[cairo] buggy_repeat for Xorg servers < 1.4

Carl Worth cworth at cworth.org
Sat Apr 5 23:38:45 PDT 2008

On Sat, 05 Apr 2008 03:28:57 +0300, Mart Raudsepp wrote:
> Has anyone tried xorg-server 1.4 actually?

It's actually really tricky.

> I'm asking because is a prerelease of 1.5 and is a
> 1.3 version, so 1.4 seems completely untested, but buggy_repeat
> workaround is now disabled for them.

Yes, I know that. And if anyone has any data on that this would be
helpful. If we enable the workaround when it's not needed then there's
a *big* performance hit. But if we don't enable it when it is needed,
then there's a potential for triggering an X server crash, (though, so
far, I think I've only heard of the extend-reflect test in cairo's
test suite doing this, and not any application). So we do want to get
it right.

The tricky part is that I haven't figured out a recipe for replicating
the bug other than "Install Fedora 8". When I first heard about the
bug I rebuilt Xorg 1.3.0, 1.4.0, and the latest git master all from
scratch and I never found the bug.

Then today, on my Fedora 8 machine, (where the packaged version of
1.3.0 crashes when I run extend-reflect), I rebuilt 1.3.0 from
upstream source, but I didn't get the crash, (in fact cairo's
extend-reflect test actually passes just fine).

So it could be that there's a Fedora-specific patch that's necessary
for the bug, (but I looked through the X server patches in Fedora 8 a
while ago and nothing looks likely---the crash occurs in fbCopyAreaMMX
but the patches don't seem to touch that).

Or it's possible there's a critical build flag that the package uses
and that my testing missed. I'll try rebuilding with the package
tools, (and with the patches). I want to see a server crashing with
debugging symbols so I can see what the actual bug is, (because then
it should be much easier to find the version in which the bug actually
got fixed).

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