Operating System Practice Test 2

1. Complex scheduling algorithms ____________

2. The program follows to use a shared binary semaphore T.

Process A  
int Y;            
A1: Y = X*2;      
A2: X = Y;        
signal(T);        

Process B
int Z;
B1: wait(T);
B2: Z = X+1;
X = Z;

T is set to 0 before either process begins execution and, as before, X is set to 5.
Now, how many different values of X are possible after both processes finish executing?

3. Consider the methods used by processes P1 and P2 for accessing their critical sections whenever needed, as given below. The initial values of shared boolean variables S1 and S2 are randomly assigned. (GATE 2010)

Method used by P1 :
while(S1==S2);
Critical section
S1 = S2;

Method used by P2 :
while(S1!=S2);
Critical section
S2 = not(S1);

Which of the following statements describes properties achieved?

4. A monitor is a type of ____________

5. Which one of the following is a visual ( mathematical ) way to determine the deadlock occurrence?

6. An SJF algorithm is simply a priority algorithm where the priority is ____________

7. For sharable resources, mutual exclusion ____________

8. What is a reusable resource?

9. Choose one of the disadvantages of the priority scheduling algorithm?

10. Consider a transaction T1 that committed prior to checkpoint. The <T1 commits> record appears in the log before the <checkpoint> record. Any modifications made by T1 must have been written to the stable storage either with the checkpoint or prior to it. Thus at recovery time ____________

11. For non sharable resources like a printer, mutual exclusion ____________

12. Which of the following conditions must be satisfied to solve the critical section problem?

13. Mutual exclusion implies that ____________

14. The following program consists of 3 concurrent processes and 3 binary semaphores. The semaphores are initialized as S0 = 1, S1 = 0, S2 = 0.

Process P0
while(true)
{
    wait(S0);
    print '0';
    release(S1);
    release(S2);
}

Process P1
wait(S1);
release(S0);

Process P2
wait(S2);
release(S0);

How many times will P0 print '0'?

15. Bounded waiting implies that there exists a bound on the number of times a process is allowed to enter its critical section ____________

16. A deadlock free solution to the dining philosophers problem ____________

17. The dining - philosophers problem will occur in case of ____________

18. What are Spinlocks?

19. Which is the process of invoking the wait operation?

20. All processes share a semaphore variable mutex, initialized to 1. Each process must execute wait(mutex) before entering the critical section and signal(mutex) afterward.
Suppose a process executes in the following manner.

signal(mutex);
.....
critical section
.....
wait(mutex);

In this situation :