Hi,

>> Decreasing the realtime clock across the y2k38 threshold is one reliable way 
>> to reproduce.
>> Allegedly this can also happen just by running ntpd, I have not managed to 
>> reproduce that other
>> than booting with rtc at >2038 and then running ntp.

> Isn't it the expected behavior. Here is what I see for powermac:
>...    gives us a time in the documented 1904..2040 year range. I decided not

This (or some related issue involving monotonic time going wonky) surfaced on a 
system running 4.5 kernel with sane clock values running ntpd. It may not be 
limited to setting the clock beyond 2038, that is just a convenient way to 
reproduce something visibly wrong.

If the "ntpd-related monotonic" issue is separate from what I reported, I did 
not find anything in the commit history that looks likely to have fixed that, 
so I think that is still a thing.

Another way of looking at the issue is that when you set the clock beyond 2038 
(or the mystery ntpd thing happens), vdso and syscall versions of clock_gettime 
start reporting wildly different values for CLOCK_MONOTONIC. If someone manages 
to somehow interlace calls to those two assuming they are consistent, crazy 
bugs will ensue...

Regards,
Jakub

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