[Linaro-mm-sig] [PATCH v2 3/5] dma-buf: Move all dma-bufs to dynamic locking specification

[Christian König]

Am 10.08.22 um 20:53 schrieb Dmitry Osipenko:
> On 8/10/22 21:25, Christian König wrote:
>> Am 10.08.22 um 19:49 schrieb Dmitry Osipenko:
>>> On 8/10/22 14:30, Christian König wrote:
>>>> Am 25.07.22 um 17:18 schrieb Dmitry Osipenko:
>>>>> This patch moves the non-dynamic dma-buf users over to the dynamic
>>>>> locking specification. The strict locking convention prevents deadlock
>>>>> situation for dma-buf importers and exporters.
>>>>>
>>>>> Previously the "unlocked" versions of the dma-buf API functions weren't
>>>>> taking the reservation lock and this patch makes them to take the lock.
>>>>>
>>>>> Intel and AMD GPU drivers already were mapping imported dma-bufs under
>>>>> the held lock, hence the "locked" variant of the functions are added
>>>>> for them and the drivers are updated to use the "locked" versions.
>>>> In general "Yes, please", but that won't be that easy.
>>>>
>>>> You not only need to change amdgpu and i915, but all drivers
>>>> implementing the map_dma_buf(), unmap_dma_buf() callbacks.
>>>>
>>>> Auditing all that code is a huge bunch of work.
>>> Hm, neither of drivers take the resv lock in map_dma_buf/unmap_dma_buf.
>>> It's easy to audit them all and I did it. So either I'm missing
>>> something or it doesn't take much time to check them all. Am I really
>>> missing something?
>> Ok, so this is only changing map/unmap now?
> It also vmap/vunmap and attach/detach: In the previous patch I added the
> _unlocked postfix to the func names and in this patch I made them all to
> actually take the lock.


Take your patch "[PATCH v2 2/5] drm/gem: Take reservation lock for 
vmap/vunmap operations" as a blueprint on how to approach it.

E.g. one callback at a time and then document the result in the end.

Regards,
Christian.

>
>> In this case please separate this from the documentation change.
> I'll factor out the doc in the v3.
>
>> I would also drop the _locked postfix from the function name, just
>> having _unlocked on all functions which are supposed to be called with
>> the lock held should be sufficient.
> Noted for the v3.
>
>> Thanks for looking into this,
>> Christian.
> Thank you for the review.
>