UNIX continues!

[jbray%bbn-unix at sri-unix.UUCP]

From:  James Bray <jbray at bbn-unix>

I have never worked on a VAX, but would venture a guess as to what's happening.
I  assume that the HALT/CONTINUE sequence on a VAX leaves the PC unchanged when
resuming; it would be interesting to know what happens regarding interrupts, as
it  sounds  like  your  machine  is hanging on a tight loop at interrupt level,
probably waiting for something to happen that isn't happening, and when you  do
the  H/C,  it either allows other interrupts to break in, thus breaking you out
of the loop, or causes whatever was being awaited to actually occur, or  appear
to.  I  would  suggest  that  once  you have halted, you record such context as
processor status and PC, and then adb your kernel and see where it is  sitting.
You may well see it in a disk-driver; another amusing possibilility would be if
the system machine managed to idle itself at interrupt level...
-- Jim Bray