Path: csiph.com!weretis.net!feeder9.news.weretis.net!panix!.POSTED.spitfire.i.gajendra.net!not-for-mail
From: cross@spitfire.i.gajendra.net (Dan Cross)
Newsgroups: comp.lang.c++
Subject: Re: std::atomic work as volatile, or not, I think not...
Date: Mon, 11 May 2026 11:53:10 -0000 (UTC)
Organization: PANIX Public Access Internet and UNIX, NYC
Message-ID: <10tsfv6$3fe$1@reader1.panix.com>
References: <10trn7n$s8gl$1@dont-email.me> <10trspj$t8pr$2@dont-email.me> <10ts3vt$3v1g3$1@dont-email.me> <10ts5ur$updt$2@dont-email.me>
Injection-Date: Mon, 11 May 2026 11:53:10 -0000 (UTC)
Injection-Info: reader1.panix.com; posting-host="spitfire.i.gajendra.net:166.84.136.80"; logging-data="3566"; mail-complaints-to="abuse@panix.com"
X-Newsreader: trn 4.0-test77 (Sep 1, 2010)
Originator: cross@spitfire.i.gajendra.net (Dan Cross)
Xref: csiph.com comp.lang.c++:123825

In article <10ts5ur$updt$2@dont-email.me>,
David Brown  <david.brown@hesbynett.no> wrote:
>On 11/05/2026 10:28, boltar@caprica.universe wrote:
>> On Mon, 11 May 2026 08:25:55 +0200
>> David Brown <david.brown@hesbynett.no> gabbled:
>>> On 11/05/2026 06:51, Chris M. Thomasson wrote:
>>>> Well, damn. It seems that std::atomic might not be sufficient, and 
>>>> volatile needs to be used.
>>>>
>>>
>>> I very much hope to be corrected if someone thinks my reasoning below 
>>> is incorrect - I am not an expert here by any means.
>> 
>> Whats the point of std::atomic anyway? Just how often does a thread 
>> critical
>> section just require the test and set of a single value? And if you do
>> want to do that posix semaphores have been a thing since the early 90s
>> and SysV ones since at least the 80s if not earlier.
>> 
>
>Atomics are for shared information /without/ needing semaphores, 
>critical sections or other more expensive operations.  Read up about 
>non-blocking or lock-free algorithms.

And also for implementing such things.

	- Dan C.