Xorg segmentation fault when drawing PolyArcs (under kicad)

Renato Caldas seventhguardian at gmail.com
Tue Oct 20 05:57:23 PDT 2009

2009/10/20 Renato Caldas <seventhguardian at gmail.com>:
> Hello,
> Thanks for looking into this!
> 2009/10/20 Michel Dänzer <michel at daenzer.net>:
>> On Mon, 2009-10-12 at 20:12 +0100, Renato Caldas wrote:
>>> Hello,
>>> First of all, I'm not subscribed to this list, so please include my
>>> e-mail in the CC.
>>> When using (trying to use...), kicad I managed to get consistent Xorg
>>> segmentation faults. I've filed a bug report on fedora's bugzilla:
>>> https://bugzilla.redhat.com/show_bug.cgi?id=528475. There I've
>>> included a very basic test case that works all the time. In the
>>> meantime, I've also got my hands dirty, and tried to debug Xorg using
>>> gdb.
>>> The symptom is that the function fbBltOne is called with src=0x0, so
>>> Xorg segfaults as soon as it tries to use src (in LoadBits; at
>>> fb/fbbltone.c:292).
>>> I've traced its value back to fbPushPixels, where it is created and
>>> fed to the function chain, in the macro fbGetStipDrawable (defined at
>>> fb/fb.h:720).
>>> Here pDrawable->type seems to be DRAWABLE_PIXMAP, so _pPix is simply
>>> cast from pDrawable. Then the _pPix -> devPrivate.ptr is used as
>>> "src", after a couple of castings and copying around.
>> Please provide a full backtrace ('bt full' in gdb) from when the crash
>> occurs.
> Attached. I've also attached it to the bug report, just in case.
>> If you're using EXA, the problem is most likely that some code path
>> isn't calling exaPrepareAccess(Reg) for the pixmap in question before
>> calling down to the fb module.
> I am using EXA. I'll try enabling XAA and report back.

Nouveau doesn't support XAA, but I've disabled the acceleration. It
doesn't crash anymore, so you must be correct :) I'll try to figure
out a patch.

Everything is slow now, but at least I can do some work. Thanks!


> Thanks,
>  Renato

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