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

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Date:	Mon, 01 Jun 2015 07:57:49 -0400
From:	Prarit Bhargava <prarit@...hat.com>
To:	John Stultz <john.stultz@...aro.org>
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 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.

P.
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