[Bug 1896614] Re: Race condition when starting dbus services

[Victor Tapia]

In the original report, the issue happened randomly on boot when a
service[1] was triggering a reload while systemd-logind was starting,
resulting in a list of queued jobs that were never executed.

The issue can happen too under high load conditions, as reported upstream:
https://github.com/systemd/systemd/issues/12956

To simplify the reproducer I went with systemd-logind+daemon-reload, but
it can be done with any other dbus service.


[1]

[Unit]
Description=Disable unattended upgrades
After=network-online.target local-fs.target

[Service]
Type=oneshot
ExecStart=/bin/bash -c "/bin/chmod 644 /etc/cron.daily/apt-compat ; /bin/systemctl disable apt-daily-upgrade.timer apt-daily.timer ; /bin/systemctl stop apt-daily-upgrade.timer apt-daily.timer"

[Install]
WantedBy=multi-user.target

** Bug watch added: github.com/systemd/systemd/issues #12956
   https://github.com/systemd/systemd/issues/12956

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https://bugs.launchpad.net/bugs/1896614

Title:
  Race condition when starting dbus services

Status in systemd package in Ubuntu:
  New
Status in systemd source package in Bionic:
  New

Bug description:
  In certain scenarios, such as high load environments or when
  "systemctl daemon-reload" runs at the same time a dbus service is
  starting (e.g. systemd-logind), systemd is not able to track properly
  when the service has started, keeping the job 'running' forever.

  The issue appears when systemd runs the "AddMatch" dbus method call to
  track the service's "NameOwnerChange" once it has already ran. A
  working instance would look like this:

  https://pastebin.ubuntu.com/p/868J6WBRQx/

  A failing instance would be:

  https://pastebin.ubuntu.com/p/HhJZ4p8dT5/

  I've been able to reproduce the issue on Bionic (237-3ubuntu10.42)
  running:

  sudo systemctl daemon-reload & sudo systemctl restart systemd-logind

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