[TAG] using smp kernel, get 100% cpu usage one one cpu without any real load on the system

[Ramon van Alteren]

Ben Okopnik wrote:
> On Mon, Oct 08, 2007 at 02:21:21PM -0400, jim ruxton wrote:
>   
>> Hi I'm on a P4 running an smp kernel ie.
>>
>> uname -a :
>>  
>> Linux jims-laptop 2.6.20-16-386 #2 Sun Sep 23 19:47:10 UTC 2007 i686
>> GNU/Linux
>>
>> For some reason occasionaly one of my cpu's runs away and starts showing
>> 100% cpu usage, however top only shows the program using the most cpu at
>> 7% or less. Where is that 93% going? This is driving me crazy. I have to
>> reboot the machine to get it back to normal. I've tried Fedora and
>> Kubuntu. Though Kubuntu appeared more stable it still happened. Played
>> around with changing max_cstate without success.I've just downgraded to
>> a 386 kernel to see if that helps. This isn't a real solution however.
>> Do you have any suggestions? I've asked around on forums and irc
>> channels without luck. Thanks.
>>     
>
> One of the things that might be worth trying is reducing everything to a
> minimum and seeing if it still happens. That is, try booting into single
> mode and shutting down any non-critical processes, then just letting the
> system "cook" for a little while. If it happens again, you've most
> likely narrowed it down to either a) the kernel or b) the hardware. For
> troubleshooting the former, check out the kernel compilation options (I
> seem to recall a developer/debugging option accessible via 'make
> config'.) For the latter, try a hairdryer aimed at the offending CPU. :)
>
>   
I've seen this behaviour before in combination with run-away acpi
processes (acpid and friends)
My own laptop (a dell D810 with a dual-core with Hyperthreading) shows
the same behaviour if I try to hot-(un)dock it from it's docking station

Ramon