To show that the progress requirement is not met, we need only show a trace of one possible schedule for which progress is not met.

In the trace that follows, a schedule of switches between Thread 0 and Thread 1 is constructed which illustrates that progress is not met.

The line numbers indicate that the thread is about to execute that line in its code; that is, that line will be the next instruction executed.

Context switches between threads could occur after any instruction. So we are free to switch at any point in our attempt to find a switching schedule for which progress is not met.