set, and the prototype of devm_mutex_init() when CONFIG_DEBUG_MUTEXES is
> set.

Something like this:

diff --git a/include/linux/mutex.h b/include/linux/mutex.h
index a33aa9eb9fc3..4a6041a7fd44 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
+
+extern 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..d50dfa06e82c 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 +105,25 @@ 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);
\ No newline at end of file


--
Best regards
George