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

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Message-ID: <4B4553DF.30207@redhat.com>
Date:	Thu, 07 Jan 2010 11:24:15 +0800
From:	Xiaotian Feng <dfeng@...hat.com>
To:	Marc Dionne <marc.c.dionne@...il.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 01/07/2010 11:20 AM, Marc Dionne wrote:
> On Wed, Jan 6, 2010 at 10:07 PM, Marc Dionne<marc.c.dionne@...il.com>  wrote:
>> 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.
>
> And after doing a bit more testing, it turns out that applying this
> patch also makes suspend/resume work normally again, so it looks like
> the hang on suspend was also related to this.
Thanks for the testing, patch is sent to upstream :-)
>
> Thanks,
> Marc
>

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