[Linaro-mm-sig] [PATCH 1/2] dma-buf.rst: Document why indefinite fences are a bad idea

[Christian König]

Am 21.07.20 um 09:41 schrieb Daniel Vetter:
> On Mon, Jul 20, 2020 at 01:15:17PM +0200, Thomas Hellström (Intel) wrote:
>> Hi,
>>
>> On 7/9/20 2:33 PM, Daniel Vetter wrote:
>>> Comes up every few years, gets somewhat tedious to discuss, let's
>>> write this down once and for all.
>>>
>>> What I'm not sure about is whether the text should be more explicit in
>>> flat out mandating the amdkfd eviction fences for long running compute
>>> workloads or workloads where userspace fencing is allowed.
>> Although (in my humble opinion) it might be possible to completely untangle
>> kernel-introduced fences for resource management and dma-fences used for
>> completion- and dependency tracking and lift a lot of restrictions for the
>> dma-fences, including prohibiting infinite ones, I think this makes sense
>> describing the current state.
> Yeah I think a future patch needs to type up how we want to make that
> happen (for some cross driver consistency) and what needs to be
> considered. Some of the necessary parts are already there (with like the
> preemption fences amdkfd has as an example), but I think some clear docs
> on what's required from both hw, drivers and userspace would be really
> good.

I'm currently writing that up, but probably still need a few days for this.

Christian.

>> Reviewed-by: Thomas Hellstrom <thomas.hellstrom at intel.com>
> Thanks for taking a look, first 3 patches here with annotations and docs
> merged to drm-misc-next. I'll ask Maarten/Dave whether another pull is ok
> for 5.9 so that everyone can use this asap.
> -Daniel