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From:   Brian Starkey <Brian.Starkey@arm.com>
To:     "Lowry Li (Arm Technology China)" <Lowry.Li@arm.com>
CC:     Liviu Dudau <Liviu.Dudau@arm.com>,
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        "airlied@linux.ie" <airlied@linux.ie>,
        "daniel@ffwll.ch" <daniel@ffwll.ch>,
        "Julien Yin (Arm Technology China)" <Julien.Yin@arm.com>,
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Subject: Re: [PATCH v1 2/2] drm: Clear the fence pointer when writeback job
 signaled
Thread-Topic: [PATCH v1 2/2] drm: Clear the fence pointer when writeback job
 signaled
Thread-Index: AQHVR4/KbU4UCRFzvkaBT5qon3yv66bsjx6A
Date:   Mon, 5 Aug 2019 13:10:17 +0000
Message-ID: <20190805131014.u2kei5tvbkcf7aeo@DESKTOP-E1NTVVP.localdomain>
References: <1564571048-15029-1-git-send-email-lowry.li@arm.com>
 <1564571048-15029-3-git-send-email-lowry.li@arm.com>
In-Reply-To: <1564571048-15029-3-git-send-email-lowry.li@arm.com>
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Hi Lowry,

Based on Daniel's input, this patch looks fine:

Reviewed-by: Brian Starkey <brian.starkey@arm.com>

I think there's some opportunity for improvement around
prepare_signaling/complete_signaling, but that can be treated as
separate from fixing this bug.

Thanks,
-Brian

On Wed, Jul 31, 2019 at 11:04:45AM +0000, Lowry Li (Arm Technology China) w=
rote:
> During it signals the completion of a writeback job, after releasing
> the out_fence, we'd clear the pointer.
>=20
> Check if fence left over in drm_writeback_cleanup_job(), release it.
>=20
> Signed-off-by: Lowry Li (Arm Technology China) <lowry.li@arm.com>
> ---
>  drivers/gpu/drm/drm_writeback.c | 23 +++++++++++++++--------
>  1 file changed, 15 insertions(+), 8 deletions(-)
>=20
> diff --git a/drivers/gpu/drm/drm_writeback.c b/drivers/gpu/drm/drm_writeb=
ack.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_j=
ob *job)
>  	if (job->fb)
>  		drm_framebuffer_put(job->fb);
> =20
> +	if (job->out_fence)
> +		dma_fence_put(job->out_fence);
> +
>  	kfree(job);
>  }
>  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;
> =20
>  	spin_lock_irqsave(&wb_connector->job_lock, flags);
>  	job =3D 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);
> -		}
> -	}
> +
>  	spin_unlock_irqrestore(&wb_connector->job_lock, flags);
> =20
>  	if (WARN_ON(!job))
>  		return;
> =20
> +	out_fence =3D 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 =3D NULL;
> +	}
> +
>  	INIT_WORK(&job->cleanup_work, cleanup_work);
>  	queue_work(system_long_wq, &job->cleanup_work);
>  }
> --=20
> 1.9.1
>=20