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From: Simon Clubley <clubley@remove_me.eisner.decus.org-Earth.UFP>
Newsgroups: comp.lang.ada
Subject: Re: Forcing GNAT to use 32-bit load/store instructions on ARM?
Date: Thu, 10 Jul 2014 00:11:11 +0000 (UTC)
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Date: 2014-07-10T00:11:11+00:00
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On 2014-07-09, Dmitry A. Kazakov <mailbox@dmitry-kazakov.de> wrote:
> On Tue, 8 Jul 2014 15:34:04 -0500, Randy Brukardt wrote:
>
>> To make 
>> "Read-Modify-Write" indivisible, you'd need a test-and-set instruction, 
>> which would require far more restrictions than Atomic does. (I don't see any 
>> way to make a general Read-Modify-Write to be indivisible on Windows or 
>> Linux, for instance, as that requires shutting off interrupts.)
>
> I don't think this should be the semantics of "indivisible". Because as you
> said it incredibly difficult to ensure, but more importantly is that this
> is mot what programmers actually need. They need it rather be logically
> indivisible from the process' point of view. If the process could lose the
> processor in between would be no problem for most if not all applications.
>

Oh, I agree with this. :-)

I was just wondering if a newcomer to Ada might be confused by the
use of the word Atomic.

BTW, I'm planning on writing up the partial aggregate submission
sometime at the weekend (spare time permitting :-)).

I'm also planning on a second submission which is a request for a
formal decision regarding if Atomic on a record applies to the access
of a individual record component or not.

The wording identified by Niklas ("as a whole") would suggest not
but Randy appears to think it does. I think we need a firm decision
one way or another so we know for sure.

Simon.

-- 
Simon Clubley, clubley@remove_me.eisner.decus.org-Earth.UFP
Microsoft: Bringing you 1980s technology to a 21st century world