[Bug 1932525] Re: This bug is back on my pc - bug #1722481 Systemd Sync twice at shutdown

[Todd Taft]

I am seeing something similar on 20.04.  If my network fails and I have
any network filesystems mounted (including nfs3 or nfs4 via autofs or
iSCSI via fstab) when I issue a shutdown or reboot command, then I am
likely to have a 10+ minute delay after the console displays that it has
reached target shutdown.  The console will then cycle through displaying
information about each filesystem, such as the fact that the system is
trying to unmount it, the unmount failed, and it is now forcibly killing
processes.  While I have not looked at the source, the timing of the
console messages would imply that the process to unmount filesystems and
kill processes is single-threaded, as there is a significant delay as it
goes through this process with each filesystem.  After it has cycled
through all filesystems, it then slowly cycles through each filesystem
again.  Unfortunately, the logging system has already shut down by the
time any of this happens, so I have no logs in journald or syslog to
submit in relationship to this issue.

Can the process be fixed to only cycle through each filesystem once, and
also to attempt to do multiple filesystems simultaneously so that, at
worst, I only have to wait through one timeout cycle?  I could possibly
see a reason that you might need to wait the timeout multiple times in
the event of nested remote filesystems (e.g. if every level of
/dont/try/this/at/home was a different filesystem on non-local disk),
but that is not the configuration that I have.

-- 
You received this bug notification because you are a member of Ubuntu
Foundations Bugs, which is subscribed to systemd in Ubuntu.
https://bugs.launchpad.net/bugs/1932525

Title:
  This bug is back on my pc -  bug #1722481  Systemd Sync twice at
  shutdown

Status in systemd package in Ubuntu:
  Confirmed

Bug description:
  
  systemd should sync disks, before killing all processes on shutdown: bug #1722481 has returned.

  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.  my laptop is a HP
  elitebook 820 with ssd hdd.

  
   - snap of text of original bugreport -

  [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.

To manage notifications about this bug go to:
https://bugs.launchpad.net/ubuntu/+source/systemd/+bug/1932525/+subscriptions