[gvfs/gdbus] gdbus: Use a static lock for metadata proxy instead of GPrivate

[Tomas Bzatek <tbzatek src gnome org>]

commit 81122277cc4aa8ec71dc679297aa929512a4c159
Author: Tomas Bzatek <tbzatek redhat com>
Date:   Mon Jun 4 17:31:10 2012 +0200

    gdbus: Use a static lock for metadata proxy instead of GPrivate
    
    Using GPrivate turned to be problematic wrt thread safety, better
    to use the standard way of locks.

 client/gdaemonfile.c |   52 ++---------------------------------
 client/gdaemonvfs.c  |   74 +++++++++++++++++++++++++++++--------------------
 client/gdaemonvfs.h  |    4 +++
 3 files changed, 51 insertions(+), 79 deletions(-)
---
diff --git a/client/gdaemonfile.c b/client/gdaemonfile.c
index 5c4f76b..5ab98d6 100644
--- a/client/gdaemonfile.c
+++ b/client/gdaemonfile.c
@@ -29,6 +29,7 @@
 #include <sys/socket.h>
 
 #include "gdaemonfile.h"
+#include "gdaemonvfs.h"
 #include "gvfsdaemondbus.h"
 #include "gdaemonmount.h"
 #include <gvfsdaemonprotocol.h>
@@ -55,8 +56,6 @@ G_DEFINE_TYPE_WITH_CODE (GDaemonFile, g_daemon_file, G_TYPE_OBJECT,
 			 G_IMPLEMENT_INTERFACE (G_TYPE_FILE,
 						g_daemon_file_file_iface_init))
 
-static GPrivate metadata_proxy = G_PRIVATE_INIT (g_object_unref);
-
 static void
 g_daemon_file_finalize (GObject *object)
 {
@@ -2209,52 +2208,6 @@ g_daemon_file_query_writable_namespaces (GFile                      *file,
   return list;
 }
 
-static void
-metadata_daemon_vanished (GDBusConnection *connection,
-                          const gchar *name,
-                          gpointer user_data)
-{
-  guint *watcher_id = user_data;
-
-  g_private_replace (&metadata_proxy, NULL);
-  if (*watcher_id > 0)
-    g_bus_unwatch_name (*watcher_id);
-}
-
-static GVfsMetadata *
-get_metadata_proxy (GCancellable *cancellable, GError **error)
-{
-  GVfsMetadata *proxy;
-  guint *watcher_id;
-
-  proxy = g_private_get (&metadata_proxy);
-  if (proxy == NULL)
-    {
-      proxy = gvfs_metadata_proxy_new_for_bus_sync (G_BUS_TYPE_SESSION,
-                                                    G_DBUS_PROXY_FLAGS_NONE,
-                                                    G_VFS_DBUS_METADATA_NAME,
-                                                    G_VFS_DBUS_METADATA_PATH,
-                                                    cancellable,
-                                                    error);
-      g_private_replace (&metadata_proxy, proxy);
-
-      if (proxy == NULL)
-        return NULL;
-
-      /* a place in memory to store the returned ID in */
-      watcher_id = g_malloc0 (sizeof (guint));
-      *watcher_id = g_bus_watch_name_on_connection (g_dbus_proxy_get_connection (G_DBUS_PROXY (proxy)),
-                                                    G_VFS_DBUS_METADATA_NAME,
-                                                    G_BUS_NAME_WATCHER_FLAGS_AUTO_START,
-                                                    NULL,
-                                                    metadata_daemon_vanished,
-                                                    watcher_id,
-                                                    g_free);
-    }
-
-  return proxy;
-}
-
 static gboolean
 set_metadata_attribute (GFile *file,
 			const char *attribute,
@@ -2279,7 +2232,7 @@ set_metadata_attribute (GFile *file,
   g_free (treename);
   
