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SubjectRe: [BUG] get_rtc_time() triggers NMI watchdog in hpet_rtc_interrupt()
Ingo Molnar wrote:
> * Alan Jenkins <alan-jenkins@tuffmail.co.uk> wrote:
>
>
>> I beat you :-). I noticed the problem myself. It does trigger if I
>> run hwclock in a loop.
>>
>> while true; do hwclock; done
>>
>> However it is fine in latest git. Looks like Ingo's patch has been
>> merged, and has fixed it.
>>
>
> ah, good - thanks for testing it. I havent seen a lockup on the T60
> either - but it was very sporadic to begin with. (and now we understand
> why: hwclock is running only once per reboot.)
>
> Plus, the real bug has to be found as well: who in the rtc ioctl path
> calls this code with irqs disabled - it's not nice.
>

Isn't the problem that it gets called from a timer IRQ? So irqs are
enabled globally, but the timer IRQ is masked.

[<c0139cc0>] hrtimer_run_pending+0x20/0x90
[<c01478a8>] handle_IRQ_event+0x28/0x50
[<c0148f71>] handle_edge_irq+0xa1/0x120
[<c010615b>] do_IRQ+0x3b/0x70
[<c0113225>] smp_apic_timer_interrupt+0x55/0x80
[<c0103c4f>] common_interrupt+0x23/0x28

Which in turn is probably because the userspace "RTC interrupt"
interface is emulated using RTC reads within the main timer interrupt
handler.

Alan


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