Analysis of the correctness and efficiency of mutex usage

Conduct a review of the provided code: identify potential issues, suggest improvements, and evaluate the correctness of mutex usage. Explain how the operator< works in a multithreaded environment.

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

struct Data {
    explicit Data(size_t value)
        : m_value(value) {}

    friend bool operator<(Data& lhs, Data& rhs);

private:
    size_t m_value = 0u;
    size_t m_compare_counter = 0u;
    mutable std::mutex m_mutex;
};

bool operator<(Data& lhs, Data& rhs) {
    std::lock_guard<std::mutex> lhs_lock(lhs.m_mutex);
    std::lock_guard<std::mutex> rhs_lock(rhs.m_mutex);

    ++lhs.m_compare_counter;
    ++rhs.m_compare_counter;

    return lhs.m_value < rhs.m_value;
}

Data data_1(10u);
Data data_2(20u);

void compare_1() {
    for (size_t i = 0u; i < 100u; ++i) {
        const bool result = data_1 < data_2;
    }
}

void compare_2() {
    for (size_t i = 0u; i < 100u; ++i) {
        const bool result = data_2 < data_1;
    }
}

int main(int argc, char** argv) {
    std::thread thread_1(compare_1);
    std::thread thread_2(compare_2);

    if (thread_1.joinable()) {
        thread_1.join();
    }

    if (thread_2.joinable()) {
        thread_2.join();
    }

    return EXIT_SUCCESS;
}