Patch "locking/mutex: Introduce devm_mutex_init()" has been added to the 6.9-stable tree

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This is a note to let you know that I've just added the patch titled

    locking/mutex: Introduce devm_mutex_init()

to the 6.9-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     locking-mutex-introduce-devm_mutex_init.patch
and it can be found in the queue-6.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 5cafcf9acd1f83e360182f161b965eb345be12be
Author: George Stark <gnstark@xxxxxxxxxxxxxxxxx>
Date:   Thu Apr 11 19:10:25 2024 +0300

    locking/mutex: Introduce devm_mutex_init()
    
    [ Upstream commit 4cd47222e435dec8e3787614924174f53fcfb5ae ]
    
    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@xxxxxxxxxx>
    Signed-off-by: George Stark <gnstark@xxxxxxxxxxxxxxxxx>
    Reviewed-by: Christophe Leroy <christophe.leroy@xxxxxxxxxx>
    Reviewed-by: Andy Shevchenko <andy.shevchenko@xxxxxxxxx>
    Reviewed-by: Marek Behún <kabel@xxxxxxxxxx>
    Acked-by: Waiman Long <longman@xxxxxxxxxx>
    Link: https://lore.kernel.org/r/20240411161032.609544-2-gnstark@xxxxxxxxxxxxxxxxx
    Signed-off-by: Lee Jones <lee@xxxxxxxxxx>
    Stable-dep-of: efc347b9efee ("leds: mlxreg: Use devm_mutex_init() for mutex initialization")
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/include/linux/mutex.h b/include/linux/mutex.h
index 67edc4ca2beeb..a561c629d89f0 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 bc8abb8549d20..6e6f6071cfa27 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 +90,17 @@ 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);
+}
+EXPORT_SYMBOL_GPL(__devm_mutex_init);
+
 /***
  * mutex_destroy - mark a mutex unusable
  * @lock: the mutex to be destroyed




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