On Thu, 28 Feb 2013 11:49:53 +0100 Hans-Peter Jansen [off-list ref] wrote:

This is what I asked for:

quoted

It really feels like a udev bug, but it is hard to be sure.
Could you edit /etc/init.d/boot.md and add
   echo BEFORE mdadm -IRs > /dev/kmsg
just before the call the "$mdadm_BIN -IRs",
   echo AFTER mdadm -IRs > /dev/kmsg
just after that call, and
   echo AFTER mdadm -Asc > /dev/mksg
just after the call to "$mdadm_BIN -A -s -c $mdadm_CONFIG"

And maybe put similar messages just before and after the  
    /sbin/udevadm settle ....
call.

If you can then reproduce the problem, the extra logging might tell us
something useful.

This is not at all the same thing:

I've enabled initrd (linuxrc=trace) and boot.md (#!/bin/sh -x) debugging, hence 
we should see the full story next time.

It might help, but I'm far from certain that it will be nearly as useful.

NeilBrown