| Re: [chrony-dev] chronyd broken on macOS Big Sur |
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- To: chrony-dev@xxxxxxxxxxxxxxxxxxxx
- Subject: Re: [chrony-dev] chronyd broken on macOS Big Sur
- From: Bryan Christianson <bryan@xxxxxxxxxxxxx>
- Date: Fri, 28 Aug 2020 16:45:10 +1200
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Hi Miroslav
> On 27/08/2020, at 8:10 PM, Miroslav Lichvar <mlichvar@xxxxxxxxxx> wrote:
>
> I guess it's also possible that the ntp_adjtime() call doesn't
> actually do anything. You could try changing the frequency in larger
> steps, e.g. 100 ppm every minute and see if it has any effect on the
> offset reported by chronyd -x. If it looks the same as when you don't
> change the frequency, ntp_adjtime() isn't doing anything.
>
It looks like Apple may have messed up signed/unsigned again in Big Sur. I played around with variations of the test code without much success in reproducing the problem. I then tried setting the frequency in the range 0 to -500pm in steps of 50ppm, with a 30 second sleep each iteration.
The frequency returned in the timex buffer was incorrect. Instead of seeing "-50 ppm => -50 ppm : ok" as expected I see "-50 ppm => 65486 ppm : failed". On macOS 10.15 I see the expected result.
I was still unable to reproduce an abrupt change in offset, but I think there is a definite 'sign' problem in the Apple code.
If Apple don't respond to my bug report it may be possible to work around this in chrony.
Maybe the test case in chrony should also look at -ve frequencies?
Bryan Christianson
bryan@xxxxxxxxxxxxx
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