Re: Preemption and priorities

[barmar@think.COM (Barry Margolin)]

In article <8801221730.AA23176@cs.sei.cmu.edu> John.Goodenough@SEI.CMU.EDU writes:
>Expiration of a delay  means  a  task  is  eligible  for  execution.   If  an
>implementation  determines that a delay has expired for a high priority task,
>then that task must be scheduled for execution.

However, I think someone already pointed out that a delay only
specifies a minimum amount of time for the task to be suspended.  An
operative point in your response is "if an implementation determines
that a delay has expired".  It would presumably be legal for an
implementation to only check whether delays have expired when a task
makes an explicit entry call.  In fact, if the only requirement of a
delay is that the task suspend for at least that long, it would
probably be valid for an implementation to never detect that it has
expired; however, the standard should (if it doesn't already) specify
that delays should be checked at entry calls.
Barry Margolin
Thinking Machines Corp.

barmar@think.com
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