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 -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1856387 Title: Freezing on boot since kernel 4.15.0-72-generic release To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1856387/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs