I have this issue as well on my laptop.
2.6.32-34-generic #38-Ubuntu x86_64 Lucid Lynx (Ubuntu 10.04) Core 2 Duo P9700 @ 2.8 GHz
It is currently occurring on CPU/1 with ksoftirq/1
It also happened with Ubuntu 9.10 but I don't remember it happening with 9.04, but that was CPU/0 and ksoftirq/0
I thought powertop might give me a clue as to what is going on, but ksoftirq/1 was only causing about 1.1% of wake-ups.
I have this issue as well on my laptop.
2.6.32-34-generic #38-Ubuntu x86_64
Lucid Lynx (Ubuntu 10.04)
Core 2 Duo P9700 @ 2.8 GHz
It is currently occurring on CPU/1 with ksoftirq/1
It also happened with Ubuntu 9.10 but I don't remember it happening with 9.04, but that was CPU/0 and ksoftirq/0
I thought powertop might give me a clue as to what is going on, but ksoftirq/1 was only causing about 1.1% of wake-ups.