[Wayland-bugs] [Bug 97353] Wayland lacks cross-process synchronisation

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=97353

--- Comment #4 from Kristian Høgsberg <krh at bitplanet.net> ---
(In reply to Tomek Bury from comment #2)
> As far as I can tell several 3D drivers put read-write synchronisation in
> user space so it works across contexts within one process but not across
> processes. Nokia had this problem, Boroadcom driver is another example. 
> 
> It's not impossible to implement but the only possible implementation that
> doesn't involve blocking CPU in the compositor I can think of is rather
> ugly: create a parallel synchronisation mechanism and deal with 2 of them:
> regular one in user pace for most things and Wayland special in kernel with
> an extra kernel round-trip for each read from or write to wl_buffer.

The wl_drm interface isn't supposed to be the only buffer sharing interface.
Similiar to how drivers can define their own buffer sharing mechanism for X, a
driver can implement its own wayland interface for sharing buffers.

For driver architectures that require userspace synchronization, you would
define your own buffer sharing interface and pass along fences for each shared
buffer.

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