[Bug 1722481] Re: systemd should sync disks, before killing all processes on shutdown

[Xeletron]

Is it possible this bug returned in ubuntu 21.04 - hirsute? see my
systemd-shutdown in the txt file attached. ..or is a workaround possible
for this?

I notice this behavior when i shutdown and reboot. the laptop needs
almost no time to shutdown, and then for 20 maybe 30 seconds the
plymouth screen comes back with the rotating sign, waiting to sync
probably, then the screen goes black and shutdown.

** Attachment added: "last view lines of journalctl-shutdown"
   https://bugs.launchpad.net/ubuntu/+source/systemd/+bug/1722481/+attachment/5504055/+files/journalctl-shutdown.txt

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https://bugs.launchpad.net/bugs/1722481

Title:
  systemd should sync disks, before killing all processes on shutdown

Status in systemd package in Ubuntu:
  Fix Released
Status in systemd source package in Xenial:
  Fix Released

Bug description:
  [Impact]

   * systemd-shutdown binary is executed to complete system shutdown. In
  xenial, it calls sync() after killing all processes, and not before
  killing them. This means that processes are racing the SIGKILL/TERM
  timeouts to sync all IO to disk. To mitigate this race condition, and
  make the shutdown process more reliable the sync() should also happen
  before process killing spree starts.

  [Fix]
  Backport upstream commit https://github.com/systemd/systemd/commit/2e79d1828a8da9b3af1b052297e3617905ec94f3

  
  [Test Case]

   * Make sure systems still shuts down, including e.g. root on raid.

  [Regression Potential]

   * Shutdowns may appear to be slower due to two sync() calls instead of one
   * However total shutdown time should not be impacted much, as there really should not be much additional IO caused by killing all processes.

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