linux-kernel - Re: [PATCH RFC 0/2] rtc-cmos: Workaround unwanted interrupt generation

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Message-ID: <20160720035659.GA4797@localhost.localdomain>
Date:	Wed, 20 Jul 2016 09:26:59 +0530
From:	Pratyush Anand <panand@...hat.com>
To:	Alexandre Belloni <alexandre.belloni@...e-electrons.com>,
	Thomas Gleixner <tglx@...utronix.de>, mingo@...nel.org,
	hpa@...or.com, x86@...nel.org
Cc:	Alessandro Zummo <a.zummo@...ertech.it>,
	rtc-linux@...glegroups.com,
	open list <linux-kernel@...r.kernel.org>,
	Prarit Bhargava <prarit@...hat.com>,
	RuiRui Yang <dyoung@...hat.com>
Subject: Re: [PATCH RFC 0/2] rtc-cmos: Workaround unwanted interrupt
 generation

On 19/07/2016:04:29:07 PM, Alexandre Belloni wrote:
> Hi,
> 
> On 18/07/2016 at 17:17:44 +0530, Pratyush Anand wrote :
> > Hi RTC-Maintainers,
> > 
> > 
> > On Mon, Jul 4, 2016 at 9:49 PM, Pratyush Anand <panand@...hat.com> wrote:
> > > On 27/06/2016:10:19:07 AM, Pratyush Anand wrote:
> > >> On 21/06/2016:10:25:34 AM, Pratyush Anand wrote:
> > >> > We have observed on few machines with rtc-cmos device that
> > >> > hpet_rtc_interrupt() is called before cmos_do_probe() could call
> > >> > hpet_rtc_timer_init(). It has not been observed during normal boot/reboot
> > >> > of machines. It *sometime* happens when system is booted with kdump
> > >> > secondary kernel. So, neither hpet_default_delta nor hpet_t1_cmp is
> > >> > initialized by the time interrupt is raised in the given situation.
> > >> > Therefore while loop of hpet_cnt_ahead() in hpet_rtc_timer_reinit() never
> > >> > completes. This leads to "NMI watchdog: Watchdog detected hard LOCKUP on
> > >> > cpu 0".
> > >> >
> > >> > I am still clueless, how can an interrupt be raised before RTC is enabled.
> > >> > But i do not have any idea about this device, so I am putting this patch as
> > >> > RFC to get feedback from hpet/rtc-cmos developer. I am sure there would be
> > >> > some better solution than this.
> > >>
> > >> Do you think that if I improve commit log of patches as pointed by Thomas and
> > >> send a formal version of these patches, then they should acceptable to upstream?
> > >
> > > A gentle reminder for your comment/feedback :-)
> > 
> > Please let me know how to make progress on this. If you think, there
> > could be some better way to handle this issue then please let me know.
> > If you need any more data then also please let me know.
> > 
> 
> Well, the change is x86 specific and I don't know much about HPET so
> until you get an ack from the x86 maintainers, I guess I can't help
> much.

Thanks Alexandre for your reply.

Thomas, Ingo, Peter, Your comment/feedback will be very helpful to make progress
on this.

~Pratyush