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[Launchpad Bug Tracker <1828596@xxxxxxxxxxxxxxxxxx>]

This bug was fixed in the package makedumpfile - 1:1.6.6-2ubuntu2

---------------
makedumpfile (1:1.6.6-2ubuntu2) eoan; urgency=medium

  [ Thadeu Lima de Souza Cascardo ]
  * Fixes for DLPAR cpu add operation (LP: #1828596)
    - d/kdump-config.in: Add a reload command.
    - d/kdump-config.in: implement try-reload.
    - d/50-kdump-tools.rules: Use kdump-config reload after cpu or memory hotplug
    - d/50-kdump-tools.rules: use try-reload instead.
  * d/rules: Use reset_devices as a cmdline parameter. (LP: #1800566)

  [ Guilherme G. Piccoli ]
  * d/kdump-tools-dump.service: Add a systemd-resolved service dependency
    in order to make kdump-tool able to resolve DNS when in kdump boot.
    (LP: #1856323)
  * d/p/0003-Increase-SECTION_MAP_LAST_BIT-to-4.patch: x86_64: Fix an error due
    to makedumpfile being out-of-sync with recent kernels. (LP: #1857616)

 -- gpiccoli@xxxxxxxxxxxxx (Guilherme G. Piccoli)  Fri, 03 Jan 2020
16:10:19 -0300

** Changed in: makedumpfile (Ubuntu Eoan)
       Status: Fix Committed => Fix Released

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https://bugs.launchpad.net/bugs/1828596

Title:
  kdump fails when crash is triggered after DLPAR cpu add operation

Status in The Ubuntu-power-systems project:
  Fix Committed
Status in makedumpfile package in Ubuntu:
  Fix Released
Status in makedumpfile source package in Xenial:
  Fix Committed
Status in makedumpfile source package in Bionic:
  Fix Committed
Status in makedumpfile source package in Cosmic:
  Won't Fix
Status in makedumpfile source package in Disco:
  Won't Fix
Status in makedumpfile source package in Eoan:
  Fix Released
Status in makedumpfile source package in Focal:
  Fix Released

Bug description:
  [Impact]
  After a CPU add/hotplug operation on Power systems, kdump will fail after a crash. The kdump kernel needs to be reloaded after a CPU add/hotplug.

  [Test case]
  Do CPU add/hotplug, trigger a crash, and check for a successful kdump.

  [Regression potential]
  Multiple reloads caused by multiple sequential CPU adds may cause spurious log results, and systemd may fail to properly reload the kdump kernel. This has been handled by resetting the failure counter when doing such reloads.

  == Comment: #0 - Hari Krishna Bathini - 2019-05-10 05:55:40 ==
  ---Problem Description---
  kdump fails when crash is triggered after CPU add operation.

  Machine Type = na

  ---System Hang---
   Crashed in early boot process of kdump kernel after crash

  Had to issue system reset from HMC to reclaim

  ---Steps to Reproduce---
   1. Configure kdump.
  2. Add cpu from HMC.
  3. Trigger crash.
  4. Machine hangs after crash as below:

  ---
  [169250.213166] IPI complete
  [169250.234331] kexec: Starting switchover sequence.
  I'm in purgatory
                               --- STRUCK HERE ---

  ---uname output---
  na

  ---Debugger---
  A debugger is not configured

  == Comment: #1 - Hari Krishna Bathini  - 2019-05-10 05:56:46 ==
  The problem is, kexec udev rule to restart kdump-tools service - when a core is added,
  is not being triggered. The old DT created by kexec (before the core is added)
  is being used by KDump Kernel. So, when system crashes on a thread from
  the added core(s), KDump kernel is failing to get the 'boot_cpuid' and
  eventually failing to boot..

  == Comment: #2 - Hari Krishna Bathini - 2019-05-10 06:02:27 ==
  The udev rule when CPU is added is not triggered because ppc64 does not
  eject add/remove event when a CPU is hot added/removed. It only ejects
  online/offline event to user space when CPU is hot added/removed.

  So, the below udev rules are never triggered when needed:

  SUBSYSTEM=="cpu", ACTION=="add", PROGRAM="/bin/systemctl try-restart kdump-tools.service"
  SUBSYSTEM=="cpu", ACTION=="remove", PROGRAM="/bin/systemctl try-restart kdump-tools.service"

  Also, with how CPU hot add & remove are handled in ppc64, a udev trigger
  to reload kdump after CPU is hot removed is NOT necessary. So, fix the CPU
  hot add case by updating the udev rule and drop the udev rule meant for CPU
  hot remove in the kdump udev rules file:

  SUBSYSTEM=="cpu", ACTION=="online", PROGRAM="/bin/systemctl try-
  restart kdump-tools.service"

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