diagnostic assertion "anon->an_lock == amap->am_lock"

[dieter roelants <dieter.NetBSD%pandora.be@localhost>]

On an amd64 kernel with DIAGNOSTIC and LOCK_DEBUG enabled, the
following assertion got triggered while building packages:
"anon->an_lock == amap->am_lock" in sys/uvm/uvm_fault.c line 1228

My kernel dates from yesterday evening, including Mindaugas' fix to
uvm_page.c, but not all xen commits (but this isn't a xen system).

I can leave the machine in ddb for a few days but someone will need to
tell me what to type to get useful information from it... (but friday
and saturday CEST I will be offline).

kind regards
dieter