Groups > comp.programming.threads > #379

Re: C++0x, 29.3 p13 "[...] atomic stores visible [...] within a reasonable amount of time."

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From	Alexander Terekhov <terekhov@web.de>
Newsgroups	comp.programming.threads
Subject	Re: C++0x, 29.3 p13 "[...] atomic stores visible [...] within a reasonable amount of time."
Date	Sat, 02 Jul 2011 10:18:20 +0200
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Joshua Maurice wrote:
[...]
> > OTOH seqcst read may yield 'old' value for "a reasonable amount of time"
> > just like relaxed read.
> 
> Is this true? I'm not disputing it. However, I don't think this is

See 

http://www.cl.cam.ac.uk/~pes20/cpp/cpp0xmappings.html

"Load Seq_Cst: MOV (from memory)"

> quite correct. I think I could use 29.3 p4 to maybe show otherwise. We
> know that there is a total order S on all seqcst operations. I am
> presuming that this has some semblance to the time at which a core
> actually executes it - which may be our point of contention. I would
> think an implementation would need to be malicious to start doing this
> and to preserve the guarantees of 29.3 p4 through p7. I'd have to
> think more about this, but suffice to say I also prefer the simple
> guaranteed things over the of the fuzzy "maybe in practice" things.

People won't be happy with XADD(0) for seqcst reads.

regards,
alexander.

Thread

Re: C++0x, 29.3 p13 "[...] atomic stores visible [...] within a   reasonable amount of time." Alexander Terekhov <terekhov@web.de> - 2011-06-27 20:55 +0200
  Re: C++0x, 29.3 p13 "[...] atomic stores visible [...] within a reasonable amount of time." Joshua Maurice <joshuamaurice@gmail.com> - 2011-07-01 04:06 -0700
    Re: C++0x, 29.3 p13 "[...] atomic stores visible [...] within a  reasonable amount of time." Alexander Terekhov <terekhov@web.de> - 2011-07-01 17:35 +0200
      Re: C++0x, 29.3 p13 "[...] atomic stores visible [...] within a reasonable amount of time." Joshua Maurice <joshuamaurice@gmail.com> - 2011-07-01 15:23 -0700
        Re: C++0x, 29.3 p13 "[...] atomic stores visible [...] within a  reasonable amount of time." Alexander Terekhov <terekhov@web.de> - 2011-07-02 10:18 +0200
          Re: C++0x, 29.3 p13 "[...] atomic stores visible [...] within a reasonable amount of time." Joshua Maurice <joshuamaurice@gmail.com> - 2011-07-05 15:10 -0700
    Re: C++0x, 29.3 p13 "[...] atomic stores visible [...] within a reasonable amount of time." Edek <edek.pienkowski@gmail.com> - 2011-07-02 13:59 +0200
      Re: C++0x, 29.3 p13 "[...] atomic stores visible [...] within a  reasonableamount of time." Alexander Terekhov <terekhov@web.de> - 2011-07-05 10:12 +0200
        Re: C++0x, 29.3 p13 "[...] atomic stores visible [...] within a  reasonableamount of time." Edek <edek.pienkowski@gmail.com> - 2011-07-05 11:36 +0200

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