linux-kernel - Re: [PATCH 2/4] drm/sched: Add callback and enable signaling on debug

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Date:   Mon, 5 Sep 2022 20:28:08 +0530
From:   "Yadav, Arvind" <arvyadav@....com>
To:     Christian König <christian.koenig@....com>,
        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 2/4] drm/sched: Add callback and enable signaling on debug


On 9/5/2022 7:16 PM, Yadav, Arvind wrote:
>
> On 9/5/2022 4:55 PM, Christian König wrote:
>>
>>
>> Am 05.09.22 um 12:56 schrieb Arvind Yadav:
>>> Here's on debug adding an enable_signaling callback for finished
>>> fences and enabling software signaling for finished fence.
>>>
>>> Signed-off-by: Arvind Yadav <Arvind.Yadav@....com>
>>> ---
>>>   drivers/gpu/drm/scheduler/sched_fence.c | 12 ++++++++++++
>>>   drivers/gpu/drm/scheduler/sched_main.c  |  4 +++-
>>>   2 files changed, 15 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/drivers/gpu/drm/scheduler/sched_fence.c 
>>> b/drivers/gpu/drm/scheduler/sched_fence.c
>>> index 7fd869520ef2..ebd26cdb79a0 100644
>>> --- a/drivers/gpu/drm/scheduler/sched_fence.c
>>> +++ b/drivers/gpu/drm/scheduler/sched_fence.c
>>> @@ -122,16 +122,28 @@ static void 
>>> drm_sched_fence_release_finished(struct dma_fence *f)
>>>         dma_fence_put(&fence->scheduled);
>>>   }
>>> +#ifdef CONFIG_DEBUG_FS
>>> +static bool drm_sched_enable_signaling(struct dma_fence *f)
>>> +{
>>> +    return true;
>>> +}
>>> +#endif
>>>     static const struct dma_fence_ops drm_sched_fence_ops_scheduled = {
>>>       .get_driver_name = drm_sched_fence_get_driver_name,
>>>       .get_timeline_name = drm_sched_fence_get_timeline_name,
>>> +#ifdef CONFIG_DEBUG_FS
>>> +    .enable_signaling = drm_sched_enable_signaling,
>>> +#endif
>>>       .release = drm_sched_fence_release_scheduled,
>>>   };
>>>     static const struct dma_fence_ops drm_sched_fence_ops_finished = {
>>>       .get_driver_name = drm_sched_fence_get_driver_name,
>>>       .get_timeline_name = drm_sched_fence_get_timeline_name,
>>> +#ifdef CONFIG_DEBUG_FS
>>> +    .enable_signaling = drm_sched_enable_signaling,
>>> +#endif
>>
>> Adding the callback should not be necessary.
> sure, I will remove this change.
>>
>>>       .release = drm_sched_fence_release_finished,
>>>   };
>>>   diff --git a/drivers/gpu/drm/scheduler/sched_main.c 
>>> b/drivers/gpu/drm/scheduler/sched_main.c
>>> index e0ab14e0fb6b..140e3d8646e2 100644
>>> --- a/drivers/gpu/drm/scheduler/sched_main.c
>>> +++ b/drivers/gpu/drm/scheduler/sched_main.c
>>> @@ -961,7 +961,9 @@ static int drm_sched_main(void *param)
>>>               s_fence->parent = dma_fence_get(fence);
>>>               /* Drop for original kref_init of the fence */
>>>               dma_fence_put(fence);
>>
>> Uff, not related to your patch but that looks wrong to me. The 
>> reference can only be dropped after the call to 
>> dma_fence_add_callback().
>>
> Shall I take care with this patch or I will submit separate one ?

This changes was recently added by  Andrey Grodzovsky (commit : 
45ecaea73) to fix the negative refcount.

>>> -
>>> +#ifdef CONFIG_DEBUG_FS
>>> + dma_fence_enable_sw_signaling(&s_fence->finished);
>>> +#endif
>>
>> This should always be called, independent of the config options set.
>>
>> Christian.
>
> sure, I will remove the Config check.
>
> ~arvind
>
>>
>>>               r = dma_fence_add_callback(fence, &sched_job->cb,
>>>                              drm_sched_job_done_cb);
>>>               if (r == -ENOENT)
>>