Chapter 3, Modularity, Objects, and State

Exercise 3.46

This is similar to earlier exercises.

Assume two processes P1 and P2 are trying to acquire same mutex object the-mutex using (the-mutex 'acquire)

Initially lets assume the the value in cell of the mutex is false.

Now in parallel execution both procedures can reach this line (begin (set-car! cell true) in proc test-and-set because the value of cell is false.

Now, again both of them sets it to true happily and believe it an exclusive access - Truth be told - they cant be more wrong :)