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Date:      Wed, 28 Nov 2001 19:24:57 -0500 (EST)
From:      Andrew Gallatin <gallatin@cs.duke.edu>
To:        Paul Herman <pherman@frenchfries.net>
Cc:        FreeBSD Alpha <freebsd-alpha@FreeBSD.ORG>
Message-ID:  <15365.32857.392495.737510@grasshopper.cs.duke.edu>
In-Reply-To: <200111282233.fASMXUA01849@tick.sc.omation.com>
References:  <200111282233.fASMXUA01849@tick.sc.omation.com>

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Paul Herman writes:
 > Hi,
 > 
 > My 4.4-RELEASE (alpha) paniced 4 times in a row today and all at
 > the same place.  I don't know what to make of it, so I thought I'd
 > start here.
 > 
 > It happens when I do a lot of NFS traffic (like "pkg_add
 > /nfs/mount/package.tgz")  What is XentUna?  Is that a trap for
 > unaligned access?  If so, what does fxdr_unsigned() do, and why
 > would XentUna fail?  Or does it not try to correct it?  I do have
 > machdep.unaligned_fix=1 if that makes a difference.

For a more complete response..

XentUna is the unaligned access trap entry point.  Eg, where the
PALcode jumps to when there's an unaligned access.  All unaligned
accesses in kernel mode are fatal, regardless of machdep.unaligned_fix
settings.

Can you characterize your environment a little more?  What's the NFS
server running?  Are you running NFS over TCP or UDP? What mount size?
Is it any file or access pattern that causes this, or just special
ones?  Can you get a tcpdump of the traffic that causes the crash
(from the server side, obviously).

There's definately a bug in the code.  Perhaps we could work around it
by altering your environment.  At Duke, I had FreeBSD/alpha (4.0 ->
4.3) running NFSv3 over UDP against Tru64 4.0f, Solaris (2.5 -> 2.8),
and FreeBSD/i386 (4.0 -> 4.3) NFS servers.  I never saw this panic.

I hope this helps some..

Drew



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