fsck required on boot for raids-1 hangs

I was trying to boot a raid-1 system with errors on the root partition.

bootup process, right after the "mdadm error exit" message said something like "need to fsck, file system will be writeable during,... bla"

However, fsck never starts. System hung and nothing happens. (may be waiting for udev or something) Only reset effective.

I had to boot from another partition and run fsck -f there.