linux-kernel - Re: [PATCH v2 1/4] drm/sched: Enable signaling for finished fence

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Date:   Tue, 6 Sep 2022 08:34:05 +0200
From:   Christian König <christian.koenig@....com>
To:     Arvind Yadav <Arvind.Yadav@....com>, andrey.grodzovsky@....com,
        shashank.sharma@....com, amaranath.somalapuram@....com,
        Arunpravin.PaneerSelvam@....com, sumit.semwal@...aro.org,
        gustavo@...ovan.org, airlied@...ux.ie, daniel@...ll.ch,
        linux-media@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        linaro-mm-sig@...ts.linaro.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/4] drm/sched: Enable signaling for finished fence

Am 05.09.22 um 18:34 schrieb Arvind Yadav:
> Here's enabling software signaling for finished fence.
>
> Signed-off-by: Arvind Yadav <Arvind.Yadav@....com>
> ---
>
> Changes in v1 :
> 1- Addressing Christian's comment to remove CONFIG_DEBUG_FS check from
> this patch.
> 2- The version of this patch is also changed and previously
> it was [PATCH 2/4]
>
> ---
>   drivers/gpu/drm/scheduler/sched_main.c | 2 ++
>   1 file changed, 2 insertions(+)
>
> diff --git a/drivers/gpu/drm/scheduler/sched_main.c b/drivers/gpu/drm/scheduler/sched_main.c
> index e0ab14e0fb6b..fe72de0e2911 100644
> --- a/drivers/gpu/drm/scheduler/sched_main.c
> +++ b/drivers/gpu/drm/scheduler/sched_main.c
> @@ -962,6 +962,8 @@ static int drm_sched_main(void *param)
>   			/* Drop for original kref_init of the fence */
>   			dma_fence_put(fence);
>   
> +			dma_fence_enable_sw_signaling(&s_fence->finished);

Ok, this makes it a lot clearer. Previously I though that we have some 
bug in dma_fence_add_callback().

This is essentially the wrong place to call this, the finished fence 
should be enabled by the caller and not here.

There is also another problem in dma_fence_enable_sw_signaling(), it 
returns early when the fence is already signaled:

         if (test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags))
                 return;

Please remove that one first.

Thanks,
Christian.


> +
>   			r = dma_fence_add_callback(fence, &sched_job->cb,
>   						   drm_sched_job_done_cb);
>   			if (r == -ENOENT)