What are some examples of mutex usage in programming?

What are some examples of mutex usage in programming?

Mutexes, or mutual exclusions, are used to prevent concurrent access to shared resources. For example, in a multi-threaded application, a mutex can be used to ensure that only one thread can access a critical section of code at a time.

Can you give me a specific code example?

Sure! Here's a simple example in C++:

#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, using a mutex to ensure that the output is not mixed.

What happens if I forget to unlock the mutex?

If you forget to unlock the mutex, it can lead to a deadlock situation where other threads are unable to acquire the lock and are stuck waiting indefinitely. This can cause your program to hang.

Are there alternatives to using mutexes?

Yes, alternatives include using read-write locks, semaphores, or lock-free programming techniques, depending on the specific use case.