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From: "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>
Newsgroups: comp.lang.ada
Subject: Re: is there a version of unix written in Ada
Date: Sat, 3 Oct 2020 08:42:03 +0200
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On 03/10/2020 05:09, Randy Brukardt wrote:
> "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de> wrote in message
> news:rl6its$10h7$1@gioia.aioe.org...

>>> [If O3 was nested in O2, then the second call to O2 could be internal.
>>> But in that case, the first path would be impossible as O1 could not see O3
>>> to call it.]
>>>
>>> Remember that the decision as to whether a call is internal or external
>>> is
>>> purely syntactic: if a protected object is given explicitly in the call,
>>> one
>>> needs to trigger the mutual exclusion mechanisms again. The only time one
>>> doesn't need to do that is when the call does not include the object
>>> (that
>>> is, directly from the body of an operation).
>>
>> Even when the object in the call is statically known to be same?
> 
> Yes. An external call *always* gets the lock again. I believe that was made
> the rule to make it obvious as to what will happen based on the form of
> call.

I mean this:

    protected body O is
       procedure P1 is
       begin
          ...
       end P1;
       procedure P2 is
       begin
          P1;   -- OK
          O.P1; -- Deadlock or Program_Error
       end P2;
    end O;

-- 
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de