Synchronization

Consider the following proposed solution for the critical section problem. There are $n$ processes: $P_0 \ldots P_{n-1}$. In the code, function pmax returns an integer not smaller than any of its arguments. For all $i$, t[i] is initialized to zero. Code for $P_i$:

do {
     c[i]=1; t[i] = pmax(t[0],...,t[n-1])+1; c[i]=0;
     for every j ≠ i in {0,...,n-1} {
          while (c[j]);
          while (t[j] != 0 && t[j]<=t[i]);
     }
     Critical Section;
     t[i]=0;
     Remainder Section;
} while (true);

Which one of the following is TRUE about the above solution?

Consider the following two-process synchronization solution.

Process 0                          Process 1
---------                          ---------
Entry: loop while (turn == 1);     Entry: loop while (turn == 0);
       (critical section)                 (critical section)
Exit:  turn = 1;                   Exit:  turn = 0;

The shared variable turn is initialized to zero. Which one of the following is TRUE?

Consider a non-negative counting semaphore S. The operation P(S) decrements S, and V(S) increments S. During an execution, 20 P(S) operations and 12 V(S) operations are issued in some order. The largest initial value of S for which at least one P(S) operation will remain blocked is ________.