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Date: Tue, 30 Aug 2016 17:10:10 +0800
From: Dave Young <dyoung@...hat.com>
To: Pratyush Anand <panand@...hat.com>
Cc: mingo@...nel.org, alexandre.belloni@...e-electrons.com,
tglx@...utronix.de, hpa@...or.com, x86@...nel.org,
rtc-linux@...glegroups.com, linux-kernel@...r.kernel.org,
prarit@...hat.com, dzickus@...hat.com, a.zummo@...ertech.it
Subject: Re: [PATCH V3 2/2] rtc/rtc-cmos: Initialize software counters before
irq is registered
On 08/30/16 at 04:38pm, Dave Young wrote:
> On 08/30/16 at 04:22pm, 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@...hat.com>
> > > [dzickus@...hat.com: edited the patch's summary]
> > > Signed-off-by: Don Zickus <dzickus@...hat.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.
>
> Hmm, seems CONFIG_HPET_EMULATE_RTC is x86 only, so maybe go to
> asm/hpet.h should be better..
Oops, asm/hpet will not work since rtc-cmos is also used in other
arches., please ignore the comment.
Thanks
Dave
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