Class ThreadPool

src/util/threadpool.h:47–194

 *   queued ones are completed.
 */
class ThreadPool
{
private:
    std::string m_name;
    Mutex m_mutex;
    std::queue<std::packaged_task<void()>> m_work_queue GUARDED_BY(m_mutex);
    std::condition_variable m_cv;
    // Note: m_interrupt must be guarded by m_mutex, and cannot be replaced by an unguarded atomic bool.
    // This ensures threads blocked on m_cv reliably observe the change and proceed correctly without missing signals.
    // Ref: https://en.cppreference.com/w/cpp/thread/condition_variable
    bool m_interrupt GUARDED_BY(m_mutex){false};
    std::vector<std::thread> m_workers GUARDED_BY(m_mutex);

    void WorkerThread() EXCLUSIVE_LOCKS_REQUIRED(!m_mutex)
    {
        WAIT_LOCK(m_mutex, wait_lock);
        for (;;) {
            std::packaged_task<void()> task;
            {
                // Wait only if needed; avoid sleeping when a new task was submitted while we were processing another one.
                if (!m_interrupt && m_work_queue.empty()) {
                    // Block until the pool is interrupted or a task is available.
                    m_cv.wait(wait_lock, [&]() EXCLUSIVE_LOCKS_REQUIRED(m_mutex) { return m_interrupt || !m_work_queue.empty(); });
                }

                // If stopped and no work left, exit worker
                if (m_interrupt && m_work_queue.empty()) {
                    return;
                }

                task = std::move(m_work_queue.front());
                m_work_queue.pop();
            }

            {
                // Execute the task without the lock
                REVERSE_LOCK(wait_lock, m_mutex);
                task();
            }
        }
    }

public:
    explicit ThreadPool(const std::string& name) : m_name(name) {}

    ~ThreadPool()
    {
        Stop(); // In case it hasn't been stopped.
    }

    /**
     * @brief Start worker threads.
     *
     * Creates and launches `num_workers` threads that begin executing tasks
     * from the queue. If the pool is already started, throws.
     *
     * Must be called from a controller (non-worker) thread.
     */