core/manager: restore bus track deserialization cleanup in manager_reload()

There's zero explanation why it got (spuriously) removed in
8402ca04d1a063c3d8a9e3d5c16df8bb8778ae98...

(cherry picked from commit 34f4b817f67b002eae7e2c09b19bf4b66c4791b6)

src/core/dbus.c

@@ -859,6 +859,8 @@ int bus_init_api(Manager *m) {
         if (r < 0)
                 return log_error_errno(r, "Failed to set up API bus: %m");
 
+        (void) bus_track_coldplug(bus, &m->subscribed, /* recursive= */ false, m->subscribed_as_strv);
+        m->subscribed_as_strv = strv_free(m->subscribed_as_strv);
         m->api_bus = TAKE_PTR(bus);
 
         return 0;
@@ -1002,8 +1004,17 @@ static void destroy_bus(Manager *m, sd_bus **bus) {
         }
 
         /* Get rid of tracked clients on this bus */
-        if (m->subscribed && sd_bus_track_get_bus(m->subscribed) == *bus)
+        if (m->subscribed && sd_bus_track_get_bus(m->subscribed) == *bus) {
+                _cleanup_strv_free_ char **subscribed = NULL;
+                int r;
+
+                r = bus_track_to_strv(m->subscribed, &subscribed);
+                if (r < 0)
+                        log_warning_errno(r, "Failed to serialize api subscribers, ignoring: %m");
+                strv_free_and_replace(m->subscribed_as_strv, subscribed);
+
                 m->subscribed = sd_bus_track_unref(m->subscribed);
+        }
 
         HASHMAP_FOREACH(j, m->jobs)
                 if (j->bus_track && sd_bus_track_get_bus(j->bus_track) == *bus)
@@ -1062,7 +1073,6 @@ void bus_done(Manager *m) {
 
         assert(!m->subscribed);
 
-        m->deserialized_subscribed = strv_free(m->deserialized_subscribed);
         m->polkit_registry = hashmap_free(m->polkit_registry);
 }
 
@@ -1151,20 +1161,19 @@ 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 bus_track_coldplug(sd_bus *bus, sd_bus_track **t, bool recursive, char **l) {
         int r;
 
-        assert(m);
         assert(t);
 
         if (strv_isempty(l))
                 return 0;
 
-        if (!m->api_bus)
+        if (!bus)
                 return 0;
 
         if (!*t) {
-                r = sd_bus_track_new(m->api_bus, t, NULL, NULL);
+                r = sd_bus_track_new(bus, t, NULL, NULL);
                 if (r < 0)
                         return r;
         }

src/core/dbus.h

@@ -19,7 +19,7 @@ void bus_done(Manager *m);
 int bus_fdset_add_all(Manager *m, FDSet *fds);
 
 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 bus_track_coldplug(sd_bus *bus, sd_bus_track **t, bool recursive, char **l);
 
 int bus_foreach_bus(Manager *m, sd_bus_track *subscribed2, int (*send_message)(sd_bus *bus, void *userdata), void *userdata);
 

src/core/manager-serialize.c

@@ -493,7 +493,7 @@ int manager_deserialize(Manager *m, FILE *f, FDSet *fds) {
                         (void) exec_shared_runtime_deserialize_one(m, val, fds);
                 else if ((val = startswith(l, "subscribed="))) {
 
-                        r = strv_extend(&m->deserialized_subscribed, val);
+                        r = strv_extend(&m->subscribed_as_strv, val);
                         if (r < 0)
                                 return r;
                 } else if ((val = startswith(l, "varlink-server-socket-address="))) {

src/core/manager.c

@@ -1803,6 +1803,9 @@ Manager* manager_free(Manager *m) {
         free(m->switch_root);
         free(m->switch_root_init);
 
+        sd_bus_track_unref(m->subscribed);
+        strv_free(m->subscribed_as_strv);
+
         unit_defaults_done(&m->defaults);
 
         FOREACH_ARRAY(map, m->units_needing_mounts_for, _UNIT_MOUNT_DEPENDENCY_TYPE_MAX) {
@@ -2161,12 +2164,6 @@ int manager_startup(Manager *m, FILE *serialization, FDSet *fds, const char *roo
                 /* Connect to the bus if we are good for it */
                 manager_setup_bus(m);
 
