220 30922 <20170216004134.4902991.82070.24891@gmail.com> article Path: news.gmane.org!.POSTED!not-for-mail From: Tony V E Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Proposed alternative approach to specifying required memory operation ordering Date: Wed, 15 Feb 2017 19:41:35 -0500 Lines: 105 Approved: news@gmane.org Message-ID: <20170216004134.4902991.82070.24891@gmail.com> References: Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable X-Trace: blaine.gmane.org 1487205700 14708 195.159.176.226 (16 Feb 2017 00:41:40 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Thu, 16 Feb 2017 00:41:40 +0000 (UTC) To: 'Walt Karas' via ISO C++ Standard - Future Proposals , ISO C++ Standard - Future Proposals Original-X-From: std-proposals+bncBCUZ5QWKNQIMF2UTYUCRUBGZWGID6@isocpp.org Thu Feb 16 01:41:35 2017 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-it0-f71.google.com ([209.85.214.71]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1ceA8c-0003L0-3s for gclcip-std-proposals@m.gmane.org; Thu, 16 Feb 2017 01:41:34 +0100 Original-Received: by mail-it0-f71.google.com with SMTP id w185sf10987711ita.5 for ; Wed, 15 Feb 2017 16:41:39 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=isocpp-org.20150623.gappssmtp.com; s=20150623; h=mime-version:content-transfer-encoding:message-id:date:subject:from :in-reply-to:references:to:x-original-sender :x-original-authentication-results:reply-to:precedence:mailing-list :list-id:x-spam-checked-in-group:list-post:list-help:list-archive :list-subscribe:list-unsubscribe; bh=9npYdBll79vAqYKtDmIF1jPC6QmxpZt0BSw2AFPLh/o=; b=YDiWwapylZbQ0jZYxrnq+3Vpp4en4MGA7axZd05gFQuGZKs11dqyCP7YstrMTD+hGq qQBmygQswTR+K2aasGEUEOwbaUW4Sdkrn9J9QBMFIgzAAY+5VpcQug8v8OOLMSmq75wF hUlKBap3FJihrTsYgIHyak+RK8EQjuSuXdSuYVvOoBC5QYubZSEodEhTFBJskiwCs4HR /NePwBpP6sxJKz72HkaXz+0UcvYyPmEG43eLZPULrYXqyPa3ShLmtDiXeZaFMEdyjsqo MwB6kEtymrdSAIfKDWaH1+oa9fx43cRaznQW/3Q1crVz4wjvQp4E7xGbBAXM7tKvF7z1 wxwQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:content-transfer-encoding :message-id:date:subject:from:in-reply-to:references:to :x-original-sender:x-original-authentication-results:reply-to :precedence:mailing-list:list-id:x-spam-checked-in-group:list-post :list-help:list-archive:list-subscribe:list-unsubscribe; bh=9npYdBll79vAqYKtDmIF1jPC6QmxpZt0BSw2AFPLh/o=; b=rpzjGWfaNcNDed7pwoGuUCNAItRhmSjJwKmZkwlnf7cdBUR6P/MOs9Kv3VsQ5fKskJ 8p3ZT1mmKKe1vKQhdG6C1I/tM9ooofqS4nYKZJ39Zf64qknqx0Kxg5OpgkomrlN9e7xO n+w8mBxktT3RELK+vpgCNBN0CUCENniuPBvVuT/u4D16X402UteDrDRTDQLqzWjJgmj7 US/C3NMZcRQvcRkzOnBUSsrxZH9rv3OWtOuU4BjgHmmrhJLY4ocvrm20NPY+Lp/FYump 9bILtj2ktfNkPwKfiC1Xsz4G61Xpz5kvkxf8aZhf/6iyJYJAQeV8MBj/k9kkAmNSjHb7 1LG X-Gm-Message-State: AMke39nD6H1b/Z8UAmAZDmJ/y9sW0KpOHfqmJXlELJCll6jRJbKn2VcMCDRr1NDSVITo4w== X-Received: by 10.107.151.140 with SMTP id z134mr5796iod.68.1487205699408; Wed, 15 Feb 2017 16:41:39 -0800 (PST) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.36.87.199 with SMTP id u190ls1540785ita.8.canary-gmail; Wed, 15 Feb 2017 16:41:38 -0800 (PST) X-Received: by 10.36.110.205 with SMTP id w196mr11435368itc.20.1487205698269; Wed, 15 Feb 2017 16:41:38 -0800 (PST) Original-Received: from mail-it0-x244.google.com (mail-it0-x244.google.com. [2607:f8b0:4001:c0b::244]) by mx.google.com with ESMTPS id 15si5593566iou.239.2017.02.15.16.41.38 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 15 Feb 2017 16:41:38 -0800 (PST) Received-SPF: pass (google.com: domain of tvaneerd@gmail.com designates 2607:f8b0:4001:c0b::244 as permitted sender) client-ip=2607:f8b0:4001:c0b::244; Original-Received: by mail-it0-x244.google.com with SMTP id 203so1203061ith.2 for ; Wed, 15 Feb 2017 16:41:38 -0800 (PST) X-Received: by 10.36.48.208 with SMTP id q199mr43773itq.28.1487205697200; Wed, 15 Feb 2017 16:41:37 -0800 (PST) Original-Received: from [127.0.0.1] (glphon2233w-lp130-08-74-15-45-73.dsl.bell.ca. [74.15.45.73]) by smtp.gmail.com with ESMTPSA id w77sm2509007iow.46.2017.02.15.16.41.35 for (version=TLS1 cipher=ECDHE-RSA-AES128-SHA bits=128/128); Wed, 15 Feb 2017 16:41:36 -0800 (PST) X-Mailer: BlackBerry Email (10.3.2.2876) In-Reply-To: X-Original-Sender: tvaneerd@gmail.com X-Original-Authentication-Results: mx.google.com; dkim=pass header.i=@gmail.com; spf=pass (google.com: domain of tvaneerd@gmail.com designates 2607:f8b0:4001:c0b::244 as permitted sender) smtp.mailfrom=tvaneerd@gmail.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=gmail.com Precedence: list Mailing-list: list std-proposals@isocpp.org; contact std-proposals+owners@isocpp.org List-ID: X-Google-Group-Id: 399137483710 List-Post: , List-Help: , List-Archive: List-Subscribe: , List-Unsubscribe: , Xref: news.gmane.org gmane.comp.lang.c++.isocpp.proposals:30922 Archived-At: =
Leaving the questions about =E2=80=8Eactually changing the stan= dard aside, and focusing on understanding (which may just mean this could b= e a std-discussion question instead of std-proposal),

