[Intel-gfx] [PATCH] drm/i915: Do not leak VMAs (and PPGTT VMs) of imported flinked objects

[Tvrtko Ursulin]

On 04/20/2015 01:58 PM, Chris Wilson wrote:
> On Mon, Apr 20, 2015 at 01:53:03PM +0100, Tvrtko Ursulin wrote:
>>> No we can't do this, as it makes close sync and so can have disasterous
>>> effects on performance (though mitigated chiefly by userspace
>>> agressively caching bo) and also the unbind is very likely to fail,
>>> though admittedly the fbcon copy should be before X starts (ab)using
>>> signals - hence nasty WARN_ON.
>>>
>>> Plus also walking this linear list is quite painful in certain abusive
>>> tests. My preference for fixing this bug would be via vma active
>>> references and auto-unbinding on retirement after a close.
>>
>> Why this is any different today with GEM_CLOSE having pretty similar
>> VMA unbind loop? Is the typical (and interesting) case not that
>> GEM_CLOSE will trigger gem_object_close and gem_object_free at the
>> same invocation?
>
> We have such a cleanup loop in free_object, but we have an active
> reference to ensure that we only do so once the object is idle (and
> unbinding won't cause to wait).

Is that a predominant situation - closing of active objects vs inactive? 
It would be surprising (to me).

Regards,

Tvrtko