From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Paul E. McKenney" Subject: Re: [c++std-parallel-1624] Re: Compilers and RCU readers: Once more unto the breach! Date: Wed, 20 May 2015 07:02:16 -0700 Message-ID: <20150520140216.GN6776@linux.vnet.ibm.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> Reply-To: paulmck@linux.vnet.ibm.com Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <31805.1432129025@warthog.procyon.org.uk> Sender: linux-kernel-owner@vger.kernel.org To: c++std-parallel@accu.org Cc: dhowells@redhat.com, Will Deacon , Linus Torvalds , Linux Kernel Mailing List , "linux-arch@vger.kernel.org" , "gcc@gcc.gnu.org" , p796231 , "mark.batty@cl.cam.ac.uk" , Peter Zijlstra , Ramana Radhakrishnan , Andrew Morton , Ingo Molnar , "michaelw@ca.ibm.com" List-Id: linux-arch.vger.kernel.org On Wed, May 20, 2015 at 02:37:05PM +0100, 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. Agreed. Unless of course y writes to x or some such. Given that there is already code in the Linux kernel relying on dependencies being carried through stores to local variables, this should not be a problem. Or am I missing something? Thanx, Paul From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from e34.co.us.ibm.com ([32.97.110.152]:42776 "EHLO e34.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753083AbbETODj (ORCPT ); Wed, 20 May 2015 10:03:39 -0400 Received: from /spool/local by e34.co.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Wed, 20 May 2015 08:03:38 -0600 Date: Wed, 20 May 2015 07:02:16 -0700 From: "Paul E. McKenney" Subject: Re: [c++std-parallel-1624] Re: Compilers and RCU readers: Once more unto the breach! Message-ID: <20150520140216.GN6776@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.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=us-ascii Content-Disposition: inline In-Reply-To: <31805.1432129025@warthog.procyon.org.uk> Sender: linux-arch-owner@vger.kernel.org List-ID: To: c++std-parallel@accu.org Cc: dhowells@redhat.com, Will Deacon , Linus Torvalds , Linux Kernel Mailing List , "linux-arch@vger.kernel.org" , "gcc@gcc.gnu.org" , p796231 , "mark.batty@cl.cam.ac.uk" , Peter Zijlstra , Ramana Radhakrishnan , Andrew Morton , Ingo Molnar , "michaelw@ca.ibm.com" Message-ID: <20150520140216.VWm3akcqZLzwBrCMuzj_l1ps3zOmMQ69wXKt7VoLx7Q@z> On Wed, May 20, 2015 at 02:37:05PM +0100, 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. Agreed. Unless of course y writes to x or some such. Given that there is already code in the Linux kernel relying on dependencies being carried through stores to local variables, this should not be a problem. Or am I missing something? Thanx, Paul