Em Wed, 16 Mar 2016 11:03:38 -0300
Javier Martinez Canillas <javier@xxxxxxxxxxxx> escreveu:
> Hello Mauro,
>
> The patch looks mostly good to me, I just have a question below:
>
> On Wed, Mar 16, 2016 at 9:04 AM, Mauro Carvalho Chehab
> <mchehab@xxxxxxxxxxxxxxx> wrote:
>
> [snip]
>
> >
> > -void media_device_cleanup(struct media_device *mdev)
> > +static void media_device_cleanup(struct media_device *mdev)
> > {
> > ida_destroy(&mdev->entity_internal_idx);
> > mdev->entity_internal_idx_max = 0;
> > media_entity_graph_walk_cleanup(&mdev->pm_count_walk);
> > - mutex_destroy(&mdev->graph_mutex);
>
> Any reason why this is removed? mutex_init() is still called in
> media_device_init() so I believe the destroy should be kept here.
This code is now called only at do_media_device_unregister, with
is protected by the mutex. If we keep the mutex_destroy there,
the mutex will be destroyed in lock state, causing an error if
mutex debug is enabled.
Btw, the standard implementation for the mutex is:
include/linux/mutex.h:static inline void mutex_destroy(struct mutex *lock) {}
Only when mutex debug is enabled, it becomes something else:
include/linux/mutex-debug.h:extern void mutex_destroy(struct mutex *lock);
With produces a warning if the mutex_destroy() is called with the
mutex is hold. This can never happen with the current implementation, as
the logic is:
mutex_lock(&mdev->graph_mutex);
kref_put(&mdev->kref, do_media_device_unregister);
mutex_unlock(&mdev->graph_mutex);
We could eventually move the mutex lock to
do_media_device_unregister() and then add there the mutex_destroy()
Regards,
Mauro
>
> Reviewed-by: Javier Martinez Canillas <javier@xxxxxxxxxxxxxxx>
>
> Best regards,
> Javier
--
Thanks,
Mauro
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