Re: BUG during shutdown - bisected to commit e2912009

[Xiaotian Feng]

On 01/07/2010 11:20 AM, Marc Dionne wrote:
> On Wed, Jan 6, 2010 at 10:07 PM, Marc Dionne<marc.c.dionne@xxxxxxxxx>  wrote:
> > On Wed, Jan 6, 2010 at 9:51 PM, Xiaotian Feng<dfeng@xxxxxxxxxx>  wrote:
> > > On 01/07/2010 08:44 AM, Marc Dionne wrote:
> > > > On Wed, Jan 6, 2010 at 4:42 AM, Xiaotian Feng<dfeng@xxxxxxxxxx>    wrote:
> > > > > On 01/06/2010 06:58 AM, Marc Dionne wrote:
> > > > > > On Tue, Jan 5, 2010 at 5:18 AM, Xiaotian Feng<dfeng@xxxxxxxxxx>
> > > > > >   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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