Avoid race between Mission Control's two names by having one wait for the other

If you do:

dbus-send --dest=org.freedesktop.Telepathy.MissionControl5 \
  --type=method_call --print-reply / org.freedesktop.DBus.Peer.Ping & \
dbus-send --dest=org.freedesktop.Telepathy.AccountManager \
--type=method_call --print-reply / org.freedesktop.DBus.Peer.Ping

then one or both of the calls will fail because the executable claims
one of its bus names, but can't get the other, and exits 1.

By making one wait for the other, we get the desired behaviour.
I've made activating MissionControl5 wait for AccountManager because
in MC's current implementation AccountManager is taken last.

Reviewed-by: Jonny Lamb <jonny.lamb@collabora.co.uk>
Bug: https://bugs.freedesktop.org/show_bug.cgi?id=53220

3 files changed, 86 insertions, 8 deletions

diff --git a/server/Makefile.am b/server/Makefile.am
index ba734500..eb74a3cd 100644
--- a/server/Makefile.am
+++ b/server/Makefile.am
@@ -24,7 +24,10 @@ servicefile_DATA=org.freedesktop.Telepathy.MissionControl5.service \
 		 org.freedesktop.Telepathy.AccountManager.service
 
 %.service: %.service.in Makefile
-	$(AM_V_GEN)sed -e 's![@]libexecdir[@]!$(libexecdir)!' $< > $@
+	$(AM_V_GEN)sed \
+		-e 's![@]libexecdir[@]!$(libexecdir)!' \
+		-e 's![@]bindir[@]!$(bindir)!' \
+		$< > $@
 
 man8_MANS = mission-control-5.8
 
diff --git a/server/org.freedesktop.Telepathy.MissionControl5.service.in b/server/org.freedesktop.Telepathy.MissionControl5.service.in
index d91d4dd8..51f4dc17 100644
--- a/server/org.freedesktop.Telepathy.MissionControl5.service.in
+++ b/server/org.freedesktop.Telepathy.MissionControl5.service.in
@@ -1,3 +1,3 @@
 [D-BUS Service]
 Name=org.freedesktop.Telepathy.MissionControl5
-Exec=@libexecdir@/mission-control-5
+Exec=@bindir@/mc-wait-for-name --activate org.freedesktop.Telepathy.AccountManager org.freedesktop.Telepathy.MissionControl5
diff --git a/util/wait-for-name.c b/util/wait-for-name.c
index af8bcdb4..4679a182 100644
--- a/util/wait-for-name.c
+++ b/util/wait-for-name.c
@@ -4,14 +4,22 @@
  * automatically (after a while) by the desktop session.
  *
  * Usage, in
- * $XDG_DATA_DIRS/dbus-1/services/org.freedesktop.Client.Something.service:
+ * $XDG_DATA_DIRS/dbus-1/services/....Client.Something.service:
  *
  * [D-BUS Service]
- * Name=org.freedesktop.Telepathy.Client.Something
- * Exec=/usr/lib/mission-control/mc-wait-for-name org.freedesktop.Telepathy.Client.Something
+ * Name=....Client.Something
+ * Exec=/usr/lib/telepathy/mc-wait-for-name ....Client.Something
+ *
+ * Alternatively, it can be used to activate something via an alternative
+ * name, e.g. in
+ * $XDG_DATA_DIRS/dbus-1/services/....AccountManager.service:
+ *
+ * [D-BUS Service]
+ * Name=....AccountManager
+ * Exec=/usr/lib/telepathy/mc-wait-for-name --activate ....MissionControl5 ....AccountManager
  *
  * Copyright (C) 2009 Nokia Corporation
- * Copyright (C) 2009 Collabora Ltd.
+ * Copyright (C) 2009, 2012 Collabora Ltd.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Lesser General Public
@@ -41,7 +49,7 @@
 
 #include <glib.h>
 
-#include <telepathy-glib/dbus.h>
+#include <telepathy-glib/telepathy-glib.h>
 
 static int exit_status = EX_SOFTWARE;
 static guint timeout_id = 0;
@@ -86,8 +94,48 @@ noc_cb (TpDBusDaemon *bus_daemon,
     }
 }
 
+static void
+start_service_cb (TpDBusDaemon *bus_daemon,
+    guint ret,
+    const GError *error,
+    gpointer user_data,
+    GObject *weak_object)
+{
+  GMainLoop *loop = user_data;
+
+  if (error != NULL)
+    {
+      g_message ("%s", error->message);
+      g_main_loop_quit (loop);
+      exit_status = EX_TEMPFAIL;
+    }
+  else
+    {
+      switch (ret)
+        {
+          case 1: /* DBUS_START_REPLY_SUCCESS */
+            g_debug ("activated name successfully started");
+            break;
+
+          case 2: /* DBUS_START_REPLY_ALREADY_RUNNING */
+            g_debug ("activated name already running");
+            break;
+
+          default:
+            g_message ("ignoring unknown result from StartServiceByName: %u", ret);
+            break;
+        }
+    }
+}
+
 #define WFN_TIMEOUT (5 * 60) /* 5 minutes */
 
+static gchar *activate = NULL;
+static GOptionEntry entries[] = {
+      { "activate", 0, 0, G_OPTION_ARG_STRING, &activate, "Activate NAME before waiting for the other name", "NAME" },
+      { NULL }
+};
+
 int
 main (int argc,
       char **argv)
@@ -95,14 +143,33 @@ main (int argc,
   TpDBusDaemon *bus_daemon;
   GMainLoop *loop;
   GError *error = NULL;
+  GOptionContext *context;
 
   g_set_prgname ("mc-wait-for-name");
 
+  context = g_option_context_new ("- wait for a bus name");
+  g_option_context_add_main_entries (context, entries, NULL);
+
+  if (!g_option_context_parse (context, &argc, &argv, &error))
+    {
+      g_message ("%s", error->message);
+      g_error_free (error);
+      return EX_USAGE;
+    }
+
+  if (activate != NULL &&
+      !tp_dbus_check_valid_bus_name (activate, TP_DBUS_NAME_TYPE_WELL_KNOWN,
+        NULL))
+    {
+      g_message ("Not a valid bus name: %s", activate);
+      return EX_USAGE;
+    }
+
   if (argc != 2 ||
       !tp_dbus_check_valid_bus_name (argv[1], TP_DBUS_NAME_TYPE_WELL_KNOWN,
         NULL))
     {
-      g_message ("Usage: mc-wait-for-name com.example.SomeBusName");
+      g_message ("Usage: mc-wait-for-name [OPTIONS] com.example.SomeBusName");
       return EX_USAGE;
     }
 
@@ -117,6 +184,14 @@ main (int argc,
     }
 
   loop = g_main_loop_new (NULL, FALSE);
+
+  if (activate != NULL)
+    {
+      tp_cli_dbus_daemon_call_start_service_by_name (bus_daemon, -1,
+          activate, 0 /* no flags */, start_service_cb, g_main_loop_ref (loop),
+          (GDestroyNotify) g_main_loop_unref, NULL);
+    }
+
   tp_dbus_daemon_watch_name_owner (bus_daemon, argv[1],
       noc_cb, g_main_loop_ref (loop), (GDestroyNotify) g_main_loop_unref);