Re: Uninterruptible (atomic) operation?

[WhiteR@CRPL.Cedar-Rapids.lib.IA.US (Robert S. White)]

In article <EACHUS.96Dec10204319@spectre.mitre.org>, eachus@spectre.mitre.org 

...snip...  using Ada95

>    The trick is to have a lock which
>all the potential modifiers respect, and to use pragma Atomic, and
>Atomic reads and writes, so that the readers can trust the value they
>see.
>
>    (Potential) Writer:
>
>       Acquire(lock);
>       Temp := Atomic_Object;
>       -- operations on Temp...
>       Atomic_Object := Temp;
>       Release(lock);
>
>    Reader:
>
>       Temp := Atomic_Object;
>       -- use value in temp.

  OK. I can live with that.  In the past using Ada83 and a local (company 
generated - DO-178BB) Real Time Executive (RTE) I could do the following 
(assuming a record structure):

  (Potential) Writer:
  with ESR;
    ...
  ESR.Enter_Critical_Section;
  -- various updating operations on Object.
  ESR.Leave_Critical_Section;

  
  Reader:
  
  with ESR;
    ...
  ESR.Enter_Critical_Section;
  Temp := Object.all;
  ESR.Leave_Critical_Section;
  -- use value in temp.

  With the real time constraint that thou use'st a minimum (1/3 of a tick max) 
time within a critical section.  ESR = Executive Service Routine package.

  But what Robert Eachus suggests is semantically equivalent and inclusive in a 
new ISO standardized language rather than a older language and a unique RTE.

_______________________________________________________________________
Robert S. White                    -- an embedded sys software engineer
WhiteR@CRPL.Cedar-Rapids.lib.IA.US --long/cheap alternate I-net address