Message-ID: <44286783.9000709@tremplin-utc.net>
Date: Tue, 28 Mar 2006 00:30:27 +0200
From: Eric Piel <Eric.Piel@tremplin-utc.net>
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To: "Peter T. Breuer" <ptb@inv.it.uc3m.es>
CC: john stultz <johnstul@us.ibm.com>, linux-kernel@vger.kernel.org
Subject: Re: uptime increases during suspend
References: <200603271953.k2RJrTR28039@inv.it.uc3m.es>
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27.03.2006 21:53, Peter T. Breuer wrote/a écrit:
> In article <1143484821.2168.16.camel@leatherman> you wrote:
>>> Would it be possible to get the old behaviour back?
> 
>> Why exactly do you want this behavior? Maybe a better explanation would
>> help stir this discussion.
> 
> I don't know why he wants it (uptime does not increase during
> hibernation) but I want it so that I can tell if I should time out or
> not on an alarm for inactivity in userspace!  The alarm should fire if
> there has been no activity for a while (30s) while activity is possible.
> If the machine is suspended, no activity is possible, so the alarm
> should not fire.
> 
> This is to counteract sysadamins playing with system time (e.g. syncing
> with a net time server after bootup) which might cause artificial time
> outs. Causing a timeout has nasty consequences when, for example, your
> root fs is mounted over the net via daemons that do the network to-ing
> and fro-ing from userspace. The only way they have of getting an
> estimate of REAL time elapsed,  without admin playing about messing
> with them, is by surreptitiously snooping uptime, which more or less
> represents kernel jiffies.
It seems that what you are really looking for in your application is a 
monotonic clock. Linux has such thing since few releases. Using 
CLOCK_MONOTONIC (cf "man 3 clock_gettime") may look much less hacky than 
using the uptime ;-)

Now... concerning the suspend effect on this clock, I don't know. It's 
probably the same problem as uptime: no official semantic has ever been 
stated yet... Does anyone know?

Eric
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