Imagine Alice acquires the lock. Before she releases it, both Bob and Cathy ask for it. So it goes to Cathy when it's released. Before Cathy releases it, Dav

Imagine Alice acquires the lock. Before she releases it, both Bob and Cathy ask for it. So it goes to Cathy when it's released. Before Cathy releases it, David requests it. If the lock goes to David (and then possibly Emma, Fred, and Gary, and so on forever) before Bob finally gets to continue executing, then the lock is not fair.