[Mesa-dev] Plumbing explicit synchronization through the Linux ecosystem

Daniel Vetter daniel at ffwll.ch
Thu Mar 19 10:37:35 UTC 2020

On Wed, Mar 18, 2020 at 11:05:48AM +0100, Michel Dänzer wrote:
> On 2020-03-17 6:21 p.m., Lucas Stach wrote:
> > That's one of the issues with implicit sync that explicit may solve: 
> > a single client taking way too much time to render something can 
> > block the whole pipeline up until the display flip. With explicit 
> > sync the compositor can just decide to use the last client buffer if 
> > the latest buffer isn't ready by some deadline.
> FWIW, the compositor can do this with implicit sync as well, by polling
> a dma-buf fd for the buffer. (Currently, it has to poll for writable,
> because waiting for the exclusive fence only isn't enough with amdgpu)

Would be great if we don't have to make this recommended uapi, just
because amdgpu leaks it's trickery into the wider world. Polling for read
really should be enough (and I guess Christian gets to fix up amdgpu more,
at least for anything that has a dma-buf attached even if it's not shared
with anything !amdgpu.ko).
Daniel Vetter
Software Engineer, Intel Corporation

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