12 Feb
2015
12 Feb
'15
4:23 a.m.
OK, I jiggled the memory board and the seqfault went away. Which is weird
because I had all the boards out of this one, thoroughly vacuumed the
backplane and all boards and deoxidized the edge connectors before
reassembling. So now the real box is behaving more like the simh and just
hanging, not panicing anymore. How can I find this startup() you mention?
On Wed, Feb 11, 2015 at 4:14 PM, Noel Chiappa <jnc(a)mercury.lcs.mit.edu>
wrote:
From: Jacob
Ritorto
I set simh to 11/34 and I managed to get actual
panics before (that I
didn't record)
Ah.
now I'm just getting hangs, mostly when
hitting ctrl-D to bring
system to
mutiuser.
The fact that it boots to the shell OK indicates things are mostly OK. I
wonder what it's trying to do, in going to multi-user, that's wedging the
system?
Same if I mount -a in single user and then try to
access /usr (works
for
a while, then hangs.).
Ah. That sounds very much like a 'lost' interrupt. The process is waiting
(inside the kernel) for the device to complete, and ..... crickets.
When hung, I can still get character echo to my
terminal
So the machine is still running OK (most echoing is done inside the TTY
interrupt handler).
but can't interrupt or background the
running command, etc.
Like I said, it's sleeping inside the kernel, and missed the wakeup event.
If you have another console logged in, it would be interesting to see if
that
one is frozen too. If not, we can use tools like 'ps', running on the
second
line, to look at the first process and see what it's waiting for.
Single user, the following hack:
sh < /dev/ttyX > /dev/ttyX &
can be used to start a shell on another tty line (since going full
multi-user
seems to wedge it).
Would it help if I traced memory and
single-stepped through the
(apparently) infinite loop?
No, because it's very likely not a loop! ;-)
here are some examples of crashes on the real
pdp11/34 (booting via
vtserver, then bringing in system from the MSCP disk), with the
original
2.9bsd-MSCP kernel (the one specifically built
for 11/23):
CONFIGURE SYSTEM:
ka6 = 2200
aps = 141572
pc = 50456 ps = 30250
__ovno = 7
trap type 11
panic: trap
That's a segmentation fault. Very odd trap to get! 2.9 uses overlays right?
Maybe there's a problem with how some overlay fits, or something? I don't
know
much about the overlay feature, never used it, sorry.
Most of the other data (PS address, PC, KDSA6 contents, etc) aren't much
use
without a dump.
and another: plain boring old hang at boot when
trying to size
devices.
Can't even echo characters this time.
If the init process hasn't got as far an opening the TTY, you might not get
character echoing.
If that randomly lost interrupt got lost very early on, you might could see
this sort of behaviour.
One thing I think is interesting is that
it's claiming 158720KW of
memory. Is that weird? ... Where's it getting that odd number?
Vanilla
2.9.1 on the real 11/34 boots with
Berkeley UNIX (Rev. 2.9.1) Sun Nov 20 14:55:50 PST 1983
mem = 135872
No idea where it's coming from, but remember Beowulf Schaeffer's advice to
Gregory Pelton in "Flatlander".
And now that I think about it, if the system thinks it has more memory
than it
actually does, that would definitely cause problems.
Probably you should put some printf()'s in startup() and see where it's
coming
from.
Noel
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