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=-0.6 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no 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 58FBAC352BE for ; Fri, 17 Apr 2020 10:38:19 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2C76D221EB for ; Fri, 17 Apr 2020 10:38:19 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="H0Myrcdg" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729121AbgDQKiR (ORCPT ); Fri, 17 Apr 2020 06:38:17 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55844 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S1726632AbgDQKiQ (ORCPT ); Fri, 17 Apr 2020 06:38:16 -0400 Received: from bombadil.infradead.org (bombadil.infradead.org [IPv6:2607:7c80:54:e::133]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B7830C061A0C for ; Fri, 17 Apr 2020 03:38:16 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=0Q4shkXgooXPUkXPVjWvprAz5T+GPx0IRz49akwY8gA=; b=H0MyrcdgRx+SjGjeXOzd4oRjUe 7Wjy45/9ipQWMMwgvGKojeyoouW2uK0yUOcA4PFWRCOx8pVWm0JTpJ9z6ifQeh27thKxIpwe1PpZq fRyLiiZkt4aScsnFxIxMGsedYh3pO6ygaJPPnYkcr2kl0zZXK608t2tHG67zYObR+bCFCzblwIZNs WUqOr1BPQEf9jn3Irnb7epVzsD1KuQKXDt2ll1ImqWbPKFeDgzvxnI+nI97dUNRGpqgdtJ1Zz3wup WcPZp3bnHgNjXqpzAYoI92Lx3/pRnaYs6a/X2GfUZ0frTVQ05kb4qNt8QJPvcqYcdVI2zPj54Bnj8 UMtb8GEw==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by bombadil.infradead.org with esmtpsa (Exim 4.92.3 #3 (Red Hat Linux)) id 1jPONu-0003Ho-Du; Fri, 17 Apr 2020 10:38:10 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id 8712C3006E0; Fri, 17 Apr 2020 12:38:08 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 6EEBB2B121452; Fri, 17 Apr 2020 12:38:08 +0200 (CEST) Date: Fri, 17 Apr 2020 12:38:08 +0200 From: Peter Zijlstra To: Jakub Jelinek Cc: Borislav Petkov , Sergei Trofimovich , Michael Matz , linux-kernel@vger.kernel.org, Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , Andy Lutomirski , x86@kernel.org Subject: Re: [PATCH v2] x86: fix early boot crash on gcc-10 Message-ID: <20200417103808.GW20730@hirez.programming.kicks-ass.net> References: <20200328084858.421444-1-slyfox@gentoo.org> <20200413163540.GD3772@zn.tnic> <20200415074842.GA31016@zn.tnic> <20200415231930.19755bc7@sf> <20200417075739.GA7322@zn.tnic> <20200417080726.GS2424@tucnak> <20200417084224.GB7322@zn.tnic> <20200417085859.GU2424@tucnak> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200417085859.GU2424@tucnak> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Apr 17, 2020 at 10:58:59AM +0200, Jakub Jelinek wrote: > Or go with the for (;;);, I don't think any compiler optimizes those away; > GCC 10 for C++ can optimize away infinite loops that have some conditional > exit because the language guarantees forward progress, but the C language > rules are different and for unconditional infinite loops GCC doesn't > optimize them away even if explicitly asked to -ffinite-loops. 'Funnily' there are people building the kernel with C++ :/