On Thu, Mar 27 2025 at 16:42, Miroslav Lichvar wrote:
On Thu, Mar 27, 2025 at 10:22:31AM +0100, Thomas Gleixner wrote:
The original implementation respected this base period, but John's approach of forwarding, which cures the coarse time getter issue, violates it. As a consequence the previous error accumulation is not longer based on the base period because the period has been reset to the random point in time when adjtimex() was invoked, which makes the error accumulation a random number.
I see, so that value of the NTP error is already wrong at that point where it's reset to 0.
To clearly see the difference with the new code, I made an attempt to update the old linux-tktest simulation that was used back when the multiplier adjustment was reworked, but there are too many missing things now and I gave up.
Can you point me to that code?
It would be probably useful to create a test mechanism which allows to exercise all of this in a simulated way so we actually don't have to wonder every time we change a bit what the consequences are.
Thanks,
tglx