On Fri, Dec 15, 2023 at 8:23 AM Christophe Leroy
[off-list ref] wrote:

From: George Stark <redacted>

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()

Missing period.

...

 } while (0)
 #endif /* CONFIG_PREEMPT_RT */

^^^ (1)

+struct device;
+
+/*
+ * devm_mutex_init() registers a function that calls mutex_destroy()
+ * when the ressource is released.
+ *
+ * When mutex_destroy() is a not, there is no need to register that
+ * function.
+ */
+#ifdef CONFIG_DEBUG_MUTEXES

Shouldn't this be

#if defined(CONFIG_DEBUG_MUTEXES) && !defined(CONFIG_PREEMPT_RT)

(see (1) as well)?

+void mutex_destroy(struct mutex *lock);
+int devm_mutex_init(struct device *dev, struct mutex *lock);
+#else
+static inline void mutex_destroy(struct mutex *lock) {}
+
+static inline int devm_mutex_init(struct device *dev, struct mutex *lock)
+{
+       mutex_init(lock);
+       return 0;
+}
+#endif

-- 
With Best Regards,
Andy Shevchenko