Re: [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.