Messages in this thread | | | From | Luboš Doležel <> | Subject | Unable to move system time back on recent Core i7 systems | Date | Tue, 29 Aug 2017 21:10:39 +0200 |
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Hello,
I'm hitting a strange bug on some of my Linux systems with various 4.x kernels.
I cannot set the system time to anything before the current system time.
This includes ntpd not being able to keep the clock in sync if the system clock is a little too fast. So it's not limited to just setting the time back to the 90s, but it actually breaks time synchronization on my server system.
Essentially, settimeofday() and clock_settime() system calls succeed, but any subsequent gettimeofday() etc. call will return unaltered time.
E.g.:
$ sudo date -s 1998-08-01 Sat Aug 1 00:00:00 CEST 1998 $ date Tue Aug 29 20:59:25 CEST 2017
I have been able to reproduce the problem on these CPUs:
* Intel(R) Core(TM) i7-5820K CPU @ 3.30GHz * Intel(R) Core(TM) i7-6820HQ CPU @ 2.70GHz
I *cannot* reproduce the problem on these CPUs, even if I boot the same kernel version as on the CPUs above:
* Intel(R) Core(TM) i7-2600 CPU @ 3.40GHz * Intel(R) Core(TM) i5-3570K CPU @ 3.40GHz * Various even older CPUs
I tried to google the problem, but turned up with nothing. This brings several questions:
1) What the hell? 2) Am I the only one having this problem? 3) Can the Linux kernel developers possibly do something about this, if this problem is confirmed?
Thanks, Lubos
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