From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from smtp1.linuxfoundation.org (smtp1.linux-foundation.org [172.17.192.35]) by mail.linuxfoundation.org (Postfix) with ESMTPS id 393892C for ; Tue, 26 Jul 2016 06:09:34 +0000 (UTC) Received: from smtp.nue.novell.com (smtp.nue.novell.com [195.135.221.5]) by smtp1.linuxfoundation.org (Postfix) with ESMTPS id 2770013A for ; Tue, 26 Jul 2016 06:09:32 +0000 (UTC) To: "Luis R. Rodriguez" , "Paul E. McKenney" References: <15500.1469183675@warthog.procyon.org.uk> <20160722164411.GJ7094@linux.vnet.ibm.com> <20160725171416.GQ5537@wotan.suse.de> From: Hannes Reinecke Message-ID: Date: Tue, 26 Jul 2016 08:09:29 +0200 MIME-Version: 1.0 In-Reply-To: <20160725171416.GQ5537@wotan.suse.de> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 8bit Cc: jakub@redhat.com, parri.andrea@gmail.com, ksummit-discuss@lists.linuxfoundation.org, peterz@infradead.org, stern@rowland.harvard.edu, ramana.radhakrishnan@arm.com, luc.maranget@inria.fr, j.alglave@ucl.ac.uk Subject: Re: [Ksummit-discuss] [TECH TOPIC] Memory model, using ISO C++11 atomic ops List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On 07/25/2016 07:14 PM, Luis R. Rodriguez wrote: > On Fri, Jul 22, 2016 at 09:44:11AM -0700, Paul E. McKenney wrote: >> On Fri, Jul 22, 2016 at 11:34:35AM +0100, David Howells wrote: >>> Earlier this year we had a discussion of the possibilities of using ISO C++11 >>> atomic operations inside the kernel to implement kernel atomic ops of sorts >>> various, posted here: >>> >>> Subject: [RFC PATCH 00/15] Provide atomics and bitops implemented with ISO C++11 atomics >>> Date: Wed, 18 May 2016 16:10:37 +0100 >>> >>> Is it worth getting together to discuss these in person in one of the tech >>> slots - especially if there are some gcc or llvm people available at plumbers >>> who could join in? >>> >>> >>> Further, Paul McKenney and others are assembling a memory model description. >> >> We are attempting to automate memory-barriers.txt, so that you could >> provide fragments of C code, and the tool would tell you whether a given >> outcome happens always, sometimes, or never. The current prototype >> handles memory accesses, memory barriers, and RCU, but not yet locking >> or read-modify-write atomics (though there is some vestigal support for >> RMW atomics). We are currently playing whack-a-mole with odd corner cases >> of various architectures' memory models. We are therefore also working >> on ways of handling the resulting uncertainty. Good clean fun! ;-) > > Consider me interested in this discussion, patches, etc. > Same here. I have been playing around with RCUs and memory barriers quite a lot recently, and found some really 'odd' use-cases in the kernel which would benefit from improvements here. Cheers, Hannes -- Dr. Hannes Reinecke zSeries & Storage hare@suse.com +49 911 74053 688 SUSE LINUX GmbH, Maxfeldstr. 5, 90409 Nürnberg GF: F. Imendörffer, J. Smithard, D. Upmanyu, G. Norton HRB 21284 (AG Nürnberg)