[glib/wip/rishi/gtask-return-cancelled: 3/4] gtask: Return cancelled tasks asynchronously

[Philip Withnall <pwithnall src gnome org>]

commit 6f3d57d2ee271017f37ebdceb1e15efa7ce0ac49
Author: Debarshi Ray <debarshir gnome org>
Date:   Mon Dec 3 20:10:41 2018 +0100

    gtask: Return cancelled tasks asynchronously
    
    Once cancelled, a GTask's callback should not only be invoked
    asynchronously with respect to the creation of the task, but also with
    respect to the GCancellable::cancelled handler. This is particularly
    relevant in cases where the cancellation happened in the same thread
    where the task is running.
    
    Spotted by Dan Winship and Michael Catanzaro.
    
    Closes https://gitlab.gnome.org/GNOME/glib/issues/1608

 gio/gtask.c | 17 +++++++++++++----
 1 file changed, 13 insertions(+), 4 deletions(-)
---
diff --git a/gio/gtask.c b/gio/gtask.c
index aa98f752c..346d2ec5b 100644
--- a/gio/gtask.c
+++ b/gio/gtask.c
@@ -1,6 +1,6 @@
 /* GIO - GLib Input, Output and Streaming Library
  *
- * Copyright 2011 Red Hat, Inc.
+ * Copyright 2011-2018 Red Hat, Inc.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Lesser General Public
@@ -1260,9 +1260,18 @@ g_task_return (GTask           *task,
        */
       if (g_source_get_time (source) > task->creation_time)
         {
-          g_task_return_now (task);
-          g_object_unref (task);
-          return;
+          /* Finally, if the task has been cancelled, we shouldn't
+           * return synchronously from inside the
+           * GCancellable::cancelled handler. It's easier to run
+           * another iteration of the main loop than tracking how the
+           * cancellation was handled.
+           */
+          if (!g_cancellable_is_cancelled (task->cancellable))
+            {
+              g_task_return_now (task);
+              g_object_unref (task);
+              return;
+            }
         }
     }