[techtalk] tty lockup

[James A. Sutherland]

On Fri, 9 Mar 2001, David Merrill wrote:

> On Fri, Mar 09, 2001 at 02:32:51PM +0000, James A. Sutherland wrote:
> > On Fri, 9 Mar 2001, David Merrill wrote:
> >
> > > Hi,
> > >
> > > I was running red-carpet and it ate up ALL my available ram. I killed
> > > it. Now I can get no responsiveness at the console. I am logged in
> > > from another machine right now so I can send this mail.
> > >
> > > I suspect that the oom condition caused Linux to kill (somewhat)
> > > random processes, and one of them was my tty (mgetty?) Am I on track
> > > or way off base?
> > >
> > > Any tips on how to fix this?
> >
> > A tty isn't a process, so it can't have killed that. It could have killed
> > the mingetty running there, but init would have respawned it straight
> > away.
> >
> > The OOM killer in Linux is a fairly recent addition (partly my concept);
> > until it was added, random processes would have died off; with it, the
> > biggest memory hog would be killed (red-carpet in this case).
>
> Yes, you're right. I've been following, loosely, the vm and oom
> conversations in l-k (or in kernel traffic, actually) but only for the
> 2.4 series.

You're still on 2.2, I take it? I've been running 2.4 without any problems
for some months now.

> > Can you switch from one VC (virtual console) to another? Did you have the
> > "Magic Alt+SysRq" support included in the kernel? If so, can you do an
> > SAK? (Alt+SysRq+K - kills all processes on the current VC, which should
> > give you a clean login screen.)
>
> I cannot. I don't have the magic sysrq enabled, not being a kernel
> hacker and not expecting to need it. That'll larn me.

Alt+SysRq can be very useful in tight corners like this... I had Adobe
Acrobat Reader blow up on me recently, taking out X in the process. A
quick SAK later, and a few minutes of disk thrashing, and everything was
back to normal!

> Hmmm. I just had the thought that I might try resetting the runlevel.
> Is that reasonable, or madness?

Could try that, yes... Can you switch VC's, though?


James.