Re: [PATCH 5/6] drm/ttm: replace dma_resv object on deleted BOs v2

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

Am 11.02.20 um 15:14 schrieb Daniel Vetter:
> On Mon, Feb 10, 2020 at 04:09:06PM +0100, Christian König wrote:
>> When non-imported BOs are resurrected for delayed delete we replace
>> the dma_resv object to allow for easy reclaiming of the resources.
>>
>> v2: move that to ttm_bo_individualize_resv
>>
>> Signed-off-by: Christian König <christian.koenig@amd.com>
>> ---
>>   drivers/gpu/drm/ttm/ttm_bo.c | 10 +++++++++-
>>   1 file changed, 9 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/gpu/drm/ttm/ttm_bo.c b/drivers/gpu/drm/ttm/ttm_bo.c
>> index d0624685f5d2..4d161038de98 100644
>> --- a/drivers/gpu/drm/ttm/ttm_bo.c
>> +++ b/drivers/gpu/drm/ttm/ttm_bo.c
>> @@ -393,6 +393,14 @@ static int ttm_bo_individualize_resv(struct ttm_buffer_object *bo)
>>   
>>   	r = dma_resv_copy_fences(&bo->base._resv, bo->base.resv);
>>   	dma_resv_unlock(&bo->base._resv);
>> +	if (r)
>> +		return r;
>> +
>> +	if (bo->type != ttm_bo_type_sg) {
>> +		spin_lock(&ttm_bo_glob.lru_lock);
>> +		bo->base.resv = &bo->base._resv;
> Having the dma_resv pointer be protected by the lru_lock for ttm internal
> stuff, but invariant everywhere else is really confusing. Not sure that's
> a great idea, I've just chased some ttm code around freaking out about
> that.

The key point is that the reference counter is zero in this moment.

Taking the LRU spinlock was just a precaution and might actually be not 
even necessary here.

I will double check,
Christian.

> -Daniel
>
>> +		spin_unlock(&ttm_bo_glob.lru_lock);
>> +	}
>>   
>>   	return r;
>>   }
>> @@ -720,7 +728,7 @@ static bool ttm_bo_evict_swapout_allowable(struct ttm_buffer_object *bo,
>>   
>>   	if (bo->base.resv == ctx->resv) {
>>   		dma_resv_assert_held(bo->base.resv);
>> -		if (ctx->flags & TTM_OPT_FLAG_ALLOW_RES_EVICT || bo->deleted)
>> +		if (ctx->flags & TTM_OPT_FLAG_ALLOW_RES_EVICT)
>>   			ret = true;
>>   		*locked = false;
>>   		if (busy)
>> -- 
>> 2.17.1
>>
>> _______________________________________________
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>> dri-devel@lists.freedesktop.org
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