[PATCH v2] Post buffer release events instead of queue when no frame callback

[Neil Roberts]

Neil Roberts <neil at linux.intel.com> writes:

> I think that would mean you could cause tearing if you are using
> eglSwapInterval(0) because you could write into the released buffer
> while the GPU is actually still rendering the previous frame using the
> buffer in a texture.
>
> I think this doesn't actually happen at the moment because as far as I
> can tell the gl-renderer immediately queues the buffer release when you
> attach a new one rather than waiting for the swap to actually
> complete.

Thanks to some explanation from Kristian and Pekka I now understand that
this is the expected behaviour. The assumption is that it will be up to
the GL driver or hardware to ensure that GL commands submitted by the
client will be executed after those submitted by the compositor so the
compositor is free to release straight after the eglSwapBuffer call. If the
hardware doesn't just do this naturally then it would still be possible
for a driver's buffer sharing implementation to also transfer fence
objects so that it can ensure these semantics in the driver.

Regards,
- Neil
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