I had left a /usr/src "make && make install" running last night,
with a current kernel. This morning it had completed, and I proceeded
to reboot to get the new daemons going. I did a "shutdown -r +1" while
in X, exited X cleanly, did a quick MH inc to get the cron mail, and
logged out before it shut down. Then I got:

syncing disks... panic: vinvalbuf: dirty bufs
Stopped at      _Debugger+0x4:    leave
db>

The stack trace showed: Debugger, panic, vinvalbuf, spec_close,
ffs_umount, doumount, vfs_unmountall, vfs_shutdown, boot, reboot,
syscall. I have most of the text of the trace if that would help,
and I got a dump (accidentally, actually, since I'm not that familiar
with the debugger) that I could look at if gdb would work with it.
Any ideas?

                                      Gary D. Duzan
                         Humble Practitioner of the Computer Arts