From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ramana Radhakrishnan Subject: Re: Compilers and RCU readers: Once more unto the breach! Date: Wed, 20 May 2015 14:44:30 +0100 Message-ID: <555C8FBE.4020505@arm.com> References: <20150520133037.GK6776@linux.vnet.ibm.com> <20150520121522.GH6776@linux.vnet.ibm.com> <20150520005510.GA23559@linux.vnet.ibm.com> <20150520024148.GD6776@linux.vnet.ibm.com> <20150520114745.GC11498@arm.com> <31547.1432127917@warthog.procyon.org.uk> <31805.1432129025@warthog.procyon.org.uk> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from foss.arm.com ([217.140.101.70]:38325 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753082AbbETNoc (ORCPT ); Wed, 20 May 2015 09:44:32 -0400 In-Reply-To: <31805.1432129025@warthog.procyon.org.uk> Sender: linux-arch-owner@vger.kernel.org List-ID: To: David Howells , "paulmck@linux.vnet.ibm.com" Cc: Will Deacon , Linus Torvalds , Linux Kernel Mailing List , "c++std-parallel@accu.org" , "linux-arch@vger.kernel.org" , "gcc@gcc.gnu.org" , p796231 , "mark.batty@cl.cam.ac.uk" , Peter Zijlstra , Andrew Morton , Ingo Molnar , "michaelw@ca.ibm.com" On 20/05/15 14:37, David Howells wrote: > Paul E. McKenney wrote: > >> I was thinking of "y" as a simple variable, but if it is something more >> complex, then the compiler could do this, right? >> >> char *x; >> >> y; >> x = z; > > Yeah. I presume it has to maintain the ordering, though. The scheduler for e.g. is free to reorder if it can prove there is no dependence (or indeed side-effects for y) between insns produced for y and `x = z'. regards Ramana > > David >