panic: APIC: Previous IPI is stuck

John Baldwin jhb at
Tue Sep 28 08:43:36 PDT 2004

On Monday 27 September 2004 05:55 pm, Brian Fundakowski Feldman wrote:
> On Mon, Sep 27, 2004 at 04:35:44PM -0400, John Baldwin wrote:
> > On Friday 24 September 2004 08:24 pm, Andy Farkas wrote:
> > > I have been having this problem for a few weeks now. Glad I'm not the
> > > only one. My box is a 4xPPro running 5.3-BETA5. It panics with either
> > > ULE or 4BSD.
> > >
> > > My theory is that a physical IPI gets lost somewhere and the kerenl
> > > spins waiting for it. But thats just a stab in the dark because nobody
> > > cares to explain why IPI's would be stuck.
> >
> > The panic has to do with a previous IPI not finished being sent from the
> > same CPU.  I've yet to determine why this happens.  You can try editing
> > sys/i386/i386/local_apic.c and turning on 'DETECT_DEADLOCK' (I think it
> > is just commented out) and seeing if that improves stability.  I also see
> > this on a 4xPIIXeon system I use for testing.
> Can KTR logging be leveraged to find the root cause(s) of these deadlocks,
> or is it just so wildly unpredictable that it would be of no use?

It might could be, but I think it would probably slow things down so much that 
they would go away.

John Baldwin <jhb at>  <><
"Power Users Use the Power to Serve"  =

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