What are mutex locks and how do they work?

What are mutex locks and how do they work?

Mutex locks, or mutual exclusions, are synchronization primitives used to manage access to shared resources in concurrent programming. They ensure that only one thread can access a resource at a time.

Why are mutex locks important in multi-threading?

They prevent race conditions, which can lead to inconsistent data and unpredictable behavior when multiple threads try to access shared resources simultaneously.

Can you give me an example of how to implement a mutex lock?

Sure! In C++, you can use the std::mutex class. Here's a simple example:

#include <iostream>
#include <thread>
#include <mutex>

std::mutex mtx;

void printThreadId(int id) {
    mtx.lock();  // Lock the mutex
    std::cout << "Thread ID: " << id << '\n';
    mtx.unlock();  // Unlock the mutex
}

int main() {
    std::thread threads[5];
    for (int i = 0; i < 5; ++i) {
        threads[i] = std::thread(printThreadId, i);
    }
    for (auto& th : threads) th.join();
    return 0;
}

This code creates multiple threads that print their IDs while ensuring that only one thread accesses the output at a time.

What happens if I forget to unlock a mutex?

If you forget to unlock a mutex, it can lead to a deadlock situation where other threads are blocked indefinitely, waiting for the mutex to be released. This can cause your program to hang.