Hi Kieran,
On Wednesday, 28 March 2018 17:10:10 EEST Kieran Bingham wrote:
> On 26/02/18 21:45, Laurent Pinchart wrote:
> > The DRM pipeline handling code uses the entity's pipe list head to check
> > whether the entity is already included in a pipeline. This method is a
> > bit fragile in the sense that it uses list_empty() on a list_head that
> > is a list member. Replace it by a simpler check for the entity pipe
> > pointer.
>
> Yes, excellent.
>
> > Signed-off-by: Laurent Pinchart
> > <laurent.pinchart+renesas@xxxxxxxxxxxxxxxx>
>
> Reviewed-by: Kieran Bingham <kieran.bingham+renesas@xxxxxxxxxxxxxxxx>
>
> > ---
> >
> > drivers/media/platform/vsp1/vsp1_drm.c | 8 ++++----
> > 1 file changed, 4 insertions(+), 4 deletions(-)
> >
> > diff --git a/drivers/media/platform/vsp1/vsp1_drm.c
> > b/drivers/media/platform/vsp1/vsp1_drm.c index a7ad85ab0b08..e210917fdc3f
> > 100644
> > --- a/drivers/media/platform/vsp1/vsp1_drm.c
> > +++ b/drivers/media/platform/vsp1/vsp1_drm.c
> > @@ -119,9 +119,9 @@ int vsp1_du_setup_lif(struct device *dev, unsigned int
> > pipe_index,>
> > * Remove the RPF from the pipe and the list of BRU
> > * inputs.
> > */
> >
> > - WARN_ON(list_empty(&rpf->entity.list_pipe));
> > + WARN_ON(!rpf->entity.pipe);
>
> Does this WARN_ON() have much value any more ?
>
> I think it could probably be removed... unless there is a race between
> potential calls through vsp1_du_atomic_flush() and vsp1_du_setup_lif() -
> but I would be very surprised if that wasn't protected at the DRM levels.
It should indeed be protected at the DRM level. The purpose of the WARN_ON()
is twofold, it catches both bugs in the VSP1 driver (but I don't expect any
bug here, so from that point of view the WARN_ON isn't needed), but also
misbehaviours in the callers. There hasn't been any so far though, so maybe we
could indeed remove the WARN_ON(). It just makes me feel a bit safer but
probably not in any rational way :-)
> (Removing it if chosen doesn't need to be in this patch though)
>
> > rpf->entity.pipe = NULL;
> >
> > - list_del_init(&rpf->entity.list_pipe);
> > + list_del(&rpf->entity.list_pipe);
> >
> > pipe->inputs[i] = NULL;
> >
> > bru->inputs[rpf->bru_input].rpf = NULL;
> >
> > @@ -537,7 +537,7 @@ void vsp1_du_atomic_flush(struct device *dev, unsigned
> > int pipe_index)>
> > continue;
> >
> > }
> >
> > - if (list_empty(&rpf->entity.list_pipe)) {
> > + if (!rpf->entity.pipe) {
> >
> > rpf->entity.pipe = pipe;
> > list_add_tail(&rpf->entity.list_pipe, &pipe->entities);
> >
> > }
> >
> > @@ -566,7 +566,7 @@ void vsp1_du_atomic_flush(struct device *dev, unsigned
> > int pipe_index)>
> > VI6_DPR_NODE_UNUSED);
> >
> > entity->pipe = NULL;
> >
> > - list_del_init(&entity->list_pipe);
> > + list_del(&entity->list_pipe);
> >
> > continue;
> >
> > }
--
Regards,
Laurent Pinchart
