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

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Date:	Thu, 12 Sep 2013 13:35:02 -0700
From:	John Stultz <john.stultz@...aro.org>
To:	Herbert Xu <herbert@...dor.apana.org.au>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	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 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.

thanks
-john
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