[systemd-devel] systemd has not the same behaviour following the version of the kernel ; StopWhenUnneeded no longer works

Tue Sep 27 15:16:40 UTC 2022

Hi,

I'm using debian 10 (systemd 241) . I launch a service (tank.service) when a
specific USB device is connected. For that, i have written an udev rule that
requests the service start in case of < add > event, thanks to <
SYSTEMD_WANTS > :

SUBSYSTEM=="usb", ACTION=="add", ATTRS{idVendor}=="04b4",
ATTRS{idProduct}=="6570", TAG+="systemd", ENV{SYSTEMD_WANTS}="tank.service"

I want service to be stopped when the USB device is removed. For that, I use
< StopWhenUnneeded > feature.

tank.service : 

[Unit]

Description= tank routine

StopWhenUnneeded=true

[Service]

Type=simple

ExecStartPre=-/bin/bash /actimyo/bin/tankinsert.sh

ExecStart=/bin/bash /actimyo/bin/tank.sh

ExecStop=/bin/bash /actimyo/bin/tankremove.sh

With kernel 4.9.150 ,  it works well : the service is stopped when the USB
device is removed. 

However, I updated the kernel to version 5.15.32 and the service do not stop
when the USB device is removed . The feature < StopWhenUnneeded > no longer
works. 

Does anybody understand why ? Could anybody give me a solution ?

Systemd logs when USB device is removed with kernel 4.9.150 (complete logs
in attached file < logs systemd removing tank-4-9-150.txt >) :

Jun 17 09:21:34 b-0024 kernel: usb 1-1: USB disconnect, device number 2

Jun 17 09:21:34 b-0024 kernel: usb 1-1.2: USB disconnect, device number 3

Jun 17 09:21:34 b-0024 systemd[1]: tank.service: Unit is not needed anymore.

Jun 17 09:21:34 b-0024 systemd[1]: tank.service: Trying to enqueue job
tank.service/stop/fail

Jun 17 09:21:34 b-0024 systemd[1]: Added job tank.service/stop to
transaction.

Jun 17 09:21:34 b-0024 systemd[1]: tank.service: Installed new job
tank.service/stop as 724

Jun 17 09:21:34 b-0024 systemd[1]: tank.service: Enqueued job
tank.service/stop as 724

Jun 17 09:21:34 b-0024 systemd[1]: Sent message type=signal sender=n/a
destination=n/a path=/org/freedesktop/systemd1/unit/tank_2eservice
interface=org.freedesktop.DBus.Properties member=PropertiesChanged
cookie=605 reply_cookie=0 signature=sa{sv}as error-name=n/a
error-message=n/a

Jun 17 09:21:34 b-0024 systemd[1]: Sent message type=signal sender=n/a
destination=n/a path=/org/freedesktop/systemd1/unit/tank_2eservice
interface=org.freedesktop.DBus.Properties member=PropertiesChanged
cookie=606 reply_cookie=0 signature=sa{sv}as error-name=n/a
error-message=n/a

Jun 17 09:21:34 b-0024 systemd[1]: Sent message type=signal sender=n/a
destination=n/a path=/org/freedesktop/systemd1
interface=org.freedesktop.systemd1.Manager member=JobNew cookie=607
reply_cookie=0 signature=uos error-name=n/a error-message=n/a

Jun 17 09:21:34 b-0024 systemd[1]: tank.service: About to execute: /bin/bash
/actimyo/bin/tankremove.sh

Jun 17 09:21:34 b-0024 systemd[1]: tank.service: Forked /bin/bash as 2496

Jun 17 09:21:34 b-0024 systemd[1]: Sent message type=signal sender=n/a
destination=n/a path=/org/freedesktop/systemd1/unit/tank_2eservice
interface=org.freedesktop.DBus.Properties member=PropertiesChanged
cookie=608 reply_cookie=0 signature=sa{sv}as error-name=n/a
error-message=n/a

Jun 17 09:21:34 b-0024 systemd[1]: Sent message type=signal sender=n/a
destination=n/a path=/org/freedesktop/systemd1/unit/tank_2eservice
interface=org.freedesktop.DBus.Properties member=PropertiesChanged
cookie=609 reply_cookie=0 signature=sa{sv}as error-name=n/a
error-message=n/a

Jun 17 09:21:34 b-0024 systemd[1]: tank.service: Changed running -> stop

Jun 17 09:21:34 b-0024 systemd[1]: Stopping Detect tank presence...

Jun 17 09:21:34 b-0024 systemd[2496]: tank.service: Executing: /bin/bash
/actimyo/bin/tankremove.sh

Systemd logs when USB device is removed with kernel 5.15.32 (complete logs
in attached file < logs systemds removing tank kernel-5-15-32.txt >):

Jun 17 09:21:33 b-0021 kernel: [  438.934344] usb 1-1: USB disconnect,
device number 2

Jun 17 09:21:33 b-0021 kernel: [  438.939373] usb 1-1.2: USB disconnect,
device number 3

Jun 17 09:21:33 b-0021 systemd[1]: tank.service: tank.service lost
dependency
WantedBy=sys-devices-platform-soc-2100000.bus-2184000.usb-ci_hdrc.0-usb1-1\x
2d1.device

Jun 17 09:21:33 b-0021 systemd[1]: tank.service: tank.service lost
dependency
ReferencedBy=sys-devices-platform-soc-2100000.bus-2184000.usb-ci_hdrc.0-usb1
-1\x2d1.device

Best regards

---
Eric-Olivier Perrin
 <mailto:eric-olivier.perrin at sysnav.fr> eric-olivier.perrin at sysnav.fr

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