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Message-ID: <56e74264-6f98-4216-9f9a-e8f718375602@redhat.com>
Date:   Thu, 14 Dec 2023 10:16:47 +0100
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Subject: Re: [PATCH v3 03/11] devm-helpers: introduce devm_mutex_init
To:     Andy Shevchenko <andy.shevchenko@gmail.com>,
        George Stark <gnstark@salutedevices.com>
Cc:     pavel@ucw.cz, lee@kernel.org, vadimp@nvidia.com,
        mpe@ellerman.id.au, npiggin@gmail.com, christophe.leroy@csgroup.eu,
        mazziesaccount@gmail.com, peterz@infradead.org, mingo@redhat.com,
        will@kernel.org, longman@redhat.com, boqun.feng@gmail.com,
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        linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org,
        kernel@salutedevices.com
References: <20231213223020.2713164-1-gnstark@salutedevices.com>
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From:   Hans de Goede <hdegoede@redhat.com>
In-Reply-To: <CAHp75Vdxa5k-CLhL+PmK0iTPTNSpP77DA6ooWnxfViwSKiEOSw@mail.gmail.com>
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Hi,

On 12/13/23 23:38, Andy Shevchenko wrote:
> On Thu, Dec 14, 2023 at 12:36 AM Andy Shevchenko
> <andy.shevchenko@gmail.com> wrote:
>> On Thu, Dec 14, 2023 at 12:30 AM George Stark <gnstark@salutedevices.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...

With a static inline we are pretty much back to the original
v3 patch.

I believe the best way to reduce the ifdef-ery is to remove
the #ifdef around devm_mutex_release() having unused
static inline ... functions in .h files is quite common,
so this one does not need a #ifdef around it and with
that removed we are down to just one #ifdef so just
removing the #ifdef around devm_mutex_release() seems
the best fix.

With that fixed you may add my:

Reviewed-by: Hans de Goede <hdegoede@redhat.com>

to the patch and I'm fine with this being routed
upstream through whatever tree is convenient.

Regards,

Hans