In your model, if X and Y are relaxed atomic operations in thread T1, can = thread T2 see them as Y before X while thread T3 sees them as =E2=80=8EX be= fore Y?
= Sent=  from my BlackBerry portable Babbage Device = =
=
From: 'Walt Karas' via ISO C++ Standard - Future Proposals
Sent: Wednesday, February 15, 2017 2:17 PM
To: = ISO C++ Standard - Future Proposals
Reply To: std-prop= osals@isocpp.org
Subject: [std-proposals] Proposed alterna= tive approach to specifying required memory operation ordering
<= /td>

- In a program ex= ecution, each thread defines a nominal order of (thread local) memory = and fence operations.
- For any operations X and Y in thread T, e= ither X before Y, or Y before X.
- A program execution defines a = nominal global order of global memory operations.
- If X and Y ar= e atomic global operations, then either X before Y or Y before X in the glo= bal order.
- If X is a global operation, and there exists a globa= l store S where neither X before S nor S before X in the global order, then= the result of X is undefined.
- A program execution defines a pa= rtial function f(T, LO) -> GO where LO is a local memory operation in th= read T, and GO is a global operation.  If LO is atomic, then GO must b= e atomic. The result of LO is the result of GO.  If the result of GO i= s undefined, the result of LO is undefined.  (Even if f(T, LO) is not = required to exist, it none the less _may_ exist.)
- If LO1 and LO= 2 are operations in thread T, and LO1 before LO2 in T, and f(T, LO1) and f(= T, LO2) both exist, then f(T, LO2) before f(T, LO1) in the global order is = not allowed.
- If:
1.  In a thread T, X and Y are = memory operations, and F is a fence operation.
2.  X before&= nbsp;F and F before Y.
3.  F is sequentially consistent= and both X and Y are atomic, or
4.  F is acquire and both X= and Y are loads, or
5.  F is release and both X and Y are s= tores.
then F is activated for X and Y.
- In a thr= ead T, if X and Y are memory operations (where X before Y) with an activate= d fence F, then f(T, X) must exist.
- For every global operation = GO, there must exist a local operation LO in some thread T where f(T, LO) -= > GO.  (Assuming no intense gamma radiation.)
- A sequent= ially consistent (thread local) atomic memory operation implies two sequent= ially consistent fences, one before and one after it (as well as a precedin= g release for a store, and a succeeding acquire for a load).

--
You received this message because you are subscribed to the Google Groups "= ISO C++ Standard - Future Proposals" group.
To unsubscribe from this group and stop receiving emails from it, send an e= mail to std-proposa= ls+unsubscribe@isocpp.org.
To post to this group, send email to std-proposals@isocpp.org.
To view this discussion on the web visit https://groups.goo= gle.com/a/isocpp.org/d/msgid/std-proposals/d0fdabcd-f04a-46e6-b93a-0b9ea85c= b5bd%40isocpp.org.

--
You received this message because you are subscribed to the Google Groups &= quot;ISO C++ Standard - Future Proposals" group.
To unsubscribe from this group and stop receiving emails from it, send an e= mail to std-proposa= ls+unsubscribe@isocpp.org.
To post to this group, send email to std-proposals@isocpp.org.
To view this discussion on the web visit https://groups.google.com= /a/isocpp.org/d/msgid/std-proposals/20170216004134.4902991.82070.24891%40gm= ail.com.
.