Em Tue, 29 Mar 2016 01:06:42 +0300
Sakari Ailus <sakari.ailus@xxxxxx> escreveu:
> Hi Mauro,
>
> Please see my comments below.
>
> On Mon, Mar 28, 2016 at 03:11:04PM -0300, Mauro Carvalho Chehab wrote:
> > Add a note at the headers telling that the link setup
> > callbacks are called with the mutex hold. Also, removes a
> > double lock at the PM suspend callbacks.
> >
> > Signed-off-by: Mauro Carvalho Chehab <mchehab@xxxxxxxxxxxxxxx>
> > ---
> > drivers/media/media-device.c | 1 -
> > drivers/media/v4l2-core/v4l2-mc.c | 4 ----
> > include/media/media-device.h | 3 ++-
> > include/media/media-entity.h | 3 +++
> > 4 files changed, 5 insertions(+), 6 deletions(-)
> >
> > diff --git a/drivers/media/media-device.c b/drivers/media/media-device.c
> > index 6cfa890af7b4..6af5e6932271 100644
> > --- a/drivers/media/media-device.c
> > +++ b/drivers/media/media-device.c
> > @@ -93,7 +93,6 @@ static struct media_entity *find_entity(struct media_device *mdev, u32 id)
> > media_device_for_each_entity(entity, mdev) {
> > if (((media_entity_id(entity) == id) && !next) ||
> > ((media_entity_id(entity) > id) && next)) {
> > - mutex_unlock(&mdev->graph_mutex);
>
> Unrelated to this patch.
Yes. This belongs to patch 1.
>
> Please do also consider compat IOCTL handling code.
>
> > return entity;
> > }
> > }
> > diff --git a/drivers/media/v4l2-core/v4l2-mc.c b/drivers/media/v4l2-core/v4l2-mc.c
> > index 2228cd3a846e..d44ff2ec314f 100644
> > --- a/drivers/media/v4l2-core/v4l2-mc.c
> > +++ b/drivers/media/v4l2-core/v4l2-mc.c
> > @@ -348,8 +348,6 @@ int v4l2_pipeline_pm_use(struct media_entity *entity, int use)
> > int change = use ? 1 : -1;
> > int ret;
> >
> > - mutex_lock(&mdev->graph_mutex);
>
> What's the motivation for this change and the one below?
>
> As far as I can see, they remove access serialisation of graph state during
> graph walk, which certainly is not the right thing to do.
You're right. This is not correct. I was thinking that v4l2_pipeline_pm_use()
was called by v4l2_pipeline_link_notify(), but this is not the case. The
function called there is pipeline_pm_use_count(), with doesn't hold the mutex.
> > -
> > /* Apply use count to node. */
> > entity->use_count += change;
> > WARN_ON(entity->use_count < 0);
> > @@ -359,8 +357,6 @@ int v4l2_pipeline_pm_use(struct media_entity *entity, int use)
> > if (ret < 0)
> > entity->use_count -= change;
> >
> > - mutex_unlock(&mdev->graph_mutex);
> > -
> > return ret;
> > }
> > EXPORT_SYMBOL_GPL(v4l2_pipeline_pm_use);
> > diff --git a/include/media/media-device.h b/include/media/media-device.h
> > index b04cfa907350..e6ad30c323fc 100644
> > --- a/include/media/media-device.h
> > +++ b/include/media/media-device.h
> > @@ -312,7 +312,8 @@ struct media_entity_notify {
> > * @enable_source: Enable Source Handler function pointer
> > * @disable_source: Disable Source Handler function pointer
> > *
> > - * @link_notify: Link state change notification callback
> > + * @link_notify: Link state change notification callback. This callback is
> > + * Called with the graph_mutex hold.
>
> I don't mind adding documentation such as this, but I'd put it into a
> separate patch.
Ok. Patch 2 will be just a documentation patch. I'll resend the series in
a few.
>
> > *
> > * This structure represents an abstract high-level media device. It allows easy
> > * access to entities and provides basic media device-level support. The
> > diff --git a/include/media/media-entity.h b/include/media/media-entity.h
> > index 6dc9e4e8cbd4..0b16ebe36db7 100644
> > --- a/include/media/media-entity.h
> > +++ b/include/media/media-entity.h
> > @@ -179,6 +179,9 @@ struct media_pad {
> > * @link_validate: Return whether a link is valid from the entity point of
> > * view. The media_entity_pipeline_start() function
> > * validates all links by calling this operation. Optional.
> > + *
> > + * Note: Those ioctls should not touch the struct media_device.@graph_mutex
> > + * field, as they're called with it already hold.
> > */
> > struct media_entity_operations {
> > int (*link_setup)(struct media_entity *entity,
>
--
Thanks,
Mauro
--
To unsubscribe from this list: send the line "unsubscribe linux-media" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
