What are semaphore and mutex in programming?

Can you explain the difference between semaphore and mutex?

Sure! A mutex is a mutual exclusion object that allows only one thread to access a resource at a time, while a semaphore can allow multiple threads to access a resource, up to a specified limit.

When should I use a semaphore instead of a mutex?

You should use a semaphore when you need to control access to a resource that can be shared by multiple threads, like a pool of connections. Use a mutex when you need to ensure exclusive access to a single resource.

Can you give me a code example of using a semaphore?

Certainly! Here's a simple example in Python using the threading module:

import threading

semaphore = threading.Semaphore(2)  # Allow 2 threads to access the resource

def access_resource():
    with semaphore:
        print('Accessing resource...')
        # Simulate some work
        time.sleep(1)

threads = [threading.Thread(target=access_resource) for _ in range(5)]
for thread in threads:
    thread.start()
for thread in threads:
    thread.join()

What are some common pitfalls when using mutexes?

Common pitfalls include deadlocks, where two or more threads are waiting on each other to release a mutex, and priority inversion, where a lower-priority thread holds a mutex needed by a higher-priority thread.