I'm getting a lot of this at boottime:
udev still not settled. Waiting. udevadm settle - timeout of 0 seconds reached, the event queue contains: /sys/module/scsi_wait_scan (11707)
udev still not settled. Waiting. udevadm settle - timeout of 0 seconds reached, the event queue contains: /sys/module/scsi_wait_scan (11709)
udev still not settled. Waiting. udevadm settle - timeout of 0 seconds reached, the event queue contains: /sys/module/scsi_wait_scan (11711)
udev still not settled. Waiting. udevadm settle - timeout of 0 seconds reached, the event queue contains: /sys/module/scsi_wait_scan
It takes a few minutes to boot.
The machine is a Dell PRECISION T5600 with a PERC H310 RAID controller.