[PATCH] drm/etnaviv: fix another potential dma_resv DAG violation

[Christian König]

Am 22.09.21 um 14:28 schrieb Lucas Stach:
> Am Mittwoch, dem 22.09.2021 um 13:41 +0200 schrieb Christian König:
>> Setting the exclusive fence without waiting for the shared
>> fences violates the DAG and is illegal.
>>
>> We really need to get away from this ASAP and make the
>> driver interface more bullet prove.
> Uh, what happened to Daniels patch "drm/etnaviv: Don't break exclusive
> fence ordering", which fixed this without totally doing away with the
> no-implicit handling?

I was wondering the same thing. My memory was that Daniel has already 
fixed this, but that still looks totally broken to me.

> I have to admit that I haven't followed up with
> that patch series due to ETOOMUCHOTHERSTUFF, but from a quick glance
> this patch looked better than what you propose here.

This patch here should have the same result as Daniels version, just 
with CC: stable on it, fewer changes lines and not depending on the 
drm_sched_job_await_implicit() change.

Regards,
Christian.

>
> Regards,
> Lucas
>
>> Signed-off-by: Christian König <christian.koenig at amd.com>
>> Cc: <stable at vger.kernel.org>
>> ---
>>   drivers/gpu/drm/etnaviv/etnaviv_gem_submit.c | 6 +-----
>>   1 file changed, 1 insertion(+), 5 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/etnaviv/etnaviv_gem_submit.c b/drivers/gpu/drm/etnaviv/etnaviv_gem_submit.c
>> index 7e17bc2b5df1..4db40e88f67f 100644
>> --- a/drivers/gpu/drm/etnaviv/etnaviv_gem_submit.c
>> +++ b/drivers/gpu/drm/etnaviv/etnaviv_gem_submit.c
>> @@ -185,19 +185,15 @@ static int submit_fence_sync(struct etnaviv_gem_submit *submit)
>>   				return ret;
>>   		}
>>   
>> -		if (submit->flags & ETNA_SUBMIT_NO_IMPLICIT)
>> -			continue;
>> -
>>   		if (bo->flags & ETNA_SUBMIT_BO_WRITE) {
>>   			ret = dma_resv_get_fences(robj, &bo->excl,
>>   						  &bo->nr_shared,
>>   						  &bo->shared);
>>   			if (ret)
>>   				return ret;
>> -		} else {
>> +		} else if (!(submit->flags & ETNA_SUBMIT_NO_IMPLICIT)) {
>>   			bo->excl = dma_fence_get(dma_resv_excl_fence(robj));
>>   		}
>> -
>>   	}
>>   
>>   	return ret;
>