Subject: Re: i386 1.4Q hangs nonrandomly?
To: None <>
From: maximum entropy <>
List: current-users
Date: 01/27/2000 15:11:49
>From: Jason Thorpe <>
>Date: Thu, 27 Jan 2000 08:58:24 -0800
>On Thu, 27 Jan 2000 04:44:32 -0500 (EST) 
> maximum entropy <> wrote:
> > When it hung I was running: [lots of stuff]
>do you have DDB enabled in your kernel?  If so, dropping into DDB
>while running X is going to give the appearance of a "hang".

Yes, I do.

>I'm thinking what happened there is that you ran out of kernel virtual
>address space, and went boom.
>softdeps is known to be pretty evil with memory management (Frank and
>I have some ideas on how to fix it, but there's a decent bit of work
>involved).  These other applications that you ran could certainly put
>a strain on your KVA space, as well...

OK, that sounds like a perfectly reasonable explanation.  Especially
in combination with the "livelock" softdeps bug being discussed in
another thread, all this is starting to make a little bit more sense

I'll remove DDB from the kernel, and see if I get a crashdump next
time instead of a lockup.

By the way, does "options XSERVER_DDB" have any effect on how the
system behaves during a panic with X running?  Or does it only enable
the F12 keystroke?  I'd rather not enable that option, because 1) F12 is
mighty close to backspace, and I don't feel like educating my wife
about DDB, and 2) I already learned the hard way from the pmax port,
that a single-key entry to DDB doesn't mix well with a house full of
cats.  But if it will help get more information about these hangs, I
could enable it at least for a few days.