What is a Deadlock situation in Java? What are the minimum requirements for a Deadlock situation in a program in Java? How can we prevent a Deadlock in Java?

What is a Deadlock situation in Java?

A Deadlock is a situation in which two or more threads are waiting on each other to release a resource. Each thread is waiting for a resource that is held by the other waiting thread. At times there is a circular wait when more than two threads are waiting on each other’s resources.

What are the minimum requirements for a Deadlock situation in a program in Java?

For a deadlock to occur following are the minimum requirements:

1. Mutual exclusion: There has to be a resource that can be accessed by only one thread at any point of time.

2. Resource holding: One thread locks one resource and holds it, and at the same time it tries to acquire lock on another mutually exclusive resource.

3. No preemption: There is no pre-emption mechanism by which resource held by a thread can be freed after a specific period of time.

4. Circular wait: There can be a scenario in which two or more threads lock one resource each and they wait for each other’s resource to get free.

This causes circular wait among threads for same set of resources.

How can we prevent a Deadlock in Java?

To prevent a Deadlock from occurring at least one requirement for a deadlock has to be removed:

1. Mutual exclusion: We can use optimistic locking to prevent mutual exclusion among resources.

2. Resource holding: A thread has to release all its exclusive locks if it does not succeed in acquiring all exclusive locks for resources required.

3. No preemption: We can use timeout period for an exclusive lock to get free after a given amount of time.

4. Circular wait: We can check and ensure that circular wait does not occur, when all exclusive locks have been acquired by all the threads in the same sequence.

Comments

Defination of the essential properties of operating systems

Define the essential properties of the following types of operating sys-tems: Batch Interactive Time sharing Real time Network Parallel Distributed Clustered Handheld ANSWERS: a. Batch processing:- Jobs with similar needs are batched together and run through the computer as a group by an operator or automatic job sequencer. Performance is increased by attempting to keep CPU and I/O devices busy at all times through buffering, off-line operation, spooling, and multi-programming. Batch is good for executing large jobs that need little interaction; it can be submitted and picked up later. b. Interactive System:- This system is composed of many short transactions where the results of the next transaction may be unpredictable. Response time needs to be short (seconds) since the user submits and waits for the result. c. Time sharing:- This systems uses CPU scheduling and multipro-gramming to provide economical interactive use of a system. The CPU switches rapidl

What is a Fair lock in multithreading?

Photo by João Jesus from Pexels In Java, there is a class ReentrantLock that is used for implementing Fair lock. This class accepts optional parameter fairness. When fairness is set to true, the RenentrantLock will give access to the longest waiting thread. The most popular use of Fair lock is in avoiding thread starvation. Since longest waiting threads are always given priority in case of contention, no thread can starve. The downside of Fair lock is the low throughput of the program. Since low priority or slow threads are getting locks multiple times, it leads to slower execution of a program. The only exception to a Fair lock is tryLock() method of ReentrantLock. This method does not honor the value of the fairness parameter.

How do clustered systems differ from multiprocessor systems? What is required for two machines belonging to a cluster to cooperate to provide a highly available service?

How do clustered systems differ from multiprocessor systems? What is required for two machines belonging to a cluster to cooperate to provide a highly available service? Answer: Clustered systems are typically constructed by combining multiple computers into a single system to perform a computational task distributed across the cluster. Multiprocessor systems on the other hand could be a single physical entity comprising of multiple CPUs. A clustered system is less tightly coupled than a multiprocessor system. Clustered systems communicate using messages, while processors in a multiprocessor system could communicate using shared memory. In order for two machines to provide a highly available service, the state on the two machines should be replicated and should be consistently updated. When one of the machines fails, the other could then take‐over the functionality of the failed machine. Some computer systems do not provide a privileged mode of operation in hardware. Is it possible t

CODING PUSH

Search This Blog