Weird interaction between chroot jail and shell-mode

[Sean McAfee <eefacm@gmail.com>]

This is probably the most perplexing Emacs issue I've ever
encountered...

I've been trying to build the debian "apt" package in a shell-mode bash
shell, inside of which I've entered a chroot jail.  The build process
(initiated with the command "dpkg-buildpackage") would reach a point
where it executes the command:

  po4a --previous --no-backups po4a.conf

...whereupon the command hangs, consuming 100% of the CPU until I kill
it.

A co-worker had no trouble building the package in an ordinary terminal
window on his own machine, and, unable to find any reason for my issue,
suggested that Emacs might be to blame.  I was dubious, to say the
least, but to humor him I repeated the process in my own terminal
window.  To my astonishment, the package didn't get hung up on the po4a
command, but ran to completion successfully.

I tried building the package inside a terminal emulator window inside
Emacs.  It built.  I tried again using eshell, which I ordinarily never
use.  The build got hung up at the same point as originally, with the
additional delightfulness that I couldn't interrupt the hung command
with C-c C-c.  Finally, I tried building the package in a shell-mode
shell again, but without entering the chroot jail.  It built.  WTF.

I tried dumping my environment variables in the jail in shell-mode and
term-mode and comparing them.  The only differences were in OLDPWD,
LSCOLORS, and TERM ("dumb" in shell-mode, "vt100" in term-mode).  I
repeated the build in shell-mode after setting TERM to vt100, but it
still got hung.

I am utterly perplexed.  Does anyone have any possible explanation for
the behavior I'm seeing?  How in the world can any command produce
different behavior when run inside vs. outside of a chroot jail, but
only when run from a bash shell which itself is running inside a
shell-mode buffer?