udev seems to require a resynchronization before starting an X session; otherwise, no input would be available! Well, it could happen...
[ -d ${SV_RUNDIR}/udev ] || dmsetup_opts="${dmsetup_opts} --noudevsync"
[ -d ${SV_RUNDIR}/udev ] || lvm_opts="--noudevsync"
There is a workaround for this... just wait udev to be ready.
IMPORTANT NOTE: udev need a system logger to be able to start processing device events. Otherwise, it will simply refuse to do anything. Secondly, kernel modules should loaded after udev initialisation; or else, udev would silently ignore old devices events.