g_cancellable_source_new: don't use a file descriptor

Rather than implementing GCancellableSource by polling on its fd,
implement it by just waking its GMainContext up from the "cancelled"
signal handler, thereby helping to reduce file descriptor usage.
Suggested by Ryan Lortie.

https://bugzilla.gnome.org/show_bug.cgi?id=680121

diff --git a/gio/gcancellable.c b/gio/gcancellable.c
index 8fb1195..0ba3a01 100644 (file)
--- a/gio/gcancellable.c
+++ b/gio/gcancellable.c
@@ -632,9 +632,17 @@ typedef struct {
   GSource       source;
 
   GCancellable *cancellable;
-  GPollFD       pollfd;
 } GCancellableSource;
 
+static void
+cancellable_source_cancelled (GCancellable *cancellable,
+                             gpointer      user_data)
+{
+  GSource *source = user_data;
+
+  g_main_context_wakeup (g_source_get_context (source));
+}
+
 static gboolean
 cancellable_source_prepare (GSource *source,
                            gint    *timeout)
@@ -670,7 +678,12 @@ cancellable_source_finalize (GSource *source)
   GCancellableSource *cancellable_source = (GCancellableSource *)source;
 
   if (cancellable_source->cancellable)
-    g_object_unref (cancellable_source->cancellable);
+    {
+      g_signal_handlers_disconnect_by_func (cancellable_source->cancellable,
+                                           G_CALLBACK (cancellable_source_cancelled),
+                                           cancellable_source);
+      g_object_unref (cancellable_source->cancellable);
+    }
 }
 
 static gboolean
@@ -733,11 +746,12 @@ g_cancellable_source_new (GCancellable *cancellable)
   g_source_set_name (source, "GCancellable");
   cancellable_source = (GCancellableSource *)source;
 
-  if (g_cancellable_make_pollfd (cancellable,
-                                 &cancellable_source->pollfd))
+  if (cancellable)
     {
       cancellable_source->cancellable = g_object_ref (cancellable);
-      g_source_add_poll (source, &cancellable_source->pollfd);
+      g_signal_connect (cancellable, "cancelled",
+                       G_CALLBACK (cancellable_source_cancelled),
+                       source);
     }
 
   return source;