linux-kernel - Re: [RFC][PATCH 4/4] time: Do leapsecond adjustment in gettime fastpaths

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Message-ID: <20150605141259.GA9406@localhost.localdomain>
Date:	Fri, 5 Jun 2015 16:12:59 +0200
From:	Richard Cochran <richardcochran@...il.com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	John Stultz <john.stultz@...aro.org>,
	Ingo Molnar <mingo@...nel.org>,
	lkml <linux-kernel@...r.kernel.org>,
	Prarit Bhargava <prarit@...hat.com>,
	Daniel Bristot de Oliveira <bristot@...hat.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 4/4] time: Do leapsecond adjustment in gettime
 fastpaths

On Fri, Jun 05, 2015 at 11:10:08AM +0200, Peter Zijlstra wrote:
> Firstly I would strongly suggest such applications not use UTC because
> of this, I think TAI was invented for just this reason.

So I wonder whether the bug in the original post affects TAI timers as
well...

> Secondly, how would John's patches help with this? Usespace loops
> reading time would be using the VDSO and would still not get the right
> time, and timers would be subject to the same IRQ latency that a hrtimer
> based leap second insert would, and would still very much not be in-sync
> across the cluster.

But we have a tick based insertion.  (IIRC, it used to be hrtimer
based, but that was buggy, too).

Thanks,
Richard
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