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

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Message-ID: <48B3DA02.9080002@tuffmail.co.uk>
Date:	Tue, 26 Aug 2008 11:25:06 +0100
From:	Alan Jenkins <alan-jenkins@...fmail.co.uk>
To:	Vegard Nossum <vegard.nossum@...il.com>
CC:	Mikael Pettersson <mikpe@...uu.se>, hpa@...or.com,
	mingo@...hat.com, tglx@...utronix.de,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: Re: [BUG] get_rtc_time() triggers NMI watchdog in hpet_rtc_interrupt()

Vegard Nossum wrote:
> 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 :-)
>
>   
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.

Alan
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