diff mbox series

[v7,1/8] locking/mutex: introduce devm_mutex_init()

Message ID 20240314201856.1991899-2-gnstark@salutedevices.com
State Superseded
Headers show
Series devm_led_classdev_register() usage problem | expand

Commit Message

George Stark March 14, 2024, 8:18 p.m. UTC 
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().

Suggested-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: George Stark <gnstark@salutedevices.com>
Reviewed-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Reviewed-by: Marek Behún <kabel@kernel.org>
Acked-by: Waiman Long <longman@redhat.com>
---
 include/linux/mutex.h        | 27 +++++++++++++++++++++++++++
 kernel/locking/mutex-debug.c | 11 +++++++++++
 2 files changed, 38 insertions(+)

Comments

Andy Shevchenko March 14, 2024, 11:33 p.m. UTC | #1 
On Thu, Mar 14, 2024 at 10:19 PM George Stark <gnstark@salutedevices.com> wrote:
>
> 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().

...

>  /***

Unrelated to your patch, but there are too many asterisks :-)

>   * mutex_destroy - mark a mutex unusable
>   * @lock: the mutex to be destroyed
diff mbox series

Patch

diff --git a/include/linux/mutex.h b/include/linux/mutex.h
index 67edc4ca2bee..a561c629d89f 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 +119,31 @@  do {							\
 } while (0)
 #endif /* CONFIG_PREEMPT_RT */
 
+#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)
+{
+	/*
+	 * When CONFIG_DEBUG_MUTEXES is off mutex_destroy() is just a nop so
+	 * no really need to register it in the devm subsystem.
+	 */
+	return 0;
+}
+
+#endif
+
+#define devm_mutex_init(dev, mutex)			\
+({							\
+	typeof(mutex) mutex_ = (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..f7e848defd50 100644
--- a/kernel/locking/mutex-debug.c
+++ b/kernel/locking/mutex-debug.c
@@ -12,6 +12,7 @@ 
  */
 #include <linux/mutex.h>
 #include <linux/delay.h>
+#include <linux/device.h>
 #include <linux/export.h>
 #include <linux/poison.h>
 #include <linux/sched.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 __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