--- a/shutdown	2012-08-06 11:49:31.167007331 +0200
+++ b/shutdown	2012-08-06 11:47:53.021777130 +0200
@@ -5,6 +5,10 @@
 stop_device() {
     local devtype= devname=
 
+    # Disable udev checking, should prevent hanging cryptsetup (FS#30995).
+    # Does this make lvm vgchange option '--noudevsync' unneeed?
+    local DM_UDEV_DISABLE_CHECKING=1
+
     # the device must still be active
     [ -e "/sys/class/block/$1" ] || return 1