Re: [PATCH RFC v4-bis] locking: introduce devm_mutex_init

[Waiman Long]

On 12/15/23 10:58, Andy Shevchenko wrote:
> On Fri, Dec 15, 2023 at 8:23 AM Christophe Leroy
> <christophe.leroy@xxxxxxxxxx> wrote:
> > From: George Stark <gnstark@xxxxxxxxxxxxxxxxx>
> >
> > 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()
> Missing period.
>
> ...
>
> >   } while (0)
> >   #endif /* CONFIG_PREEMPT_RT */
> ^^^ (1)
>
> > +struct device;
> > +
> > +/*
> > + * devm_mutex_init() registers a function that calls mutex_destroy()
> > + * when the ressource is released.
> > + *
> > + * When mutex_destroy() is a not, there is no need to register that
> > + * function.
> > + */
> > +#ifdef CONFIG_DEBUG_MUTEXES
> Shouldn't this be
>
> #if defined(CONFIG_DEBUG_MUTEXES) && !defined(CONFIG_PREEMPT_RT)
>
> (see (1) as well)?

CONFIG_DEBUG_MUTEXES and CONFIG_PREEMPT_RT are mutually exclusive. At 
most one of them can be set.

Cheers,
Longman