Re: systemctl stop going through timeout even though all processes have exited

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Hi Mantas,

Yes, it looks like cgroups v1.

Would this be a kernel bug?  systemd bug?

Thanks...

peace & happiness,
martin

On Wed, 11 Oct 2023 08:19:59 +0300, Mantas Mikulėnas
<grawity@xxxxxxxxx> wrote:

> Is this with cgroups v1 or v2? If cgroups v1 is involved (thanks Docker), I
> recall it was a bit complex for systemd to get notified when the cgroup
> actually empties – via /sys/fs/cgroup/systemd/release_agent that specifies
> a helper executable that the kernel runs... I wonder if that mechanism is
> broken on your system.
> 
> On Wed, Oct 11, 2023 at 7:38 AM Martin Schwenke <martin@xxxxxxxxxx> wrote:
> 
> > I'm seeing "systemctl stop <service>" for several services taking a
> > long time because it goes through the timeout process, even though all
> > relevant processes have exited.
> >
> > I'll give 2 examples.  Both examples are running inside a privileged
> > Rocky Linux 8.8 Docker container on a Rocky Linux 8.8 host.  The
> > systemd version, reported by "systemctl --version" in the container
> > is:
> >
> >   systemd 239 (239-74.el8_8.5)
> >
> > Here is ctdb.system:
> >
> >   [Unit]
> >   Description=CTDB
> >   Documentation=man:ctdbd(1) man:ctdb(7)
> >   After=network-online.target time-sync.target
> >   ConditionFileNotEmpty=/etc/ctdb/nodes
> >
> >   [Service]
> >   Type=forking
> >   LimitCORE=infinity
> >   LimitNOFILE=1048576
> >   TasksMax=4096
> >   PIDFile=/var/run/ctdb/ctdbd.pid
> >   ExecStart=/usr/sbin/ctdbd
> >   ExecStop=/usr/bin/ctdb shutdown
> >   KillMode=control-group
> >   Restart=no
> >
> >   [Install]
> >   WantedBy=multi-user.target
> >
> > "/usr/bin/ctdb shutdown" causes a controlled shutdown.  In many cases,
> > starting and then stopping using systemctl works fine.  However, many
> > times it takes >90s to stop, as per TimeoutStopSec.  If I reduce that
> > value then the duration reduces accordingly.  I can confirm using both
> > "ps auxfww" and "systemd-cgls" that within the container there are no
> > relevant processes a moment after "systemctl stop ctdb" is run.  In
> > particular, in systemd-cgls ctdb.service is gone but "systemctl stop
> > ctdb" is still waiting.
> >
> > Before attempting to stop, the service is successfully started:
> >
> >   Oct 11 00:56:44 rocky1 systemd[710741]: ctdb.service: Executing:
> > /usr/sbin/ctdbd
> >   Oct 11 00:56:44 rocky1 ctdbd[710741]: CTDB logging to location
> > file:/var/log/log.ctdb
> >   Oct 11 00:56:44 rocky1 systemd[1]: Received SIGCHLD from PID 710741
> > (ctdbd).
> >   Oct 11 00:56:44 rocky1 systemd[1]: Child 710741 (ctdbd) died
> > (code=exited, status=0/SUCCESS)
> >   Oct 11 00:56:44 rocky1 systemd[1]: ctdb.service: Child 710741 belongs to
> > ctdb.service.
> >   Oct 11 00:56:44 rocky1 systemd[1]: ctdb.service: Control process exited,
> > code=exited status=0
> >   Oct 11 00:56:44 rocky1 systemd[1]: ctdb.service: Got final SIGCHLD for
> > state start.
> >   Oct 11 00:56:44 rocky1 systemd[1]: ctdb.service: New main PID 710742
> > belongs to service, we are happy.
> >   Oct 11 00:56:44 rocky1 systemd[1]: ctdb.service: Main PID loaded: 710742
> >   Oct 11 00:56:44 rocky1 systemd[1]: ctdb.service: Changed start -> running
> >   Oct 11 00:56:44 rocky1 systemd[1]: ctdb.service: Job ctdb.service/start
> > finished, result=done
> >   Oct 11 00:56:44 rocky1 systemd[1]: Started CTDB.
> >   -- Subject: Unit ctdb.service has finished start-up
> >   -- Defined-By: systemd
> >   -- Support: https://lists.freedesktop.org/mailman/listinfo/systemd-devel
> >   --
> >   -- Unit ctdb.service has finished starting up.
> >   --
> >   -- The start-up result is done.
> >
> > The relevant part of the log while stopping seems to be:
> >
> >   Oct 11 00:56:47 rocky1 systemd[1]: Received SIGCHLD from PID 710743
> > (ctdb-eventd).
> >   Oct 11 00:56:47 rocky1 systemd[1]: Child 710742 (ctdbd) died
> > (code=exited, status=0/SUCCESS)
