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I am running 32bit Ubuntu 10.04. A lot of the times ksoftirqd/0 or ksoftirqd/1 start using up 100% CPU for no apparent reason, and I am forced to reboot my laptop.

Incidentally this also happens when I maximize my (youtube) videos on Chrome and Fireox, but once I un-maximize the videos the CPU usage goes down to the original levels.

Any ideas what it going on?

--- Addendum ---

dmesg produces a ~2000 line output. I searched for 'error' and 'warning' in the output, and here are the relevant lines (along with some headers):

[ 0.000000] Initializing cgroup subsys cpuset

[ 0.000000] Initializing cgroup subsys cpu

[ 0.000000] Linux version 2.6.32-21-generic (buildd@yellow) (gcc version 4.4.3 (Ubuntu 4.4.3-4ubuntu5) ) #32-Ubuntu SMP Fri Apr 16 08:09:38 UTC 2010 (Ubuntu 2.6.32-21.32-generic 2.6.32.11+drm33.2)

[ 0.000000] Command line: BOOT_IMAGE=/boot/vmlinuz-2.6.32-21-generic root=UUID=157dcfda-acd6-4d1b-a6a8-ff9ccff61906 ro quiet splash

[ 0.000000] KERNEL supported cpus:

[ 0.000000] Intel GenuineIntel

[ 0.000000] AMD AuthenticAMD

[ 0.000000] Centaur CentaurHauls

[ 0.000000] BIOS-provided physical RAM map:

[ 24.775546] EXT3-fs warning: mounting fs with errors, running e2fsck is recommended

[44920.210518] ata1: SError: { PHYRdyChg CommWake 10B8B Dispar LinkSeq TrStaTrns }

[44920.210531] res 40/00:00:f0:4b:7f/00:00:18:00:00/40 Emask 0x10 (ATA bus error)

[58673.134623] chrome[20101]: segfault at 7f38bc4ad000 ip 00007f38be769ecc sp 00007fff24616850 error 4 in libpepflashplayer.so[7f38bdc08000+e55000]

[ 24.775546] EXT3-fs warning: mounting fs with errors, running e2fsck is recommended

[44920.210531] res 40/00:00:f0:4b:7f/00:00:18:00:00/40 Emask 0x10 (ATA bus error)

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Any ideas on this please? I have looked around a lot and haven't found anything useful for my situation. –  andy Nov 11 '12 at 17:01

1 Answer 1

ksoftirqds are kernel threads that run when the machine is under heavy soft-interrupt load. You should have one ksoftirq for each CPU.

The soft interrupts are normally serviced on return from a hard interrupt. It is possible that the soft interrupts can be triggered faster than they can be serviced. If a soft interrupt is triggered again while the soft interrupt is being handled then the ksoftirq daemon handles the soft interrupts in a kernel thread. If this happens a lot you will see a heavy soft interrupt load on the ksoftirqd threads.

100% CPU utilisation in a ksoftirqds and the need to reboot sounds like some hardware is saturating the machine with an interrupt storm. Does the kernel produce any errors or warnings? (Use dmesg to see what it is reporting).

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Just updated the question with output from dmesg. –  andy Nov 13 '12 at 3:27

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