Bounded Waiting

Question

how this solution does not satisfy bounded waiting?

// initially turn = 0
while (turn != 0);
turn = 1
CS
turn = 0

Comments

well bounded waiting should be satisfied..its working like peterson problem

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Can you please cite the origin of the question? Where did you find this question?

I think, bounded waiting will be satisfied. If we assume that P1 is busy waiting for P0 to leave, it will next move to the CS.

Answer 1

bounded waiting says that no process should wait for infinite amount of time to enter into CS.....

that is synchronization technique should implement proper mechanism so that all the process has equal share to enter into CS...

now consider your code....

say P1 and p2 are willing to enter into CS....p1 enters but as soon as it leaves CS....it can again occupy the CS...that means there is no compulsion on p1 that after gaining CS once it should not again grab CS...if its able to take CS....it indicate that P1 may take CS always...

so here bounded wait doesn't gurantee...

Answer 2

if P$_{0}$ enter in critical section then it means that initial value of turn is 0 if P$_{1}$ is waiting to enter in critical section it will enter only when P$_{0}$ is exit from CS let it enter in CS(only after completion of $P_{0}$) first time after execution from CS if it want to enter again then it will re-enter  again and again so there is no any strict alternation  between $P_{0}$ and $P_{1}$ that's why it does not satisfy bounded waiting.

Comments

According to me bounded waiting will be satisfy

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@Prince why we even consider the case of context switch? I mean is it always advised to think in terms of context switch ?

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Actually in these type of questions

We have to see that what can be done wrong and we have to see each possible case if anything goes wrong then we have to consider that case

Like in this example if a process read turn =0 after reading turn =0

Definitely there can be a case when context switch can be there and another process can also read turn =0

Answer 3

• If we take turn=1 then then while condition become true and both of the process never enter into critical section And both will wait for infinite time  . So bounded wating is not satisfy when turn=1.

• If we  take turn =0 then both of the process can enter into critical section and no posiblites of infinite waiting so when turn =0 then bounded waiting is satisfy.

Comments

@abhishekmehta why you have taken turn=1 when qsn itself mention that initally turn=0

 alwys turn would be set to 0 after coming out of CS  i dnn think any infinite waiting could occur.Both can set turn=1 but only after executing while statement..so mutual exclusion wont be satisfied in that case

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Yes in this question turn=0 . But i am also explain if turn=1 .

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@abhishekmehta if turn =1 than question wont have any meaning.....:(