bug#19776: timerfd doesn't work when busy-looping

[Eli Zaretskii]

> From: Lars Ingebrigtsen <larsi@gnus.org>
> Cc: Eli Zaretskii <eliz@gnu.org>,  stefan@marxist.se,
>   19776@debbugs.gnu.org,  rms@gnu.org,  monnier@iro.umontreal.ca, Andreas
>  Schwab <schwab@linux-m68k.org>
> Date: Mon, 25 Oct 2021 17:05:10 +0200
> 
> Dmitry, the issue is that with timerfd, no atimers are delivered when
> Emacs is busy-looping, like:
> 
>   (with-delayed-message 2 "Yes"
>     (while t))

Btw, the above signals an error; I need to use

  (with-delayed-message (2 "Yes")
    (while t))

instead, to make it work.