Comment # 5 on bug 1202589 from Walter Haidinger

md config is as follows:

# linear array of two older disks used as emergency spare for md4 
md2 : active linear sdi2[0] sdh[1]
      15626694215 blocks super 1.2 0k rounding

# data VG: main data array (3,5" disks)
md4 : active raid6 md2[4](S) sdg1[6] sde1[7] sdf1[8] sdd1[5]
      31251688448 blocks super 1.2 level 6, 512k chunk, algorithm 2 [4/4]
[UUUU]
      bitmap: 2/8 pages [8KB], 1048576KB chunk

# /boot
md0 : active raid1 sdb1[3](W) sdc1[2] sda1[4]
      1959884 blocks super 1.0 [3/3] [UUU]

# ssd VG with /dev/ssd/root mounted (sda and sdc are ssd, sdb is a 2,5" disk)
md1 : active raid1 sdb2[2](W) sda2[4] sdc2[3]
      220069888 blocks super 1.2 [3/3] [UUU]

And yes, stopping md2 is present in the cycle. But md2 isn't part of DM.

However, noticed something else. Occasionally there's another log:
"block device autoloading is deprecated and will be removed."

A recent cycle:
...
md: md2 stopped.
Stopping MD /dev/md1 (9:1).
Could not stop MD /dev/md1: Device or resource busy
Not all MD devices stopped, 1 left.
Detaching DM devices.
Not all DM devices detached, 1 left.
Stopping MD devices.
Stopping MD /dev/md2 (9:2).
block device autoloading is deprecated and will be removed.
md: md2 stopped.
Stopping MD /dev/md1 (9:1).
Could not stop MD /dev/md1: Device or resource busy
Not all MD devices stopped, 1 left.
Detaching DM devices.
Not all DM devices detached, 1 left.
Stopping MD devices.
Stopping MD /dev/md2 (9:2).
md: md2 stopped.
Stopping MD /dev/md1 (9:1).
Could not stop MD /dev/md1: Device or resource busy
Not all MD devices stopped, 1 left.
Detaching DM devices.
Not all DM devices detached, 1 left.
Stopping MD devices.
Stopping MD /dev/md2 (9:2).
md: md2 stopped.
Stopping MD /dev/md1 (9:1).
...