linux-kernel - [PATCH v2 01/10] devm-helpers: introduce devm_mutex

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Date:   Mon, 4 Dec 2023 21:05:54 +0300
From:   George Stark <gnstark@...utedevices.com>
To:     <pavel@....cz>, <lee@...nel.org>, <vadimp@...dia.com>,
        <mpe@...erman.id.au>, <npiggin@...il.com>,
        <christophe.leroy@...roup.eu>, <hdegoede@...hat.com>,
        <mazziesaccount@...il.com>, <andy.shevchenko@...il.com>,
        <jic23@...nel.org>
CC:     <linux-leds@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <linuxppc-dev@...ts.ozlabs.org>, <kernel@...utedevices.com>,
        George Stark <gnstark@...utedevices.com>
Subject: [PATCH v2 01/10] devm-helpers: introduce devm_mutex_init

Using of devm API leads to 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() is
extended so introduce devm_mutex_init().

Signed-off-by: George Stark <gnstark@...utedevices.com>
---
 include/linux/devm-helpers.h | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/include/linux/devm-helpers.h b/include/linux/devm-helpers.h
index 74891802200d..2f56e476776f 100644
--- a/include/linux/devm-helpers.h
+++ b/include/linux/devm-helpers.h
@@ -76,4 +76,22 @@ static inline int devm_work_autocancel(struct device *dev,
 	return devm_add_action(dev, devm_work_drop, w);
 }
 
+static inline void devm_mutex_release(void *res)
+{
+	mutex_destroy(res);
+}
+
+/**
+ * devm_mutex_init - Resource-managed mutex initialization
+ * @dev:	Device which lifetime work is bound to
+ * @lock:	Pointer to a mutex
+ *
+ * Initialize mutex which is automatically destroyed when driver is detached.
+ */
+static inline int devm_mutex_init(struct device *dev, struct mutex *lock)
+{
+	mutex_init(lock);
+	return devm_add_action_or_reset(dev, devm_mutex_release, lock);
+}
+
 #endif
-- 
2.38.4