From mboxrd@z Thu Jan  1 00:00:00 1970
Message-ID: <435CF3D7.60004@lanl.gov>
Date: Mon, 24 Oct 2005 08:46:47 -0600
From: Ronald G Minnich <rminnich@lanl.gov>
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To: Fans of the OS Plan 9 from Bell Labs <9fans@cse.psu.edu>
Subject: Re: [9fans] xcpu fix for Plan9.c
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kokamoto@hera.eonet.ne.jp wrote:

> 1) why I got 131072 instead of 0 or 1?
>     Am I on the right way?

you are. I've had to go to this stilly numbering scheme to handle some 
LInux issues. It's a dentry cache thing, I can find the email and 
describe the problem if you wish. As nice as the dentry cache in Linux 
is, it is perilous when you venture outside its 'modus operandi'.

> 2) why the /mnt/cpu/131072/exec file accepts cp command
>     only once?

this is intentional. Consider the open of the clone file as a 'session'. 
In the original xcpu, as written by Vic Zandy, you could do all kinds of 
execs for a single session:
cp /bin/date exec
echo exec > ctl
cp /bin/whoami exec
echo exec > ctl

I initially copied this style for this implementation of xcpu.

There are lots of problems here, and it turned out to be simpler to just 
allow one and only one exec per session. Note that the child you start 
can also exec lots of things:
cp /bin/sh exec
echo exec > ctl

Please look at xsh.c -- it is what I am hoping people will actually use. 
The interface presented by the server is very low level -- by intent -- 
and xsh is something like what I think people will use.

Andrey starts here tomorrow,so we will be getting his help on this too :-)

Thanks so much for trying this out, and for getting your comments out to 
the list.

ron