In this paper, we address the problem of production systems having two characteristics. First, the manufacturing times can be chosen between given bounds. Such a production system is said to have controllable processing times. Second, an operation must start as soon as the previous operation on the same part (if any) is completed. A production system having this characteristic is said to be no-wait. Several on-line schedules are considered to minimize the makespan in flow shop and job shop situations. We prove that in the worst case, the makespan provided by these schedules is m times longer than the optimal one (for different flow shops and job shops), m being the number of machines. We give several related results on competitive ratio.