beta6/7 machine freeze

Max Laier max at
Mon Oct 11 08:09:29 PDT 2004

On Monday 11 October 2004 16:25, Volker wrote:
> Hi folks!
> Back from a one week vacation, I immediately updated my machine to BETA
> 7. Before I left, my machine had panics serveral times a day. Since BETA
> 6 the panics are gone but the machine locked up a few times (experienced
> two days before I left for a week). The machine freeze has been mostly
> while hanging up or shortly after a ppp (userland) connection has been
> hang up.
> Now I've updated to BETA 7 and the machine seem to lock up faster. The
> machine freezes most times while having an established ppp connection to
> the public internet. The machine is acting as a router, dial-up client,
> proxy, mailserver, webserver etc. etc.

Guess at large, are you using any IPFW uid/gid/jail rules or PF user/group 
rules? If so, you must deactivate debug.mpsafenet (=0) in the loader. This is 
something you can try in any case.

> When the machine locks up, there's no console or network response from
> the machine. The only way out is the reset switch.

You might want to build a custom kernel with WITNESS turned on and KDB, DDB 
built in. That way you will get warnings for lock order reversals, that can 
be the source of a hard lockup.

> One of my guesses has been that either i4b or userland ppp is causing
> the machine freeze. To figure out if that might be the case, I've set up
> a 2nd machine (releng_4) acting as a dial-up client (i4b/ppp) and
> router. The 2nd machine is now being used as a default route for the
> server machine.
> Since using that test setup the server machine didn't had a lockup. So
> my guess might be probably right to have a problem somewhere at i4b or
> user-ppp in releng_5.
> How does one debug a dead machine? Is there any way to get a backtrace
> or call the debugger while the machine has been frozen?
> Thanks,
> Volker

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