[BUG] r200 dri driver deadlocks

[Patrick McFarland <diablod3@gmail.com>]

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I'm currently using an r200 (specifically, an agp 'ATI Technologies
Inc Radeon R200 QM [Radeon 9100]') on a uniproc Pentium 3 board
equipped with an intel 440bx/piix4 type chipset (the agp controller is
identified as 'Intel Corp. 440BX/ZX/DX - 82443BX/ZX/DX AGP bridge (rev
03)'

All of this was tested with a virgin 2.6.8.1 (with debug info and
frame pointers enabled) and Debian's XFree86 4.3.0.1, using DarkPlaces
and Twilight (both popular quakeGL engine forks) as test apps, unless
otherwise noted.

Thanks to wli (who I owe at least one beer for this, may be an entire
case), we've been able to figure exactly whats going on. The driver is
turning off interrupts, then deadlocking. (No sysrq, no sshing in,
capslock's light doesn't work.)

Turning the NMI watchdog on, it 'fixes' the deadlock (and thanks to
the watchdog, ssh and sysrq now work, but capslock's light still
doesn't work), but the app and X are still dead, but now I can ssh in
and kill -9 them both,  however, and quite obviously, I can't start
another X, but I can reboot cleanly.

Things already tested that don't effect bug:
Turning SMP on or off
Turning 4k stacks on or off
Using new radeon fbcon, using old radeon fbcon, using no fbcon
Turning Local APIC for uniproc and/or IO-APIC for uniproc on or off
Turning preempt on or off
Using mem=nopentium
Waving a dead chicken over the box

Things already tested for:
Kernels as far back as 2.6.0 have this bug, haven't tested any earlier

Thanks to netconsole (who I recommend to anyone that can't setup
serial console stuff), I was able to capture the entire kernel output,
including sysrq-t output right after my test app crashes.

I'm including both the netconsole output and the .config. vmlinux and
radeon.ko (and anything else you need) are available upon request.

-- 
Patrick "Diablo-D3" McFarland || diablod3@gmail.com
"Computer games don't affect kids; I mean if Pac-Man affected us as kids, we'd 
all be running around in darkened rooms, munching magic pills and listening to
repetitive electronic music." -- Kristian Wilson, Nintendo, Inc, 1989

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