Comment 12 for bug 802626

AIUI udevcomplete_all will clean up any hanging vgchange -a y processes, but it won't solve the problem. udev is supposed to, in response to the lvs created by vgchange, call 55-dm again, and thereby create the /dev/{vg}/{lv} links (before calling dmsetup udevcomplete ${DM_COOKIE} to un-hang vgchange). Those links won't get created.

(I've tested this. In a case where /dev/schroots/kvm-1 did not get created and vgchange was hanging, I did dmsetup udevcomplete ${DM_COOKIE}" (using the cookie shown by ipcs -a). vgchange happily went away, /dev/schroots/kvm-1 did not show up.