[Mesa-dev] [RFC PATCH] egl/android: Dequeue buffers inside EGL calls

[Tomasz Figa]

On Thu, Mar 30, 2017 at 11:17 PM, Emil Velikov <emil.l.velikov at gmail.com> wrote:
>
> On 30 March 2017 at 11:55, Tomasz Figa <tfiga at chromium.org> wrote:
> > Android buffer queues can be abandoned, which results in failing to
> > dequeue next buffer. Currently this would fail somewhere deep within
> > the DRI stack calling loader's getBuffers*(), without any error
> > reporting to the client app. However Android framework code relies on
> > proper signaling of this event, so we move buffer dequeue to
> > createWindowSurface() and swapBuffers() call, which can generate proper
> > EGL errors. To keep the performance benefits of delayed buffer handling,
> > if any, fence wait and DRI image creation is kept delayed until
> > getBuffers*() is called by the DRI driver.
> >
> Thank you Tomasz.
>
> I'm fairly confident that this should resolve the crash [in
> swap_buffers] that Mauro was seeing.
> Mauro can you give it a test ?

Ah, I actually noticed a problem with existing code, supposedly fixed
by [1], but I'm afraid it's still wrong.

Current swap_buffers calls get_back_bo(), but doesn't call
update_buffers(), which is the function that should be called before
to actually dequeue a buffer from Android's buffer queue. Given that,
get_back_bo() would simply fail with !dri2_surf->buffer, because no
buffer was dequeued.

My patch removes update_buffers() and changes the buffer management so
that there is always a buffer dequeued, starting from surface
creation, unless there was an error somewhere.

[1] https://cgit.freedesktop.org/mesa/mesa/commit/src/egl/drivers/dri2/platform_android.c?id=4d4558411db166d2d66f8cec9cb581149dbe1597

>
>
> Not that huge of an expert on the Android specifics, so just a humble request:
> Can we seek the code resuffle (droid_{alloc,free}_local_buffer,
> other?) separate from the functionality changes ?

Sure. Thanks for suggestion.

Best regards,
Tomasz