@luis, thanks for the backtrace; it is interesting that this does not
match the backtrace posted by Matt (comment #52), although they're both
ending with "#0  0xffffe410 in __kernel_vsyscall ()".

For everyone else, the #1 most important thing you can post to help with
this specific bug is backtraces (see
https://wiki.ubuntu.com/DebuggingXorg).  lspci, Xorg.0.log, and
xorg.conf don't give the info we need here (although it doesn't hurt to
post them).

@luis, the -dbg and -dbgsym packages aren't the same thing, but for our
purposes either will suit our needs, and -dbg are typically fine for
Xorg.  From your backtrace, all function calls are displayed so you've
done the correct thing.  It is not unknown for issues to change when a
debug package is installed - sometimes this affects the timings and can
delay things long enough for deadlocks to break, or race conditions to
disappear.  However those are rare, and I doubt will affect our
debugging.

This particular backtrace is describing a fault during output flushing.
I suspect this is a secondary issue (i.e., X failed on our unknown
issue, then you connected and told it to keep going, and it did for a
bit, but the original issue left the system in a bad state, so it
crashed again later).  So what we need is a backtrace for that original
lockup.

@luis, please see if you can capture a few more backtraces, perhaps
taking them in different ways (such as immediately after attaching,
before doing cont).

I was sort of able to reproduce a lockup on an ATI R350 9800 using
firefox 3, without Compiz enabled.  In this case, I was able to switch
to a virtual terminal (ctrl-alt-f1) and pkill firefox, and everything
came back.  I could reproduce that situation at will (seems to have
something to do with ff3's URL autocomplete dropdown).  After re-reading
through every comment on this bug, I suspect that perhaps it is a client
application triggering this bug (screensavers, games, office
applications, proprietary software, compiz, etc. all are potential
suspects).  So a secondary troubleshooting approach after this problem
occurs might be to go to a vt and kill apps, and see if that unlocks the
system.  If it does, then attaching to that process (just like in the
DebuggingXorg procedure) and getting a backtrace may be of use.

Ultimately, what we're looking for is a common function call and/or
invalid function parameters that result in jamming up the system.  After
that, we can then explore what in the driver is failing under those
circumstances.

For those of you who haven't given up and gone back to 'doze and that
are willing to help in this work of troubleshooting down deep, thanks
ahead of time!

-- 
X freezes when compiz is enabled on ATI cards
https://bugs.launchpad.net/bugs/108527
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