Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754105AbXL2LW2 (ORCPT ); Sat, 29 Dec 2007 06:22:28 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752069AbXL2LWS (ORCPT ); Sat, 29 Dec 2007 06:22:18 -0500 Received: from [194.117.236.238] ([194.117.236.238]:34887 "EHLO heracles.linux360.ro" rhost-flags-FAIL-FAIL-OK-OK) by vger.kernel.org with ESMTP id S1751931AbXL2LWR (ORCPT ); Sat, 29 Dec 2007 06:22:17 -0500 Date: Sat, 29 Dec 2007 13:19:40 +0200 From: Eduard-Gabriel Munteanu To: Richard Harman Cc: LKML Subject: Re: [PATCH] Option to disable AMD C1E (allows dynticks to work) Message-ID: <20071229131940.31d82752@linux360.ro> In-Reply-To: <47760ED5.6060207@richardharman.com> References: <47754735.1050009@richardharman.com> <20071229095242.1300e19c@linux360.ro> <47760ED5.6060207@richardharman.com> X-Mailer: Claws Mail 3.0.2 (GTK+ 2.12.1; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2183 Lines: 49 On Sat, 29 Dec 2007 04:09:41 -0500 Richard Harman wrote: > Right now, with your patch and the 'noirqdebug' option or disabling > nohz the system appears to be stable. This laptop otherwise locks up > trying to configure apic/lapic, or locks up solid later with NO > oops/bug and nothing will bring it out of it (eg, sysrq has no > effect). NMI watchdog was also inoperable, which I believe was due > to the apic/lapic being disabled. > > With your patch, the lapic is used: > > ACPI: LAPIC (acpi_id[0x00] lapic_id[0x00] enabled) > ACPI: LAPIC (acpi_id[0x01] lapic_id[0x01] enabled) The kernel should display these messages even without my patch. > These kernel dmesg logs are hand-transcribed, and are from 2.6.22.5, > but this shows where the kernel would lock up good and solid: > > http://www.richardharman.com/pavilion/2.6.22.5/dmesg.txt I doubt it is my patch that makes your laptop work. C1E detection was added by the following commit: $ git-describe fb79d22e1d4b06385796cc0db0084a2e07beccee v2.6.23-2294-gfb79d22 Try building a 2.6.24-rc6 without my patch and see if it still works (apply it again in reverse mode, for example). I guess it will work, because the kernel shouldn't use the LAPIC as a timer at all (except as a dummy one), with or without dynticks support. When I started investigating the "nohz is not working problem", I stumbled across a few threads on LKML where a few people had similar problems with their laptops and they where instructed to pass "nolapic" or something similar as a boot parameter to the kernel. I guess the problem disappeared after the commit I mentioned previously, since such reports weren't that recent. IIRC, that was on kernels previous to 2.6.24-*, where x86 and x86-64 weren't unified and there were no dynticks on the latter. To be more clear, my patch disables C1E instead of disabling the LAPIC, as these two don't agree with each other. -- 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/