From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Date: Wed, 30 Jul 2014 09:27:47 +0200 From: Markus Trippelsdorf To: Jakub Jelinek 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: <20140730072747.GG22904@x4> References: <20140730014827.565626091@linuxfoundation.org> <20140730014829.344302554@linuxfoundation.org> <20140730065312.GA1652@laptop.redhat.com> <20140730071308.GF22904@x4> <20140730072120.GB1652@laptop.redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20140730072120.GB1652@laptop.redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: On 2014.07.30 at 09:21 +0200, Jakub Jelinek wrote: > 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. Yes, I'm talking about wrong-code issues, too. For example the pr61801.c testcase was reduced from kernel/exit.c. -- Markus