[PATCH 2/2] loader_dri3: Variant 2: Wait for pending swaps to complete before drawable_fini.

[Mario Kleiner]

On Sat, May 5, 2018 at 4:08 AM, Mike Lothian <mike at fireburn.co.uk> wrote:
> I definately saw the steam bug with patch 1 but not with plasmashell,
> I started seeing it with patch 2 but it seemed to fix itself
>

I had two hangs of kwin_x11 within the last 6 hours when alt-tabbing
between windows, where it got stuck in the
loader_dri3_swapbuffer_barrier() from patch 1/2. Not sure how that is
possible, or if the stacktrace was misleading, because i had to VT
switch to a text console to attach the debugger and this might be just
a side effect of that. But if it is true, then patch 1/2 would not be
it. Also 1/2 has a potential performance impact, whereas 2/2 doesn't.
However 2/2 would also need more work, as i can think of more complex
scenarios where it would filter the wrong events, although not in the
case of plasmashell or steam. Probably we'd need to sacrifice a few
sbc bits in the Present events serial field to transport a unique tag
for each incarnation of the loader_dri3_drawable, like a mini-hash of
the draw->eid. Ugly ugly...

-mario