[PATCH v1 2/2] drm: Clear the fence pointer when writeback job signaled

[Lowry Li (Arm Technology China)]

Hi Liviu,

On Wed, Jul 31, 2019 at 01:15:25PM +0000, Liviu Dudau wrote:
> Hi Lowry,
> 
> On Wed, Jul 31, 2019 at 11:04:45AM +0000, Lowry Li (Arm Technology China) wrote:
> > During it signals the completion of a writeback job, after releasing
> > the out_fence, we'd clear the pointer.
> > 
> > Check if fence left over in drm_writeback_cleanup_job(), release it.
> > 
> > Signed-off-by: Lowry Li (Arm Technology China) <lowry.li at arm.com>
> > ---
> >  drivers/gpu/drm/drm_writeback.c | 23 +++++++++++++++--------
> >  1 file changed, 15 insertions(+), 8 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/drm_writeback.c b/drivers/gpu/drm/drm_writeback.c
> > index ff138b6..43d9e3b 100644
> > --- a/drivers/gpu/drm/drm_writeback.c
> > +++ b/drivers/gpu/drm/drm_writeback.c
> > @@ -324,6 +324,9 @@ void drm_writeback_cleanup_job(struct drm_writeback_job *job)
> >  	if (job->fb)
> >  		drm_framebuffer_put(job->fb);
> >  
> > +	if (job->out_fence)
> > +		dma_fence_put(job->out_fence);
> > +
> >  	kfree(job);
> >  }
> 
> This change looks good.
> 
> >  EXPORT_SYMBOL(drm_writeback_cleanup_job);
> > @@ -366,25 +369,29 @@ static void cleanup_work(struct work_struct *work)
> >  {
> >  	unsigned long flags;
> >  	struct drm_writeback_job *job;
> > +	struct dma_fence *out_fence;
> >  
> >  	spin_lock_irqsave(&wb_connector->job_lock, flags);
> >  	job = list_first_entry_or_null(&wb_connector->job_queue,
> >  				       struct drm_writeback_job,
> >  				       list_entry);
> > -	if (job) {
> > +	if (job)
> >  		list_del(&job->list_entry);
> > -		if (job->out_fence) {
> > -			if (status)
> > -				dma_fence_set_error(job->out_fence, status);
> > -			dma_fence_signal(job->out_fence);
> > -			dma_fence_put(job->out_fence);
> 
> *Here*
> 
> > -		}
> > -	}
> > +
> >  	spin_unlock_irqrestore(&wb_connector->job_lock, flags);
> >  
> >  	if (WARN_ON(!job))
> >  		return;
> >  
> > +	out_fence = job->out_fence;
> > +	if (out_fence) {
> > +		if (status)
> > +			dma_fence_set_error(out_fence, status);
> > +		dma_fence_signal(out_fence);
> > +		dma_fence_put(out_fence);
> > +		job->out_fence = NULL;
> > +	}
> > +
> 
> I don't get the point of this change. Why not just add job->out_fence = NULL
> where *Here* is?
>
> Best regards,
> Liviu 
Besides setting NULL, also did a refine by moving the fence operation
out of the lock block.

Best regards,
Lowry 
> >  	INIT_WORK(&job->cleanup_work, cleanup_work);
> >  	queue_work(system_long_wq, &job->cleanup_work);
> >  }
> > -- 
> > 1.9.1
> > 
> 
> -- 
> ====================
> | I would like to |
> | fix the world,  |
> | but they're not |
> | giving me the   |
>  \ source code!  /
>   ---------------
>     ¯\_(ツ)_/¯

-- 
Regards,
Lowry