Two of our current job types are special:
JOB_TRY_RESTART, JOB_RELOAD_OR_START.
They differ from other job types by being sensitive to the unit active state.
They perform some action when the unit is active and some other action
otherwise. This raises a question: when exactly should the unit state be
checked to make the decision?
Currently the unit state is checked when the job becomes runnable. It's more
sensible to check the state immediately when the job is added by the user.
When the user types "systemctl try-restart foo.service", he really intends
to restart the service if it's running right now. If it isn't running right
now, the restart is pointless.
Consider the example (from Bugzilla[1]):
sleep.service takes some time to start.
hello.service has After=sleep.service.
Both services get started. Two jobs will appear:
hello.service/start waiting
sleep.service/start running
Then someone runs "systemctl try-restart hello.service".
Currently the try-restart operation will block and wait for
sleep.service/start to complete.
The correct result is to complete the try-restart operation immediately
with success, because hello.service is not running. The two original
jobs must not be disturbed by this.
To fix this we introduce two new concepts:
- a new job type: JOB_NOP
A JOB_NOP job does not do anything to the unit. It does not pull in any
dependencies. It is always immediately runnable. When installed to a unit,
it sits in a special slot (u->nop_job) where it never conflicts with
the installed job (u->job) of a different type. It never merges with jobs
of other types, but it can merge into an already installed JOB_NOP job.
- "collapsing" of job types
When a job of one of the two special types is added, the state of the unit
is checked immediately and the job type changes:
JOB_TRY_RESTART -> JOB_RESTART or JOB_NOP
JOB_RELOAD_OR_START -> JOB_RELOAD or JOB_START
Should a job type JOB_RELOAD_OR_START appear later during job merging, it
collapses immediately afterwards.
Collapsing actually makes some things simpler, because there are now fewer
job types that are allowed in the transaction.
[1] Fixes: https://bugzilla.redhat.com/show_bug.cgi?id=753586
Jobs were not preserved correctly over a daemon-reload operation.
A systemctl process waiting for a job completion received a job removal
signal. The job itself changed its id. The job timeout started ticking all
over again.
This fixes the deficiencies.
Split the uninstallation of the job from job_free() into a separate function.
Adjust the callers.
job_free() now only works on unlinked and uninstalled jobs. This enforces clear
thinking about job lifetimes.
We finally got the OK from all contributors with non-trivial commits to
relicense systemd from GPL2+ to LGPL2.1+.
Some udev bits continue to be GPL2+ for now, but we are looking into
relicensing them too, to allow free copy/paste of all code within
systemd.
The bits that used to be MIT continue to be MIT.
The big benefit of the relicensing is that closed source code may now
link against libsystemd-login.so and friends.