-                /* Now that we are connected to all possible buses, let's deserialize who is tracking us. */
-                r = bus_track_coldplug(m, &m->subscribed, false, m->deserialized_subscribed);
-                if (r < 0)
-                        log_warning_errno(r, "Failed to deserialized tracked clients, ignoring: %m");
-                m->deserialized_subscribed = strv_free(m->deserialized_subscribed);
-
                 r = manager_varlink_init(m);
                 if (r < 0)
                         log_warning_errno(r, "Failed to set up Varlink, ignoring: %m");
@@ -3830,15 +3827,16 @@ int manager_reload(Manager *m) {
         (void) manager_setup_handoff_timestamp_fd(m);
         (void) manager_setup_pidref_transport_fd(m);
 
+        /* Clean up deserialized bus track information. They're never consumed during reload (as opposed to
+         * reexec) since we do not disconnect from the bus. */
+        m->subscribed_as_strv = strv_free(m->subscribed_as_strv);
+
         /* Third, fire things up! */
         manager_coldplug(m);
 
         /* Clean up runtime objects no longer referenced */
         manager_vacuum(m);
 
-        /* Clean up deserialized tracked clients */
-        m->deserialized_subscribed = strv_free(m->deserialized_subscribed);
-
         /* Consider the reload process complete now. */
         assert(m->n_reloading > 0);
         m->n_reloading--;

src/core/manager.h

@@ -340,7 +340,7 @@ struct Manager {
         considered subscribes, since they last for very short only,
         and it is much simpler that way. */
         sd_bus_track *subscribed;
-        char **deserialized_subscribed;
+        char **subscribed_as_strv;
 
         /* This is used during reloading: before the reload we queue
          * the reply message here, and afterwards we send it */

src/core/unit.c

@@ -3521,6 +3521,32 @@ int unit_load_related_unit(Unit *u, const char *type, Unit **_found) {
         return r;
 }
 
+static int signal_name_owner_changed_install_handler(sd_bus_message *message, void *userdata, sd_bus_error *error) {
+        Unit *u = ASSERT_PTR(userdata);
+        const sd_bus_error *e;
+        int r;
+
+        e = sd_bus_message_get_error(message);
+        if (!e) {
+                log_unit_trace(u, "Successfully installed NameOwnerChanged signal match.");
+                return 0;
+        }
+
+        r = sd_bus_error_get_errno(e);
+        log_unit_error_errno(u, r,
+                             "Unexpected error response on installing NameOwnerChanged signal match: %s",
+                             bus_error_message(e, r));
+
+        /* If we failed to install NameOwnerChanged signal, also unref the bus slot of GetNameOwner(). */
+        u->match_bus_slot = sd_bus_slot_unref(u->match_bus_slot);
+        u->get_name_owner_slot = sd_bus_slot_unref(u->get_name_owner_slot);
+
+        if (UNIT_VTABLE(u)->bus_name_owner_change)
+                UNIT_VTABLE(u)->bus_name_owner_change(u, NULL);
+
+        return 0;
+}
+
 static int signal_name_owner_changed(sd_bus_message *message, void *userdata, sd_bus_error *error) {
         const char *new_owner;
         Unit *u = ASSERT_PTR(userdata);
@@ -3603,10 +3629,10 @@ int unit_install_bus_match(Unit *u, sd_bus *bus, const char *name) {
         r = bus_add_match_full(
                         bus,
                         &u->match_bus_slot,
-                        true,
+                        /* asynchronous = */ true,
                         match,
                         signal_name_owner_changed,
-                        NULL,
+                        signal_name_owner_changed_install_handler,
                         u,
                         timeout_usec);
         if (r < 0)

src/libsystemd/sd-bus/bus-track.c

@@ -3,6 +3,7 @@
 #include "sd-bus.h"
 
