zvol snapshot recursive rename hang

[Richard Kojedzinszky]

Dear ZFS devs,

I've attached a script, which on releng/9.2 causes a deadlock somewhere.

And what is strange to me that deadman does not cause a panic. It should, 
right?

Thanks in advance,
Kojedzinszky Richard
-------------- next part --------------
#!/bin/bash

fs="vol0/data"

zfs destroy -r "$fs/vol"
zfs create -s -V 1G -b 128k "$fs/vol"

(while : ; do
	s=1
	echo "Creating snapshot"
	zfs snapshot -r "$fs@$s"
	for n in 2 3 4 5 ; do
		echo "Renaming snapshot $s -> $n"
		zfs rename -r "$fs@$s" "$fs@$n"
		s=$n
	done
	echo "Destroying snapshot"
	zfs destroy -r "$fs@$s"
done) &
(while : ; do
	dd if=/dev/urandom of=/dev/zvol/$fs/vol bs=1M count=1
done)