This problem was reported against 2.4 by Eddie.Williams@SteelEye.com

There's a problem in the sd spinup code in that if the unit returns NOT
READY, we begin to spin it up, but thereafter if it returns anything
other than NOT READY or success, the while loop in the spinup code will
be executed *without* the 1s delay that's in the NOT READY case.

The problem was seen with a real device: Compaq multi-path storage
arrays return NOT READY to probes down inactive paths, but when the
start unit is sent to activate the path, they can then respond back with
error conditions.

The fix is to terminate the while loop for any unexpected return.