Re: [PATCH v3 03/11] devm-helpers: introduce devm_mutex_init

[George Stark]

Hello Christophe

On 12/14/23 13:06, Christophe Leroy wrote:
>
...
> So you abandonned the idea of using mutex.h ?

I'm not the one who make a choice here. The patch [1] you're talking 
about was seen by everyone but it seems like no one had shown interest.
For me personally approach with #define mutex_destroy is not very usual
but if even slight mixing device with mutex.h is unacceptable what else
can we do? Avoiding the need to allocate devm slot for empty 
mutex_destroy is more important.

Should I make series #4 with the patch [1] to give it a last chance?

[1] 
https://lore.kernel.org/lkml/377e4437-7051-4d88-ae68-1460bcd692e1@xxxxxxxxxx/T/#m3f6df30ffccaccb1df4669a327f349164f572931


> I can't see the point to spread mutex functions into devm-helpers.h
>
> Adding a mutex_destroy macro for this purpose looks odd. And if someone
> defines a new version of mutex_destroy() and forget the macro, it will
> go undetected.
>
> Usually macros of that type serve the purpose of defining a fallback
> when the macro is not defined. In that case, when someone adds a new
> version without defining the macro, it gets detected because if
> conflicts with the fallback.
> But in your case it works the other way round, so I will just go undetected.
>
> For me the best solution remains to use mutex.h and have
> devm_mutex_init() defined or declared at the same place as mutex_destroy().


> > Signed-off-by: George Stark <gnstark@xxxxxxxxxxxxxxxxx>
> > ---
> >    include/linux/devm-helpers.h | 27 +++++++++++++++++++++++++++
> >    1 file changed, 27 insertions(+)
> >
> > diff --git a/include/linux/devm-helpers.h b/include/linux/devm-helpers.h
> > index 74891802200d..4043c3481d2e 100644
> > --- a/include/linux/devm-helpers.h
> > +++ b/include/linux/devm-helpers.h
> > @@ -24,6 +24,7 @@
> >     */
> >
> >    #include <linux/device.h>
> > +#include <linux/mutex.h>
> >    #include <linux/workqueue.h>
> >
> >    static inline void devm_delayed_work_drop(void *res)
> > @@ -76,4 +77,30 @@ static inline int devm_work_autocancel(struct device *dev,
> >           return devm_add_action(dev, devm_work_drop, w);
> >    }
> >
> > +#ifdef mutex_destroy
> > +static inline void devm_mutex_release(void *res)
> > +{
> > +       mutex_destroy(res);
> > +}
> > +#endif
> > +
> > +/**
> > + * 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.
> > + */
> > +static inline int devm_mutex_init(struct device *dev, struct mutex *lock)
> > +{
> > +       mutex_init(lock);
> > +#ifdef mutex_destroy
> > +       return devm_add_action_or_reset(dev, devm_mutex_release, lock);
> > +#else
> > +       return 0;
> > +#endif
> > +}
> > +
> >    #endif
> > --
> > 2.25.1

--
Best regards
George