From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754789AbYFEJUc (ORCPT ); Thu, 5 Jun 2008 05:20:32 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753189AbYFEJUX (ORCPT ); Thu, 5 Jun 2008 05:20:23 -0400 Received: from mx3.mail.elte.hu ([157.181.1.138]:46444 "EHLO mx3.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752904AbYFEJUU (ORCPT ); Thu, 5 Jun 2008 05:20:20 -0400 Date: Thu, 5 Jun 2008 11:19:50 +0200 From: Ingo Molnar To: "Maciej W. Rozycki" Cc: Thomas Gleixner , "H. Peter Anvin" , linux-kernel@vger.kernel.org, the arch/x86 maintainers Subject: Re: [PATCH 8/8] x86: I/O APIC: Timer through 8259A second-chance Message-ID: <20080605091949.GA2307@elte.hu> References: <20080531101832.GA15170@elte.hu> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20080531101832.GA15170@elte.hu> User-Agent: Mutt/1.5.18 (2008-05-17) 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 Maciej, -tip testing found an IO-APIC related hang, and i bisected it down to the problem below. What do you think about my solution? Another option would be to add the lapic as a clockevent device in the failure path. (since we know the NMI watchdog wont work) Ingo ------------> Subject: x86, io-apic: fix nmi_watchdog=1 bootup hang From: Ingo Molnar nmi_watchdog=1 hangs on 64-bit: [ 0.250000] Detected 12.564 MHz APIC timer. [ 0.254178] APIC timer registered as dummy, due to nmi_watchdog=1! [ 0.260366] Testing NMI watchdog ... <4>WARNING: CPU#0: NMI appears to be stuck (0->0)! [ ... ] [ 0.470003] calling genl_init+0x0/0xd0 [ hard hang ] bisected it down to: git-bisect start git-bisect good 1beee8dc8cf58e3f605bd7b34d7a39939be7d8d2 git-bisect bad 11582ece0aaa2d0f94f345c08a4ab9997078a083 git-bisect bad 5479c623bb44089844022c03d4c0eb16d5b7a15f git-bisect bad cfb4c7fabeb499e1c29f9d1878968e37a938e28a git-bisect good 246dd412d31e4f5de1d43aa6422a325b785f36e4 git-bisect bad 3f8237eaff7dc1e35fa791dae095574fd974e671 git-bisect good 90e23b13ab849e2a11f00c655eb3a2011b4623be git-bisect bad 833526a34eeefc117df3191a594c3c3a4f15a9ac git-bisect good 791b93d3dfaf16c23e978bec0cc0a3dd9d855d63 git-bisect bad 65767c64068f2c93e56a1accfed5c78230ac12d7 git-bisect bad 2abc5c05dd82c188e3bdf6641a274f013348d14b git-bisect bad 317e1f2597ffb4d4db940577bbe56dc6e881ef07 | 317e1f2597ffb4d4db940577bbe56dc6e881ef07 is first bad commit | commit 317e1f2597ffb4d4db940577bbe56dc6e881ef07 | Author: Maciej W. Rozycki | Date: Wed May 21 22:10:22 2008 +0100 | x86: I/O APIC: clean up the 8259A on a NMI watchdog failure the problem is that in the dummy-lapic branch we rely on the i8259A but if the NMI watchdog fails we turn off IRQ 0 - which doesnt work too well ;-) Signed-off-by: Ingo Molnar --- arch/x86/kernel/apic_32.c | 6 ++++-- arch/x86/kernel/apic_64.c | 6 ++++-- 2 files changed, 8 insertions(+), 4 deletions(-) Index: linux/arch/x86/kernel/apic_32.c =================================================================== --- linux.orig/arch/x86/kernel/apic_32.c +++ linux/arch/x86/kernel/apic_32.c @@ -547,11 +547,13 @@ void __init setup_boot_APIC_clock(void) * PIT/HPET going. Otherwise register lapic as a dummy * device. */ - if (nmi_watchdog != NMI_IO_APIC) + if (nmi_watchdog != NMI_IO_APIC) { lapic_clockevent.features &= ~CLOCK_EVT_FEAT_DUMMY; - else + } else { printk(KERN_WARNING "APIC timer registered as dummy," " due to nmi_watchdog=1!\n"); + timer_through_8259 = 1; + } } /* Setup the lapic or request the broadcast */ Index: linux/arch/x86/kernel/apic_64.c =================================================================== --- linux.orig/arch/x86/kernel/apic_64.c +++ linux/arch/x86/kernel/apic_64.c @@ -413,11 +413,13 @@ void __init setup_boot_APIC_clock(void) * PIT/HPET going. Otherwise register lapic as a dummy * device. */ - if (nmi_watchdog != NMI_IO_APIC) + if (nmi_watchdog != NMI_IO_APIC) { lapic_clockevent.features &= ~CLOCK_EVT_FEAT_DUMMY; - else + } else { printk(KERN_WARNING "APIC timer registered as dummy," " due to nmi_watchdog=1!\n"); + timer_through_8259 = 1; + } setup_APIC_timer(); }