linux-kernel - Re: BUG during shutdown - bisected to commit e2912009

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Date:	Wed, 6 Jan 2010 22:07:05 -0500
From:	Marc Dionne <marc.c.dionne@...il.com>
To:	Xiaotian Feng <dfeng@...hat.com>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...e.hu>
Subject: Re: BUG during shutdown - bisected to commit e2912009

On Wed, Jan 6, 2010 at 9:51 PM, Xiaotian Feng <dfeng@...hat.com> wrote:
> On 01/07/2010 08:44 AM, Marc Dionne wrote:
>>
>> On Wed, Jan 6, 2010 at 4:42 AM, Xiaotian Feng<dfeng@...hat.com>  wrote:
>>>
>>> On 01/06/2010 06:58 AM, Marc Dionne wrote:
>>>>
>>>> On Tue, Jan 5, 2010 at 5:18 AM, Xiaotian Feng<dfeng@...hat.com>
>>>>  wrote:
>>>>>
>>>>> This is outputed by sound module, but it will not affect clockevents,
>>>>> could
>>>>> you please try following patch and let me know the output before BUG_ON
>>>>> happens? We can gather more information on the BUG_ON. Thank you.
>>>>>
>>>>> diff --git a/kernel/time/clockevents.c b/kernel/time/clockevents.c
>>>>> index 6f740d9..7c945e8 100644
>>>>> --- a/kernel/time/clockevents.c
>>>>> +++ b/kernel/time/clockevents.c
>>>>> @@ -260,6 +260,9 @@ void clockevents_notify(unsigned long reason, void
>>>>> *arg)
>>>>>                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("invalid dev %s mode %d
>>>>> on
>>>>> cpu %d\n", dev->name,
>>>>> +                                               dev->mode, cpu);
>>>>>                                BUG_ON(dev->mode !=
>>>>> CLOCK_EVT_MODE_UNUSED);
>>>>>                                list_del(&dev->list);
>>>>
>>>> I don't get anything on screen from the printk - is there a trick
>>>> needed to getting printk output at that stage of shutting down?  I
>>>> tried inserting an mdelay() before the BUG, which delayed the bug
>>>> output but still didn't print the invalid dev message.
>>>
>>> Did you notice this BUG when you're doing suspend/resume?
>>>
>>> Does the BUG still appear if we changed BUG_ON line to BUG_ON(dev->mode
>>> !=
>>> CLOCK_EVT_MODE_UNUSED&&  dev->mode != CLOCK_EVT_MODE_SHUTDOWN)?
>>
>> I only see the BUG on halt - reboot works normally and suspend
>> actually freezes and doesn't suspend, but that's perhaps unrelated.
>>
>> I managed to get your suggested printk to work by adding KERN_CRIT
>> (otherwise I got no output), and the offending dev is:
>>  "hpet", mode 3 (CLOCK_EVT_MODE_ONESHOT?), cpu 4.
>
> It looks like kernel is trying to remove broadcast device, could you please
> try following patch?
>
> diff --git a/kernel/time/clockevents.c b/kernel/time/clockevents.c
> index 6f740d9..d7395fd 100644
> --- a/kernel/time/clockevents.c
> +++ b/kernel/time/clockevents.c
> @@ -259,7 +259,8 @@ void clockevents_notify(unsigned long reason, void *arg)
>                cpu = *((int *)arg);
>                list_for_each_entry_safe(dev, tmp, &clockevent_devices, list)
> {
>                        if (cpumask_test_cpu(cpu, dev->cpumask) &&
> -                           cpumask_weight(dev->cpumask) == 1) {
> +                           cpumask_weight(dev->cpumask) == 1 &&
> +                           !tick_is_broadcast_device(dev)) {
>                                BUG_ON(dev->mode != CLOCK_EVT_MODE_UNUSED);
>                                list_del(&dev->list);
>                        }

That works - no problem shutting down with that patch applied.

Marc
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