Suppose process A and process B are sharing time on the same machine, a« d each needs the same non-shareable resource for short periods of time. (For example, each process may be printing a series of independent, short reports.) Each process may then repeatedly acquire the resource, release it, and later request it again. What is a drawback to controlling access to the resource in the following manner:

 

Begin by assigning a flag the value 0. If process A requests the resource and the flag is 0, grant the request. Otherwise, make process a wait. If process B requests the resource and the flag is 1, grant the request. Otherwise, make process B wait. Each time process a finishes with the resource, change the flag to 1. Each time process B finishes with the resource, change the flag to 0.