Bug 86520

Summary: Race condition on systemd-run --scope
Product: systemd Reporter: Umut Tezduyar <umut>
Component: generalAssignee: systemd-bugs
Status: RESOLVED FIXED QA Contact: systemd-bugs
Severity: critical    
Priority: medium    
Version: unspecified   
Hardware: Other   
OS: All   
Whiteboard:
i915 platform: i915 features:

Description Umut Tezduyar 2014-11-21 11:07:40 UTC 
Follow up on thread: http://lists.freedesktop.org/archives/systemd-devel/2014-October/024482.html

I have stumbled on a race condition on systemd-run --scope command. Due to race condition, unit might show up as active/running even though there is no process in the cgroup.

The impact is big for us. We are starting some legacy scripts as scopes and a script might have something like this in the beginning.

systemd-run --unit hello --scope /myscript

#!/bins/h

. /etc/configuration

if [ $ENABLED == 'no' ]
    return

Later on, when the script is enabled with ENABLED=yes, running systemd-run --unit hello --scope /myscript is returning immediately since systemd is considering hello.scope already active.
Comment 1 Umut Tezduyar 2015-03-05 07:58:35 UTC 
How to reproduce:

[root@axis-00408cc563e5 /mnt/flash/root]27929# cat stress
#!/bin/sh

systemd-run --scope /bin/true &
systemd-run --scope /bin/true &
systemd-run --scope /bin/true &
systemd-run --scope /bin/true &
systemd-run --scope /bin/true &
systemd-run --scope /bin/true &
systemd-run --scope /bin/true &
systemd-run --scope /bin/true &
[root@axis-00408cc563e5 /mnt/flash/root]27929# ./stress
[root@axis-00408cc563e5 /mnt/flash/root]27929# Running as unit run-27947.scope.
Running as unit run-27946.scope.
Running as unit run-27945.scope.
Running as unit run-27948.scope.
Running as unit run-27952.scope.
Running as unit run-27950.scope.
Running as unit run-27951.scope.
Running as unit run-27949.scope.

[root@axis-00408cc563e5 /mnt/flash/root]27929# systemctl -t scope
UNIT            LOAD   ACTIVE SUB     DESCRIPTION
run-27945.scope loaded active running /bin/true
run-27946.scope loaded active running /bin/true
run-27947.scope loaded active running /bin/true
run-27948.scope loaded active running /bin/true
run-27949.scope loaded active running /bin/true
run-27950.scope loaded active running /bin/true
run-27951.scope loaded active running /bin/true
run-27952.scope loaded active running /bin/true

LOAD   = Reflects whether the unit definition was properly loaded.
ACTIVE = The high-level unit activation state, i.e. generalization of SUB.
SUB    = The low-level unit activation state, values depend on unit type.

8 loaded units listed. Pass --all to see loaded but inactive units, too.
To show all installed unit files use 'systemctl list-unit-files'.
[root@axis-00408cc563e5 /mnt/flash/root]27929# systemctl status run-27945.scope
● run-27945.scope - /bin/true
   Loaded: loaded (/run/systemd/system/run-27945.scope; static)
  Drop-In: /run/systemd/system/run-27945.scope.d
           └─50-Description.conf
   Active: active (running) since Fri 2014-10-24 13:13:26 GMT; 15s ago

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