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, 10 insertions, 7 deletions

diff --git a/src/core/job.c b/src/core/job.c
index 7557874d4d..7faf2ef686 100644
--- a/src/core/job.c
+++ b/src/core/job.c
@@ -997,7 +997,10 @@ char *job_dbus_path(Job *j) {
         return p;
 }
 
-int job_serialize(Job *j, FILE *f, FDSet *fds) {
+int job_serialize(Job *j, FILE *f) {
+        assert(j);
+        assert(f);
+
         fprintf(f, "job-id=%u\n", j->id);
         fprintf(f, "job-type=%s\n", job_type_to_string(j->type));
         fprintf(f, "job-state=%s\n", job_state_to_string(j->state));
@@ -1008,15 +1011,16 @@ int job_serialize(Job *j, FILE *f, FDSet *fds) {
         if (j->begin_usec > 0)
                 fprintf(f, "job-begin="USEC_FMT"\n", j->begin_usec);
 
-        bus_track_serialize(j->clients, f);
+        bus_track_serialize(j->clients, f, "subscribed");
 
         /* End marker */
         fputc('\n', f);
         return 0;
 }
 
-int job_deserialize(Job *j, FILE *f, FDSet *fds) {
+int job_deserialize(Job *j, FILE *f) {
         assert(j);
+        assert(f);
 
         for (;;) {
                 char line[LINE_MAX], *l, *v;
@@ -1106,7 +1110,7 @@ int job_deserialize(Job *j, FILE *f, FDSet *fds) {
                 } else if (streq(l, "subscribed")) {
 
                         if (strv_extend(&j->deserialized_clients, v) < 0)
-                                return log_oom();
+                                log_oom();
                 }
         }
 }
@@ -1118,9 +1122,8 @@ int job_coldplug(Job *j) {
 
         /* After deserialization is complete and the bus connection
          * set up again, let's start watching our subscribers again */
-        r = bus_track_coldplug(j->manager, &j->clients, &j->deserialized_clients);
-        if (r < 0)
-                return r;
+        (void) bus_track_coldplug(j->manager, &j->clients, false, j->deserialized_clients);
+        j->deserialized_clients = strv_free(j->deserialized_clients);
 
         if (j->state == JOB_WAITING)
                 job_add_to_run_queue(j);