Re: [9fans] 'wall' messages

[Jim Choate <ravage@einstein.ssz.com>]

On Wed, 8 Oct 2003, Bruce Ellis wrote:

>  drawterm sets up and maintains a namespace
> which is exported to the cpu server just as a p9 terminal does.

Exactly! So if a write to the structures on the cpu would work locally they
will work with drawterm, since the processes are running on the cpu server
side and that is the box that wants to send the shutdown warning. The fact
that I'm accessing those resources via drawterm is really moot.

With reference to the box the drawterm itself is running on, that's a
function of that OS and isn't an issue with drawterm or the cpu server.
When that box goes down drawterm will be killed in some manner and as a
result the connection to the cpu server is closed and those resources are
released and there isn't anything else to send a message to about the cpu
shutdown (assuming there aren't other users on of course) because that
resource pool has already been released.

And I challenge the 'just as a P9 terminal does', I am assuming by
'terminal' you mean I/O server. The difference is that the I/O server can
run processes locally whereas drawterm can't. So there is clearly a
difference in the way namespaces can interact, and the limits on which
the two approaches can interact with that data stream. One example is that
a I/O server could export its local kfs to a process on that cpu server, but
drawterm can't export its local filesystem. Near as I can tell if you want
that you need to use native tools to export that to the cpu server and
then you can import it into a namespace.

The final observation about drawterm is that it's one way, a user can use
drawterm on a box to modify the cpu server but the cpu server can't modify
the drawterm host outside of the drawterm resources. If you could run a
process on the cpu server and use that to 'tunnel' through drawterm and,
for example, reset the drawterm host that would clearly be a bug in
drawterm.


 -- --

God exists because mathematics is consistent, and the Devil exist because we
can't prove it.
                          Andre Weil, in H. Eves, Mathematical Circles Adieu

      ravage@ssz.com                            jchoate@open-forge.com
      www.ssz.com                               www.open-forge.com