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SubjectRe: uptime increases during suspend
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?

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