4. (10 points) Solve the critical section problem using the atomic decrement instruction. Its definition is: int Dec(int &x): { x = x return x; } 1; This instruction executes atomically. Note also that x is a reference parameter. You are to provide the entry and exit() routines, as in the Test-and-Set example in class. CS solution with Test-and-Set Initially, s == false; entry 0 { bool spin; spin = TestAndSet(s); while (spin) spin = TestAnd Set(s); }" exit() { s = false; }