Question

need answer for this question please explain in detail. Appreciate it! thank you so much!

Consider the following three threads and four semaphores: /Initialize x / x = 1; /Initialize semaphores/ s1 = s2 = s3 = s4 = void threadl () void thread2) void thread3 () while (x != 5400) while (x != 5400) while (x != 5400) x=x*2; x=x*3; x=x*5; exit (0)i exit (0) exit (0) Provide initial values for the four semaphores and add PO, VO semaphore operations (using the four semsphores) in the code for dhread , 2 c that the processuaraneed lo terinate

Answer 1

I am taking semaphore values as below

      S₁ = 1 , S₂ = 0 , S₃ = 0 , S₄ = 1

with this intial conditions we are making only thread 1 to execute 1st

so we are taking S₁ = 1 for thread 1 and S₂ = 0 , S₃ = 0 for threads 2 and 3.

we are making S4 common for all threads if it is 1 then only they can access x.

Now after thread1 execution it will up S2 so that thread1 can run after thread1

and after thread2 execution it will up S3 so that thread3 can run after thread2.

void thread1() {

    while (x != 5400){

          P(S1);

          P(S4);

           x = x * 2;

         V(S4);

         V(S1);

         V(S2);

    }

}

void thread2() {

    while (x != 5400){

          P(S2);

          P(S4);

           x = x * 2;

         V(S4);

         V(S2);

         V(S3);

    }

}

void thread3() {

    while (x != 5400){

          P(S3);

          P(S4);

           x = x * 5;

         V(S4);

         V(S3);

    }

}