killing all subprocess childrens

[Astan Chee]

Hi,
I have a piece of code that looks like this:

import subprocess
retcode = subprocess.call(["java","test","string"])
print "Exited with retcode " + str(retcode)

What I'm trying to do (and wondering if its possible) is to make sure 
that any children (and any descendants) of this process is killed when 
the main java process is killed (or dies).
How do I do this in windows, linux and OSX?
Thanks
Astan