From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752249AbdEJJZJ (ORCPT ); Wed, 10 May 2017 05:25:09 -0400 Received: from mx2.suse.de ([195.135.220.15]:51618 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751893AbdEJJZH (ORCPT ); Wed, 10 May 2017 05:25:07 -0400 Date: Wed, 10 May 2017 11:25:05 +0200 From: Michal Hocko To: Nick Desaulniers Cc: akpm@linux-foundation.org, hannes@cmpxchg.org, mgorman@techsingularity.net, vbabka@suse.cz, minchan@kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm/vmscan: fix unsequenced modification and access warning Message-ID: <20170510092505.GH31466@dhcp22.suse.cz> References: <20170510065328.9215-1-nick.desaulniers@gmail.com> <20170510071511.GA31466@dhcp22.suse.cz> <20170510084602.qchu4psnughxrmsz@lostoracle.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170510084602.qchu4psnughxrmsz@lostoracle.net> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed 10-05-17 01:46:03, Nick Desaulniers wrote: > > You can add > > Something that's not clear to me when advised to add, should I be > uploading a v3 with your acked by? I think I got that wrong the last > time I asked (which was my first patch to Linux). If there are no further changes to the patch/changelog then it is not necessary. The maintainer usually just grabs ackes and reviewed-bys from the list. > > But I still do not understand which part of the code is undefined and > > why. > > It's not immediately clear to me either, but it's super later here... I would really like to understand that... > > is this a bug in -Wunsequenced in Clang > > Possibly, I think I already found one earlier tonight. > > https://bugs.llvm.org/show_bug.cgi?id=32985 this seems unrelated. I would try to report this and clarify in the llvm bugzilla. > Tomorrow, I'll try to cut down a test case to see if this is indeed a > compiler bug. Would you like me to change the commit message to call > this just a simple clean up, in the meantime? I would go with the following wording. " Clang and its -Wunsequenced emits a warning (PUT THE FULL WARNING HERE). While it is not clear to me whether the initialization code violates the specification (6.7.8 par 19 (ISO/IEC 9899) looks it disagrees) the code is quite confusing and worth cleaning up anyway. Fix this by reusing sc.gfp_mask rather than the updated input gfp_mask parameter. " -- Michal Hocko SUSE Labs