Comment # 15 on bug 1202589 from Walter Haidinger

Removed md2 but now the cycle shows md4 and the infinite loop still persists:

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/md4 (9:4).
md: md4 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/md4 (9:4).
md: md4 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.
...

The break set as mentioned in dracut-shutdown.service(8) wasn't hit but that's
pretty clear if systemd never relinquished control back to initramfs.

How do I enable that udev tracing during shutdown?