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Date:      Fri, 18 Feb 2000 03:47:38 -0500
From:      "David E. Cross" <crossd@cs.rpi.edu>
To:        Matthew Dillon <dillon@apollo.backplane.com>
Cc:        "David E. Cross" <crossd@cs.rpi.edu>, freebsd-hackers@FreeBSD.ORG, crossd@cs.rpi.edu
Subject:   Re: stuck NFS procs (LONG) 
Message-ID:  <200002180847.DAA15592@cs.rpi.edu>
In-Reply-To: Message from Matthew Dillon <dillon@apollo.backplane.com>  of "Fri, 18 Feb 2000 00:39:13 PST." <200002180839.AAA75699@apollo.backplane.com> 

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>     Ah!... ok, it is an NFS bug.  I've been trying to track this down
>     for a while ever since you reported the 3.4 lockup bug.  This is probably
>     related to a similar problem. 
> 
>     There is a bug somewhere related to NFS locking up while doing a
>     pagein from the executable image.   It can occur when the binary
>     is ripped out from under the client but it also can apparently occur
>     if the program takes a signal during a pagein on a valid binary
>     that hasn't been ripped out.
> 
>     If you still have this machine up, can you idle it and do a tcpdump
>     looking for NFS packets for a few minutes?  I'd like to know if it is
>     doing an infinite retry of the page it got stuck on.  Knowing what
>     it is trying to do and why it isn't aborting on error with a segfault
>     is the key.
> 
>     After that, is there any chance you can panic this machine and get
>     a kernel dump?

I can come close to idle... It should be realtively easy to identify the
NFS packets in question, they will be stale FH replies from the server
(as I pulled the backing store out from under it hoping that the retry would
trigger a SEGV).  Panic-ing it will be a bit trickier... the kernel is
compiled with DDB *BUT* the only console is a serial console and I forgot to
enable the ENABLE_DB_ON_SERIAL_BREAK thing-y.  I am sure with gdb -k
/kernel.debug /dev/mem and your expertise we could trip a panic somehow.

For now, let me get you that NFS packetlog...

--
David Cross                               | email: crossd@cs.rpi.edu 
Acting Lab Director                       | NYSLP: FREEBSD
Systems Administrator/Research Programmer | Web: http://www.cs.rpi.edu/~crossd 
Rensselaer Polytechnic Institute,         | Ph: 518.276.2860            
Department of Computer Science            | Fax: 518.276.4033
I speak only for myself.                  | WinNT:Linux::Linux:FreeBSD


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