From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.6 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 366F4C10F03 for ; Tue, 23 Apr 2019 23:46:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id F0C57218DA for ; Tue, 23 Apr 2019 23:46:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1556063171; bh=KShJLaIh7Y00W+VLzml9osh15UHoCz6UzicFmsUsmi8=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=epQtU+wxDm0I/URoV5AUnlv0FF7ntKaeRz/eaa23xiUACv3fG/bd22KMjXD3ZFqbB 91/3qfVqcxvs+D85Mql7yi27F4uFrIOU3kvQKNT1kySgvoplufu1LYu6dRvIyuSDHB fqEF9YNQBRTylotfoTRUjmgbm4mPBv86C+jURjhs= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728354AbfDWXqK (ORCPT ); Tue, 23 Apr 2019 19:46:10 -0400 Received: from mail.kernel.org ([198.145.29.99]:43736 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727045AbfDWXqK (ORCPT ); Tue, 23 Apr 2019 19:46:10 -0400 Received: from localhost (c-73-47-72-35.hsd1.nh.comcast.net [73.47.72.35]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 47A7C218B0; Tue, 23 Apr 2019 23:46:09 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1556063169; bh=KShJLaIh7Y00W+VLzml9osh15UHoCz6UzicFmsUsmi8=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=ZG2UQZ7a4gHQns/Npk5ITOM1TA0WTjOBr30HvP50OSNB836hn5zeJjtqVLSBVUw/7 NTfhISDEtdUX9LmSTqpmqzDhzaXKOIcy73r8xRvjgZlw2AHe+HOgSWWuYZCmYZFSd4 KsF//eG4/facRidHFWbWOpIMiN6oP8PQmXVggTGA= Date: Tue, 23 Apr 2019 19:46:08 -0400 From: Sasha Levin To: Nathan Chancellor Cc: Matthias Kaehlcke , Greg Kroah-Hartman , stable@vger.kernel.org, Nick Desaulniers , clang-built-linux@googlegroups.com Subject: Re: Backport of commit a75bb4eb9e565b9f5115e2e8c07377ce32cbe69a Message-ID: <20190423234608.GU17719@sasha-vm> References: <20190423190426.18720-1-natechancellor@gmail.com> <20190423193512.GP17719@sasha-vm> <20190423194512.GA31444@archlinux-i9> <20190423195628.GD112750@google.com> <20190423200355.GA17824@archlinux-i9> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Disposition: inline In-Reply-To: <20190423200355.GA17824@archlinux-i9> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org On Tue, Apr 23, 2019 at 01:03:55PM -0700, Nathan Chancellor wrote: >On Tue, Apr 23, 2019 at 12:56:28PM -0700, Matthias Kaehlcke wrote: >> On Tue, Apr 23, 2019 at 12:45:12PM -0700, Nathan Chancellor wrote: >> > On Tue, Apr 23, 2019 at 03:35:12PM -0400, Sasha Levin wrote: >> > > On Tue, Apr 23, 2019 at 12:04:21PM -0700, Nathan Chancellor wrote: >> > > > Hi Greg and Sasha, >> > > > >> > > > Please apply this commit to 4.4 through 5.0 (patches are threaded in >> > > > reply to this one), which will prevent Clang from emitting references >> > > > to compiler runtime functions and doing some performance-killing >> > > > optimization when using CONFIG_CC_OPTIMIZE_FOR_SIZE. >> > > > >> > > > Please let me know if I did something wrong or if there are any >> > > > objections. >> > > >> > > This looks like a fix for a performance regression, which don't usually >> > > end up in stable unless they are severe enough. >> > > >> > >> > Yes and no. The original reason for the revert was because of the >> > compiler runtime functions: >> > >> > https://lore.kernel.org/lkml/CAG5bF+S6OvBnsaR6UpMCqjDR9_hMo6qRMHGiW+iCaRYQW4C3YA@mail.gmail.com/ >> > >> > The Chromium guys hit this [1] and have applied the patch for their >> > kernels, I think it should be applied for everyone. >> >> We picked it into our kernels because we needed a fix *now* to unbreak >> our builds, but I agree it should be fixed at least in relevant LTS >> versions. >> > >Of course, I wasn't implying that was a bad thing :) it's further >justification for this being a stable worthy patch as it fixes a real >world issue and could fix more. Okay, this makes more sense. The upstream commit message failed to mention this. I've queued it up. -- Thanks, Sasha