file monitor: Construct synchronously

g_file_monitor_file() is a sync call anyway, so doing some sync i/o
in the constructor doesn't make a difference, and doing so avoids
races where you would not get change events for operations you do.

We don't actually need to wait for the subscribe event, and proxy
construction in this case does not do any i/o, so we're really only
doing sync i/o to look up the connection, and it should be cached from
the earlier call in g_daemon_file_monitor_file(), so in practice
this should make little difference.

https://bugzilla.gnome.org/show_bug.cgi?id=749317

1 files changed, 58 insertions, 83 deletions

diff --git a/client/gdaemonfilemonitor.c b/client/gdaemonfilemonitor.c
index 4de3b24d..313b06ff 100644
--- a/client/gdaemonfilemonitor.c
+++ b/client/gdaemonfilemonitor.c
@@ -47,7 +47,7 @@ struct _GDaemonFileMonitor
   char *remote_obj_path;
   char *remote_id;
   GDBusConnection *connection;
-  GVfsDBusMonitor *proxy;
+  GVfsDBusMonitor *proxy;              /* Non-null if we're subscribed */
   GVfsDBusMonitorClient *skeleton;
 };
 
@@ -57,7 +57,7 @@ static void
 g_daemon_file_monitor_finalize (GObject* object)
 {
   GDaemonFileMonitor *daemon_monitor;
-  
+
   daemon_monitor = G_DAEMON_FILE_MONITOR (object);
 
   if (daemon_monitor->skeleton)
@@ -107,7 +107,7 @@ handle_changed (GVfsDBusMonitorClient *object,
   g_mount_spec_unref (spec1);
 
   file2 = NULL;
-  
+
   if (strlen (arg_other_file_path) > 0)
     {
       spec2 = g_mount_spec_from_dbus (arg_other_mount_spec);
@@ -118,9 +118,9 @@ handle_changed (GVfsDBusMonitorClient *object,
   g_file_monitor_emit_event (G_FILE_MONITOR (monitor),
                              file1, file2,
                              arg_event_type);
-  
+
   gvfs_dbus_monitor_client_complete_changed (object, invocation);
-  
+
   return TRUE;
 }
 
@@ -167,94 +167,69 @@ subscribe_cb (GVfsDBusMonitor *proxy,
   g_object_unref (monitor);
 }
 
-static void
-async_proxy_new_cb (GObject *source_object,
-                    GAsyncResult *res,
-                    gpointer user_data)
-{
-  GDaemonFileMonitor* monitor = user_data;
-  GVfsDBusMonitor *proxy;
-  GError *error = NULL;
-
-  proxy = gvfs_dbus_monitor_proxy_new_finish (res, &error);
-  if (proxy == NULL)
-    {
-      g_printerr ("Error creating monitor proxy: %s (%s, %d)\n",
-                  error->message, g_quark_to_string (error->domain), error->code);
-      g_error_free (error);
-      g_clear_object (&monitor->connection);
-      g_object_unref (monitor);
-      return;
-    }
-
-  if (g_file_monitor_is_cancelled (G_FILE_MONITOR (monitor)))
-    {
-      g_clear_object (&monitor->connection);
-      g_object_unref (proxy);
-      g_object_unref (monitor);
-      return;
-    }
-
-  gvfs_dbus_monitor_call_subscribe (proxy,
-                                    monitor->object_path,
-                                    NULL,
-                                    (GAsyncReadyCallback) subscribe_cb,
-                                    monitor);
-  g_object_unref (proxy);
-}
-
-static void
-async_got_connection_cb (GDBusConnection *connection,
-                         GError *io_error,
-                         gpointer callback_data)
-{
-  GDaemonFileMonitor* monitor = callback_data;
-  GError *error;
-
-  if (! connection)
-    {
-      g_printerr ("Error getting connection for monitoring: %s (%s, %d)\n",
-                   io_error->message, g_quark_to_string (io_error->domain), io_error->code);
-      g_object_unref (monitor);
-      return;
-    }
-
-  error = NULL;
-  if (!g_dbus_interface_skeleton_export (G_DBUS_INTERFACE_SKELETON (monitor->skeleton),
-                                         connection,
-                                         monitor->object_path,
-                                         &error))
-    {
-      g_warning ("Error registering path: %s (%s, %d)\n",
-                  error->message, g_quark_to_string (error->domain), error->code);
-      g_error_free (error);
-    }
-
-  monitor->connection = g_object_ref (connection);
-  gvfs_dbus_monitor_proxy_new (connection,
-                               G_DBUS_PROXY_FLAGS_DO_NOT_LOAD_PROPERTIES | G_DBUS_PROXY_FLAGS_DO_NOT_CONNECT_SIGNALS,
-                               monitor->remote_id,
-                               monitor->remote_obj_path,
-                               NULL,
-                               async_proxy_new_cb,
-                               monitor);
-}
-
 GFileMonitor*
 g_daemon_file_monitor_new (const char *remote_id,
-				const char *remote_obj_path)
+                           const char *remote_obj_path)
 {
   GDaemonFileMonitor* daemon_monitor;
+  GDBusConnection *connection;
+  GError *error = NULL;
+  GVfsDBusMonitor *proxy;
 
