build.sh soft-halts machine on 4.99.49 kernel, with 4.99.48 userland.

[Marc Tooley <netbsdMLpostNO%spam.quake.ca@localhost>]

uname -a: 

NetBSD shog 4.99.49 NetBSD 4.99.49 (shog) #0: Thu Jan 10 21:01:10 PST 
2008  root@shog:/v/src-current-build/sys/arch/i386/compile/shog i386

The machine itself is:

. Pentium D 930 (obviously running in 32-bit mode.)
. Intel D945GNT motherboard
. 2.5 GB RAM (already run through memtest86+)

Kenel is an i386 debug kernel built from sources rsync'd from I believe 
January 9. Userland was from 4.99.48, which I believe was sync'd and 
built about two weeks earlier.

The symptoms are that the machine will happily churn along doing its 
thing with a build.sh -j 4 until.. suddenly it'll stop. Interactive 
bash commands seem to function, until I try to create a new process or 
a run a non-builtin bash command. Then that session will simply never 
return.

I can hit enter and the keyboard is responsive. Breaking into the kernel 
debugger gives me a list of processes that are sitting in vm_map.

I have no backtraces, as there is no panic. It's just sitting there, 
responsive to keyboard input and *already running* network login 
sessions; but nothing new gets done.

I was trying to watch vmstat -i but I lost my screen session.

Hints appreciated.

-Marc