2.4.2-pre2(&3) loopback fs hang

[Colonel]

>mount -o loop=/dev/loop1 net.i /var/mnt/image/

ends up in an uninterruptable sleep state (system cannot umount /
during shutdown).

The test system is a 100MHz 486 Planar wall mount, same problem with
or without modules.  The proper fs support is present in the kernel,
while CONFIG_DEVFS_FS is not set.  The linux distribution base was a
fresh slackware-current, it meets all requirements mentioned in
linux/Documentation/Changes.  Everything else tested has worked fine
so far, the 2.2.18 kernel did not have this loopback problem.

How do I track this down?