[Intel-gfx] [PATCH 07/26] Revert "drm/i915/gem: Split eb_vma into its own allocation"

[Maarten Lankhorst]

Op 30-06-2020 om 14:31 schreef Tvrtko Ursulin:
>
> On 30/06/2020 12:52, Maarten Lankhorst wrote:
>> Op 29-06-2020 om 17:08 schreef Tvrtko Ursulin:
>>>
>>> On 23/06/2020 15:28, Maarten Lankhorst wrote:
>>>> This reverts commit 0f1dd02295f35dcdcbaafcbcbbec0753884ab974.
>>>> This conflicts with the ww mutex handling, which needs to drop
>>>> the references after gpu submission anyway, because otherwise we
>>>> may risk unlocking a BO after first freeing it.
>>>
>>> What is the problem here? eb_vma_array_put in eb_move_to_gpu? If so, could you just move this put to later in the sequence? I am simply thinking how to avoid controversial reverts. Because on the other hand I did not figure out what 0f1dd02295f35dcdcbaafcbcbbec0753884ab974 fixed in a few minutes I spent staring at the patch.
>>
>>
>> We need to unlock before we unref to prevent a use-after-free in unlock, so freeing and releasing in eb_move_to_gpu() is too early. This means we only end up with 1 path for unlock, so it's fine to revert.
>
> You are saying the reason 0f1dd02295f35dcdcbaafcbcbbec0753884ab974 was added for will not be there after your changes?
>
> Regards,
>
> Tvrtko

Yes. :)