[glib] Add advice on g_cancellable_reset

[Matthias Clasen <matthiasc src gnome org>]

commit de82b641b05ee32812d945a9d4ecd1c1bbc3401e
Author: Matthias Clasen <mclasen redhat com>
Date:   Mon Oct 6 22:41:06 2014 -0400

    Add advice on g_cancellable_reset
    
    Don't use it at home.

 gio/gcancellable.c |    7 +++++++
 1 files changed, 7 insertions(+), 0 deletions(-)
---
diff --git a/gio/gcancellable.c b/gio/gcancellable.c
index fcfca3f..800e8f3 100644
--- a/gio/gcancellable.c
+++ b/gio/gcancellable.c
@@ -244,6 +244,13 @@ g_cancellable_get_current  (void)
  *
  * If cancellable is currently in use by any cancellable operation
  * then the behavior of this function is undefined.
+ *
+ * Note that it is generally not a good idea to reuse an existing
+ * cancellable for more operations after it has been cancelled once,
+ * as this function might tempt you to do. The recommended practice
+ * is to drop the reference to a cancellable after cancelling it,
+ * and let it die with the outstanding async operations. You should
+ * create a fresh cancellable for further async operations.
  **/
 void 
 g_cancellable_reset (GCancellable *cancellable)