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

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From	Edek <edek.pienkowski@gmail.com>
Newsgroups	comp.programming.threads
Subject	Re: C++0x, 29.3 p13 "[...] atomic stores visible [...] within a reasonableamount of time."
Date	Tue, 05 Jul 2011 11:36:00 +0200
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My understanding is not _that_ shallow.

>>> C++0x, 29.3 p13. In draft n3242, the exact text is:
>>> "Implementations should make atomic stores visible to atomic loads
>>> within a reasonable amount of time."
>>>
>>
>> If you have the time, this point somehow interests me a lot.
>>
>> To start: does it apply to relaxed only?
>
> It applies to all stores.

Different question: are any stores with a guarantee of better
immediacy?

>
>>
>> The main question: Does it apply to release
>
> Yes.
>
>> (and acquire/consume)?
>
> There are no acquire/consume stores.

Thread1: store, Thread2: consume. For me these two are a pair;
of course these are not stores, these are the points where the store
should be visible.

>
>> (I am ignoring other orderings on purpose, as irrelevant for
>> release/acquire, or consume, pair)
>>
>> What I am basically wondering about, is how to release a lock
>> (or anything else blocking another thread)
>> in a way that assures it is done 'now' [1]; I care more
>
> Simply do a store or RMW. The lock acquiring thread will perform an RMW
> attempting to acquire the lock.

Again: which memory ordering should I use to make a store which will
be visible sooner than "within a reasonable amount of time",
and which load will see this?

Locked RMW on x86_64 will work, but that's not the point.

>
> regards,
> alexander.

Thanks,
Edek

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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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