linux-kernel - Re: [PATCHv3 linux-next] hrtimer: Add notifier when clock_was

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Message-ID: <alpine.DEB.2.02.1309122240210.4089@ionos.tec.linutronix.de>
Date:	Thu, 12 Sep 2013 22:41:07 +0200 (CEST)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	John Stultz <john.stultz@...aro.org>
cc:	Herbert Xu <herbert@...dor.apana.org.au>,
	Fan Du <fan.du@...driver.com>,
	Steffen Klassert <steffen.klassert@...unet.com>,
	David Miller <davem@...emloft.net>,
	Daniel Borkmann <dborkman@...hat.com>,
	LKML <linux-kernel@...r.kernel.org>,
	netdev <netdev@...r.kernel.org>
Subject: Re: [PATCHv3 linux-next] hrtimer: Add notifier when clock_was_set
 was called

On Thu, 12 Sep 2013, John Stultz wrote:
> On Thu, Sep 12, 2013 at 6:44 AM, Herbert Xu <herbert@...dor.apana.org.au> wrote:
> > On Thu, Sep 12, 2013 at 03:21:24PM +0200, Thomas Gleixner wrote:
> >>
> >> > (3): http://www.spinics.net/lists/netdev/msg245169.html
> >>
> >> Thanks for the explanation so far.
> >>
> >> What's still unclear to me is why these timeouts are bound to wall
> >> time in the first place.
> >>
> >> Is there any real reason why the key life time can't simply be
> >> expressed in monotonic time, e.g. N seconds after creation or M
> >> seconds after usage? Looking at the relevant RFCs I can't find any
> >> requirement for binding the life time to wall time.
> >>
> >> A life time of 10 minutes does not change when the wall clock is
> >> adjusted for whatever reasons. It's still 10 minutes and not some
> >> random result of the wall clock adjustments. But I might be wrong as
> >> usual :)
> >
> > Well we started out with straight timers.  It was changed because
> > people wanted IPsec SAs to expire after a suspect/resume which
> > AFAIK does not touch normal timers.
> 
> I'm not sure I've totally groked the specific need here, but if you're
> wanting a monotonic clockbase that includes suspend time, then you
> might checkout CLOCK_BOOTTIME.

Duh, completely forgot about that one. Sure that would avoid the whole
business.

Thanks,

	tglx
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