Previously transactions could reference installed jobs. It made some issues
difficult to fix.
This sets new rules for jobs:
A job cannot be both a member of a transaction and installed. When jobs are
created, they are linked to a transaction. The whole transaction is constructed
(with merging of jobs within, etc.). When it's complete, all the jobs are
unlinked from it one by one and let to install themselves. It is during the
installation when merging with previously installed jobs (from older
transactions) is contemplated.
Merging with installed jobs has different rules than merging within a
transaction:
- An installed conflicting job gets cancelled. It cannot be simply deleted,
because someone might be waiting for its completion on DBus.
- An installed, but still waiting, job can be safely merged into.
- An installed and running job can be tricky. For some job types it is safe to
just merge. For the other types we merge anyway, but put the job back into
JOB_WAITING to allow it to run again. This may be suboptimal, but it is not
currently possible to have more than one installed job for a unit.
Note this also fixes a bug where the anchor job could be deleted during merging
within the transaction.
This makes it obvious that transactions are short-lived. They are created in
manager_add_job() and destroyed after the application of jobs.
It also prepares for a split of the transaction code to a new source.
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.
job_free() is IMO too helpful when it unlinks the job from the transaction.
The callers should ensure the job is already unlinked before freeing.
The added assertions check if anyone gets it wrong.
We shouldn't print a status message on the console if we skipped a unit
due to a condition. Hence make unit_start() return -ENOEXEC in such a
case which is mapped to JOB_SKIPPED which results in no console message.
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.
