Recursive lock wait_cv

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

class RecursiveMutex {
public:
    void lock() {
        std::unique_lock<std::mutex> lock(m_mutex);
        if (m_owner == std::this_thread::get_id()) {
            // This thread already owns the lock, so increment the recursion count
            m_recursion_count++;
            return;
        }
        // This thread does not yet own the lock, so wait until it can acquire it
        m_cv.wait(lock, [this](){ return m_owner == std::thread::id{}; });
        m_owner = std::this_thread::get_id();
        m_recursion_count = 1;
    }

    void unlock() {
        std::unique_lock<std::mutex> lock(m_mutex);
        if (m_owner != std::this_thread::get_id()) {
            throw std::runtime_error("Thread does not own the lock");
        }
        m_recursion_count--;
        if (m_recursion_count == 0) {
            m_owner = std::thread::id{};
            m_cv.notify_one();
        }
    }

private:
    std::mutex m_mutex;
    std::condition_variable m_cv;
    std::thread::id m_owner{};
    int m_recursion_count = 0;
};