我在示例代码中遗漏了一部分。这个功能应该存在于线程的上下文中，并且需要以下内容。这是从示例中逐字引用的。我将删除我不使用的部分。总的来说，pselect可能是让它工作的关键。

while (true)
   {
      /* Step #4.  Create set of file descriptors to pass to 'pselect()'.
       * You can put anything in here that you want (files, sockets, serial ports,
       * descriptors from other sources).
       *
       * IMPORTANT: If you want to catch 'NOTIFY' events, you MUST add the
       * 'db.sock()' descriptor!  This is the socket for the database connection,
       * where notifications from the database backend come in.
       */
      fd_set read_fds;
      FD_ZERO(&read_fds);
      FD_SET(STDIN_FILENO, &read_fds);  // optional (just part of the demo)
      FD_SET(db.sock(), &read_fds);    // postgres connection (mandatory)
      const int max_fd = db.sock() + 1;

      /* Optional timeout (in case your process wanted to take action if no events
       * occur for a period of time).
       */
      struct timespec ts;
      ts.tv_sec = 5;
      ts.tv_nsec = 0;

      /* Step #5.  Magic happens here!  Put process to sleep until something
       * "interesting" happens.
       *
       * Unix was built to do "synchronous IO multiplexing".
       *
       * pselect() can return the following information values:
       * -1 = pselect() failed or was interrupted (errno == EINTR).
       *  0 = timeout expired (timeout is optional).
       * >1 = count of file descriptors in any of the sets that have activity.
       *
       * If the return value is positive, pselect() will have modified the file
       * descriptor sets: descriptors with activity will remain set, but all
       * others will be cleared.
       *
       * pselect() can return "failure" (-1) for only one acceptable reason: it
       * was interrupted by a signal.  For this demo, we assume that that signal
       * is SIGCHLD.  Any other errno value is beyond the scope of the demo.
       */
      switch (pselect(max_fd, &read_fds, NULL, NULL, &ts, &origmask))
      {
         case -1:
            if (errno != EINTR) throw CStandardError("pselect");

            /* Interrupted by signal, which we assume is SIGCHLD.
             *
             * We reap children here, but without updating read_fds.  So don't
             * re-use it when we're done reaping.
             */
            reap_children(db);
            break;

         case 0:
            // No file descriptors ready; we got here through timeout.
            std::cout << "pselect() timeout" << std::endl;
            break;

         default:
            // Check for, and handle, incoming data on stdin.
            if (FD_ISSET(STDIN_FILENO, &read_fds))
               handle_stdin_data();

            // Check for, and handle, notifications.  Calls MyNoticer::operator().
            if (FD_ISSET(db.sock(), &read_fds))
               db.get_notifs();

            break;
      }
   }