https://bugs.freedesktop.org/show_bug.cgi?id=104214
--- Comment #53 from Thomas Hellström <thellst...@vmware.com> ---
(In reply to Jason Ekstrand from comment #51)
> Can we write a piglit test or two that reproduces this bug? It would be
> very good if had a nice self-contained test that we can run in CI and avoid
> these types of issues in the future.
As a comment to this, the origin of this bug is in itself an interesting
sequence of events that might in one way answer your question:
1) Implemented and enabled dri3 support in the vmware Xorg driver.
2) A lot of glretrace automated tests started failing.
3) Fixed / worked around a number of viewport issues in the mesa dri3 core.
3a) Fixed a number of synchronization issues in the mesa dri3 core.
4) Some glretrace automated tests still failing.
5) Implemented dri3 SWAP_COPY_OML to have glretrace mimic the capturing
platform behaviour (which was in some cases WGL)
6) SWAP_COPY_OML didn't work due to a long standing bug in mesa core dri.
7) Fixed that. glretrace started to render transparently with SWAP_COPY_OML
fbconfigs.
8) This was caused by a long standing issue in the Xorg GLX layer. Worked
around that.
9) Kwin and other applications started having transparent rendering issues.
10) Implemented a proper fix for 8)
11) Item 3) was reported to cause a multi-threaded game to fail to start on
some platforms with page-flip only. Turned out mesa core dri3 is not
thread-safe. Implemented a game-specific workaround.
12) This bug surfaced (was caused by 5)) and was fixed in a way that will
decrease the chances of it ever happening again. (Perhaps an extra comment in
the source is needed).
So why am I listing this? The reason is that I agree we need more piglit tests
to verify GLX and dri3 functionality, but while this bug probably has had the
strongest user impact, that doesn't necessarily mean it's likely to happen
again. I think the biggest problem with the mesa dri3 implementation currently
is that it was written without multi-threading in mind, and adding
thread-safety as a hindsight might prove difficult and error-prone. It's also
currently lacking a well-documented and well defined strategy to handle
drawable size-changes and viewport changes.
So IMHO we should try to write piglit tests for the areas where we know there
are remaining issues.
/Thomas
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