[Intel-gfx] [PATCH] drm/i915: Do not cleanup obj with NULL bo->resource

[Christian König]

Am 20.09.22 um 19:13 schrieb Matthew Auld:
> On 20/09/2022 18:06, Nirmoy Das wrote:
>> For delayed BO release i915_ttm_delete_mem_notify()
>> gets called twice, once with proper bo->resource and
>> another time with NULL. We shouldn't do anything for
>> the 2nd time as we already cleanedup the obj once.
>>
>> References: https://gitlab.freedesktop.org/drm/intel/-/issues/6850
>> Signed-off-by: Nirmoy Das <nirmoy.das at intel.com>
>
> Reviewed-by: Matthew Auld <matthew.auld at intel.com>
>
> Christian, as per above it looks like ttm calls into the 
> delete_mem_notify() hook twice if the object ends up on the delayed 
> destroy list, is that expected/normal?

Yeah, that's expected. IIRC some driver depended on this for some reason.

I already wanted to change this behavior, but forgot to do so after the 
patch set which made bo->resource a pointer landed.

Going to look into it once more.

Thanks,
Christian.

>
>> ---
>>   drivers/gpu/drm/i915/gem/i915_gem_ttm.c | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_ttm.c 
>> b/drivers/gpu/drm/i915/gem/i915_gem_ttm.c
>> index 0544b0a4a43a..e3fc38dd5db0 100644
>> --- a/drivers/gpu/drm/i915/gem/i915_gem_ttm.c
>> +++ b/drivers/gpu/drm/i915/gem/i915_gem_ttm.c
>> @@ -511,7 +511,7 @@ static void i915_ttm_delete_mem_notify(struct 
>> ttm_buffer_object *bo)
>>       struct drm_i915_gem_object *obj = i915_ttm_to_gem(bo);
>>       intel_wakeref_t wakeref = 0;
>>   -    if (likely(obj)) {
>> +    if (bo->resource && likely(obj)) {
>>           /* ttm_bo_release() already has dma_resv_lock */
>>           if (i915_ttm_cpu_maps_iomem(bo->resource))
>>               wakeref = 
>> intel_runtime_pm_get(&to_i915(obj->base.dev)->runtime_pm);