** Tags added: oem-priority originate-from-1813901 somerville -- You received this bug notification because you are a member of Kernel Packages, which is subscribed to linux in Ubuntu. https://bugs.launchpad.net/bugs/1840239
Title: tsc marked unstable after entered PC10 on Intel CoffeeLake Status in HWE Next: New Status in linux package in Ubuntu: Incomplete Bug description: This is actually a duplicate to https://bugzilla.kernel.org/show_bug.cgi?id=203183 that is for internal tracking. [Overview] On Intel CoffeeLake it's observed tsc is always marked unstable after turning off screen and let cpu enter idle state Package C10(PC10), and then clock source is switched to hpet. Following messages are printed in dmesg when this occurs: [ 115.454117] clocksource: timekeeping watchdog on CPU2: Marking clocksource 'tsc' as unstable because the skew is too large: [ 115.454146] clocksource: 'hpet' wd_now: a44e6960 wd_last: a42fe23b mask: ffffffff [ 115.454151] clocksource: 'tsc' cs_now: 69ee1f8d9f cs_last: 699580f6fd mask: ffffffffffffffff [ 115.454160] tsc: Marking TSC unstable due to clocksource watchdog [ 115.454675] TSC found unstable after boot, most likely due to broken BIOS. Use 'tsc=unstable'. [ 115.454679] sched_clock: Marking unstable (115712298090, -257671127)<-(115460381128, -5706726) [ 115.455825] clocksource: Switched to clocksource hpet [Step to reproduce] 1. use `powertop` to observe if CPU has ever enter PC10, 2. issue `xset dpms force off` to turn off screen and idle for some minutes, 3. check dmesg for above tsc marked unstable messages [Actual Results] TSC marked unstable and clock source switched to HPET. [Expected Results] TSC remains the clock source across the PC10 event. [Build Date & Hardware] This is reproducible on kernel version 4.14 through 5.1-rc2. Order kernel versions are not tested. [Additional Information] This was first found on Ubuntu (all versions) that system doesn't go suspend after stayed idle for 20 minutes. Clock source was switched to HPET, the system time is no correctly synced with reality so that the system doesn't consider it has stayed idle long enough to begin suspend process. To manage notifications about this bug go to: https://bugs.launchpad.net/hwe-next/+bug/1840239/+subscriptions -- Mailing list: https://launchpad.net/~kernel-packages Post to : kernel-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~kernel-packages More help : https://help.launchpad.net/ListHelp
