core: add Ref()/Unref() bus calls for units

This adds two (privileged) bus calls Ref() and Unref() to the Unit interface.
The two calls may be used by clients to pin a unit into memory, so that various
runtime properties aren't flushed out by the automatic GC. This is necessary
to permit clients to race-freely acquire runtime results (such as process exit
status/code or accumulated CPU time) on successful service termination.

Ref() and Unref() are fully recursive, hence act like the usual reference
counting concept in C. Taking a reference is a privileged operation, as this
allows pinning units into memory which consumes resources.

Transient units may also gain a reference at the time of creation, via the new
AddRef property (that is only defined for transient units at the time of
creation).

1 files changed, 2 insertions, 3 deletions

diff --git a/src/core/dbus.h b/src/core/dbus.h
index 6baaffbd75..a092ed9d76 100644
--- a/src/core/dbus.h
+++ b/src/core/dbus.h
@@ -28,9 +28,8 @@ void bus_done(Manager *m);
 
 int bus_fdset_add_all(Manager *m, FDSet *fds);
 
-void bus_track_serialize(sd_bus_track *t, FILE *f);
-int bus_track_deserialize_item(char ***l, const char *line);
-int bus_track_coldplug(Manager *m, sd_bus_track **t, char ***l);
+void bus_track_serialize(sd_bus_track *t, FILE *f, const char *prefix);
+int bus_track_coldplug(Manager *m, sd_bus_track **t, bool recursive, char **l);
 
 int manager_sync_bus_names(Manager *m, sd_bus *bus);