Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755727Ab3JJIpl (ORCPT ); Thu, 10 Oct 2013 04:45:41 -0400 Received: from mail-ee0-f47.google.com ([74.125.83.47]:61857 "EHLO mail-ee0-f47.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755340Ab3JJIpi (ORCPT ); Thu, 10 Oct 2013 04:45:38 -0400 Date: Thu, 10 Oct 2013 10:45:35 +0200 From: Ingo Molnar To: Jakub Jelinek Cc: Peter Zijlstra , Oleg Nesterov , Fengguang Wu , Linus Torvalds , Linux Kernel Mailing List , Richard Henderson Subject: Re: [PATCH] gcc4: Add 'asm goto' miscompilation quirk Message-ID: <20131010084535.GA10620@gmail.com> References: <20131009143359.GU26785@twins.programming.kicks-ass.net> <20131009144656.GV26785@twins.programming.kicks-ass.net> <20131009181613.GW30970@tucnak.zalov.cz> <20131009190231.GI13848@laptop.programming.kicks-ass.net> <20131009190851.GX30970@tucnak.zalov.cz> <20131010062238.GB9853@gmail.com> <20131010065104.GY30970@tucnak.zalov.cz> <20131010080457.GC21875@tucnak.zalov.cz> <20131010082430.GA20577@gmail.com> <20131010083107.GZ30970@tucnak.zalov.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20131010083107.GZ30970@tucnak.zalov.cz> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1458 Lines: 43 * Jakub Jelinek wrote: > On Thu, Oct 10, 2013 at 10:24:30AM +0200, Ingo Molnar wrote: > > Something like the patch below? (Totally untested and all that.) > > > > Notes: > > > > - If the bug is fixed in 4.8.3 then the version check can be sharpened > > from 99999 to 40803. > > The bug is likely going to be fixed already for 4.8.2 (to be released > next week or so). > > > - I'd really prefer this quirk versus having to add the extra barrier to > > the label, as it makes the actual usage sites a lot less painful. > > Please check how much it bloats the generated code. on Linus's latest tree plain 'asm goto' is only rarely used, so the size impact of the patch, on x86-64 defconfig, is zero: vmlinux: text data bss dec hex filename 11166823 1448024 1187840 13802687 d29cbf vmlinux.before 11166823 1448024 1187840 13802687 d29cbf vmlinux.after 1f7c3c1fd71b4b1327965bcfbc7a77fb vmlinux.before 3b246add801bc170e47096b712942395 vmlinux.after Using GCC 4.8.1. > Also, for the bitops patch, you probably want an asm_volatile_goto variant. Also, for mutex_64.h - good point, will fix that. Thanks, Ingo -- 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/