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From: "Jeffrey R. Carter" <spam.jrcarter.not@spam.not.acm.org>
Newsgroups: comp.lang.ada
Subject: Re: Advice, tasking and hardware
Date: Thu, 26 May 2016 12:35:04 -0700
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Date: 2016-05-26T12:35:04-07:00
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On 05/26/2016 12:26 AM, Dmitry A. Kazakov wrote:
> 
> If you want interlocking for doing blocking calls use a mutex etc. A mutex
> implementation based on protected objects is two actions: Seize and Release.

To the OP: This is terrible advice. One should only use a low-level mechanism
such as a semaphore when one can't achieve what one needs with the high-level
mechanisms provided by the language: tasks and protected objects. Since there's
no way for the compiler to know that the subprogram is potentially blocking,
there's no reason not to put the call in a PO and make use of the high-level
mutual exclusion it provides. Even if the system has problems with the call
being in a protected operation, it's better to put a request for the call on a
protected queue and have a task that gets the requests from the queue and makes
the calls than to use a semaphore.

-- 
Jeff Carter
"This trial is a travesty. It's a travesty of a mockery of a
sham of a mockery of a travesty of two mockeries of a sham. ...
Do you realize there's not a single homosexual on that jury?"
Bananas
27