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From: "Randy Brukardt" <randy@rrsoftware.com>
Newsgroups: comp.lang.ada
Subject: Re: is there a version of unix written in Ada
Date: Thu, 1 Oct 2020 17:13:14 -0500
Organization: JSA Research & Innovation
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"Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de> wrote in message 
news:rl4uql$1569$1@gioia.aioe.org...
> On 01/10/2020 17:38, Niklas Holsti wrote:
>
>> If the protected procedures belong to different protected objects, yes it 
>> is legal. But not if they belong to the same object, as J-P noted.
>
> But then you have a problem when two independently running protected 
> procedures of *different* objects call a procedure of a third object. You 
> must serialize these calls, and that is effectively blocking.

Not really: blocking inplies task scheduling (and possible preemption and 
priority inversion), whereas no scheduling happens on a protected call. 
There's just a possible wait. It's a subtle difference, admittedly, but it 
makes a world of difference to analysis.

               Randy.