What are some examples of livelocks in programming?

What are some examples of livelocks in programming?

Livelocks occur when two or more processes continuously change states in response to each other without making progress. A classic example is two threads trying to acquire two locks in a different order, leading to a situation where they keep releasing and trying to acquire the locks but never succeed.

Can you give me a specific code example?

Sure! Here's a simple example in Python:

import threading
import time

lock1 = threading.Lock()
lock2 = threading.Lock()

def thread1():
    while True:
        with lock1:
            print('Thread 1 acquired lock1')
            time.sleep(0.1)
            with lock2:
                print('Thread 1 acquired lock2')
                break

def thread2():
    while True:
        with lock2:
            print('Thread 2 acquired lock2')
            time.sleep(0.1)
            with lock1:
                print('Thread 2 acquired lock1')
                break

threading.Thread(target=thread1).start()
threading.Thread(target=thread2).start()

In this example, both threads keep trying to acquire the locks in a way that leads to a livelock.

How can we prevent livelocks?

To prevent livelocks, you can implement strategies like using a timeout for lock acquisition, introducing randomness in the order of lock requests, or using a more sophisticated locking mechanism like a semaphore.