[PATCH v2 1/2] timekeeping: add EXPORT_SYMBOL_GPL for do_adjtimex()

Thomas Gleixner tglx at linutronix.de
Tue Oct 21 08:23:40 UTC 2014

On Tue, 21 Oct 2014, Thomas Shao wrote:
> I didn't find a way to detect whether NTPd is running in the hyper-v module.  

And you better do not try at all.
> In http://doc.ntp.org/4.1.0/ntpd.htm, it mentioned: Normally, the
> time is slewed if the offset is less than the step threshold, which
> is 128 ms by default, and stepped if above the threshold.
> In my implementation, I use 100ms as the threshold (maybe I should
> change to 128?).  If the time difference is less than 100ms, I just
> do nothing. So, if NTPd is running, ideally it could keep the time
> drift less than 128, so the adjustment in my patch will not get
> triggered.

Your implementation has nothing to do with NTP at all. It's not even
close to NTP. It's a random hack to inject host time or slew into
timekeeping with the precision of a random number generator.

> And moreover, by default, the guest-host time sync is turn
> off. There is a module parameter to control it. We'll also document
> customer that do not turn on this if NTP is configured.

Pretty well thought out mechanism to ensure that people will get it
wrong in the first place.



More information about the devel mailing list