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

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Date:	Wed, 6 Jan 2010 19:44:29 -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 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.

Marc
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