From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755319AbaG3HVh (ORCPT ); Wed, 30 Jul 2014 03:21:37 -0400 Received: from mx1.redhat.com ([209.132.183.28]:4411 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754900AbaG3HVf (ORCPT ); Wed, 30 Jul 2014 03:21:35 -0400 Date: Wed, 30 Jul 2014 09:21:20 +0200 From: Jakub Jelinek To: Markus Trippelsdorf Cc: Greg Kroah-Hartman , linux-kernel@vger.kernel.org, stable@vger.kernel.org, Michel =?iso-8859-1?Q?D=E4nzer?= , Linus Torvalds Subject: Re: [PATCH 3.15 33/37] Fix gcc-4.9.0 miscompilation of load_balance() in scheduler Message-ID: <20140730072120.GB1652@laptop.redhat.com> Reply-To: Jakub Jelinek References: <20140730014827.565626091@linuxfoundation.org> <20140730014829.344302554@linuxfoundation.org> <20140730065312.GA1652@laptop.redhat.com> <20140730071308.GF22904@x4> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20140730071308.GF22904@x4> 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, Jul 30, 2014 at 09:13:08AM +0200, Markus Trippelsdorf wrote: > On 2014.07.30 at 08:53 +0200, Jakub Jelinek wrote: > > On Tue, Jul 29, 2014 at 06:49:09PM -0700, Greg Kroah-Hartman wrote: > > > 3.15-stable review patch. If anyone has any objections, please let me know. > > > > IMNSHO this is a too big hammer approach. The bug happened on a single > > file only (right?), so if anything, IMHO it could be disabled for that > > single file only, and better do it only for compilers with the bug. > > No. There are many more files affected. It just happens that Linus > analyzed the assembly of this single file (fair.c) and found a bug. > Just build your redhat distro kernel with GCC_COMPARE_DEBUG=1 and you'll > see. So unless someone analyzes the assembly output of all other > affected files by hand and finds no issues, one has to assume the worst. I'm talking about wrong-code issues. For -fcompare-debug, we indeed check it primarily during gcc bootstrap (through bootstrap-debug) and some testcases, and we'll certainly try to build some more code with -fcompare-debug and fix the issues. Jakub