"vnlru_proc: vnode recycler stopped working!" when doing a make buildkernel

[Jan Martin Mathiassen <reaper@xxxxxxxxxxx>]

I thought this was just a problem with the oct 16 copy I had, since I 
knew that was when the VFS layer was in severe flux, but I've reproduced 
it several times afterwards with an dec 5 copy as well.

The following appears to semi-reliably trigger the abovementioned error 
message:

make buildworld/quickworld
make buildkernel KERNCONF=DOOM
make installkernel KERNCONF=DOOM
make installworld

It appears to most commonly happen during buildkernel, but I'm not 
entirely sure.

The message in the subject pops up regularly, everything related to disk 
seems to grind to a halt, and I'm unable to shut down the box in a 
normal fashion. This is on a playbox, so if  you're unable to reproduce 
this, I'll be happy to assist in trying to find the bug, given good 
enough instructions for how to proceed.