linux-kernel - Re: [Xen-devel] [PATCH 2/3] timekeeping: sync persistent clock and RTC on system time step changes

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Message-ID: <51A50F75.7040703@linaro.org>
Date:	Tue, 28 May 2013 13:11:33 -0700
From:	John Stultz <john.stultz@...aro.org>
To:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
CC:	David Vrabel <david.vrabel@...rix.com>,
	Jan Beulich <JBeulich@...e.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	"xen-devel@...ts.xen.org" <xen-devel@...ts.xen.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [Xen-devel] [PATCH 2/3] timekeeping: sync persistent clock and
 RTC on system time step changes

On 05/28/2013 01:03 PM, John Stultz wrote:
> On 05/28/2013 12:48 PM, Konrad Rzeszutek Wilk wrote:
>> On Tue, May 28, 2013 at 12:09:14PM -0700, John Stultz wrote:
>>> On 05/28/2013 11:31 AM, Konrad Rzeszutek Wilk wrote:
>>>> On Tue, May 28, 2013 at 07:26:14PM +0100, David Vrabel wrote:
>>>>> On 15/05/13 19:10, John Stultz wrote:
>>>>>> Ok, so really, as soon as the Dom0 time is set by NTP, all guests 
>>>>>> will
>>>>>> see the right time? That makes more sense, and means the window for
>>>>>> these sorts of issues is reasonably quite small.
>>>>> It's a small window but it's occurring in our automated test system.
>>>>>
>>>>>> David: So I'm less inclined to merge this individual change, but 
>>>>>> if you
>>>>>> still feel strongly about it, let me know and we can circle 
>>>>>> around on it
>>>>>> after you've addressed the specific issues I pointed out earlier.
>>>>> This patch was the actual bug fix but I've reworked it to use the
>>>>> pvclock_gtod notifier chain as this seemed to be what KVM hosts were
>>>>> using to maintain a clock for guests.  Please review the new 
>>>>> series, thanks.
>>>> Looks good.
>>>>
>>>> John if you are OK I am thinking to push this to Linus shortly as 
>>>> it is
>>>> fixing a bug.
>>> I'm really not sure I'd call this a bug.  That seems like an
>>> over-reaction to a misconfigured system.
>>>
>>> Or if there is a bug, I'm not sure its been clearly explained.
>> The #1 patch - b/c you try to set the RTC time and it actually never 
>> takes. Meaning
>> on the next time the machine is booted the time is again off.
>
> Ok. Yea, that one I'm fine with and have queued for 3.11.
>
> If you want to push it as a bug fix for 3.10, I'll leave it to you to 
> push to Linus.

Probably obvious, but just in case its not clear:

Though if that one patch goes to linus for 3.10, it needs to be reworked 
to not depend on the mach_set_rtc_mmss() interface change it currently 
depends on. The interface change is not bugfix material.

thanks
-john

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