Re: question about linux time change

George Anzinger
2004-10-12T23:38:26Z

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