critical section

Question

getting A) given D)

Comments

Initially P1 enters into while loop because lock is false and preempt the process execute process P2.

it also enters into while .

now two process can go into the CS ,so ME is not satisfied.

If one process is keep on entering into CS bounded waiting not satisfied.

Intially lock =false then two process enter no dead lock.

if lock=true means already one process in CS,there is no chance of block two process.

Hence all are wrong.

Answer 1

Yes, D should be Answer

S1: Consider the situation when a process P1 enters, looked at lock=0, going to make lock=ture, suddenly preempted. Other process P2 comes looked at lock, Oh.. it is still false, going to make lock=true.. success; go to Critical section. When P1 again came and start execution from where it has left i,e make lock=true (instead of checking lock, bcz already done). Enters Critical Section; - success - So, No mutual exclusion

S2: There is no strict rule of FIFO or something, So after leaving CS a process make lock=false, and after that same process may go to CS again and again, It is not compulsory that other want to go CS so i should wait. There may be starvation and hence no BW.

S3: No deadlock.

Comments

From S1 itself you can derive S3 is false. Since there is no mutual exclusion there will be no deadlock as M.E is a necessary condition for deadlock.