1. ADVANCED OPERATING SYSTEMS
PART A (10*2=20 marks)
1. Mention the functions of operating systems?
2. Why does the interrupt disable method to achieve mutual exclusion not work for multi-
processor systems?
3. State the purpose of control site in completely centralized deadlock detection?
4. How does Lamport’s algorithm guarantee mutual exclusion?
5. Sender-initiated algorithms cause system instability at high system loads. Predict
analytically at what system load the instability will occur. Assume probe limit is 5,
average service requirement of a task is 1 second, overhead incurred by a processor to
poll or to reply to a poll is 3 milliseconds.
6. Why is mapping function required in the central server algorithm?
7. Differentiate between forward error and backward error recovery?
8. Define global atomicity. Give an example.
9. List out the issues in pre-processor scheduling that causes performance degradation in
multi-processor systems?
10. Write the difference between tightly coupled systems and loosely coupled systems
with an example.
PART B-(5*16=80 MARKS)
11. (a) 1) Describe bankers algorithm for deadlock avoidance with supporting example?
(8)
2) Consider a computer system which has four identical units of a resource R.
There are three processes each with a maximum claim of two units of resource R.
Processes can request these resources in any way, that is, two in one shot or one
by one. The system always satisfies a request if enough resources are available. If
the process does not request any other kind of resource, show that the system
never deadlocks. (8)
OR
(b) Give a solution for the following synchronization problems using semaphores.
1) Producer-Consumer problem (8)
2) Readers-Writers problem (8)
12. (a) Discuss in detail about the communication models that provide communication
primitives. (16)
OR
(b) Consider the following scheme to reduce message traffic in distributed deadlock
detection:Transactions are assigned unique priorities, and an antagonistic conflict
occurs when a transaction waits for a data object that is locked by a lower priority
transaction. Deadlock detection is initiated only when an antagonistic conflict occurs.
When a writing transaction receives a probe that is initiated by a lower priority
transaction, the probe is discarded.

2. 1) Determine the number of messages exchange to detect a deadlock in the “best
case” (4)
2) Determine the number of messages exchange to detect a deadlock in the
“average case” (4)
3) Determine the number of messages exchange to detect a deadlock in the
“worst case” (4)
4) Determine the saving (in %) in the average number of messages exchange
under this message traffic reduction scheme as compared to when no such is
used. (4)
13. (a) 1) With a neat diagram explain the architecture and data access of a distributed
system. (8)
2) Predict the performance of the receiver initiated load sharing algorithm when
the entire system work load is generated at only a few nodes in the system instead of
equally at all nodes in the system. (8)
OR
(b) Describe about the distributed shared memory. Explain the algorithm that are
developed for implementing the DSM. (16)
14. (a) 1) Define live locks. What is the difference between a deadlock and live lock?(6)
2) Explain the asynchronous check pointing recovery method and give an
example where the recovery algorithm will need to execute for [N] iterations
where [N] is the number of processors in the system. (10)
OR
(b) Design a de-centralized two-phase commit protocol.
1) Where no site is designated to be a coordinator. (8)
2) Which uses only O ( √N )messages where N is the number of sites in the system.
(8)
15. (a) 1) Can the performance of a multi-processor system with two processors be worse
than the performance of a uni-processor (with an identical CPU)? Explain the answer
with an example. (8)
2) A task consists of several subtasks. If these communicate synchronously with
each other frequently which scheduling policy will suit for this scenario and why? (8)
OR
(b) Discuss in detail about the lightweight process and its different levels. Write its
advantages, disadvantages and performance of supporting lightweight process at these
levels. (16)