Re: alarm_signal_handler is called too frequently

[YAMAMOTO Mitsuharu <mituharu@math.s.chiba-u.ac.jp>]

>>>>> On Thu, 28 Oct 2004 20:02:13 +0200, "Jan D." <jan.h.d@swipnet.se> said:

> Timers are running (scheduled), The version that uses Xt has a timer
> that runs every 0.1 seconds, and I also have a blinking cursor.

There may be some confusion between two kinds of timers: the OS-level
alarm timer and the Emacs-level (cooperative?) timer.  The timer for
Xt timeout events is the former, and the cursor blinking uses the
latter.  The function timer_check is also for the latter.

> The reason no timers are actualy run is this code in
> alarm_signal_handler in atimer.c:
>
>   while (atimers
>	 && (pending_atimers = interrupt_input_blocked) == 0
>	 && EMACS_TIME_LE (atimers->expiration, now))
>   ...
>

The above code is about the OS-level timer, which I was concerning
about in my original message.

> Since popups are within BLOCK/UNBLOCK__INPUT, the signal handler
> just reschedules the alarm without running any timer code.

Actually, the signal handler only sets the interval timer value
(set_alarm) without calling schedule_atimer in this situation.  The
new interval may become a small value, 1msec, by the following code in
set_alarm.

      /* Don't set the interval to 0; this disables the timer.  */
      if (EMACS_TIME_LE (atimers->expiration, now))
	{
	  EMACS_SET_SECS (time, 0);
	  EMACS_SET_USECS (time, 1000);
	}

      bzero (&it, sizeof it);
      it.it_value = time;
      setitimer (ITIMER_REAL, &it, 0);

That's the reason why I did the following question:

  I think we don't have to call set_alarm when pending_atimers is
  non-zero because do_pending_atimers is supposed to be called
  eventually in such a case.  Is that correct?

				     YAMAMOTO Mitsuharu
				mituharu@math.s.chiba-u.ac.jp