emacs -nw FILE incurs 2-second wait before displaying anything

[Jim Meyering]

I've been annoyed with emacs -nw for a while (always building
from latest), and finally have investigated enough to report this.

When I run emacs -nw on an existing file, e.g.,

  echo xxx > foo
  emacs -nw foo

I see the normal start-up signs, then a two-second pause,
and then finally the contents of "foo" are displayed.

However, if I type anything before that two-minute pause,
I avoid the delay. Likewise, if I run emacs without -nw, this
two-second pause does not appear.

I traced it to the pselect call in wait_reading_process_output
that is in turn called from kbd_buffer_get_event.

It seems to me that it would be fine to wait for keyboard events
*after* the buffer has been displayed.  Not before.

Thanks for improving emacs!