   daemon_monitor = g_object_new (G_TYPE_DAEMON_FILE_MONITOR, NULL);
 
   daemon_monitor->remote_id = g_strdup (remote_id);
   daemon_monitor->remote_obj_path = g_strdup (remote_obj_path);
 
-  _g_dbus_connection_get_for_async (daemon_monitor->remote_id,
-                                    async_got_connection_cb,
-                                    g_object_ref (daemon_monitor),
-                                    NULL);
+  daemon_monitor->connection = _g_dbus_connection_get_sync (daemon_monitor->remote_id, NULL, &error);
+  if (daemon_monitor->connection == NULL)
+    {
+      g_printerr ("Error getting connection for monitoring: %s (%s, %d)\n",
+                  error->message, g_quark_to_string (error->domain), error->code);
+      g_error_free (error);
+    }
+  else
+    {
+      if (!g_dbus_interface_skeleton_export (G_DBUS_INTERFACE_SKELETON (daemon_monitor->skeleton),
+                                             daemon_monitor->connection,
+                                             daemon_monitor->object_path,
+                                             &error))
+        {
+          g_warning ("Error registering path: %s (%s, %d)\n",
+                     error->message, g_quark_to_string (error->domain), error->code);
+          g_error_free (error);
+        }
+
+      /* This looks like a sync call, but since the remote_id is a
+         unique id we don't actually send any messages */
+      proxy = gvfs_dbus_monitor_proxy_new_sync (daemon_monitor->connection,
+                                                G_DBUS_PROXY_FLAGS_DO_NOT_LOAD_PROPERTIES | G_DBUS_PROXY_FLAGS_DO_NOT_CONNECT_SIGNALS,
+                                                daemon_monitor->remote_id,
+                                                daemon_monitor->remote_obj_path,
+                                                NULL,
+                                                &error);
+      if (proxy == NULL)
+        {
+          g_printerr ("Error creating monitor proxy: %s (%s, %d)\n",
+                      error->message, g_quark_to_string (error->domain), error->code);
+          g_error_free (error);
+        }
+      else
+        {
+          /* We set the proxy in the callback, meaning we're subscribed if it is set */
+          gvfs_dbus_monitor_call_subscribe (proxy,
+                                            daemon_monitor->object_path,
+                                            NULL,
+                                            (GAsyncReadyCallback) subscribe_cb,
+                                            g_object_ref (daemon_monitor));
+          g_object_unref (proxy);
+
+          /* At this point it is safe to return the monitor, even if we have not gotten
+             the reply to the subscribe yet, because any i/o we do to the mount such
+             as listing a directory will happen after the mount receives the subscribe
+             message */
+        }
+    }
 
   return G_FILE_MONITOR (daemon_monitor);
 }