Re: PROBLEM: monotonic clock going backwards on ppc64

Hi,

quoted

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