From 4529942307166053089 X-Google-Thread: f78e5,edf2eb1d3f0f9755 X-Google-Attributes: gidf78e5,public X-Google-Language: ENGLISH,ASCII-7-bit From: terekhov@web.de (Alexander Terekhov) Newsgroups: comp.std.c++ Subject: Re: Multithreaded programming: is the C++ standardization committeelistening? Date: Sat, 21 Aug 2004 22:18:49 GMT Lines: 49 Sender: mail2news@demon.net Approved: fjh@cs.mu.oz.au (Fergus Henderson , moderator of comp.std.c++) Message-ID: <41279FFB.5D570142@web.de> References: <2ofbepFa2tpoU1@uni-berlin.de> <6uh6i0tbr0j0urbnocg5t9ucb5gfpr8gr3@4ax.com> <2ohmmiFavqsiU1@uni-berlin.de> <4123BD01.BCF1DC67@web.de> <2oig7mFb30cmU1@uni-berlin.de> <412533CA.82703A04@web.de> NNTP-Posting-Host: news.news.demon.net Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Trace: news.demon.co.uk 1093126733 7239 158.152.254.254 (21 Aug 2004 22:18:53 GMT) X-Complaints-To: abuse@demon.net NNTP-Posting-Date: Sat, 21 Aug 2004 22:18:53 +0000 (UTC) X-Robomod: STUMP, ichudov@algebra.com (Igor Chudov) X-Spam-Checker-Version: SpamAssassin 2.64-mulga_r1 (2004-01-11) on mulga.cs.mu.OZ.AU X-Orig-X-Trace: news.uni-berlin.de wQ0rqvlgXPmNHI93SZ8tNw5XYhgmhgjk8ZvJ5wsjEYvg4Nii7t X-Spam-Status: No, hits=-4.8 required=5.0 tests=AWL,BAYES_00 autolearn=ham version=2.64-mulga_r1 X-Accept-Language: en X-Reply-To: terekhov@web.de X-Received: (from fjh@localhost) by mulga.cs.mu.OZ.AU (8.12.10+Sun/8.12.9/Submit) id i7LMInAr015872; Sun, 22 Aug 2004 08:18:49 +1000 (EST) X-Path: comp-std-cpp-robomod!not-for-mail X-Delivered-To: std-c++@ucar.edu X-Authentication-Warning: mulga.cs.mu.OZ.AU: fjh set sender to devnull@stump.algebra.com using -f X-Newsgroups: comp.std.c++ Path: g2news1.google.com!news2.google.com!proxad.net!fr.ip.ndsoftware.net!216.196.110.149.MISMATCH!border2.nntp.ams.giganews.com!nntp.giganews.com!news.zanker.org!news.amigo.co.uk!news.clara.net!wagner.news.clara.net!194.159.246.34.MISMATCH!peer-uk.news.demon.net!kibo.news.demon.net!news.demon.co.uk!demon!stump.algebra.com!devnull Xref: g2news1.google.com comp.std.c++:1986 "David B. Held" wrote: > > Alexander Terekhov wrote: > > [...] > > Well, LL/SC is actually superior to CAS (LL/SC is ABA-proof), but > > is less portable than CAS. And i386 doesn't have CAS, BTW. > > [...] > > That's interesting, because: > > http://www.research.ibm.com/people/m/michael/ieeetpds-2004.pdf > > claims that LL/SC is fairly watered down in practice. Well, Alpha and MIPS aside for a moment, see http://www.ibm.com/developerworks/eserver/pdfs/archpub2.pdf (1.7.3 Atomic Update) One use of lwarx and stwcx. is to emulate a "Compare and Swap" primitive like that provided by the IBM System/370 Compare and Swap instruction; see Section B.1, "Atomic Update Primitives" on page 39. A System/370-style Compare and Swap checks only that the old and current values of the word being tested are equal, with the result that programs that use such a Compare and Swap to control a shared resource can err if the word has been modified and the old value subsequently restored. The combination of lwarx and stwcx. improves on such a Compare and Swap, because the reservation reliably binds the lwarx and stwcx. together. The reservation is always lost if the word is modified by another processor or mechanism between the lwarx and stwcx., so the stwcx. never succeeds unless the word has not been stored into (by another processor or mechanism) since the lwarx. regards, alexander. --- [ comp.std.c++ is moderated. To submit articles, try just posting with ] [ your news-reader. If that fails, use mailto:std-c++@ncar.ucar.edu ] [ --- Please see the FAQ before posting. --- ] [ FAQ: http://www.jamesd.demon.co.uk/csc/faq.html ]