Bug#426692: One CPU slow down with kernel 2.6.18-4-686 (etch2)

[Unas Mérnöki Iroda <unas@unas.hu>]

Package: linux-image
Version: 2.6.18-4-686 (etch2)

I have a dual xeon system with 2 xeon 5050 dual core processors with HyperTreading.
Sometimes one of the physical cores slow down and never speed up again. There is
a lot of "system" and "user" load (~80-90%) and a lot of "soft irq" (~20-30%) on
that CPU (on 2 virtual CPU because of HyperTreading). When a process running on
the slow CPU it finished approximately 10 times slower than on one of the other CPUs.

The slow CPU speed up only when I reboot the system.

I am using Debian GNU/Linux 4.0, kernel 2.6.18-4-686 (etch2).
Used packages: apache2, bind9, postfix, courier, mysql, proftpd, etc...
I am not using x-window.