[PATCH 02/25] dma-fence: prime lockdep annotations

[Christian König]

Am 10.07.20 um 14:43 schrieb Jason Gunthorpe:
> On Thu, Jul 09, 2020 at 10:09:11AM +0200, Daniel Vetter wrote:
>> Hi Jason,
>>
>> Below the paragraph I've added after our discussions around dma-fences
>> outside of drivers/gpu. Good enough for an ack on this, or want something
>> changed?
>>
>> Thanks, Daniel
>>
>>> + * Note that only GPU drivers have a reasonable excuse for both requiring
>>> + * &mmu_interval_notifier and &shrinker callbacks at the same time as having to
>>> + * track asynchronous compute work using &dma_fence. No driver outside of
>>> + * drivers/gpu should ever call dma_fence_wait() in such contexts.
> I was hoping we'd get to 'no driver outside GPU should even use
> dma_fence()'

My last status was that V4L could come use dma_fences as well.

I'm not 100% sure, but wouldn't MMU notifier + dma_fence be a valid use 
case for things like custom FPGA interfaces as well?

> Is that not reasonable?
>
> When your annotations once anything uses dma_fence it has to assume
> the worst cases, right?

Well a defensive approach is usually the best idea, yes.

Christian.

>
> Jason