Re: System crash after "No irq handler for vector" linux 2.6.19

[Eric W. Biederman]

"Luigi Genoni" <luigi.genoni@xxxxxxxxxxx> writes:

> (e-mail resent because not delivered using my other e-mail account)
>
> Hi,
> this night a linux server 8 dual core CPU Optern 2600Mhz crashed just after
> giving this message
>
> Jan 22 04:48:28 frey kernel: do_IRQ: 1.98 No irq handler for vector

Ok.  This indicates that the hardware is doing something we didn't expect.
We don't know which irq the hardware was trying to deliver when it
sent vector 0x98 to cpu 1.

> I have no other logs, and I eventually lost the OOPS since I have no net
> console setled up.

If you had an oops it may have meant the above message was a secondary
symptom.  Groan.  If it stayed up long enough to give an OOPS then
there is a chance the above message appearing only once had nothing
to do with the actual crash.

How long had the system been up?

> As I said sistem is running linux 2.6.19 compiled with gcc 4.1.1 for AMD
> Opteron (attached see .config), no kernel preemption excepted the BKL
> preemption. glibc 2.4.
>
> System has 16 GB RAM and 8 dual core Opteron 2600Mhz.
>
> I am running irqbalance 0.55.
>
> any hints on what has happened?

Three guesses.

- A race triggered by irq migration (but I would expect more people to be yelling).
  The code path where that message comes from is new in 2.6.19 so it may not have
  had all of the bugs found yet :(
- A weird hardware or BIOS setup.
- A secondary symptom triggered by some other bug.

If this winds up being reproducible we should be able to track it down.
If not this may end up in the files of crap something bad happened that
we don't understand.

The one condition I know how to test for (if you are willing) is an
irq migration race.  Simply by triggering irq migration much more often,
and thus increasing our chances of hitting a problem.

Stopping irqbalance and running something like:
for irq in 0 24 28 29 44 45 60 68 ; do
	while :; do
		for mask in 1 2 4 8 10 20 40 80 100 200 400 800 1000 2000 4000 8000 ; do
        		echo mask > /proc/irq/$irq/smp_affinity
	                sleep 1
	        done
	done &
done

Should force every irq to migrate once a second, and removing the sleep 1
is even harsher, although we max at one irq migration by irq received.

If some variation of the above loop does not trigger the do_IRQ ??? No irq handler
for vector message chances are it isn't a race in irq migration.

If we can rule out the race scenario it will at least put us in the right direction
for guessing what went wrong with your box.

Eric
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