In this paper, we study the problem of scheduling hard real-time periodic t
ask sets on a single processor with the rate monotonic scheduler. We are co
ncerned with the feasibility test given by Liu and Layland, based on the le
ast upper bound of the utilization factor. We show that the result is incom
plete and that the argument is incorrect. We complete and correct the resul
t. (C) 2000 Elsevier Science B.V. All rights reserved.