From: George Anzinger <george@mvista.com>
To: Chris Friesen <cfriesen@nortelnetworks.com>
Cc: Linux kernel <linux-kernel@vger.kernel.org>
Subject: Re: question about linux time change
Date: Tue, 12 Oct 2004 16:35:15 -0700 [thread overview]
Message-ID: <416C6A33.6030202@mvista.com> (raw)
In-Reply-To: <4165AFBC.8010605@nortelnetworks.com>
Chris Friesen wrote:
>
> I have been asked to add the ability to notify userspace when the time
> of day changes. The actual notification is the easy part. I'm having
> issues with where exactly the time is really changed.
Just what sort of time changes do you want to notify on? The ntp code "drifts"
time a lot. Do you want to know about this? If it is only cases where there is
a jump in time, you might do well to look at "clock_was_set()". It is in
kernel/posix-timers.c and is called when ever do_settimeofday() is called AND on
leap second calls.
You will even find code in there to push the ladder out of the softirq context.
>
> do_settimeofday() is pretty straightforward. No problems there.
> adjtimex() with ADJ_OFFSET_SINGLESHOT mode seems reasonable as well.
>
> adjtimex() with ADJ_OFFSET is a bit harder to follow. Can you give me
> any pointers on what's going on with ADJ_OFFSET?
>
> Thanks,
>
> Chris
>
--
George Anzinger george@mvista.com
High-res-timers: http://sourceforge.net/projects/high-res-timers/
Preemption patch: http://www.kernel.org/pub/linux/kernel/people/rml
next prev parent reply other threads:[~2004-10-12 23:38 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-10-07 21:06 question about linux time change Chris Friesen
2004-10-12 23:35 ` George Anzinger [this message]
2004-10-13 0:34 ` Chris Friesen
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