   res = FALSE;
-  proxy = get_metadata_proxy (cancellable, error);
+  proxy = _g_daemon_vfs_get_metadata_proxy (cancellable, error);
 
   if (proxy)
     {
@@ -2313,6 +2266,7 @@ set_metadata_attribute (GFile *file,
         res = FALSE;
 
       g_variant_builder_unref (builder);
+      g_object_unref (proxy);
     }
 
   meta_tree_unref (tree);
diff --git a/client/gdaemonvfs.c b/client/gdaemonvfs.c
index 33c218a..c131545 100644
--- a/client/gdaemonvfs.c
+++ b/client/gdaemonvfs.c
@@ -41,7 +41,6 @@
 #include "gvfsiconloadable.h"
 #include <glib/gi18n-lib.h>
 #include <glib/gstdio.h>
-#include <metadata-dbus.h>
 
 typedef struct  {
   char *type;
@@ -77,7 +76,9 @@ struct _GDaemonVfsClass
 G_DEFINE_DYNAMIC_TYPE (GDaemonVfs, g_daemon_vfs, G_TYPE_VFS)
 
 static GDaemonVfs *the_vfs = NULL;
-static GPrivate metadata_proxy = G_PRIVATE_INIT (g_object_unref);
+
+G_LOCK_DEFINE_STATIC (metadata_proxy);
+static GVfsMetadata *metadata_proxy = NULL;
 
 G_LOCK_DEFINE_STATIC(mount_cache);
 
@@ -1289,42 +1290,52 @@ metadata_daemon_vanished (GDBusConnection *connection,
 {
   guint *watcher_id = user_data;
 
-  g_private_replace (&metadata_proxy, NULL);
+  G_LOCK (metadata_proxy);
+  g_clear_object (&metadata_proxy);
+  G_UNLOCK (metadata_proxy);
+
   if (*watcher_id > 0)
     g_bus_unwatch_name (*watcher_id);
 }
 
-static GVfsMetadata *
-get_metadata_proxy (GError **error)
+GVfsMetadata *
+_g_daemon_vfs_get_metadata_proxy (GCancellable *cancellable, GError **error)
 {
   GVfsMetadata *proxy;
   guint *watcher_id;
 
-  proxy = g_private_get (&metadata_proxy);
-  if (proxy == NULL)
+  G_LOCK (metadata_proxy);
+
+  proxy = NULL;
+  if (metadata_proxy == NULL)
     {
-      proxy = gvfs_metadata_proxy_new_for_bus_sync (G_BUS_TYPE_SESSION,
-                                                    G_DBUS_PROXY_FLAGS_NONE,
-                                                    G_VFS_DBUS_METADATA_NAME,
-                                                    G_VFS_DBUS_METADATA_PATH,
-                                                    NULL,
-                                                    error);
-      g_private_replace (&metadata_proxy, proxy);
-
-      if (proxy == NULL)
-        return NULL;
-
-      /* a place in memory to store the returned ID in */
-      watcher_id = g_malloc0 (sizeof (guint));
-      *watcher_id = g_bus_watch_name_on_connection (g_dbus_proxy_get_connection (G_DBUS_PROXY (proxy)),
-                                                    G_VFS_DBUS_METADATA_NAME,
-                                                    G_BUS_NAME_WATCHER_FLAGS_AUTO_START,
-                                                    NULL,
-                                                    metadata_daemon_vanished,
-                                                    watcher_id,
-                                                    g_free);
+      metadata_proxy = gvfs_metadata_proxy_new_for_bus_sync (G_BUS_TYPE_SESSION,
+                                                             G_DBUS_PROXY_FLAGS_NONE,
+                                                             G_VFS_DBUS_METADATA_NAME,
+                                                             G_VFS_DBUS_METADATA_PATH,
+                                                             cancellable,
+                                                             error);
+
+      if (proxy != NULL)
+        {
+          /* a place in memory to store the returned ID in */
+          watcher_id = g_malloc0 (sizeof (guint));
+          *watcher_id = g_bus_watch_name_on_connection (g_dbus_proxy_get_connection (G_DBUS_PROXY (proxy)),
+                                                        G_VFS_DBUS_METADATA_NAME,
+                                                        G_BUS_NAME_WATCHER_FLAGS_AUTO_START,
+                                                        NULL,
+                                                        metadata_daemon_vanished,
+                                                        watcher_id,
+                                                        g_free);
+        }
     }
 
