[glib] gdbus: Fix atomic accesses to global name watch ID

[Philip Withnall <pwithnall src gnome org>]

commit c131865f57c2786d1a498d58b9b4c1333397798c
Author: Philip Withnall <withnall endlessm com>
Date:   Fri Feb 3 10:03:56 2017 +0000

    gdbus: Fix atomic accesses to global name watch ID
    
    https://bugzilla.gnome.org/show_bug.cgi?id=777307

 gio/gdbusnamewatching.c |    9 ++++++---
 1 files changed, 6 insertions(+), 3 deletions(-)
---
diff --git a/gio/gdbusnamewatching.c b/gio/gdbusnamewatching.c
index 01ab4ce..14603c5 100644
--- a/gio/gdbusnamewatching.c
+++ b/gio/gdbusnamewatching.c
@@ -77,7 +77,10 @@ typedef struct
   gboolean                  initialized;
 } Client;
 
-static guint next_global_id = 1;
+/* Must be accessed atomically. */
+static volatile guint next_global_id = 1;
+
+/* Must be accessed with @lock held. */
 static GHashTable *map_id_to_client = NULL;
 
 static Client *
@@ -562,7 +565,7 @@ g_bus_watch_name (GBusType                  bus_type,
 
   client = g_new0 (Client, 1);
   client->ref_count = 1;
-  client->id = next_global_id++; /* TODO: uh oh, handle overflow */
+  client->id = g_atomic_int_add (&next_global_id, 1); /* TODO: uh oh, handle overflow */
   client->name = g_strdup (name);
   client->flags = flags;
   client->name_appeared_handler = name_appeared_handler;
@@ -624,7 +627,7 @@ guint g_bus_watch_name_on_connection (GDBusConnection          *connection,
 
   client = g_new0 (Client, 1);
   client->ref_count = 1;
-  client->id = next_global_id++; /* TODO: uh oh, handle overflow */
+  client->id = g_atomic_int_add (&next_global_id, 1); /* TODO: uh oh, handle overflow */
   client->name = g_strdup (name);
   client->flags = flags;
   client->name_appeared_handler = name_appeared_handler;