Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753462Ab0AMBtJ (ORCPT ); Tue, 12 Jan 2010 20:49:09 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752154Ab0AMBtH (ORCPT ); Tue, 12 Jan 2010 20:49:07 -0500 Received: from mx1.redhat.com ([209.132.183.28]:63702 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752131Ab0AMBtH (ORCPT ); Tue, 12 Jan 2010 20:49:07 -0500 Message-ID: <4B4D2678.5090601@redhat.com> Date: Wed, 13 Jan 2010 09:48:40 +0800 From: Xiaotian Feng User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.1.5) Gecko/20091209 Fedora/3.0-4.fc12 Lightning/1.0pre Thunderbird/3.0 MIME-Version: 1.0 To: Thomas Gleixner CC: linux-kernel@vger.kernel.org, Magnus Damm , H Hartley Sweeten Subject: Re: [PATCH] clockevent: don't remove broadcast device when cpu is dead References: <1262834564-13033-1-git-send-email-dfeng@redhat.com> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3217 Lines: 86 On 01/12/2010 09:20 PM, Thomas Gleixner wrote: > On Thu, 7 Jan 2010, Xiaotian Feng wrote: > >> Marc reported BUG during shutdown, after debugging, kernel is trying >> to remove a broadcast device which mode is CLOCK_EVT_MODE_ONESHOT. >> >> The root cause for this bug is that in clockevents_notify, >> "cpumask_weight(dev->cpumask) == 1" is always true even if dev is a > > Why is cpumask_weight(dev->cpumask) == 1 always true when we shutdown > a non boot cpu ? > > The broadcast device is not a per cpu device and the cpumask should > not only contain the CPU which is shut down ! At least for hpet broadcast dev, it's dev->cpumask is only contain the CPU which it is initialized from. And for broadcast device, kernel is using tick_broadcast_mask not dev->cpumask, right? > > The patch is papering over the real problem. > > Marc, can you please apply the following debug patch and provide the > dmesg outputs from boot and shutdown ? > > Thanks, > > tglx > --- > > Index: linux-2.6-tip/kernel/time/clockevents.c > =================================================================== > --- linux-2.6-tip.orig/kernel/time/clockevents.c > +++ linux-2.6-tip/kernel/time/clockevents.c > @@ -186,7 +186,7 @@ void clockevents_register_device(struct > BUG_ON(!dev->cpumask); > > raw_spin_lock_irqsave(&clockevents_lock, flags); > - > + printk(KERN_ERR "CE register %p %s\n", dev, dev->name); > list_add(&dev->list,&clockevent_devices); > clockevents_do_notify(CLOCK_EVT_NOTIFY_ADD, dev); > clockevents_notify_released(); > @@ -220,6 +220,7 @@ void clockevents_exchange_device(struct > * released list and do a notify add later. > */ > if (old) { > + printk(KERN_INFO "CE Release %p %s\n", old, old->name); > clockevents_set_mode(old, CLOCK_EVT_MODE_UNUSED); > list_del(&old->list); > list_add(&old->list,&clockevents_released); > @@ -260,6 +261,13 @@ void clockevents_notify(unsigned long re > list_for_each_entry_safe(dev, tmp,&clockevent_devices, list) { > if (cpumask_test_cpu(cpu, dev->cpumask)&& > cpumask_weight(dev->cpumask) == 1) { > + if (dev->mode != CLOCK_EVT_MODE_UNUSED) { > + printk(KERN_INFO > + "CE Remove %p %s bc: %d\n", > + dev, dev->name, > + tick_is_broadcast_device(dev)); > + continue; > + } > BUG_ON(dev->mode != CLOCK_EVT_MODE_UNUSED); > list_del(&dev->list); > } > Index: linux-2.6-tip/kernel/time/tick-broadcast.c > =================================================================== > --- linux-2.6-tip.orig/kernel/time/tick-broadcast.c > +++ linux-2.6-tip/kernel/time/tick-broadcast.c > @@ -72,6 +72,8 @@ int tick_check_broadcast_device(struct c > (dev->features& CLOCK_EVT_FEAT_C3STOP)) > return 0; > > + printk(KERN_INFO "CE set broadcast %p %s\n", dev, dev->name); > + > clockevents_exchange_device(NULL, dev); > tick_broadcast_device.evtdev = dev; > if (!cpumask_empty(tick_get_broadcast_mask())) > -- 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/