[Fedora-livecd-list] unmount failure kaboom

[Warren Togami]

chroot-creator does:
         creator.mount()
         # --bind mount a directory like /opt/ltsp/i386 upon instroot
         creator.install()
         creator.configure()
         creator.unmount()
         # Umount all the bind mounts then unmount instroot
         ...
         creator.cleanup()
         # Recursively delete the temp directory

Between unmount() and cleanup() in other LiveCD workflows is a time 
consuming step where an image is created.  Unfortunately, in my case 
there is no time consuming step between unmount() and cleanup() which 
sometimes leads to this failure:

   Installing: xorg-x11-drv-spaceorb        ##################### [308/308]
umount: /var/tmp/imgcreate-C_SsuB/install_root: device is busy

Thankfully none of the bind mounts from the host were still mounted 
during the recursive delete.  But it did blow away the payload of the 
chroot-creator run.

Is there any safe way to detect that processes within the chroot are 
truly done before trusting that the unmount was complete?

Warren Togami
wtogami(a)redhat.com