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

[Andy Shevchenko]

On Thu, Dec 14, 2023 at 12:36 AM Andy Shevchenko
<andy.shevchenko@xxxxxxxxx> wrote:
> On Thu, Dec 14, 2023 at 12:30 AM George Stark <gnstark@xxxxxxxxxxxxxxxxx> 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 wrapper.
> > 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().

...

> > +#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
> > +}
>
> If this is going to be accepted, you may decrease the amount of ifdeffery.
>
> #ifdef ...
> #else
> #define devm_mutex_init(dev, lock)  mutex_init(lock)

More precisely ({ mutex_init(lock); 0; }) or as a static inline...

> #endif

-- 
With Best Regards,
Andy Shevchenko