Hello,
I have completed the bisect as requested and identified the problem commit. The 
bisect message is as follows:-

git bisect good
f723dd269d0740e09af47bb5590ffc4f61766153 is the first bad commit
commit f723dd269d0740e09af47bb5590ffc4f61766153
Author: Thomas Gleixner <t...@linutronix.de>
Date:   Thu Nov 7 09:05:00 2019 +0100

    x86/timer: Skip PIT initialization on modern chipsets

    BugLink: https://bugs.launchpad.net/bugs/1851216

    Recent Intel chipsets including Skylake and ApolloLake have a special
    ITSSPRC register which allows the 8254 PIT to be gated.  When gated, the
    8254 registers can still be programmed as normal, but there are no IRQ0
    timer interrupts.

    Some products such as the Connex L1430 and exone go Rugged E11 use this
    register to ship with the PIT gated by default. This causes Linux to fail
    to boot:

      Kernel panic - not syncing: IO-APIC + timer doesn't work! Boot with
      apic=debug and send a report.

    The panic happens before the framebuffer is initialized, so to the user, it
    appears as an early boot hang on a black screen.

    Affected products typically have a BIOS option that can be used to enable
    the 8254 and make Linux work (Chipset -> South Cluster Configuration ->
    Miscellaneous Configuration -> 8254 Clock Gating), however it would be best
    to make Linux support the no-8254 case.

    Modern sytems allow to discover the TSC and local APIC timer frequencies,
    so the calibration against the PIT is not required. These systems have
    always running timers and the local APIC timer works also in deep power
    states.

    So the setup of the PIT including the IO-APIC timer interrupt delivery
    checks are a pointless exercise.

    Skip the PIT setup and the IO-APIC timer interrupt checks on these systems,
    which avoids the panic caused by non ticking PITs and also speeds up the
    boot process.

    Thanks to Daniel for providing the changelog, initial analysis of the
    problem and testing against a variety of machines.

    Reported-by: Daniel Drake <dr...@endlessm.com>
    Signed-off-by: Thomas Gleixner <t...@linutronix.de>
    Tested-by: Daniel Drake <dr...@endlessm.com>
    Cc: b...@alien8.de
    Cc: h...@zytor.com
    Cc: li...@endlessm.com
    Cc: rafael.j.wyso...@intel.com
    Cc: hdego...@redhat.com
    Link: https://lkml.kernel.org/r/20190628072307.24678-1-dr...@endlessm.com

    (backported from commit c8c4076723daca08bf35ccd68f22ea1c6219e207)
    Signed-off-by: You-Sheng Yang <vicamo.y...@canonical.com>
    Acked-by: Stefan Bader <stefan.ba...@canonical.com>
    Acked-by: Connor Kuehl <connor.ku...@canonical.com>
    Signed-off-by: Stefan Bader <stefan.ba...@canonical.com>

:040000 040000 9c51f067713006f928684555c3254e89bdc10361
ad4d7a34eed39a733c78e630f4d9125f67e001bb M      arch


Regards

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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/1856387

Title:
  Freezing on boot since kernel 4.15.0-72-generic release

Status in linux package in Ubuntu:
  Confirmed

Bug description:
  After the update to install kernel 4.15.0-72-generic (a bit over a week ago) 
my computer will not boot. On boot, all I see is the purple screen with:
  Loading Linux 4.15.0-72-generic ...
  Loading initial ramdisk ...
  and nothing happens. Just sits there. I've waited about 5-10 minutes on 
occasion but to no avail.
  I've checked a number of logs in /var/log but not found anything.

  If I go into the advanced options and select kernel
  4.15.0-70-generic, the computer boots normally.

  ProblemType: Bug
  DistroRelease: Ubuntu 18.04
  Package: linux-image-4.15.0-72-generic 4.15.0-72.81
  ProcVersionSignature: Ubuntu 4.15.0-70.79-generic 4.15.18
  Uname: Linux 4.15.0-70-generic x86_64
  ApportVersion: 2.20.9-0ubuntu7.9
  Architecture: amd64
  AudioDevicesInUse:
   USER        PID ACCESS COMMAND
   /dev/snd/controlC0:  tony       1977 F.... pulseaudio
  CurrentDesktop: ubuntu:GNOME
  Date: Sat Dec 14 21:53:14 2019
  HibernationDevice: RESUME=UUID=5475ce25-e091-45e2-9811-9b5cddc08dd1
  InstallationDate: Installed on 2018-09-16 (454 days ago)
  InstallationMedia: Ubuntu 18.04.1 LTS "Bionic Beaver" - Release amd64 
(20180725)
  Lsusb:
   Bus 002 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub
   Bus 001 Device 003: ID 04f2:b59e Chicony Electronics Co., Ltd 
   Bus 001 Device 002: ID 046d:c063 Logitech, Inc. DELL Laser Mouse
   Bus 001 Device 004: ID 8087:0aaa Intel Corp. 
   Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
  MachineType: GIGABYTE Sabre 17WV8
  ProcFB: 0 inteldrmfb
  ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-4.15.0-70-generic 
root=UUID=9455257c-d3b7-4d61-853d-ab0b0ee40013 ro acpi=off
  RelatedPackageVersions:
   linux-restricted-modules-4.15.0-70-generic N/A
   linux-backports-modules-4.15.0-70-generic  N/A
   linux-firmware                             1.173.13
  SourcePackage: linux
  UpgradeStatus: No upgrade log present (probably fresh install)
  dmi.bios.date: 05/22/2018
  dmi.bios.vendor: American Megatrends Inc.
  dmi.bios.version: F05
  dmi.board.asset.tag: Tag 12345
  dmi.board.name: Sabre 17WV8
  dmi.board.vendor: GIGABYTE
  dmi.board.version: Not Applicable
  dmi.chassis.asset.tag: No Asset Tag
  dmi.chassis.type: 10
  dmi.chassis.vendor: GIGABYTE
  dmi.chassis.version: N/A
  dmi.modalias: 
dmi:bvnAmericanMegatrendsInc.:bvrF05:bd05/22/2018:svnGIGABYTE:pnSabre17WV8:pvrNotApplicable:rvnGIGABYTE:rnSabre17WV8:rvrNotApplicable:cvnGIGABYTE:ct10:cvrN/A:
  dmi.product.family: Sabre
  dmi.product.name: Sabre 17WV8
  dmi.product.version: Not Applicable
  dmi.sys.vendor: GIGABYTE

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