1.Let A and B be two semaphores initialized to 1, whether this following code ha

Question

1.Let A and B be two semaphores initialized to 1, whether this following code has problem, if so, which problem and explain your answer

                P0                             P1

              wait(A);                   wait(B);

wait(B);                   wait(A);

signal(A);                         signal(B);

signal(B);                            signal(A);

2.Philosophers spend their lives thinking and eating . These Philosophers don’t interact with their neighbors, occasionally try to pick up 2 chopsticks (one at a time) to eat from bowl and they need both to eat, then release both when done

In the case of 5 philosophers, Semaphore chopstick [5] initialized to 1

Does the following codes have problem? If so, which kind(s) problem(s)? How to deal with the problem(s)?

do {

        wait (chopstick[i] );

     wait (chopStick[ (i + 1) % 5] );

             // eat

     signal (chopstick[i] );

     signal (chopstick[ (i + 1) % 5] );

                 // think

} while (TRUE);

Explanation / Answer

Solution:

The first question is done as per Chegg guidelines, please repost others.

So we have this code

P0                             P1

              wait(A);                   wait(B);

wait(B);                   wait(A);

signal(A);                         signal(B);

signal(B);                            signal(A);

A and B are set to 1.

In the given code a deadlock is possible to occur, let me tell you how

A = 1, B = 1.

Now P1 executes wait(A); and preempts. Now A = 0

now P2 executes wait(B) and now B = 0

Now there is no way any of the processes can proceed further.

This is the problem with the above code.

I hope this helps if you find any problem. Please comment below. Don't forget to give a thumbs up if you liked it. :)

Related Questions

Navigate

• Browse (All)
• Browse 1
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.