xorg takes 100% CPU (nv driver)

[Charlie Brady]

Like previous reporters (e.g. Rod Butcher on this list last month) I have 
nVidia hardware, but unlike previous reporters I'm seeing this problem 
quite often with the nv driver.

...
01:00.0 VGA compatible controller: nVidia Corporation NV37GL [Quadro FX 
330/Quadro NVS280] (rev a2) (prog-if 00 [VGA])
         Subsystem: nVidia Corporation: Unknown device 0215
         Flags: bus master, fast devsel, latency 0, IRQ 169
         Memory at dd000000 (32-bit, non-prefetchable) [size=16M]
         Memory at c0000000 (32-bit, prefetchable) [size=256M]
         Memory at de000000 (32-bit, non-prefetchable) [size=16M]
         Expansion ROM at dfe00000 [disabled] [size=128K]
         Capabilities: <available only to root>
00: de 10 fd 00 07 00 10 00 a2 00 00 03 10 00 00 00
10: 00 00 00 dd 08 00 00 c0 00 00 00 de 00 00 00 00
20: 00 00 00 00 00 00 00 00 00 00 00 00 de 10 15 02
30: 00 00 e0 df 60 00 00 00 00 00 00 00 0b 01 00 00
...

Software platform is CentOS build of RHEL4, currently running 
xorg-x11-6.8.2-1.EL.13.37.2 and kernel 2.6.9-42.0.3.ELsmp.

Strace of X shows:

...
Process 20577 attached - interrupt to quit
--- SIGALRM (Alarm clock) @ 0 (0) ---
sigreturn()                             = ? (mask now [])
--- SIGALRM (Alarm clock) @ 0 (0) ---
sigreturn()                             = ? (mask now [])
--- SIGALRM (Alarm clock) @ 0 (0) ---
sigreturn()                             = ? (mask now [])
--- SIGALRM (Alarm clock) @ 0 (0) ---
sigreturn()                             = ? (mask now [])
...

Mouse cursor moves, but X doesn't respond otherwise to keyboard or mouse.

I've found multiple similar reports:

http://www.nvnews.net/vbulletin/printthread.php?t=31858&page=6&pp=40
http://my.opera.com/CrazyTerabyte/blog/index.dml/tag/X
http://www.nvnews.net/vbulletin/showthread.php?t=31858
http://www.mail-archive.com/debian-bugs-dist@lists.debian.org/msg132215.html
http://www.is-design.com/wiki/?NVidiaGraphicsIssue

plus my report to RedHat:

https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=210584

I can ssh in and kill X and get things running again, for somewhere 
between a few minutes and a few days. Occurrence is only sporadic, and I 
don't know how to provoke it. Frequency of lockup seems to vary depending 
on what kernel I run, but that's just a gut feel.

I'm looking for pointers as to exactly what I should do next time it 
happens to try to find the root cause.

Thanks

---
Charlie