[Libre-soc-dev] gpus and fences

Jonathan Neuschäfer j.neuschaefer at gmx.net
Tue Apr 20 20:00:05 BST 2021

On Tue, Apr 20, 2021 at 09:52:41AM -0700, Jacob Lifshay wrote:
> This thread on dri-devel is relevant for Kazan, having to do with what kind
> of synchronization primitives the linux gpu ecosystem should use:
> https://lists.freedesktop.org/archives/dri-devel/2021-April/303865.html
> Kazan runs into issues due to being in user-space and the standard linux
> gpu sync primitive being a dma-fence which is required to have kernel-level
> finite completion time guarantees. user-space can't directly provide
> something like that since someone could send sigstop or something to the
> user process, causing a kernel-level deadlock.

Silly question perhaps — but would Kazan need to touch DRI and the
kernel, at all?

It seems to me that, like llvmpipe and OpenSWR, it wouldn't need any
kernel component, because it just runs in userspace on the same CPUs as
the application.


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