Question

Consider the following variation in Peterson’s solution for 2 processes.

shared char want[2] = {0,0};
shared int turn = 0;
1. P_i()
2.  { while (1) {
3.      turn = |1-i|;
4.      want[i] = 1;
5.      while (want [j] && turn!=i);
6.      critical_section();
7.      want[i] = 0;
8.      remainder_section();
9.   }
10. }

Which of the following statements is/are true?
i) Mutual exclusion guaranteed
ii)Progress is achieved

1.   Both i and ii
2.   Only i
3.   Only ii
4.   None

for ME,I got the solution but couldn't understand about progress.Please explain.

Comments

THanks a lot ..:-)

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I think in this qs there is merely a variation in Peterson's solution. They flipped the turn value and also flipped turn check condition @while.

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without specifying in the question what is i and what is j how did u people come to these many conslusions ??

i think the question is incomplete ..????

Answer 1

Progress: The process which is not interested to enter in Critical Section should not stop the other processes to enter CS

If any process doesn't want to go to CS, then it will make want = false, i,e. any other process can go to CS, bcz for other process want[j] will become false and while loop will break.

Comments

@anwer_zaki ,acc to me also progress is satisfied but answer given is voilated.hence,i was just checking.

can you think of any situation in which progress dis satisfies??