variable hang when starting APs on Westmere processors

[Steven Hartland]

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


----- Original Message ----- 
From: "Mike Karels" <mike at karels.net>
To: <freebsd-amd64 at freebsd.org>
Cc: <mike_karels at mcafee.com>
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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