Re: [PATCH] drm/rockchip: Return -EBUSY if there's already a pending flip event v2

[Mark yao]

On 2016å04æ01æ 19:47, Tomeu Vizoso wrote:
> On 04/01/2016 01:26 PM, Mark yao wrote:
> > On 2016å03æ31æ 16:08, Tomeu Vizoso wrote:
> > > As per the docs, atomic_commit should return -EBUSY "if an asycnhronous
> > > updated is requested and there is an earlier updated pending".
> > >
> > > v2: Use the status of the workqueue instead of vop->event, and don't add
> > > a superfluous wait on the workqueue.
> > >
> > > Signed-off-by: Tomeu Vizoso <tomeu.vizoso@xxxxxxxxxxxxx>
> > > ---
> > >   drivers/gpu/drm/rockchip/rockchip_drm_fb.c | 3 +++
> > >   1 file changed, 3 insertions(+)
> > >
> > > diff --git a/drivers/gpu/drm/rockchip/rockchip_drm_fb.c b/drivers/gpu/drm/rockchip/rockchip_drm_fb.c
> > > index 3b8f652698f8..285f8cd5afe1 100644
> > > --- a/drivers/gpu/drm/rockchip/rockchip_drm_fb.c
> > > +++ b/drivers/gpu/drm/rockchip/rockchip_drm_fb.c
> > > @@ -282,6 +282,9 @@ int rockchip_drm_atomic_commit(struct drm_device *dev,
> > >   	struct rockchip_atomic_commit *commit = &private->commit;
> > >   	int ret;
> > >   
> > > +	if (async && work_busy(&commit->work))
> > > +		return -EBUSY;
> > > +
> > Sorry for reply late.
> >
> > There is a comment on work_busy function describe :
> >
> >      "the test result is  unreliable and only useful as advisory hints or
> > for debugging."
> >
> > I don't know if it's suitable to use it here, does some guys know it?
> I'm not sure, but if the reason is the caveat explained in
> find_worker_executing_work(), then it's probably safe (and would explain
> how the function is used in other parts in the kernel).
>
> > And then, the "flush_work(&commit->work);" is no needed if return -EBUSY
> > here.
> > you can remove it at this patch.
> We still need to wait if it's being called in sync mode.
>
> Regards,
>
> Tomeu
Hi Tomeuïï

on sync mode, flush is no needed, because that:
1, there is mutex_lock/mutex_unlock on this context, So only single 
process run into commit work;

2, sync mode will block on:
rockchip_atomic_commit_complete-->rockchip_atomic_wait_for_complete,

Thanks.

> > >   	ret = drm_atomic_helper_prepare_planes(dev, state);
> > >   	if (ret)
> > >   		return ret;
> >
> >
> > --
> > ïark Yao


--
ïark Yao