[PATCH 1/1] drm/ttm: Ignore signaled move fences

[Felix Kuehling]

It fixed an intermittent failure to allocate page tables in the page
fault handler (turning retry faults into no-retry faults). I'm not sure
if this caused real problems. I think it could potentially result in
fault storms and a failure to report page faults properly. I'm not sure
if it's a regression or was always present. So I'm not sure if it's an
urgent fix.

Regards,
  Felix

Am 2021-03-05 um 2:56 a.m. schrieb Christian König:
>
>
> Am 05.03.21 um 02:21 schrieb Felix Kuehling:
>> Am 2021-03-01 um 10:09 a.m. schrieb Christian König:
>>> Am 27.02.21 um 04:45 schrieb Felix Kuehling:
>>>> Move fences that have already signaled should not prevent memory
>>>> allocations with no_wait_gpu.
>>>>
>>>> Signed-off-by: Felix Kuehling <Felix.Kuehling at amd.com>
>>> Reviewed-by: Christian König <christian.koenig at amd.com>
>> I work on this on Alex's rebased amd-staging-drm-next. Should this go
>> into any other branches?
>
> I have a branch with stuff for 5.13 which I want to push to
> drm-misc-next as soon as 5.12-rc1 is out.
>
> Going to add this one here to that collection as well unless you say
> that this is really a bug fix and we need it earlier.
>
> Regards,
> Christian.
>
>>
>> Thanks,
>>    Felix
>>
>>
>>>> ---
>>>>    drivers/gpu/drm/ttm/ttm_bo.c | 3 ++-
>>>>    1 file changed, 2 insertions(+), 1 deletion(-)
>>>>
>>>> diff --git a/drivers/gpu/drm/ttm/ttm_bo.c
>>>> b/drivers/gpu/drm/ttm/ttm_bo.c
>>>> index 3a10bebb75d6..de1ec838cf8b 100644
>>>> --- a/drivers/gpu/drm/ttm/ttm_bo.c
>>>> +++ b/drivers/gpu/drm/ttm/ttm_bo.c
>>>> @@ -730,8 +730,9 @@ static int ttm_bo_add_move_fence(struct
>>>> ttm_buffer_object *bo,
>>>>            return 0;
>>>>          if (no_wait_gpu) {
>>>> +        ret = dma_fence_is_signaled(fence) ? 0 : -EBUSY;
>>>>            dma_fence_put(fence);
>>>> -        return -EBUSY;
>>>> +        return ret;
>>>>        }
>>>>          dma_resv_add_shared_fence(bo->base.resv, fence);
>