Diskless PowerMac G4 hangs on reboot/poweroff

["John D. Baker" <jdbaker%mylinuxisp.com@localhost>]

I rarely get time to work with my various PowerMacs, but it's Spring
Break and I finally have some time.

I have a G4 PowerMac w/AGP graphics and 100Mb ethernet (I think that's
a "sawtooth" machine).  I netboot it and run it diskless.

Odd problem is that when I attempt to reboot or power off the machine
(shutdown -r or reboot ; shutdown -p or poweroff) it doesn't actually
do it.  I get:

  Shutdown NOW!
  shutdown: [pid xxxxx]

and that's it.  wscons remains active as I can switch virtual terminals,
but the machine is otherwise completely unresponsive--and it never goes
ahead and reboots or powers off.

Possibly related is that under heavy NFS operation (attempting to build
larger packages out of pkgsrc) the machine will hang and be completely
unresponsive, again except for wscons although that's probably a side
effect of the NFS going off in the weeds.  It never complains that the
server isn't responding, though--at least that I can see.

Unfortunately, due the sporadic nature of my experience with any of
these machines, it's hard to say when this problem (the reboot/poweroff
hangs) started.  It was probably in the early 5.99.2x days that it
didn't hang like this.  The NFS-activity hangs have been there ever
since I started playing with this machine, but became much worse in
the 5.99.3x series of kernels.  Haven't tried building anything with
5.99.48 yet as I just updated to it yesterday (14 March 2011).

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