I am also experiencing this bug. My system is configured thus:
/dev/sd{a,b,c,d}{1,2} are partitions for devices
/dev/md1{0,1} are the MD devices for the boot and root, respectively
/dev/md10p1 is the PV for the VG vgboot
/dev/md11p1 is the PV for the VG vg0
/dev/vgboot/boot is an ext4 filesystem mounted at /boot
/dev/vg0/root is an ext4 filesystem mounted at /
In this configuration, the system fails to boot; it drops to an
initramfs prompt. If I run "lvm vgchange -a y" and hit Ctrl+D, the
system boots. This same system using ext4 directly over /dev/md10p1
booted successfully.
I'm pretty confident that the problem is the use of LVM over MD partitions. I agree that this is a problem in the mdadm boot script, which should ensure that the partitions are settled and available before allowing the system to continue booting. I suppose the only question is the appropriate policy for the mdadm boot script. Should it wait for all partitions before booting? Should it always do so or should that be a configuration option? I'd think that the most sensible default would be to wait for MD partitions to settle, since any MD with partitions being assembled at boot time is probably, y'know, important. :)