Messages in this thread | | | Date | Thu, 14 Dec 2023 13:48:52 -0500 | Subject | Re: [PATCH v4 02/10] locking: introduce devm_mutex_init | From | Waiman Long <> |
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On 12/14/23 12:36, George Stark wrote: > 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() > > Signed-off-by: George Stark <gnstark@salutedevices.com> > --- > include/linux/mutex.h | 23 +++++++++++++++++++++++ > kernel/locking/mutex-debug.c | 22 ++++++++++++++++++++++ > 2 files changed, 45 insertions(+) > > diff --git a/include/linux/mutex.h b/include/linux/mutex.h > index a33aa9eb9fc3..ebd03ff1ef66 100644 > --- a/include/linux/mutex.h > +++ b/include/linux/mutex.h > @@ -21,6 +21,8 @@ > #include <linux/debug_locks.h> > #include <linux/cleanup.h> > > +struct device; > + > #ifdef CONFIG_DEBUG_LOCK_ALLOC > # define __DEP_MAP_MUTEX_INITIALIZER(lockname) \ > , .dep_map = { \ > @@ -127,6 +129,20 @@ extern void __mutex_init(struct mutex *lock, const char *name, > */ > extern bool mutex_is_locked(struct mutex *lock); > > +#ifdef CONFIG_DEBUG_MUTEXES > + > +int devm_mutex_init(struct device *dev, struct mutex *lock); Please add "extern" to the function declaration to be consistent with other functional declarations in mutex.h. > + > +#else > + > +static inline int devm_mutex_init(struct device *dev, struct mutex *lock) > +{ > + mutex_init(lock); > + return 0; > +}
I would prefer you to add a devm_mutex_init macro after the function declaration and put this inline function at the end of header if the devm_mutex_init macro isn't defined. In this way, you don't need to repeat this inline function twice as it has no dependency on PREEMPT_RT.
By doing this, you can also move the function declaration right after mutex_destroy() without the need to add another #ifdef CONFIG_DEBUG_MUTEXES block.
> + > +#endif > + > #else /* !CONFIG_PREEMPT_RT */ > /* > * Preempt-RT variant based on rtmutexes. > @@ -169,6 +185,13 @@ do { \ > \ > __mutex_init((mutex), #mutex, &__key); \ > } while (0) > + > +static inline int devm_mutex_init(struct device *dev, struct mutex *lock) > +{ > + mutex_init(lock); > + return 0; > +} > + > #endif /* CONFIG_PREEMPT_RT */ > > /* > diff --git a/kernel/locking/mutex-debug.c b/kernel/locking/mutex-debug.c > index bc8abb8549d2..c9efab1a8026 100644 > --- a/kernel/locking/mutex-debug.c > +++ b/kernel/locking/mutex-debug.c > @@ -19,6 +19,7 @@ > #include <linux/kallsyms.h> > #include <linux/interrupt.h> > #include <linux/debug_locks.h> > +#include <linux/device.h> > > #include "mutex.h" > > @@ -104,3 +105,24 @@ void mutex_destroy(struct mutex *lock) > } > > EXPORT_SYMBOL_GPL(mutex_destroy); > + > +static void devm_mutex_release(void *res) > +{ > + mutex_destroy(res); > +} > + > +/** > + * devm_mutex_init - Resource-managed mutex initialization > + * @dev: Device which lifetime mutex is bound to > + * @lock: Pointer to a mutex > + * > + * Initialize mutex which is automatically destroyed when the driver is detached. > + * > + * Returns: 0 on success or a negative error code on failure. > + */ > +int devm_mutex_init(struct device *dev, struct mutex *lock) > +{ > + mutex_init(lock); > + return devm_add_action_or_reset(dev, devm_mutex_release, lock); > +} > +EXPORT_SYMBOL_GPL(devm_mutex_init);
The mutex-debug.c change looks fine to me.
Cheers, Longman
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