On Tue, Feb 04, 2025 at 07:52:51AM +0100, Thomas Weißschuh 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 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 which can not be annotated,
> annotate __devm_mutex_init() instead.
> Unfortunately __must_check/warn_unused_result don't propagate through
> statement expression. To work around this move the statement expression
> into the argument list of the call to __devm_mutex_init() so
> devm_mutex_init() directly expands to __devm_mutex_init().
>
> Signed-off-by: Thomas Weißschuh <linux@xxxxxxxxxxxxxx>
> ---
> include/linux/mutex.h | 17 ++++++++---------
> 1 file changed, 8 insertions(+), 9 deletions(-)
>
> diff --git a/include/linux/mutex.h b/include/linux/mutex.h
> index 2bf91b57591b49e4668752e773419ae945f124da..65b28c9e6efc123982d923d1ed171eae471c82c1 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
> @@ -141,13 +141,12 @@ static inline int __devm_mutex_init(struct device *dev, struct mutex *lock)
>
> #endif
>
> -#define devm_mutex_init(dev, mutex) \
> -({ \
> - typeof(mutex) mutex_ = (mutex); \
> - \
> - mutex_init(mutex_); \
> - __devm_mutex_init(dev, mutex_); \
> -})
> +#define devm_mutex_init(dev, mutex) __devm_mutex_init(dev, ({ \
> + typeof(mutex) mutex_ = (mutex); \
> + \
> + mutex_init(mutex_); \
> + mutex_; \
> +}))
Urgh, that's a bit ugly isn't it.
Now we can either write a helper for that like:
#define mutex_init_ret(mutex) \
({ \
typeof(mutex) mutex_ = (mutex); \
mutex_init(mutex_); \
mutex_; \
})
#define devm_mutex_init(dev, mutex) \
__devm_mutex_init(dev, mutex_init_ret(mutex))
Or we can try and make mutex_init() return the pointer itself. I don't
think that will break anything, but its best to feel that to the robots
to make sure.
