linux-kernel - Re: [BUG] get_rtc_time() triggers NMI watchdog in hpet_rtc

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Date:	Sun, 24 Aug 2008 13:48:47 +0200
From:	"Vegard Nossum" <vegard.nossum@...il.com>
To:	"Mikael Pettersson" <mikpe@...uu.se>
Cc:	linux-kernel@...r.kernel.org, hpa@...or.com, mingo@...hat.com,
	tglx@...utronix.de
Subject: Re: [BUG] get_rtc_time() triggers NMI watchdog in hpet_rtc_interrupt()

On Sun, Aug 24, 2008 at 12:32 PM, Mikael Pettersson <mikpe@...uu.se> wrote:
>  > I also just got this during shutdown:
>  >
>  > Syncing hardware clock to system time BUG: NMI Watchdog detected
>  > LOCKUP on CPU0, ip c011d922, registers:
>  > Pid: 4181, comm: hwclock Not tainted (2.6.27-rc3-00464-g1fca254-dirty #42)
[...]

> See my reply in the thread following Ingo's patch
> <http://lkml.org/lkml/2008/8/23/158>. I've only seen the lockup
> while hwclock was setting or flushing the system time, so I suspect
> broken interaction between the hpet rtc emulation and the rtc
> user-space interface.

Oops, I picked the wrong thread :-)

Anyway, I guess it wouldn't be too hard to make a test cast by running
"hwclock" (or the corresponding initscript) in a tight loop? (Sorry, I
am not able to test this myself at the moment). That would make it
easier to test the patch too, I guess. Maybe something like:

    $ while true; do /etc/init.d/ntpdate up; /etc/init.d/ntpdate down; done

(At least "ntpdate" is the one that runs hwclock for me on F9.)

I will try this later unless you beat me to it :-)

Thanks,


Vegard

-- 
"The animistic metaphor of the bug that maliciously sneaked in while
the programmer was not looking is intellectually dishonest as it
disguises that the error is the programmer's own creation."
	-- E. W. Dijkstra, EWD1036
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