Method put

src/linux/ns.hpp:273–279

Add an element to the queue and notify one client.

    // Add an element to the queue and notify one client.
    void put(T&& t)
    {
      synchronized (mutex) {
        queue.push(std::forward<T>(t));
        cond.notify_one();
      }
    }

    // NOTE: This function blocks the thread. It returns the oldest
    // element from the queue and returns None() if the queue is