> >   Oct 11 00:56:47 rocky1 systemd[1]: ctdb.service: Child 710742 belongs to
> > ctdb.service.
> >   Oct 11 00:56:47 rocky1 systemd[1]: ctdb.service: Can't open PID file
> > /var/run/ctdb/ctdbd.pid (yet?) after stop: No such file or directory
> >   Oct 11 00:56:47 rocky1 systemd[1]: ctdb.service: Main process exited,
> > code=exited, status=0/SUCCESS
> >   Oct 11 00:56:47 rocky1 systemd[1]: Sent message type=signal
> > sender=org.freedesktop.systemd1 destination=n/a
> > path=/org/freedesktop/systemd1/unit/ctdb_2eservice
> > interface=org.freedesktop.DBus.Properties member=PropertiesChanged
> > cookie=54 reply_cookie=0 signature=sa{sv}as error-name=n/a error-message=n/a
> >   Oct 11 00:56:47 rocky1 systemd[1]: Sent message type=signal
> > sender=org.freedesktop.systemd1 destination=n/a
> > path=/org/freedesktop/systemd1/unit/ctdb_2eservice
> > interface=org.freedesktop.DBus.Properties member=PropertiesChanged
> > cookie=55 reply_cookie=0 signature=sa{sv}as error-name=n/a error-message=n/a
> >   Oct 11 00:56:47 rocky1 systemd[1]: Child 710743 (ctdb-eventd) died
> > (code=exited, status=0/SUCCESS)
> >   Oct 11 00:56:47 rocky1 systemd[1]: ctdb.service: Child 710743 belongs to
> > ctdb.service.
> >   Oct 11 00:56:47 rocky1 systemd[1]: systemd-journald.service: Received
> > EPOLLHUP on stored fd 18 (stored), closing.
> >   Oct 11 00:56:47 rocky1 systemd[1]: Received SIGCHLD from PID 710860
> > (ctdb).
> >   Oct 11 00:56:47 rocky1 systemd[1]: Child 710860 (ctdb) died
> > (code=exited, status=0/SUCCESS)
> >   Oct 11 00:56:47 rocky1 systemd[1]: ctdb.service: Child 710860 belongs to
> > ctdb.service.
> >   Oct 11 00:56:47 rocky1 systemd[1]: ctdb.service: Control process exited,
> > code=exited status=0
> >   Oct 11 00:56:47 rocky1 systemd[1]: ctdb.service: Got final SIGCHLD for
> > state stop.
> >   Oct 11 00:56:47 rocky1 systemd[1]: ctdb.service: Changed stop ->
> > stop-sigterm
> >   Oct 11 00:56:47 rocky1 systemd[1]: Sent message type=signal
> > sender=org.freedesktop.systemd1 destination=n/a
> > path=/org/freedesktop/systemd1/unit/ctdb_2eservice
> > interface=org.freedesktop.DBus.Properties member=PropertiesChanged
> > cookie=56 reply_cookie=0 signature=sa{sv}as error-name=n/a error-message=n/a
> >   Oct 11 00:56:47 rocky1 systemd[1]: Sent message type=signal
> > sender=org.freedesktop.systemd1 destination=n/a
> > path=/org/freedesktop/systemd1/unit/ctdb_2eservice
> > interface=org.freedesktop.DBus.Properties member=PropertiesChanged
> > cookie=57 reply_cookie=0 signature=sa{sv}as error-name=n/a error-message=n/a
> >   Oct 11 00:56:47 rocky1 systemd[1]: Received SIGCHLD from PID 710834
> > (ctdb_lock_helpe).
> >   Oct 11 00:56:47 rocky1 systemd[1]: Child 710834 (ctdb_lock_helpe) died
> > (code=exited, status=0/SUCCESS)
> >   Oct 11 00:56:47 rocky1 systemd[1]: ctdb.service: Child 710834 belongs to
> > ctdb.service.
> >   Oct 11 00:56:47 rocky1 systemd[1]: Received SIGCHLD from PID 710835
> > (ctdb_lock_helpe).
> >   Oct 11 00:56:47 rocky1 systemd[1]: Child 710832 (ctdb_lock_helpe) died
> > (code=exited, status=0/SUCCESS)
> >   Oct 11 00:56:47 rocky1 systemd[1]: ctdb.service: Child 710832 belongs to
> > ctdb.service.
> >   Oct 11 00:56:47 rocky1 systemd[1]: Child 710835 (ctdb_lock_helpe) died
> > (code=exited, status=0/SUCCESS)
> >   Oct 11 00:56:47 rocky1 systemd[1]: ctdb.service: Child 710835 belongs to
> > ctdb.service.
> >   Oct 11 00:56:47 rocky1 systemd[1]: Child 710833 (ctdb_lock_helpe) died
> > (code=exited, status=0/SUCCESS)
> >   Oct 11 00:56:47 rocky1 systemd[1]: ctdb.service: Child 710833 belongs to
> > ctdb.service.
> >   Oct 11 00:56:47 rocky1 systemd[1]: Child 710836 (ctdb_lock_helpe) died
> > (code=exited, status=0/SUCCESS)
> >   Oct 11 00:56:47 rocky1 systemd[1]: ctdb.service: Child 710836 belongs to
> > ctdb.service.
> >   Oct 11 00:56:47 rocky1 systemd[1]: Child 710837 (ctdb_lock_helpe) died
> > (code=exited, status=0/SUCCESS)
> >   Oct 11 00:56:47 rocky1 systemd[1]: ctdb.service: Child 710837 belongs to
> > ctdb.service.
