[issue647] rough-draft VKERNEL host-initiated shutdown patch

[Matthew Dillon]

:
:In any case,
:hoping to clean up / resubmit this weekend, more than likely with a
:second signal handler to take advantage of Matt's new reboot code.
:
:Thanks,
:
:- Chris

    Definitely!  Having a properly working shutdown signal would be good.
    In fact, it might be easiest to just set it up as a mailbox signal and
    monitor it in the clock interrupt, then create a kernel thread to initiate
    the actual shutdown when the signal is detected.  Or something like that.

    --

    I noticed another thing, which is when you run the vkernel from
    a shell script, and you interrupt it with ^\ + ^C (that sequence
    will enter ddb, then kill the vkernel), it currently causes the vkernel
    to do its shutdown/reboot thing, but also kills the shell script and
    disconnects the terminal so you wind up getting a shell prompt with the
    vkernel still running in the background.  Its very odd and annoying
    behavior.

    I think there is some sort of termios / tty session magic we have
    to do to make the tty interrupt signals only go to the vkernel,
    but I'm not sure what it is.

					-Matt
					Matthew Dillon 
					<dillon at backplane.com>