From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754784AbYAIQai (ORCPT ); Wed, 9 Jan 2008 11:30:38 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751910AbYAIQab (ORCPT ); Wed, 9 Jan 2008 11:30:31 -0500 Received: from mx2.mail.elte.hu ([157.181.151.9]:59791 "EHLO mx2.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751844AbYAIQaa (ORCPT ); Wed, 9 Jan 2008 11:30:30 -0500 Date: Wed, 9 Jan 2008 17:30:18 +0100 From: Ingo Molnar To: Andi Kleen Cc: tglx@linutronix.de, linux-kernel@vger.kernel.org, "H. Peter Anvin" Subject: Re: More breakage in native_rdtsc out of line in git-x86 Message-ID: <20080109163017.GG17739@elte.hu> References: <20080109035534.GA30321@basil.nowhere.org> <20080109090956.GA14274@elte.hu> <20080109141908.GB12855@one.firstfloor.org> <20080109152208.GA21280@elte.hu> <20080109155124.GB12923@one.firstfloor.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20080109155124.GB12923@one.firstfloor.org> User-Agent: Mutt/1.5.17 (2007-11-01) X-ELTE-VirusStatus: clean X-ELTE-SpamScore: -1.5 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-1.5 required=5.9 tests=BAYES_00 autolearn=no SpamAssassin version=3.2.3 -1.5 BAYES_00 BODY: Bayesian spam probability is 0 to 1% [score: 0.0000] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Andi Kleen wrote: > On Wed, Jan 09, 2008 at 04:22:08PM +0100, Ingo Molnar wrote: > > > > * Andi Kleen wrote: > > > > > > nope, it's a 64-bit setup/dependency bug/problem: the vsyscall mappings > > > > are installed via an __initcall, and that's too late for early use. The > > > > combo patch below fixed the crash for me, does it work on your box too? > > > > > > That gives > > > > > > /home/lsrc/quilt/linux/arch/x86/kernel/setup_64.c: In function 'setup_arch': > > > /home/lsrc/quilt/linux/arch/x86/kernel/setup_64.c:468: error: implicit declarati > > > on of function 'map_vsyscall' > > > > i guess you have an old repository. > > I just applied the patch you sent out against yesterday's git-x86. then you have a truly ancient x86.git repository ;-) think of x86.git#mm as an open development tree. It's high-flux, based against Linux-bleeding-edge, it's frequently updated (daily, sometimes hourly), breakages are possible (and likely) and fixes and other feedback is more than welcome. And please feel free to complain about patches that are included. (like you did in the past) Also please try to post your patches as early as possible instead of in big chunks - last week's 75 patches patchbomb from you was (and still is) ... challenging ;-) > > since yesterday there's a full barrier around rdtsc. > > Great. i have measured the impact of the barriers and it was in the noise level. Barriers are notoriously easy to get wrong (because almost nothing tells the programmer that they are wrong), that's why i did this barrier-safe rdtsc() [& friends]. We had so much trouble with RDTSC during the past 10 years of its existence that being a bit more conservative with it is the only really maintainable option. Ingo