 #include "alloc-util.h"
+#include "bus-error.h"
 #include "bus-internal.h"
 #include "bus-track.h"
 #include "string-util.h"
@@ -11,6 +12,7 @@ struct track_item {
         unsigned n_ref;
         char *name;
         sd_bus_slot *slot;
+        sd_bus_track *track;
 };
 
 struct sd_bus_track {
@@ -163,18 +165,39 @@ static sd_bus_track *track_free(sd_bus_track *track) {
 
 DEFINE_PUBLIC_TRIVIAL_REF_UNREF_FUNC(sd_bus_track, sd_bus_track, track_free);
 
-static int on_name_owner_changed(sd_bus_message *message, void *userdata, sd_bus_error *error) {
-        sd_bus_track *track = ASSERT_PTR(userdata);
+static int on_name_owner_changed(sd_bus_message *message, void *userdata, sd_bus_error *reterr_error) {
+        struct track_item *item = ASSERT_PTR(userdata);
         const char *name;
         int r;
 
         assert(message);
+        assert(item->track);
 
         r = sd_bus_message_read(message, "sss", &name, NULL, NULL);
         if (r < 0)
                 return 0;
 
-        bus_track_remove_name_fully(track, name);
+        bus_track_remove_name_fully(item->track, name);
+        return 0;
+}
+
+static int name_owner_changed_install_callback(sd_bus_message *message, void *userdata, sd_bus_error *reterr_error) {
+        struct track_item *item = ASSERT_PTR(userdata);
+        const sd_bus_error *e;
+        int r;
+
+        assert(message);
+        assert(item->track);
+        assert(item->name);
+
+        e = sd_bus_message_get_error(message);
+        if (!e)
+                return 0;
+
+        r = sd_bus_error_get_errno(e);
+        log_debug_errno(r, "Failed to install match for tracking name '%s': %s", item->name, bus_error_message(e, r));
+
+        bus_track_remove_name_fully(item->track, item->name);
         return 0;
 }
 
@@ -216,6 +239,7 @@ _public_ int sd_bus_track_add_name(sd_bus_track *track, const char *name) {
 
         *n = (struct track_item) {
                 .n_ref = 1,
+                .track = track,
         };
 
         n->name = strdup(name);
@@ -227,7 +251,7 @@ _public_ int sd_bus_track_add_name(sd_bus_track *track, const char *name) {
 
         bus_track_remove_from_queue(track); /* don't dispatch this while we work in it */
 
-        r = sd_bus_add_match_async(track->bus, &n->slot, match, on_name_owner_changed, NULL, track);
+        r = sd_bus_add_match_async(track->bus, &n->slot, match, on_name_owner_changed, name_owner_changed_install_callback, n);
         if (r < 0) {
                 bus_track_add_to_queue(track);
                 return r;

src/shared/bus-util.c

@@ -698,6 +698,27 @@ int bus_track_add_name_many(sd_bus_track *t, char **l) {
         return r;
 }
 
+int bus_track_to_strv(sd_bus_track *t, char ***ret) {
+        _cleanup_strv_free_ char **subscribed = NULL;
+        int r;
+
+        assert(ret);
+
+        for (const char *n = sd_bus_track_first(t); n; n = sd_bus_track_next(t)) {
+                int c = sd_bus_track_count_name(t, n);
+                assert(c >= 0);
+
+                for (int j = 0; j < c; j++) {
+                        r = strv_extend(&subscribed, n);
+                        if (r < 0)
+                                return r;
+                }
+        }
+
+        *ret = TAKE_PTR(subscribed);
+        return 0;
+}
+
 int bus_open_system_watch_bind_with_description(sd_bus **ret, const char *description) {
         _cleanup_(sd_bus_close_unrefp) sd_bus *bus = NULL;
         const char *e;

src/shared/bus-util.h

@@ -63,6 +63,7 @@ int bus_path_encode_unique(sd_bus *b, const char *prefix, const char *sender_id,
 int bus_path_decode_unique(const char *path, const char *prefix, char **ret_sender, char **ret_external);
 
 int bus_track_add_name_many(sd_bus_track *t, char **l);
+int bus_track_to_strv(sd_bus_track *t, char ***ret);
 
 int bus_open_system_watch_bind_with_description(sd_bus **ret, const char *description);
 static inline int bus_open_system_watch_bind(sd_bus **ret) {