Bug#489608: mdadm: similar kernel call traces

[Neil Brown]

This bug is a kernel bug rather than an mdadm bug.

It is almost certainly the bug fixed by 
  commit 9744197c3d7b329590c2be33ad7b17409bd798fe
which went into 2.6.27.

Nothing is actually going wrong.  It is just an annoying message.
If it bothers you, run the command
   echo 0 > /proc/sys/kernel/hung_task_timeout_secs
as the message suggests.

NeilBrown