Hang with heavy build on cgd and MP

[David Brownlee <abs%netbsd.org@localhost>]

I have a largish java app which hang my netbsd-5 amd64 X60s when
building on cgd. It normally happens on the second consecutive build,
using the native openjdk7.

I originally noticed in on cgd on dk, but removing
DKWEDGE_METHOD_BSDLABEL didn't affect matters. Moving the tree from
the cgd partition on to a normal one (on the same disk) avoids the
issue, as does using cpuctl to take one of the two cpu core offline.

It hangs hard - I can't drop into ddb. This is happening under sources
from a day or so ago, and from early January.

Does anyone have any thoughts?

Thanks