Page 152 - DCAP103_Principle of operating system

Unit 4: Process Management-III

Notes
flag[i] = in-cs;
j = 0;
while ((j < n) && (j == i || flag[j] != in_cs))
j++;
if ((j >= n) && (turn ++ i || flag[turn) == idle)) break;
}
turn = i;
critical section

j — (turn + 1) % n:
while (flag [j] == idle)

j = (j+1) % n;
turn = j;
flag[i] = idle;

remainder section
}while (1)
The structure of process Pi in Eisenberg and McGuire’s algorithm.
Prove that the algorithm satisfies all three requirements for the critical section problem.
5. Demonstrate that monitors, conditional critical regions, and semaphore are all equivalent,
insofar as the same types of synchronization problems can be implemented with them.
6. Write a bounded-buffer monitor in which the buffers (portions) are embedded within the
monitor itself.
7. List three examples of deadlocks that are not related to a computer-system environment.
8. Is it possible to have a deadlock involving only one process? Explain your answer.
9. Suppose that a system is in an unsafe state. Show that it is possible for the processes to
complete their execution without entering a deadlock state.
10. Consider a system consisting of four resources of the same type that are shared by three
processes, each of which needs at most two resources. Show that the system is deadlock-
free.
11. Can a system detect that some of its processes are starving? If you answer “yes,” explain
how it can. If you answer “no,” explain how the system can deal with the starvation
problem.

12. Consider the following snapshot of a system:
Allocation Max Available

A B C A B C A B C
P 0 0012 1520
P 1 1000 1750
P 2 1354 2356
P 3 0632 0652
P 4 0014 0656

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