From mboxrd@z Thu Jan 1 00:00:00 1970 From: Christian Borntraeger Subject: Re: linux-next: build warnings after merge of the access_once tree Date: Thu, 26 Mar 2015 19:54:20 +0100 Message-ID: <551455DC.4080604@de.ibm.com> References: <20150326193112.2c87eb39@canb.auug.org.au> <20150326103442.GV21418@twins.programming.kicks-ass.net> <20150326132750.GA2805@arm.com> <20150326142220.GY21418@twins.programming.kicks-ass.net> <551440C5.8040104@de.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Return-path: Received: from e06smtp11.uk.ibm.com ([195.75.94.107]:39143 "EHLO e06smtp11.uk.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751278AbbCZSy0 (ORCPT ); Thu, 26 Mar 2015 14:54:26 -0400 Received: from /spool/local by e06smtp11.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Thu, 26 Mar 2015 18:54:25 -0000 In-Reply-To: Sender: linux-next-owner@vger.kernel.org List-ID: To: Linus Torvalds Cc: Peter Zijlstra , Will Deacon , Stephen Rothwell , Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , "linux-next@vger.kernel.org" , "linux-kernel@vger.kernel.org" , Davidlohr Bueso , Paul McKenney Am 26.03.2015 um 18:52 schrieb Linus Torvalds: > On Thu, Mar 26, 2015 at 10:24 AM, Christian Borntraeger > wrote: >> >> Oh I just added that check back then because some guy named >> Linus suggested something like that ;-) > > Yes, my bad. > > In my defense, that was when we were talking about ACCESS_ONCE() > causing bugs with gcc due to the blind use of "volatile" that it turns > out gcc doesn't necessarily like. > > With the memcpy fallback (and the simpler "scalar pointer copy by > hand"), I think READ_ONCE() (and WRITE_ONCE()) are safe. > > Linus > FWIW, I dropped the warning fixp patch from my linux-next branch so everything should be back to normal and we can merge Peters patch for 4.0 or 4.1. Christian