#include <iostream>

#include <list>

#include <mutex>

#include <thread>

std::list<int> my_list;

std::mutex m1, m2;

void get_size() {

m1.lock();

int size = my_list.size();

m1.unlock();

std::cout << "size of the list is : " << size << std::endl;

}

void add_to_list__mutex(int const &x) {

m1.lock();

my_list.push_front(x);

m1.unlock();

}

void add_to_list__lock_guard(int const &x) {

std::lock_guard<std::mutex> lock(m1);

my_list.push_front(x);

}

void add_to_list__scoped_lock(int const &x) {

std::scoped_lock<std::mutex, std::mutex> lock(m1, m2);

my_list.push_front(x);

}

int main() {

std::thread thread_1;

std::thread thread_2;

// access is guaranteed to be mutually exclusive

thread_1 = std::thread(add_to_list__mutex, 4);

thread_2 = std::thread(get_size);

thread_1.join();

thread_2.join();

// RAII style - lock guard

thread_1 = std::thread(add_to_list__lock_guard, 4);

thread_2 = std::thread(get_size);

thread_1.join();

thread_2.join();

// RAII style - lock guard

thread_1 = std::thread(add_to_list__scoped_lock, 4);

thread_2 = std::thread(get_size);

thread_1.join();

thread_2.join();

}