[sf-lug] Pointers for how to track down source of system hang

[Mark K. Zanfardino]

I'm looking for pointers on how I can go about discovering what is
causing my system to hang periodically.  Let me first define hang in
these terms: the GUI freezes and is unresponsive to either a reload via
ctrl-alt-backspace now does the system respond to the magic sysrq keys. 
I typically attempt the "Raising Elephants Is So Utterly Boring"
sequence without any results.  I inevitably have to resort to a hard-boot.

Let me start by laying out the system:
Distro:
Kubuntu Gutsy Gibon
uname -a:
Linux mycroft-lx 2.6.22-14-generic #1 SMP Tue Dec 18 08:02:57 UTC 2007
i686 GNU/Linux
lspci:
00:00.0 Host bridge: ATI Technologies Inc RS480 Host Bridge (rev 10)
00:02.0 PCI bridge: ATI Technologies Inc RS480 PCI-X Root Port
00:07.0 PCI bridge: ATI Technologies Inc RS480 PCI Bridge
00:12.0 SATA controller: ATI Technologies Inc SB600 Non-Raid-5 SATA
00:13.0 USB Controller: ATI Technologies Inc SB600 USB (OHCI0)
00:13.1 USB Controller: ATI Technologies Inc SB600 USB (OHCI1)
00:13.2 USB Controller: ATI Technologies Inc SB600 USB (OHCI2)
00:13.3 USB Controller: ATI Technologies Inc SB600 USB (OHCI3)
00:13.4 USB Controller: ATI Technologies Inc SB600 USB (OHCI4)
00:13.5 USB Controller: ATI Technologies Inc SB600 USB Controller (EHCI)
00:14.0 SMBus: ATI Technologies Inc SBx00 SMBus Controller (rev 13)
00:14.1 IDE interface: ATI Technologies Inc SB600 IDE
00:14.2 Audio device: ATI Technologies Inc SBx00 Azalia
00:14.3 ISA bridge: ATI Technologies Inc SB600 PCI to LPC Bridge
00:14.4 PCI bridge: ATI Technologies Inc SBx00 PCI to PCI Bridge
00:18.0 Host bridge: Advanced Micro Devices [AMD] K8 [Athlon64/Opteron]
HyperTransport Technology Configuration
00:18.1 Host bridge: Advanced Micro Devices [AMD] K8 [Athlon64/Opteron]
Address Map
00:18.2 Host bridge: Advanced Micro Devices [AMD] K8 [Athlon64/Opteron]
DRAM Controller
00:18.3 Host bridge: Advanced Micro Devices [AMD] K8 [Athlon64/Opteron]
Miscellaneous Control
02:00.0 VGA compatible controller: nVidia Corporation G70 [GeForce 7600
GS] (rev a1)
3f:00.0 Ethernet controller: Broadcom Corporation NetXtreme BCM5755
Gigabit Ethernet PCI Express (rev 02)

NOTE: As you can see from the hardware, it's running on an ATI chipset
with the exception of the video card which is a e-GeForce 7600 GS via
the PCI-E bus and the NIC which is integrated.

Desktop:
I use KDE (as it's kubuntu) with Compiz.

 - What I've checked already and what I've tested -
I've looked at the following files after each hang:
/var/log/syslog and syslog.0
/var/log/message and message.0
/var/log/kern.log and kern.log.0
/var/log/dmesg and dmesg.0

I've tried to identify any anomaly (as far as I can ascertain) in these
files around the time of the hang.  The only thing I've ever found that
stands out is a reference to my audio driver (snd-hda-intel).  In an
attempt to resolve whether or not it the audio driver causing the
problem I've removed the file snd-hda-intel.ko from
/lib/modules/2.6.22-14-generic/ubuntu/media/snd-hda-intel (I've kept a
copy) and rebooted.

I've also disabled Compiz (which is actually the first thing I did) and
run it without Compiz.

Bottom line: even with the sound driver removed and Compiz turned off
the system still periodically hangs.

I'm not sure where else I ought to be looking and would like some
suggestions for where I might turn next.

Cheers!

Mark