diskless sparc locks up under memory pressure

[Valery Ushakov <uwe%stderr.spb.ru@localhost>]

I've upgraded my Krups (64MB RAM, diskless) to 9.99.75 as of Nov 6 and
the machine is locking up at boot time in rc.d/fccache.  If I disable
fccache in rc.conf it boots but then eventually locks up when
makemandb is run.  The machine doesn't respond to pings, etc, but can
enter ddb.  In all cases the ddb stacktrace goes through:

...
uvm_fault_internal
mem_access_fault4m
memfault_sun4m
copyout

with the top part of the stack trace varying.

-uwe