Can you do a kernel bisection?

First, find the last good -rc kernel and the first bad -rc kernel from

$ sudo apt build-dep linux
$ git clone git://
$ cd linux
$ git bisect start
$ git bisect good $(the good version you found)
$ git bisect bad $(the bad version found)
$ make localmodconfig
$ make -j`nproc` deb-pkg
Install the newly built kernel.
If the issue still happens,
$ git bisect bad
$ git bisect good
Repeat to "make -j`nproc` deb-pkg" until you find the commit that causes the 

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  error loading realtime clock since upgrading to 17.10

Status in linux package in Ubuntu:

Bug description:
  (originally asked over at, but is still unresolved:

  I recently upgraded from Ubuntu 17.04 to Ubuntu 17.10 using the
  software update process. The update completed without any errors, and
  Ubuntu 17.10 is now running without any major issues.

  However, I was running a script previously that uses rtcwake which has
  since stopped working. The script automatically hibernates my laptop
  after a set period of time in sleep mode, and was working perfectly in
  Ubuntu 17.04.

  In the process of troubleshooting, I discovered that the problem was
  with rtcwake which is complaining about /dev/rtc0 missing.

  Here is output from a sample rtcwake command:

  peter@haven:~$ rtcwake -m no -s 1300
  rtcwake: assuming RTC uses UTC ...
  rtcwake: /dev/rtc0: unable to find device: No such file or directory

  I verified that in fact, that directory is missing. Since this was
  working prior to the upgrade, I have to assume that it was there
  previously, but I don't know for sure.

  In researching the error, I found some suggestions to get further
  information with timedatectl and hwclock, so here are the results from
  those commands as well.

  Output of timedatectl:

  peter@haven:~$ timedatectl
        Local time: Fri 2017-10-27 19:06:26 EDT
    Universal time: Fri 2017-10-27 23:06:26 UTC
          RTC time: n/a
         Time zone: America/New_York (EDT, -0400)
   Network time on: yes
  NTP synchronized: yes
   RTC in local TZ: no

  Output of hwclock --debug:

  peter@haven:~$ sudo hwclock --debug
  [sudo] password for peter: 
  hwclock from util-linux 2.30.1
  Trying to open: /dev/rtc0
  Trying to open: /dev/rtc
  Trying to open: /dev/misc/rtc
  No usable clock interface found.
  hwclock: Cannot access the Hardware Clock via any known method.


  When I boot with my old kernel, 4.10.0-37-generic the real-time clock
  works fine.

  I get the following RTC messages in dmesg when I boot the
  4.13.0-16-generic kernel:

  peter@haven:~$ dmesg | grep -i rtc
  [    0.089393] RTC time: 17:03:55, date: 11/01/17
  [    1.238784] rtc_cmos 00:01: RTC can wake from S4
  [    1.238794] rtc_cmos: probe of 00:01 failed with error -16
  [    1.295459] hctosys: unable to open rtc device (rtc0)


  Well, I was starting to believe that I had a hardware issue, since
  discovering I was unable to save changes to my BIOS and could not boot
  from USB. As it turns out, my laptop was bitten by this bug: causing
  my BIOS to be locked in a read-only state.

  Once I resolved the BIOS issue, and fixed the USB boot problem, I did
  a live boot of Ubuntu 17.10. The issue with my real time clock still
  exists under this clean boot scenario, yet when I boot other distros,
  like Linux Mint 18.3 and the real time clock works fine. I feel this
  definitely has something to do with the Ubuntu install, perhaps even a
  kernel bug.


  More evidence to suggest this is a kernel bug: I live-booted a copy of
  Antergos Linux, which was using the Arch kernel 4.14.12-1-ARCH and it
  exhibited the same problem with the real time clock as Ubuntu 17.10.
  In addition, I confirmed that the Linux Mint version I booted earlier
  (see Update #2) was on the Ubuntu kernel 4.10.0-38-generic.

  So, I suspect that sometime between kernels 4.10 and 4.13 this bug was 
  ApportVersion: 2.20.7-0ubuntu3.7
  Architecture: amd64
   /dev/snd/controlC0:  peter      1832 F.... pulseaudio
   /dev/snd/controlC1:  peter      1832 F.... pulseaudio
  CurrentDesktop: ubuntu:GNOME
  DistroRelease: Ubuntu 17.10
  HibernationDevice: RESUME=UUID=a602efe1-467d-4ac4-806f-1b931c91cdad
  InstallationDate: Installed on 2017-04-05 (292 days ago)
  InstallationMedia: Ubuntu 16.10 "Yakkety Yak" - Release amd64 (20161012.2)
  MachineType: LENOVO 20354
  Package: linux (not installed)
   PATH=(custom, no user)
  ProcFB: 0 inteldrmfb
  ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-4.13.0-25-generic.efi.signed 
root=UUID=fa5454aa-9072-475d-b515-acd51a6166cc ro quiet splash vt.handoff=7
  ProcVersionSignature: Ubuntu 4.13.0-25.29-generic 4.13.13
   linux-restricted-modules-4.13.0-25-generic N/A
   linux-backports-modules-4.13.0-25-generic  N/A
   linux-firmware                             1.169.1
  Tags:  wayland-session artful
  Uname: Linux 4.13.0-25-generic x86_64
  UpgradeStatus: Upgraded to artful on 2017-10-24 (90 days ago)
  UserGroups: adm cdrom dip kismet lpadmin plugdev sambashare sudo
  _MarkForUpload: True 07/21/2015
  dmi.bios.vendor: LENOVO
  dmi.bios.version: 9BCN91WW
  dmi.board.asset.tag: No Asset Tag Lancer 5A5
  dmi.board.vendor: LENOVO
  dmi.board.version: 31900058WIN
  dmi.chassis.asset.tag: No Asset Tag
  dmi.chassis.type: 10
  dmi.chassis.vendor: LENOVO
  dmi.chassis.version: Lenovo Z50-70
dmi:bvnLENOVO:bvr9BCN91WW:bd07/21/2015:svnLENOVO:pn20354:pvrLenovoZ50-70:rvnLENOVO:rnLancer5A5:rvr31900058WIN:cvnLENOVO:ct10:cvrLenovoZ50-70: IDEAPAD 20354
  dmi.product.version: Lenovo Z50-70
  dmi.sys.vendor: LENOVO

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