ZFS: ZFS command can block the whole ZFS subsystem!

For some security reasons, I dumped via "dd" a large file onto a 3TB
disk. The systems is 11.0-CURRENT #1 r259667: Fri Dec 20 22:43:56 CET
2013 amd64. Filesystem in question is a single ZFS pool.

Issuing the command

"rm dumpfile.txt"

and then hitting Ctrl-Z to bring the rm command into background via
fg" (I use FreeBSD's csh in that console) locks up the entire command
and even worse - it seems to wind up the pool in question for being
exported!

I expect to get the command into the background as every other UNIX
command does when sending Ctrl-Z in the console. Obviously, ZFS
related stuff in FreeBSD doesn't comply. 

The file has been removed from the pool but the console is still stuck
with "^Z fg" (as I typed this in). Process list tells me:

top
17790 root             1  20    0  8228K  1788K STOP   10   0:05
0.00% rm

for the particular "rm" command issued.

Now, having the file deleted, I'd like to export the pool for further
maintainance, but that doesn't work with

zpool export -f poolname

This command is now also stuck blocking the terminal and the pool from
further actions.

This is painful. Last time I faced the problem, I had to reboot prior
to take any action regarding any pool in the system, since one single
ZFS command could obviously block the whole subsystem (I tried to
export and import).

What is up here?