logind: reset session leader if we know for a fact that it is gone

rhel-only

Related: #2223602

src/login/logind-dbus.c

@@ -3169,6 +3169,9 @@ int match_job_removed(sd_bus_message *message, void *userdata, sd_bus_error *err
                         session->scope_job = mfree(session->scope_job);
                         (void) session_jobs_reply(session, unit, result);
 
+                        /* Scope job is done so leader should be gone as well. */
+                        session_invalidate_leader(session);
+
                         session_save(session);
                         user_save(session->user);
                 }

src/login/logind-session.c

@@ -179,6 +179,23 @@ int session_set_leader(Session *s, pid_t pid) {
         return 1;
 }
 
+int session_invalidate_leader(Session *s) {
+        assert(s);
+
+        if (s->leader <= 0)
+                return 0;
+
+        if (pid_is_alive(s->leader))
+                return 0;
+
+        (void) hashmap_remove_value(s->manager->sessions_by_leader, PID_TO_PTR(s->leader), s);
+        s->leader = 0;
+
+        (void) session_save(s);
+
+        return 1;
+}
+
 static void session_save_devices(Session *s, FILE *f) {
         SessionDevice *sd;
         Iterator i;
@@ -1096,6 +1113,7 @@ static int session_dispatch_fifo(sd_event_source *es, int fd, uint32_t revents,
         /* EOF on the FIFO means the session died abnormally. */
 
         session_remove_fifo(s);
+        session_invalidate_leader(s);
         session_stop(s, false);
 
         return 1;

src/login/logind-session.h

@@ -127,6 +127,7 @@ DEFINE_TRIVIAL_CLEANUP_FUNC(Session *, session_free);
 
 void session_set_user(Session *s, User *u);
 int session_set_leader(Session *s, pid_t pid);
+int session_invalidate_leader(Session *s);
 bool session_may_gc(Session *s, bool drop_not_started);
 void session_add_to_gc_queue(Session *s);
 int session_activate(Session *s);