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

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Date:	Thu, 12 Sep 2013 23:44:10 +1000
From:	Herbert Xu <herbert@...dor.apana.org.au>
To:	Thomas Gleixner <tglx@...utronix.de>
Cc:	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, 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.

Of course, this brought with it a new set of problems when the
system time is stepped which now cause SAs to expire even though
they probably shouldn't.

Cheers,
-- 
Email: Herbert Xu <herbert@...dor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt
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