Runaway cpu

[Anne Wilson]

On Thursday 09 November 2006 22:23, Rick Stevens wrote:
> On Thu, 2006-11-09 at 17:17 -0500, Lyvim Xaphir wrote:
> > On Thu, 2006-11-09 at 21:30 +0000, Anne Wilson wrote:
> > > I have 99-100% cpu usage, and top shows that the culprit is khubd.  I
> > > can't kill it, even as root.  I'm shutting down for the night now
> > > anyway so it's no big deal, but if it happens again I'd rather not be
> > > forced to reboot.
> > >
> > > What is khubd anyway?
> >
> > Khubd is a kernel thread which is part of the linux USB core.  It is
> > supposed to configure USB devices when they are plugged into a usb jack
> > and it also monitors the system's USB hub.]
>
> For truly gory details: http://www.linuxjournal.com/node/8093/print
>
> > > Any hints for killing it when it runs away?
> > >
> > > Anne
> >
> > If it's taking 100% there's something not right.  Start by making sure
> > there are no USB devices plugged into the system.
>
> This can be caused by a flaky connection or a low-power condition on
> the bus...the kernel gets flooded by plug/unplug event IRQs and khubd
> has to try to get rid of them all.  As Lyvim says, try unplugging ALL of
> the USB stuff (including any hubs), wait a bit and see if it calms down.
> If not, reboot and connect things one-at-a-time to see what triggers it.
>
I said earlier that the printer is attached to the back panel - but I was 
wrong.  I had forgotten that it is in fact a remote printer, on another box.  
What appears to have triggered the problem, then, is the *unplugging* of a 
usb device, the webcam.  I've plugged it and unplugged it several times over 
the last few days, but this is the only time the runaway condition has 
occurred, so perhaps it is one of those things where a combination of factors 
come into play.  If so, there's not much chance of tying it down, I think.

FWIW, I've just tried to reproduce the problem, but everything is fine.

Anne