Disc lock up on 8.0-STABLE

[Pete French]

> When you say "lock up" and "can't login" (in your original mail) - are 
> you sure this really is a lockup and not e.g. sshd dieing because of the 
> attacks? E.g. can you ping the machine, can you leave something like 
> "date >> /root/run.txt && vmstat 1 3 >> /root/run.txt" in crontab so you 
> track the moment it dies more closely?

Yes, I can ping the machine, and connect to the SSH port and
see the banner. On the console I can hit return and get a login prompt,
and then get a password prompt. Trying to login doesnt work
though - the symptoms are consistent with it not being able to
read from the discs, but not panicing or dying either. I can,
for example, connect to the mysql daemon, and see it trying to
execute queries, but never completing thhem.

I am currently running a kernel on that machine with DDB, KDB and WITNESS
in it. It has annoyingly refused to hang since I did that though - I
did have a hang with jst DDB and KDB, which I regret not investigating more.
At tghe time I though "gah, forgot witness", and so recompiled the kernel
expecting another lockup wthin a few hours.

I do think that the original "3am" thing is a red herring now - I have been
getting locks at other times of the daya. Also it is not a runaway fork, as
when I wa sin the debugger I did a 'ps' and there wasnt anything unusual
going on - i.e. a reasombale number of processes, but not excessive.

What are the best traces to do when I get a debugger again ? 'show locks'
and 'ps' I know, but I am never sure quite what else is useful.

cheers,

-pete.