> >   Oct 11 00:56:47 rocky1 systemd[1]: Child 710838 (ctdb_lock_helpe) died
> > (code=exited, status=0/SUCCESS)
> >   Oct 11 00:56:47 rocky1 systemd[1]: ctdb.service: Child 710838 belongs to
> > ctdb.service.
> >   Oct 11 00:56:47 rocky1 systemd[1]: Child 710839 (ctdb_lock_helpe) died
> > (code=exited, status=0/SUCCESS)
> >   Oct 11 00:56:47 rocky1 systemd[1]: ctdb.service: Child 710839 belongs to
> > ctdb.service.
> >   Oct 11 00:56:47 rocky1 systemd[1]: Received SIGCHLD from PID 710832
> > (n/a).
> >   Oct 11 00:57:44 rocky1 systemd[1]: systemd-journald.service: Got
> > notification message from PID 840 (WATCHDOG=1)
> >   Oct 11 00:58:17 rocky1 systemd[1]: ctdb.service: State 'stop-sigterm'
> > timed out. Killing.
> >   Oct 11 00:58:17 rocky1 systemd[1]: ctdb.service: Failed with result
> > 'timeout'.
> >   -- Subject: Unit failed
> >   -- Defined-By: systemd
> >   -- Support: https://lists.freedesktop.org/mailman/listinfo/systemd-devel
> >   --
> >   -- The unit ctdb.service has entered the 'failed' state with result
> > 'timeout'.
> >   Oct 11 00:58:17 rocky1 systemd[1]: ctdb.service: Changed stop-sigterm ->
> > failed
> >   Oct 11 00:58:17 rocky1 systemd[1]: Sent message type=signal
> > sender=org.freedesktop.systemd1 destination=n/a
> > path=/org/freedesktop/systemd1 interface=org.freedesktop.DBus.Properties
> > member=PropertiesChanged cookie=58 reply_cookie=0 signature=sa{sv}as
> > error-name=n/a error-message=n/a
> >   Oct 11 00:58:17 rocky1 systemd[1]: ctdb.service: Job ctdb.service/stop
> > finished, result=done
> >   Oct 11 00:58:17 rocky1 systemd[1]: Stopped CTDB.
> >   -- Subject: Unit ctdb.service has finished shutting down
> >   -- Defined-By: systemd
> >   -- Support: https://lists.freedesktop.org/mailman/listinfo/systemd-devel
> >   --
> >   -- Unit ctdb.service has finished shutting down.
> >   Oct 11 00:58:17 rocky1 systemd[1]: Sent message type=signal
> > sender=org.freedesktop.systemd1 destination=n/a
> > path=/org/freedesktop/systemd1 interface=org.freedesktop.systemd1.Manager
> > member=JobRemoved cookie=59 reply_cookie=0 signature=uoss error-name=n/a
> > error-message=n/a
> >   Oct 11 00:58:17 rocky1 systemd[1]: ctdb.service: Unit entered failed
> > state.
> >
> > It would be very useful if systemd could log what it is still waiting
> > for when it times out.
> >
> > Note that during start and stop, CTDB runs a lot of subprocesses,
> > including some that use systemctl to start and stop various services
> > that it, in turn, manages.
> >
> > The full debug level log, after running:
> >
> >   systemd-analyze log-level debug
> >
> > is uploaded it to:
> >
> >   https://meltin.net/uploads/systemd/ctdb-stop.log
> >
> > I'm happy to reply and attach it, but it is 48KB.
> >
> > The only theory I can come up with is some sort of race where
> > processes are created during shutdown and systemd gets confused.
> >
> > I see a similar thing for a much simpler service, winbind:
> >
> > Here is winbind.service:
> >
> >   [Unit]
> >   Description=Samba Winbind Daemon
> >   Documentation=man:winbindd(8) man:samba(7) man:smb.conf(5)
> >   After=network.target nmb.service
> >
> >   [Service]
> >   Type=notify
> >   PIDFile=/var/run/winbindd.pid
> >   EnvironmentFile=-/etc/sysconfig/samba
> >   ExecStart=/usr/sbin/winbindd --foreground --no-process-group
> > $WINBINDOPTIONS
> >   ExecReload=/bin/kill -HUP $MAINPID
> >   LimitCORE=infinity
> >
> >   [Install]
> >   WantedBy=multi-user.target
> >
> > Yesterday I watched it do the same thing as CTDB.  I could start the
> > service by hand but it would time out during stop, nearly every time,
> > even though there were no relevant processes running anymore.
> > winbindd sends a READY=1 notification after successfully starting.  It
> > does not send STOPPING=1.  winbindd is much simpler during shutdown.
> > I can get logs for this one too if necessary.
> >
> > Thanks for any help.
> >
> > peace & happiness,
> > martin
> >  
> 
> 
> -- 
> Mantas Mikulėnas
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