TEST SERIES

Question

 

I) CODE 1 guarantees Mutual Exclusion

II) CODE 2 guarantees Mutual Exclusion

III) CODE 2 leads to Deadlock

Which of the above statements are TRUE????

1.

I and II only

 

2. 

II and III only

 

3. 

I and III only

 

4.

All I,II and II

 

Comments

is th answer 4??

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@himgta

How code1 guarantees Mutual exclusion?

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@Shaik Masthan

while flag of other process is true thn it will block in the while loop...isn't it??

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given that flag of other process is false initially.

Hint:- preempt the process after checking 2^nd while loop.

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CORRECT OPTION 2ND

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@Deepanshu

i am also trying to say, only 1st statement is wrong.

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P1 is symmetric means ??

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actually in the code they have used flag[0], it should be replaced by flag[i]

What is symmetric means?

in place of i, you have to place 0 if you are P₀

in place of i, you have to place 1 if you are P₁

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@Shaik Masthan I AM JUST TELLING THE ANSWER FROM TEST SERIES  :)

I AM STILL CONFUSED ABOUT THIS MUTUAL EXCLUSION POINT

TELL ME WHERE AM I WRONG 

SO CODE 1

1ST STATEMENT------ flag[i] is false means means both processes p0 and p1 flag is false no one wants to enter critical section right now

2ND STATEMENT---------- While (true) means while condition is satisfied or true

3RD STATEMENT -------------------- While (flag[1]) is true means flag of 1st process is true . Up to then we are in while loop . when this condition false we go to next statement so this means flag[1] is false  and flag[0] can enter .

SO IT IS MUTUAL EXCLUSION MEANS PROCESS 0 ENTERS OONLY WHEN 1 IS FALSE

PLEASE HELP HOW 1 IS NOT MUTUALLY EXCLUSIVE

EDIT THIS COMMENT WHERE ANYTHING IS WRONG .THEN YOU WILL NOT HAVE TO WRITE WHOLE EXPLANATION AGAIN  :)

 

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SO CODE 1, starts with P₀

1ST STATEMENT------ flag[i] is false means means both processes p0 and p1 flag is false no one wants to enter critical section right now

2ND STATEMENT---------- While (true) means while condition is satisfied or true

3RD STATEMENT -------------------- While (flag[1]) is true means flag of 1st process is true . Up to then we are in while loop . when this condition false we go to next statement.

Preempt the process.===> P₀ is preempted ( but remember that flag[0]=false only)

starts with P₁

1ST STATEMENT------ flag[i] is false means means both processes p0 and p1 flag is false no one wants to enter critical section right now

2ND STATEMENT---------- While (true) means while condition is satisfied or true

3RD STATEMENT -------------------- While (flag[0]) is true means flag of P₀ process is true . Up to then we are in while loop . when this condition false we go to next statement. so this means flag[1] is true and entered in CS

∴ Now in Critical section P1 is present., Now Preempt the process.===> P₀ it will also can enter into CS

SO IT IS NOT SATISFIES the MUTUAL EXCLUSION

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@Shaik Masthan

Thanks for correcting me!

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I think no one is correct

1 and 2 both doesn't satisfy ME and 2 will not  go in deadlock

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@prince

Can you justify your statement s on code2 ?

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@shaikh bro

In second code flag[1] is always false no one is going to make it true ,so both p0 and P1 can enter into cs

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it is not, flag[0], it should be flag[i] in the both codes... it is a typing mistake only