$P=\left\{P_1, P_2, P_3, P_4\right\}$ consists of all active processes in an operating system.

$R=\left\{R_1, R_2, R_3, R_4\right\}$ consists of single instances of distinct types of resources in the system.

The resource allocation graph has the following assignment and claim edges.

Assignment edges: $R_1 \rightarrow P_1, R_2 \rightarrow P_2, R_3 \rightarrow P_3, R_4 \rightarrow P_4$ (the assignment edge $R_1 \rightarrow P_1$ means resource $R_1$ is assigned to process $P_1$, and so on for others) Claim edges: $P_1 \rightarrow R_2, P_2 \rightarrow R_3, P_3 \rightarrow R_1, P_2 \rightarrow R_4, P_4 \rightarrow R_2$ (the claim edge $P_1 \rightarrow R_2$ means process $P_1$ is waiting for resource $R_2$, and so on for others) Which of the following statement(s) is/are CORRECT?

Consider a multi-threaded program with two threads T1 and T2. The threads share two semaphores: s1 (initialized to 1) and s2 (initialized to 0). The threads also share a global variable x (initialized to 0). The threads execute the code shown below.

// code of T1

wait(s1);

x = x + 1;

print(x);

wait(s2);

signal(s1);

// code of T2

wait(s1);

x = x + 1;

print(x);

signal(s2);

signal(s1);

Which of the following outcomes is/are possible when threads T1 and T2 execute concurrently?

Consider the following pseudocode, where S is a semaphore intialized to 5 in line#2 an counter is a shared variable intialized to 0 in line#1. Assume that the increment operation in line#7 is not atomic.

1. int counter = 0;

2. Semaphore S = init(5);

3. void parop(void)

4. {

5. wait (S);

6. wait (S);

7. counter++;

8. signal (S);

9. signal (S);

10. }

If five threads execute the function parop concurrently, which of the following program behavior (s) is/are possible?