Re: [PATCH] drm/ttm: stop destroying pinned ghost object

["Christian König" <ckoenig.leichtzumerken@gmail.com>]

Am 01.12.20 um 17:58 schrieb Daniel Vetter:
> On Tue, Dec 1, 2020 at 2:32 PM Christian König
> <ckoenig.leichtzumerken@gmail.com> wrote:
>> Daniel added a warning for this, but we were abusing that behavior here.
>>
>> Signed-off-by: Christian König <christian.koenig@amd.com>
>> Fixes: 57fcd550eb15 ("drm/ttm: Warn on pinning without holding a reference")
>> ---
>>   drivers/gpu/drm/ttm/ttm_bo_util.c | 4 +++-
>>   1 file changed, 3 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/gpu/drm/ttm/ttm_bo_util.c b/drivers/gpu/drm/ttm/ttm_bo_util.c
>> index 7ccb2295cac1..5bbc1339d28e 100644
>> --- a/drivers/gpu/drm/ttm/ttm_bo_util.c
>> +++ b/drivers/gpu/drm/ttm/ttm_bo_util.c
>> @@ -310,7 +310,7 @@ static int ttm_buffer_object_transfer(struct ttm_buffer_object *bo,
>>          kref_init(&fbo->base.kref);
>>          fbo->base.destroy = &ttm_transfered_destroy;
>>          fbo->base.acc_size = 0;
>> -       fbo->base.pin_count = 1;
>> +       fbo->base.pin_count = 0;
> Was this just to prevent lru reaping, and let the buffer deletion code
> clean up everything when it's all done? Just kinda freaking out that
> there's no unpin anywhere ...

Yeah, didn't realized how this works before either.

> Anyway tracking ghost objects with the lru like anything else instead
> of tricks with pin count sounds like a good idea.

Well I really want to nuke ghost objects which would be an even better 
idea :)

> Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>

Thanks,
Christian.

>
> But maybe ask Dave or Thomas for a second check.
> -Daniel
>
>>          if (bo->type != ttm_bo_type_sg)
>>                  fbo->base.base.resv = &fbo->base.base._resv;
>>
>> @@ -319,6 +319,8 @@ static int ttm_buffer_object_transfer(struct ttm_buffer_object *bo,
>>          ret = dma_resv_trylock(&fbo->base.base._resv);
>>          WARN_ON(!ret);
>>
>> +       ttm_bo_move_to_lru_tail_unlocked(&fbo->base);
>> +
>>          *new_obj = &fbo->base;
>>          return 0;
>>   }
>> --
>> 2.25.1
>>
>

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