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From: "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>
Subject: Re: Multitasking and containers
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References: <ek6bqd$prc$1@cernne03.cern.ch>
Date: Fri, 24 Nov 2006 11:19:23 +0100
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Date: 2006-11-24T11:19:23+01:00
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On Fri, 24 Nov 2006 09:51:24 +0100, Maciej Sobczak wrote:

> Paragraph 3 in Annex A says that it's OK to call any standard subprogram 
> from concurrent tasks as long as the parameters do not overlap. John 
> Barnes ("Progamming in Ada 2005") suggests that in order to (for 
> example) read from the same container, the operations need to be 
> protected "by using the normal techniques such as protected objects".
> 
> But reading from the protected object is not mutually exclusive (many 
> readers are allowed) - so where's the gain? What's the difference 
> between concurrent reads of, say, a Vector via protected object vs. 
> direct access?

I think he didn't mean container being a protected object. It would be
difficult to do, because protected types alas aren't tagged. So I read it
as "by using a locking/serialization technique, such as mutex, which can be
implemented as a protected object."

[ I don't know if ARM 2005 permits mutable implementations of read
operations on the containers. I suppose it does, so the need to lock upon
read. ]

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