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

[Brian Murray]

Hello Dimitri, or anyone else affected,

Accepted systemd into xenial-proposed. The package will build now and be
available at
https://launchpad.net/ubuntu/+source/systemd/229-4ubuntu21.2 in a few
hours, and then in the -proposed repository.

Please help us by testing this new package.  See
https://wiki.ubuntu.com/Testing/EnableProposed for documentation on how
to enable and use -proposed.Your feedback will aid us getting this
update out to other Ubuntu users.

If this package fixes the bug for you, please add a comment to this bug,
mentioning the version of the package you tested and change the tag from
verification-needed-xenial to verification-done-xenial. If it does not
fix the bug for you, please add a comment stating that, and change the
tag to verification-failed-xenial. In either case, without details of
your testing we will not be able to proceed.

Further information regarding the verification process can be found at
https://wiki.ubuntu.com/QATeam/PerformingSRUVerification .  Thank you in
advance!

** Changed in: systemd (Ubuntu Xenial)
       Status: In Progress => Fix Committed

** Tags added: verification-needed verification-needed-xenial

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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 Committed

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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