This bug is awaiting verification that the kernel in -proposed solves the problem. Please test the kernel and update this bug with the results. If the problem is solved, change the tag 'verification-needed- eoan' to 'verification-done-eoan'. If the problem still exists, change the tag 'verification-needed-eoan' to 'verification-failed-eoan'.
If verification is not done by 5 working days from today, this fix will be dropped from the source code, and this bug will be closed. See https://wiki.ubuntu.com/Testing/EnableProposed for documentation how to enable and use -proposed. Thank you! ** Tags added: verification-needed-eoan -- You received this bug notification because you are a member of Kernel Packages, which is subscribed to linux-oem in Ubuntu. https://bugs.launchpad.net/bugs/1840239 Title: tsc marked unstable after entered PC10 on Intel CoffeeLake Status in HWE Next: Triaged Status in linux package in Ubuntu: Triaged Status in linux-oem package in Ubuntu: New Status in linux-oem-osp1 package in Ubuntu: New Status in linux source package in Bionic: Fix Committed Status in linux-oem source package in Bionic: Fix Released Status in linux-oem-osp1 source package in Bionic: New Status in linux source package in Disco: Fix Committed Status in linux-oem source package in Disco: Won't Fix Status in linux-oem-osp1 source package in Disco: Won't Fix Status in linux source package in Eoan: Fix Committed Status in linux-oem source package in Eoan: Won't Fix Status in linux-oem-osp1 source package in Eoan: Won't Fix Bug description: === SRU Justification === [Impact] TSC marked unstable by skewed HPET after Intel SoC reached PC10 state. [Fix] Disable HPET on affected SoC generations, currently happens to CFL and ICL. [Test] I can confirm disabling HPET can avoid this issue. [Regression Potential] Low. TSC on recent Intel SoC is now an invariant clocksource, so it's harmless to disable HPET on these platforms. === Original Bug Report === 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
