umount hangs with initramfs as root

[Chuck Meade]

Busybox umount hangs when I try to reboot, while running on a root
fs which is an initramfs.  Reboot is configured on my system to
"umount -a -r", and the umount of the initramfs root is hanging.

I have searched the web for the solution, but most of the hits for
this problem are from people trying to switch from their initramfs to
their "real" root fs - thus they have done a switch_root, and they 
just need to take certain steps to correct their procedure to be able
to umount the initramfs.  I am *not* attempting to switch_root or
pivot_root, but rather to *reboot* from a system running with a root
that is an initramfs.  Reboot is umounting the initramfs, without having
switched to a different root.

Is this a known issue?  Is there a fix?  Has this been addressed before
(perhaps even in the latest "mount" work Rob has been doing)?

Thanks for whatever info you can provide,
Chuck