From mboxrd@z Thu Jan  1 00:00:00 1970
X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on polar.synack.me
X-Spam-Level: 
X-Spam-Status: No, score=-0.3 required=5.0 tests=BAYES_00,
	REPLYTO_WITHOUT_TO_CC autolearn=no autolearn_force=no version=3.4.4
Path: 
 eternal-september.org!reader01.eternal-september.org!reader02.eternal-september.org!news.eternal-september.org!news.eternal-september.org!news.eternal-september.org!feeder.eternal-september.org!aioe.org!.POSTED!not-for-mail
From: "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>
Newsgroups: comp.lang.ada
Subject: Re: Forcing GNAT to use 32-bit load/store instructions on ARM?
Date: Wed, 9 Jul 2014 09:31:43 +0200
Organization: cbb software GmbH
Message-ID: <1l6z27vulrv65.1xwdi0b9yactc$.dlg@40tude.net>
References: <0e0b9ac2-e793-4cc5-8d8d-d3441ca28a58@googlegroups.com>
 <1j7b0m3yptffy$.1cztnkty8elrv$.dlg@40tude.net> <lou8e0$7u2$3@dont-email.me>
 <ee4cjxhhe7yi$.kqeq5ati5vrg$.dlg@40tude.net> <loupft$48j$1@dont-email.me>
 <nboccqyjxkzx$.10p3g2l6gzzdd.dlg@40tude.net> <lov4ga$3v9$1@dont-email.me>
 <lp20qc$iju$1@loke.gir.dk> <lpcck1$vtv$1@dont-email.me>
 <lpf7hv$am9$1@loke.gir.dk> <lpgn76$u7h$1@dont-email.me>
 <lphkjt$s6a$1@loke.gir.dk>
Reply-To: mailbox@dmitry-kazakov.de
NNTP-Posting-Host: ot/DC7n2aCvt5pcTM4dZCw.user.speranza.aioe.org
Mime-Version: 1.0
Content-Type: text/plain; charset="us-ascii"
Content-Transfer-Encoding: 7bit
X-Complaints-To: abuse@aioe.org
User-Agent: 40tude_Dialog/2.0.15.1
X-Notice: Filtered by postfilter v. 0.8.2
Xref: news.eternal-september.org comp.lang.ada:20822
Date: 2014-07-09T09:31:43+02:00
List-Id: <comp.lang.ada>

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.

If anybody wanted on top of that to block all other processes, system
kernel, interrupts and the very memory bus itself, he would do this by
other means.

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