How can I trace ACPI events?

[Martin Aspeli <optilude@gmx.net>]

Hello,

I'm having trouble with ACPI on my Centrino notebook; if ACPI is disabled, 
a lot of my PCI devices (e.g. onboard sound) don't get any IRQ. If ACPI is 
enabled, the system boots fine, but about a minute after startup, for no 
obvious reason keventd ("events/0", PID 3) starts chewing 99.9% CPU and 
the fan starts spinning at maximum. This is with 2.6.0-test7, although 
I've had the same problem in all kernels I've tried on this box (from 
2.4.22-ac through from 2.6.0-test5 to -test7). Chris Wright suggested 
runaway ACPI events could cause events/0 to chew CPU, which seems 
consistent with what I'm seeing here.

If I am to diagnose it further, though, I'll have to figure out what ACPI 
events (if any) are causing the massive spikes in CPU usage. How can I 
trace this? I've had acpid running, but the log in /var/log/acpid only 
shows simple messages (started service, registered 1 rule). Nothing 
particularly interesting from dmesg or TTY 12, either.

CC'd replies would be appreciated.

Thanks,
Martin