linux-kernel - Re: [PATCH v3 03/11] devm-helpers: introduce devm_mutex

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Message-ID: <CAHp75Vdxa5k-CLhL+PmK0iTPTNSpP77DA6ooWnxfViwSKiEOSw@mail.gmail.com>
Date:   Thu, 14 Dec 2023 00:38:13 +0200
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     George Stark <gnstark@...utedevices.com>
Cc:     pavel@....cz, lee@...nel.org, vadimp@...dia.com,
        mpe@...erman.id.au, npiggin@...il.com, christophe.leroy@...roup.eu,
        hdegoede@...hat.com, mazziesaccount@...il.com,
        peterz@...radead.org, mingo@...hat.com, will@...nel.org,
        longman@...hat.com, boqun.feng@...il.com, nikitos.tr@...il.com,
        linux-leds@...r.kernel.org, linux-kernel@...r.kernel.org,
        linuxppc-dev@...ts.ozlabs.org, kernel@...utedevices.com
Subject: Re: [PATCH v3 03/11] devm-helpers: introduce devm_mutex_init

On Thu, Dec 14, 2023 at 12:36 AM Andy Shevchenko
<andy.shevchenko@...il.com> wrote:
> On Thu, Dec 14, 2023 at 12:30 AM George Stark <gnstark@...utedevices.com> 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