linux-kernel - Re: [RFC][PATCH 0/4] Fixes for leapsecond expiring early ABS_TIME CLOCK

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Date:	Mon, 1 Jun 2015 10:02:27 -0700
From:	John Stultz <john.stultz@...aro.org>
To:	Prarit Bhargava <prarit@...hat.com>
Cc:	lkml <linux-kernel@...r.kernel.org>,
	Daniel Bristot de Oliveira <bristot@...hat.com>,
	Richard Cochran <richardcochran@...il.com>,
	Jan Kara <jack@...e.cz>, Jiri Bohac <jbohac@...e.cz>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	Shuah Khan <shuahkh@....samsung.com>
Subject: Re: [RFC][PATCH 0/4] Fixes for leapsecond expiring early ABS_TIME
 CLOCK_REALTIME timers

On Mon, Jun 1, 2015 at 4:57 AM, Prarit Bhargava <prarit@...hat.com> wrote:
>
>
> On 05/29/2015 04:24 PM, John Stultz wrote:
>> As Prarit reported here:
>> https://lkml.org/lkml/2015/5/27/458
>>
>> Since the leapsecond is applied at timer tick time, and not
>> the actual second edge, ABS_TIME CLOCK_REALTIME timers set for
>> right after the leapsecond could fire a second early, since
>> some timers may be expired before we trigger the timekeeping
>> timer, which then applies the leapsecond.
>>
>> Thus this patch series tries to address this isssue, including
>> extending the leap-a-day test to catch this problem, as well
>> as other relevant fixups I found while working on the code.
>>
>> This series has only had limited testing, so I wanted to send
>> it out for initial review and comment. Folks can grab this tree
>> via git for testing here:
>> https://git.linaro.org/people/john.stultz/linux.git dev/early-leap-timer
>>
>
> John, native testing went well across many 32-bit and 64-bit AMD and Intel
> boxes.  However, virtual (specifically KVM) guests failed with some sort of
> corruption:
>
> [ 1546.038479] Clock: inserting leap second 23:59:60 UTC
> [ 1559.774700] Clock: inserting leap second 23:59:60 UTC
> [ 1573.502989] Clock: inserting leap second 23:59:60 UTC
> [ 1587.235917] Clock: inserting leap second 23:59:60 UTC
> [    7.     X] Clock: inserting leap second 23:59:60 UTC
> [    7.     X] Clock: inserting leap second 23:59:60 UTC
> [    7.     X] Clock: inserting leap second 23:59:60 UTC
> [    7.     X] Clock: inserting leap second 23:59:60 UTC
>
> I'm going to see if I can figure out a way to kdump a guest with this problem.
> The issue is that it seems like all input to the console is ignored when this
> happens.

Hrm. Can you send me the qemu version and command line you're using?

thanks
-john
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