Comment 7 for bug 485619

This happens to me as well.
I believe it started to appear after some update for 9.04; after upgrade to 9.10 it happens much more often (lake every 2 days).
I do not see anything suspicious in logs (actually in most cases there is nothing in logs at all for sometime before it happens) or in /proc/interrupts.

Ireally don't know where to look. The only thing that helps is restart.

One more thing about restarts: when ksoftirqd/0 was starting to eat my CPU in 9.04 I couldn't reboot - it was just black screen after I press reboot. Now laptop reboots normally. So it seems that there is at least some progress with this bug :)