Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752625AbaBMELw (ORCPT ); Wed, 12 Feb 2014 23:11:52 -0500 Received: from mail-vc0-f182.google.com ([209.85.220.182]:34386 "EHLO mail-vc0-f182.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751511AbaBMELu (ORCPT ); Wed, 12 Feb 2014 23:11:50 -0500 MIME-Version: 1.0 In-Reply-To: References: <20131012171007.GA17167@gmail.com> Date: Wed, 12 Feb 2014 20:11:49 -0800 X-Google-Sender-Auth: tyz2X4K_t_iX4I7OPMlpLb8pp_c Message-ID: Subject: Re: [GIT PULL] compiler/gcc4: Add quirk for 'asm goto' miscompilation bug From: Linus Torvalds To: Steven Noonan Cc: Ingo Molnar , Linux Kernel mailing List , Peter Zijlstra , Jakub Jelinek , Oleg Nesterov , Fengguang Wu , Richard Henderson , Thomas Gleixner , Andrew Morton 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 Wed, Feb 12, 2014 at 7:09 PM, Steven Noonan wrote: > > If I change the GCC_VERSION check for the asm_volatile_goto quirk to > include 4.8.2, then KVM guests are properly cleaned up. Ok, I guess that means we should just make the quirk unconditional. Ingo, do you want to do that or should I? > So is there some other 'asm goto' bug we haven't yet fully uncovered > and reported to GCC upstream? Not to my knowledge. But I'm sure Jakub&co would love to have a test-case. Sadly, gcc has that really annoying habit of making small changes create *huge* changes in label numbers etc, and that's definitely the case with the extra empty asm - it's basically impossible to compare the generated asm with and without the workaround, because all the label numbers change. I have no idea how gcc people debug things like this, when the output is so unstable. Jakub, any suggestions to how Steven might be able to pinpoint where the code generation problem lies? Linus -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/