[tracker/tracker-0.10] libtracker-sparql-backend: Protect singleton weak pointer with mutex

[Martyn James Russell <mr src gnome org>]

commit 54a24828669b352c46044bc8a315886e408183a5
Author: Jürg Billeter <j bitron ch>
Date:   Thu May 19 09:18:48 2011 +0200

    libtracker-sparql-backend: Protect singleton weak pointer with mutex

 src/libtracker-sparql-backend/tracker-backend.vala |   19 ++++++++++++++++++-
 1 files changed, 18 insertions(+), 1 deletions(-)
---
diff --git a/src/libtracker-sparql-backend/tracker-backend.vala b/src/libtracker-sparql-backend/tracker-backend.vala
index b1190a8..2a1ac1a 100644
--- a/src/libtracker-sparql-backend/tracker-backend.vala
+++ b/src/libtracker-sparql-backend/tracker-backend.vala
@@ -52,6 +52,24 @@ class Tracker.Sparql.Backend : Connection {
 		}
 	}
 
+	public override void dispose () {
+		door.lock ();
+
+		try {
+			// Ensure this instance is not used for any new calls to Tracker.Sparql.Connection.get.
+			// However, a call to Tracker.Sparql.Connection.get between g_object_unref and the
+			// above lock might have increased the reference count of this instance to 2 (or more).
+			// Therefore, we must not clean up direct/bus connection in dispose.
+			if (singleton == this) {
+				singleton = null;
+			}
+		} finally {
+			door.unlock ();
+		}
+
+		base.dispose ();
+	}
+
 	public override Cursor query (string sparql, Cancellable? cancellable = null) throws Sparql.Error, IOError, DBusError
 	requires (bus != null || direct != null) {
 		debug ("%s(): '%s'", Log.METHOD, sparql);
@@ -211,7 +229,6 @@ class Tracker.Sparql.Backend : Connection {
 				}
 
 				singleton = result;
-				result.add_weak_pointer ((void**) (&singleton));
 			}
 
 			assert (direct_only == is_direct_only);