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

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Date:   Wed, 31 Jul 2019 13:20:04 +0000
From:   Brian Starkey <Brian.Starkey@....com>
To:     "Lowry Li (Arm Technology China)" <Lowry.Li@....com>
CC:     Liviu Dudau <Liviu.Dudau@....com>,
        "james qian wang (Arm Technology China)" <james.qian.wang@....com>,
        "maarten.lankhorst@...ux.intel.com" 
        <maarten.lankhorst@...ux.intel.com>,
        "seanpaul@...omium.org" <seanpaul@...omium.org>,
        "airlied@...ux.ie" <airlied@...ux.ie>,
        "daniel@...ll.ch" <daniel@...ll.ch>,
        "Julien Yin (Arm Technology China)" <Julien.Yin@....com>,
        "maxime.ripard@...tlin.com" <maxime.ripard@...tlin.com>,
        "eric@...olt.net" <eric@...olt.net>,
        "kieran.bingham+renesas@...asonboard.com" 
        <kieran.bingham+renesas@...asonboard.com>,
        "sean@...rly.run" <sean@...rly.run>,
        "laurent.pinchart@...asonboard.com" 
        <laurent.pinchart@...asonboard.com>,
        "Jonathan Chai (Arm Technology China)" <Jonathan.Chai@....com>,
        Ayan Halder <Ayan.Halder@....com>,
        "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-renesas-soc@...r.kernel.org" 
        <linux-renesas-soc@...r.kernel.org>, nd <nd@....com>
Subject: Re: [PATCH v1 2/2] drm: Clear the fence pointer when writeback job
 signaled

Hi Lowry,

Thanks for this cleanup.

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@....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)

I'm thinking it might be a good idea to signal the fence with an error
here, if it's not already signaled. Otherwise, if there's someone
waiting (which there shouldn't be), they're going to be waiting a very
long time :-)

Thanks,
-Brian

> +		dma_fence_put(job->out_fence);
> +
>  	kfree(job);
>  }