Merge pull request #14160 from mwilck/fix-shutdown-hang

Fix shutdown hang caused by recent udev change

man/systemd.link.xml

@@ -668,7 +668,7 @@ MACAddress=00:a0:de:63:7a:e6
 Name=dmz0</programlisting>
 
       <para><varname>NamePolicy=</varname> is not set, so <varname>Name=</varname> takes effect. We use the
-      <literal>10-</literal> prefix to order this file early in the list. Note that it needs to before
+      <literal>10-</literal> prefix to order this file early in the list. Note that it needs to be before
       <literal>99-link</literal>, i.e. it needs a numerical prefix, to have any effect at all.</para>
     </example>
 

src/udev/udevd.c

@@ -293,8 +293,6 @@ static void manager_free(Manager *manager) {
         if (!manager)
                 return;
 
-        manager->monitor = sd_device_monitor_unref(manager->monitor);
-
         udev_builtin_exit();
 
         if (manager->pid == getpid_cached())
@@ -791,6 +789,8 @@ static void manager_exit(Manager *manager) {
         manager->inotify_event = sd_event_source_unref(manager->inotify_event);
         manager->fd_inotify = safe_close(manager->fd_inotify);
 
+        manager->monitor = sd_device_monitor_unref(manager->monitor);
+
         /* discard queued events and kill workers */
         event_queue_cleanup(manager, EVENT_QUEUED);
         manager_kill_workers(manager);
@@ -1311,11 +1311,13 @@ static int on_sigchld(sd_event_source *s, const struct signalfd_siginfo *si, voi
                         device_delete_db(worker->event->dev);
                         device_tag_index(worker->event->dev, NULL, false);
 
+                        if (manager->monitor) {
                                 /* forward kernel event without amending it */
                                 r = device_monitor_send_device(manager->monitor, NULL, worker->event->dev_kernel);
                                 if (r < 0)
                                         log_device_error_errno(worker->event->dev_kernel, r, "Failed to send back device to kernel: %m");
                         }
+                }
 
                 worker_free(worker);
         }