[rtc-linux] Re: [PATCH V3 2/2] rtc/rtc-cmos: Initialize software counters before irq is registered

[Pratyush Anand <panand@redhat.com>]

Hi Dave,

On 30/08/2016:04:22:30 PM, Dave Young wrote:
> Hi, Pratyush
> 
> On 08/16/16 at 08:55am, Pratyush Anand wrote:
> > We have observed on few x86 machines with rtc-cmos device that
> > hpet_rtc_interrupt() is called just after irq registration and before
> > cmos_do_probe() could call hpet_rtc_timer_init().
> > 
> > So, neither hpet_default_delta nor hpet_t1_cmp is initialized by the time
> > interrupt is raised in the given situation, and this results in NMI
> > watchdog LOCKUP.
> > 
> > It has only been observed sporadically on kdump secondary kernels.
> > 
> > See the call trace:
> > ---<-snip->---
> >    27.913194] Kernel panic - not syncing: Watchdog detected hard LOCKUP on
> > cpu 0
> > [   27.915371] CPU: 0 PID: 1 Comm: swapper/0 Not tainted
> > 3.10.0-342.el7.x86_64 #1
> > [   27.917503] Hardware name: HP ProLiant DL160 Gen8, BIOS J03 02/10/2014
> > [   27.919455]  ffffffff8186a728 0000000059c82488 ffff880034e05af0
> > ffffffff81637bd4
> > [   27.921870]  ffff880034e05b70 ffffffff8163144a 0000000000000010
> > ffff880034e05b80
> > [   27.924257]  ffff880034e05b20 0000000059c82488 0000000000000000
> > 0000000000000000
> > [   27.926599] Call Trace:
> > [   27.927352]  <NMI>  [<ffffffff81637bd4>] dump_stack+0x19/0x1b
> > [   27.929080]  [<ffffffff8163144a>] panic+0xd8/0x1e7
> > [   27.930588]  [<ffffffff8111d3e0>] ? restart_watchdog_hrtimer+0x50/0x50
> > [   27.932502]  [<ffffffff8111d4a2>] watchdog_overflow_callback+0xc2/0xd0
> > [   27.934427]  [<ffffffff811612c1>] __perf_event_overflow+0xa1/0x250
> > [   27.936232]  [<ffffffff81161d94>] perf_event_overflow+0x14/0x20
> > [   27.937957]  [<ffffffff81032ae8>] intel_pmu_handle_irq+0x1e8/0x470
> > [   27.939799]  [<ffffffff8164164b>] perf_event_nmi_handler+0x2b/0x50
> > [   27.941649]  [<ffffffff81640d99>] nmi_handle.isra.0+0x69/0xb0
> > [   27.943348]  [<ffffffff81640f49>] do_nmi+0x169/0x340
> > [   27.944802]  [<ffffffff816401d3>] end_repeat_nmi+0x1e/0x2e
> > [   27.946424]  [<ffffffff81056ee5>] ? hpet_rtc_interrupt+0x85/0x380
> > [   27.948197]  [<ffffffff81056ee5>] ? hpet_rtc_interrupt+0x85/0x380
> > [   27.949992]  [<ffffffff81056ee5>] ? hpet_rtc_interrupt+0x85/0x380
> > [   27.951816]  <<EOE>>  <IRQ>  [<ffffffff8108f5a3>] ?
> > run_timer_softirq+0x43/0x340
> > [   27.954114]  [<ffffffff8111e24e>] handle_irq_event_percpu+0x3e/0x1e0
> > [   27.955962]  [<ffffffff8111e42d>] handle_irq_event+0x3d/0x60
> > [   27.957635]  [<ffffffff811210c7>] handle_edge_irq+0x77/0x130
> > [   27.959332]  [<ffffffff8101704f>] handle_irq+0xbf/0x150
> > [   27.960949]  [<ffffffff8164a86f>] do_IRQ+0x4f/0xf0
> > [   27.962434]  [<ffffffff8163faed>] common_interrupt+0x6d/0x6d
> > [   27.964101]  <EOI>  [<ffffffff8163f43b>] ?
> > _raw_spin_unlock_irqrestore+0x1b/0x40
> > [   27.966308]  [<fffff8111ff07>] __setup_irq+0x2a7/0x570
> > [   28.067859]  [<ffffffff81056e60>] ? hpet_cpuhp_notify+0x140/0x140
> > [   28.069709]  [<ffffffff8112032c>] request_threaded_irq+0xcc/0x170
> > [   28.071585]  [<ffffffff814b24a6>] cmos_do_probe+0x1e6/0x450
> > [   28.073240]  [<ffffffff814b2710>] ? cmos_do_probe+0x450/0x450
> > [   28.074911]  [<ffffffff814b27cb>] cmos_pnp_probe+0xbb/0xc0
> > [   28.076533]  [<ffffffff8139b245>] pnp_device_probe+0x65/0xd0
> > [   28.078198]  [<ffffffff813f8ca7>] driver_probe_device+0x87/0x390
> > [   28.079971]  [<ffffffff813f9083>] __driver_attach+0x93/0xa0
> > [   28.081660]  [<ffffffff813f8ff0>] ? __device_attach+0x40/0x40
> > [   28.083662]  [<ffffffff813f6a13>] bus_for_each_dev+0x73/0xc0
> > [   28.085370]  [<ffffffff813f86fe>] driver_attach+0x1e/0x20
> > [   28.086974]  [<ffffffff813f8250>] bus_add_driver+0x200/0x2d0
> > [   28.088634]  [<ffffffff81ade49a>] ? rtc_sysfs_init+0xe/0xe
> > [   28.090349]  [<ffffffff813f9704>] driver_register+0x64/0xf0
> > [   28.091989]  [<ffffffff8139b070>] pnp_register_driver+0x20/0x30
> > [   28.093707]  [<ffffffff81ade4ab>] cmos_init+0x11/0x71
> > ---<-snip->---
> > 
> > The previous patch split hpet_rtc_timer_init into
> > hpet_rtc_timer_counter_init() and hpet_rtc_timer_enable().
> > 
> > Therefore, this patch moved hpet_rtc_timer_counter_init() before IRQ
> > registration, so that we can gracefully handle such spurious interrupts.
> > 
> > We were able to reproduce the problem in maximum 15 trials of kdump
> > secondary kernel boot on an hp-dl160gen8 machine without this patch.
> > However, more than 35 trials went fine after applying this patch.
> > 
> > Signed-off-by: Pratyush Anand <panand@redhat.com>
> > [dzickus@redhat.com: edited the patch's summary]
> > Signed-off-by: Don Zickus <dzickus@redhat.com>
> > ---
> >  drivers/rtc/rtc-cmos.c | 13 ++++++++++++-
> >  1 file changed, 12 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/rtc/rtc-cmos.c b/drivers/rtc/rtc-cmos.c
> > index 43745cac0141..089d987f2638 100644
> > --- a/drivers/rtc/rtc-cmos.c
> > +++ b/drivers/rtc/rtc-cmos.c
> > @@ -129,6 +129,16 @@ static inline int hpet_rtc_dropped_irq(void)
> >  	return 0;
> >  }
> >  
> > +static inline int hpet_rtc_timer_counter_init(void)
> > +{
> > +	return 0;
> > +}
> > +
> > +static inline int hpet_rtc_timer_enable(void)
> > +{
> > +	return 0;
> > +}
> > +
> 
> Can these dummy functions go to /usr/include/linux/hpet.h alont with
> the #ifdef  etc.

