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Date: 18 Sep 92 09:05:48 GMT
From: mcsun!uknet!cam-cl!cam-cl!gxl@uunet.uu.net  (Guangxing Li)
Subject: Re: Ada delay
Message-ID: <1992Sep18.090548.20198@cl.cam.ac.uk>
List-Id: <comp.lang.ada>

_______________________
Amir Michail (amichail@plg.uwaterloo.ca) wrote:
: How is the Ada delay statement implemented?  I suppose it uses a hardware 
: timer coupled with a clock server, but this would mean that the time
: taken for a delay is unbounded (since we have to search an ordered list
: of tasks).  If this is true, then how can one possibly use it for
: realtime scheduling of periodic tasks??

By dynamically updating the delay value, people can still have accurate
periodic tasks, even through the delay statement is not
accurate. 

For example 
      start_time = now;
      for(;;) {
      load();
      next_period_start = start_time + period;
      start_time = next_period_start;
      delay = next_period_start - now;
      Ada_delay(delay);
      }