detaching usb device without unmounting it

[Alexander Best]

since the usb2 stack allows one to detach a mounted usb device without the
kernel panic'ing i'd like to know which steps are necessary to be taken after
detaching a device? because i tried the following:

1. attach device
2. mount device
3. detach device

when i tried to unmount the device i got the follwing error message:

g_vfs_done():label/usb[WRITE(offset=19456, length=4096)]error = 6

and the console got locked up (ctr+c didn't work). so i tried to reboot using
ctrl+alt+del. however after the message: "All buffers synced" there was no
reboot. so i had to do a hard reset. however after the reset freebsd fsck'ed
my harddrives. so they didn't unmount properly.

should i have used `umount -f`? or just plug the device back in again? or
isn't it possible to unmount a device that has already been detached?

i'm running r195476 btw.

alex