I kept them here because, similar functions like hpet_set_alarm_time() were
already there. So, if you suggest that I should have an additional cleanup patch
first, which moves existing #ifdef block to inlcude/linux/hpet.h and this
patch adds it's inline in linux/hpet.h, then may be I can take that. But not
sure if there is something more to be done which will help the MAINTAINER to
take it.

~Pratyush

> 
> >  static inline int hpet_rtc_timer_init(void)
> >  {
> >  	return 0;
> > @@ -707,6 +717,7 @@ cmos_do_probe(struct device *dev, struct resource *ports, int rtc_irq)
> >  		goto cleanup1;
> >  	}
> >  
> > +	hpet_rtc_timer_counter_init();
> >  	if (is_valid_irq(rtc_irq)) {
> >  		irq_handler_t rtc_cmos_int_handler;
> >  
> > @@ -729,7 +740,7 @@ cmos_do_probe(struct device *dev, struct resource *ports, int rtc_irq)
> >  			goto cleanup1;
> >  		}
> >  	}
> > -	hpet_rtc_timer_init();
> > +	hpet_rtc_timer_enable();
> >  
> >  	/* export at least the first block of NVRAM */
> >  	nvram.size = address_space - NVRAM_OFFSET;
> > -- 
> > 2.5.5
> > 
> 
> Thanks
> Dave

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