unexpected IRQ trap at vector

[Andy Green]

Lonni J Friedman wrote:
> I just performed a fresh FC5-x86 installation on a Toshiba Tecra M3
> notebook.  All was good until I updated to the latest kernel.  Now i'm
> seeing this error in dmesg about 10 times/second, non-stop:
> unexpected IRQ trap at vector 12
> 
> Anyone have any ideas on what is going on here?  I tried booting with
> both noapic and acpi=off, and neither made any difference.

Basically a device on IRQ 12 is spamming you with interrupts, Linux 
believes that is an "Illegal vector":

         /*
          * 'what should we do if we get a hw irq event on an illegal 
vector'.
          * each architecture has to answer this themself.
          */

For i386 the answer is to print that dmesg message.

What is an "illegal vector"?  I guess one that does not have a driver 
ready to service the interrupts.

Normally hardware devices don't start issuing interrupts until they are 
recognized and asked to do so by a driver.

What does

cat /proc/interrupts

say?  What devices are on your box that you are not using under Linux? 
How about a PS/2-style mouse-like device or somesuch?  Anything in 
/var/log/messages at boot-time about devices not being recognized properly?

-Andy
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