+  if (metadata_proxy != NULL)
+    /* take the reference so that we don't need to protect returned object against racy metadata_daemon_vanished() */
+    proxy = g_object_ref (metadata_proxy);
+
+  G_UNLOCK (metadata_proxy);
+
   return proxy;
 }
 
@@ -1380,7 +1391,7 @@ g_daemon_vfs_local_file_set_attributes (GVfs       *vfs,
 						FALSE,
 						&tree_path);
 	  
-	  proxy = get_metadata_proxy (error);
+	  proxy = _g_daemon_vfs_get_metadata_proxy (NULL, error);
 	  if (proxy == NULL)
 	    {
 	      res = FALSE;
@@ -1442,6 +1453,7 @@ g_daemon_vfs_local_file_set_attributes (GVfs       *vfs,
               meta_lookup_cache_free (cache);
               meta_tree_unref (tree);
               g_free (tree_path);
+              g_object_unref (proxy);
 	    }
 	}
 
@@ -1469,7 +1481,7 @@ g_daemon_vfs_local_file_removed (GVfs       *vfs,
 					&tree_path);
   if (tree)
     {
-      proxy = get_metadata_proxy (NULL);
+      proxy = _g_daemon_vfs_get_metadata_proxy (NULL, NULL);
       if (proxy)
         {
           metatreefile = meta_tree_get_filename (tree);
@@ -1483,6 +1495,7 @@ g_daemon_vfs_local_file_removed (GVfs       *vfs,
           /* flush the call with the expense of sending all queued messages on the connection */
           g_dbus_connection_flush_sync (g_dbus_proxy_get_connection (G_DBUS_PROXY (proxy)),
                                         NULL, NULL);
+          g_object_unref (proxy);
         }
       
       meta_tree_unref (tree);
@@ -1516,7 +1529,7 @@ g_daemon_vfs_local_file_moved (GVfs       *vfs,
 					 &tree_path2);
   if (tree1 && tree2 && tree1 == tree2)
     {
-      proxy = get_metadata_proxy (NULL);
+      proxy = _g_daemon_vfs_get_metadata_proxy (NULL, NULL);
       if (proxy)
         {
           metatreefile = meta_tree_get_filename (tree1);
@@ -1531,6 +1544,7 @@ g_daemon_vfs_local_file_moved (GVfs       *vfs,
           /* flush the call with the expense of sending all queued messages on the connection */
           g_dbus_connection_flush_sync (g_dbus_proxy_get_connection (G_DBUS_PROXY (proxy)),
                                         NULL, NULL);
+          g_object_unref (proxy);
         }
     }
 
diff --git a/client/gdaemonvfs.h b/client/gdaemonvfs.h
index 5b1b72e..f96ab89 100644
--- a/client/gdaemonvfs.h
+++ b/client/gdaemonvfs.h
@@ -29,6 +29,7 @@
 #include "gmounttracker.h"
 #include "gvfsuriutils.h"
 #include <metatree.h>
+#include <metadata-dbus.h>
 
 G_BEGIN_DECLS
 
@@ -78,6 +79,9 @@ int             _g_daemon_vfs_append_metadata_for_set  (GVariantBuilder *builder
 							GFileAttributeType type,
 							gpointer   value);
 
+GVfsMetadata *  _g_daemon_vfs_get_metadata_proxy       (GCancellable             *cancellable,
+                                                        GError                  **error);
+
 
 
 G_END_DECLS