[PATCH] drm/amdgpu: fix and cleanup amdgpu_gem_object_close v2

[Christian König]

The key point is that 10ms should be sufficient that either the move or 
the update is finished.

One alternative which came to my mind would be to add the exclusive 
fence as shared as well in this case.

This way we won't need to block at all.

Christian.

Am 18.03.20 um 09:00 schrieb Pan, Xinhui:
> I wonder if it really fix anything with such small delay. but it should be no harm anyway.
>
> Reviewed-by: xinhui pan <xinhui.pan at amd.com>
>
>> 2020年3月18日 15:51，Christian König <ckoenig.leichtzumerken at gmail.com> 写道：
>>
>> Ping? Xinhui can I get an rb for this?
>>
>> Thanks,
>> Christian.
>>
>> Am 16.03.20 um 14:22 schrieb Christian König:
>>> The problem is that we can't add the clear fence to the BO
>>> when there is an exclusive fence on it since we can't
>>> guarantee the the clear fence will complete after the
>>> exclusive one.
>>>
>>> To fix this refactor the function and wait for any potential
>>> exclusive fence with a small timeout before adding the
>>> shared clear fence.
>>>
>>> v2: fix warning
>>>
>>> Signed-off-by: Christian König <christian.koenig at amd.com>
>>> ---
>>>   drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c | 43 +++++++++++++++----------
>>>   1 file changed, 26 insertions(+), 17 deletions(-)
>>>
>>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c
>>> index 5bec66e6b1f8..49c91dac35a0 100644
>>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c
>>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c
>>> @@ -161,10 +161,11 @@ void amdgpu_gem_object_close(struct drm_gem_object *obj,
>>>     	struct amdgpu_bo_list_entry vm_pd;
>>>   	struct list_head list, duplicates;
>>> +	struct dma_fence *fence = NULL;
>>>   	struct ttm_validate_buffer tv;
>>>   	struct ww_acquire_ctx ticket;
>>>   	struct amdgpu_bo_va *bo_va;
>>> -	int r;
>>> +	long r;
>>>     	INIT_LIST_HEAD(&list);
>>>   	INIT_LIST_HEAD(&duplicates);
>>> @@ -178,28 +179,36 @@ void amdgpu_gem_object_close(struct drm_gem_object *obj,
>>>   	r = ttm_eu_reserve_buffers(&ticket, &list, false, &duplicates);
>>>   	if (r) {
>>>   		dev_err(adev->dev, "leaking bo va because "
>>> -			"we fail to reserve bo (%d)\n", r);
>>> +			"we fail to reserve bo (%ld)\n", r);
>>>   		return;
>>>   	}
>>>   	bo_va = amdgpu_vm_bo_find(vm, bo);
>>> -	if (bo_va && --bo_va->ref_count == 0) {
>>> -		amdgpu_vm_bo_rmv(adev, bo_va);
>>> +	if (!bo_va || --bo_va->ref_count)
>>> +		goto out_unlock;
>>>   -		if (amdgpu_vm_ready(vm)) {
>>> -			struct dma_fence *fence = NULL;
>>> +	amdgpu_vm_bo_rmv(adev, bo_va);
>>> +	if (!amdgpu_vm_ready(vm))
>>> +		goto out_unlock;
>>>   -			r = amdgpu_vm_clear_freed(adev, vm, &fence);
>>> -			if (unlikely(r)) {
>>> -				dev_err(adev->dev, "failed to clear page "
>>> -					"tables on GEM object close (%d)\n", r);
>>> -			}
>>>   -			if (fence) {
>>> -				amdgpu_bo_fence(bo, fence, true);
>>> -				dma_fence_put(fence);
>>> -			}
>>> -		}
>>> -	}
>>> +	r = amdgpu_vm_clear_freed(adev, vm, &fence);
>>> +	if (r || !fence)
>>> +		goto out_unlock;
>>> +
>>> +	r = dma_resv_wait_timeout_rcu(bo->tbo.base.resv, false, false,
>>> +				      msecs_to_jiffies(10));
>>> +	if (r == 0)
>>> +		r = -ETIMEDOUT;
>>> +	if (r)
>>> +		goto out_unlock;
>>> +
>>> +	amdgpu_bo_fence(bo, fence, true);
>>> +	dma_fence_put(fence);
>>> +
>>> +out_unlock:
>>> +	if (unlikely(r < 0))
>>> +		dev_err(adev->dev, "failed to clear page "
>>> +			"tables on GEM object close (%ld)\n", r);
>>>   	ttm_eu_backoff_reservation(&ticket, &list);
>>>   }
>>>