Freeze when running freebsd-update

[Robert Simmons]

On Tue, Jun 26, 2012 at 8:54 PM, Dieter BSD <dieterbsd at engineer.com> wrote:
> Robert writes:
>> 3) the box is responsive to hitting enter at the console (it produces
>> another login: prompt)
>
> Getty is in memory and can run.
>
>> 5) if I try to login to the console, it lets me enter a username then
>> locks up totally, it does not present me with a password: prompt.
>
> Login(1) is not in memory, and the kernel cannot read it from disk
> for some reason.
>
> I can get this symptom by writing a large file to a disk on a
> controller that FreeBSD doesn't support NCQ on. I assume there
> is a logjam in the buffer cache. Something trivial like reading
> login in from disk that would normally happen in well under a
> second can take many minutes.
>
> Perhaps geli is causing a similar logjam? Does it hang forever or
> is it just obscenely slow? If it truely hangs forever it is
> probably something else. Is there disk activity after it hangs?
> Can you try it without geli? systat -vmstat might provide a clue.

I've done some more testing with forkbomb and if I bump the memory up
to 512M I just get an error message on the console about the user
exceeding maxproc and approaching the limit on PV entries.  At that
point I'm able to Ctrl-C and stop forkbomb: no freeze.

I have a number of these instances, and I will reinstall one geli-free
and see what happens.  I will also reproduce the initial conditions
and leave it for the night to see if it comes out of it.

After a certain point there is no disk activity, and the uptime
counter in the corner of top eventially freezes too, so I don't think
it will come out of this, but we'll see.