From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752044AbaGZS2N (ORCPT ); Sat, 26 Jul 2014 14:28:13 -0400 Received: from mail-vc0-f171.google.com ([209.85.220.171]:56441 "EHLO mail-vc0-f171.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751448AbaGZS2L (ORCPT ); Sat, 26 Jul 2014 14:28:11 -0400 MIME-Version: 1.0 In-Reply-To: References: <20140723182518.GD3935@laptop> <20140723184111.GG3935@laptop> <20140723190230.GH3935@laptop> <53D064C7.5050807@daenzer.net> <53D1B1EF.7030603@daenzer.net> <20140725035527.GA30108@pg-vmw-gw1> <20140725140237.GB32669@home.goodmis.org> Date: Sat, 26 Jul 2014 11:28:10 -0700 X-Google-Sender-Auth: tVzwjslqoYLMf-MIu12GvkDDVTc Message-ID: Subject: Re: Random panic in load_balance() with 3.16-rc From: Linus Torvalds To: Steven Rostedt Cc: Alexei Starovoitov , =?UTF-8?Q?Michel_D=C3=A4nzer?= , Jakub Jelinek , Linux Kernel Mailing List , Debian GCC Maintainers , Debian Kernel Team Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Jul 25, 2014 at 11:29 AM, Linus Torvalds wrote: > > I'm sure it's possible, but it sounds potentially complicated. Hmm. The bugzilla entry just taught me a new gcc flag: "-fcompare-debug". That apparently makes gcc compile things twice, once with debugging and once without, and verify that the result is the same. And you can enable it for the whole kernel build with just a simple export GCC_COMPARE_DEBUG=1 before doing the build. It actually results in a failure for me even on my standard small localized kernel build, even with gcc-4.8.3. I get a compare failure for (at least) fs/ext4/inode.c. That's a bit worrisome. I haven't actually checked if the code generation differs in significant ways yet.. Linus