variable hang when starting APs on Westmere processors

Mike Karels mike at
Tue May 3 00:23:53 UTC 2011

> We run 8.2 happily on L5640's which are also hex-core CPU's so the issue
> could be bios / MB related and not cpu.

> Its likely unrelated given your debug info but when we have seem long
> hangs on boot in the past its been related to keyboard stuff. You might
> want to try the following at the loader to see if it helps:-

> set hint.atkbdc.0.disabled=1
> set hint.atkbd.0.disabled=1
> boot

>     Regards
>     Steve

Thanks, Steve.  We have had problems with atkbd controller emulation
on these motherboards, and have a workaround for that in place equivalent
to the hints.  I'll double-check that this isn't our problem here.

You are quite right, this could easily be related to the BIOS or MB.


----- Original Message ----- 
From: "Mike Karels" <mike at>
To: <freebsd-amd64 at>
Cc: <mike_karels at>
Sent: Monday, May 02, 2011 10:13 PM
Subject: variable hang when starting APs on Westmere processors

> Looks like freebsd-smp is gone... not sure of the right target for this.
> I just picked up a problem from another developer at work who had the good
> fortune to have scheduled a vacation this week.  The short description is
> that the start_ap() routine sometimes hangs, from 10 minutes to 3 hours,
> while starting up CPUs.  This is with a much-modified system based on
> FreeBSD 7.2.  A stock 8.2 CD hangs at the same spot almost all the time,
> although the code in the two versions appears identical.
> More details:  This is amd64, using an Intel S5520HCR 2-socket motherboard
> with two XEON X5660 2.8GHz Westmere hex-core CPUs.  The problem happens
> somewhat less with two XEON E5620 Quad core 2.4GHz CPUs.  The hang seems
> to happen with higher numbered CPUs, so the hex-core with SMT has more
> chances to hit the problem.
> We added KTRs to the code, and found that the hang happens in the
> lapic_ipi_wait() call after de-asserting RESET.
> Of course, Linux doesn't exhibit the problem.
> Has anyone else seen a problem like this?  Any ideas how to fix it, or
> debug further?
> Please copy me on responses; I'm not subscribed to this list currently.
> Mike
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