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

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Message-ID: <20150602092119.GX19282@twins.programming.kicks-ass.net>
Date:	Tue, 2 Jun 2015 11:21:19 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Ingo Molnar <mingo@...nel.org>
Cc:	John Stultz <john.stultz@...aro.org>,
	lkml <linux-kernel@...r.kernel.org>,
	Prarit Bhargava <prarit@...hat.com>,
	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 4/4] time: Do leapsecond adjustment in gettime
 fastpaths

On Tue, Jun 02, 2015 at 11:01:54AM +0200, Ingo Molnar wrote:
> > Currently, leapsecond adjustments are done at tick time.
> > 
> > As a result, the leapsecond was applied at the first timer
> > tick *after* the leapsecond (~1-10ms late depending on HZ),
> > rather then exactly on the second edge.

So why not program a hrtimer to expire at the exact right time? Then
even the VDSO gets its time 'right' and you avoid touching all the
fast paths.
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