include/linux/mutex.h | 11 +++++++---- 1 file changed, 7 insertions(+), 4 deletions(-)
Even if it's not critical, the avoidance of checking the error code
from devm_mutex_init() call today diminishes the point of using the devm
variant of it. Tomorrow it may even leak something. Enforce all callers
checking the return value through the compiler.
As devm_mutex_init() itself is a macro, it can not be annotated
directly. Annotate __devm_mutex_init() instead.
Unfortunately __must_check/warn_unused_result don't propagate through
statement expression. So move the statement expression into the argument
list of the call to __devm_mutex_init() through a helper macro.
Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
---
Changes in v5:
- Pick up review tag from Andy
- Link to v4: https://lore.kernel.org/r/20250407-must_check-devm_mutex_init-v4-1-587bacc9f6b3@weissschuh.net
Changes in v4:
- Drop already applied leds-1202 driver patch
- Rebase on v6.15-rc1
- Link to v3: https://lore.kernel.org/r/20250208-must_check-devm_mutex_init-v3-0-245e417dcc9e@weissschuh.net
Changes in v3:
- Introduce and use helper macro __mutex_init_ret()
- Link to v2: https://lore.kernel.org/r/20250204-must_check-devm_mutex_init-v2-0-7b6271c4b7e6@weissschuh.net
Changes in v2:
- Rebase on 6.14-rc1
- Fix up leds-1202 driver
- Link to v1: https://lore.kernel.org/r/20241202-must_check-devm_mutex_init-v1-1-e60eb97b8c72@weissschuh.net
---
include/linux/mutex.h | 11 +++++++----
1 file changed, 7 insertions(+), 4 deletions(-)
diff --git a/include/linux/mutex.h b/include/linux/mutex.h
index 2143d05116be1b0ac239951a9d5d0b90ad99062c..d9342341c13fc036dd9257537c85ff61f0f03da0 100644
--- a/include/linux/mutex.h
+++ b/include/linux/mutex.h
@@ -126,11 +126,11 @@ do { \
#ifdef CONFIG_DEBUG_MUTEXES
-int __devm_mutex_init(struct device *dev, struct mutex *lock);
+int __must_check __devm_mutex_init(struct device *dev, struct mutex *lock);
#else
-static inline int __devm_mutex_init(struct device *dev, struct mutex *lock)
+static inline int __must_check __devm_mutex_init(struct device *dev, struct mutex *lock)
{
/*
* When CONFIG_DEBUG_MUTEXES is off mutex_destroy() is just a nop so
@@ -141,14 +141,17 @@ static inline int __devm_mutex_init(struct device *dev, struct mutex *lock)
#endif
-#define devm_mutex_init(dev, mutex) \
+#define __mutex_init_ret(mutex) \
({ \
typeof(mutex) mutex_ = (mutex); \
\
mutex_init(mutex_); \
- __devm_mutex_init(dev, mutex_); \
+ mutex_; \
})
+#define devm_mutex_init(dev, mutex) \
+ __devm_mutex_init(dev, __mutex_init_ret(mutex))
+
/*
* See kernel/locking/mutex.c for detailed documentation of these APIs.
* Also see Documentation/locking/mutex-design.rst.
---
base-commit: 0af2f6be1b4281385b618cb86ad946eded089ac8
change-id: 20241031-must_check-devm_mutex_init-cac583bda8fe
Best regards,
--
Thomas Weißschuh <linux@weissschuh.net>
Le 05/05/2025 à 09:59, Thomas Weißschuh a écrit : > Even if it's not critical, the avoidance of checking the error code > from devm_mutex_init() call today diminishes the point of using the devm > variant of it. Tomorrow it may even leak something. Enforce all callers > checking the return value through the compiler. > > As devm_mutex_init() itself is a macro, it can not be annotated > directly. Annotate __devm_mutex_init() instead. > Unfortunately __must_check/warn_unused_result don't propagate through > statement expression. So move the statement expression into the argument > list of the call to __devm_mutex_init() through a helper macro. > > Signed-off-by: Thomas Weißschuh <linux@weissschuh.net> > Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com> Hi, git grep ^[^=]*devm_mutex_init returns: drivers/leds/leds-lp8860.c Based on -next, it would break. Should it be patched first? CJ
On Mon, May 5, 2025 at 7:02 PM Christophe JAILLET <christophe.jaillet@wanadoo.fr> wrote: > > Le 05/05/2025 à 09:59, Thomas Weißschuh a écrit : > > Even if it's not critical, the avoidance of checking the error code > > from devm_mutex_init() call today diminishes the point of using the devm > > variant of it. Tomorrow it may even leak something. Enforce all callers > > checking the return value through the compiler. > > > > As devm_mutex_init() itself is a macro, it can not be annotated > > directly. Annotate __devm_mutex_init() instead. > > Unfortunately __must_check/warn_unused_result don't propagate through > > statement expression. So move the statement expression into the argument > > list of the call to __devm_mutex_init() through a helper macro. > > > > Signed-off-by: Thomas Weißschuh <linux@weissschuh.net> > > Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com> > > Hi, > > git grep ^[^=]*devm_mutex_init > > returns: > drivers/leds/leds-lp8860.c > > Based on -next, it would break. > > Should it be patched first? > > CJ Good catch, yeah it must be patched first. I suggest informing Lee of a need for an immutable tag with this patch and then applying this one fast before someone adds another unchecked devm_mutex_init() to the tree. Bart
On Mon, May 5, 2025 at 10:00 AM Thomas Weißschuh <linux@weissschuh.net> wrote: > > Even if it's not critical, the avoidance of checking the error code > from devm_mutex_init() call today diminishes the point of using the devm > variant of it. Tomorrow it may even leak something. Enforce all callers > checking the return value through the compiler. > > As devm_mutex_init() itself is a macro, it can not be annotated > directly. Annotate __devm_mutex_init() instead. > Unfortunately __must_check/warn_unused_result don't propagate through > statement expression. So move the statement expression into the argument > list of the call to __devm_mutex_init() through a helper macro. > > Signed-off-by: Thomas Weißschuh <linux@weissschuh.net> > Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com> > --- LGTM Reviewed-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
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