dbus: allow unregistering of exported objects

dbus/bus.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef DBUS_BUS_H_
 #define DBUS_BUS_H_
 #pragma once
 
 #include <map>
 #include <set>
@@ skipping 208 matching lines @@
   // The bus will own all exported objects created by the bus, to ensure
   // that the exported objects are unregistered at the shutdown time of
   // the bus.
   //
   // The exported object is used to export methods of local objects, and
   // send signal from them.
   //
   // Must be called in the origin thread.
   virtual ExportedObject* GetExportedObject(const ObjectPath& object_path);
 
+  // Unregisters the exported object for the given object path |object_path|.
+  //
+  // Getting an exported object for the same object path after this call
+  // will return a new object, method calls on any remaining copies of the
+  // previous object will not be called.
+  //
+  // BLOCKING CALL. Must be called in the origin thread.

[satorux1, 2012/03/13 18:27:25]

On what thread this function is called? For instance, we shouldn't block the UI
thread.

[keybuk, 2012/03/13 18:32:41]

probably the UI thread ... alternate suggestions welcome

[satorux1, 2012/03/13 18:42:01]

maybe:

1) add a callback parameter to UnregisterExportedObject, and let
BluetoothAgentServiceProviderImpl use it properly, before the destructor is
called. would it be difficult?

2) rather than block in UnregisterExportedObject, block in
Bus::ShutdownAndBlockOnDBusThreadInternal? we can probably do this by
dbus_thread_message_loop_->RunAllPendings()

[keybuk, 2012/03/13 18:53:31]

1) there's no place to call because the destructor is called as a result of the
scoped_ptr<> freeing the contained object - there isn't a sensible shutdown path
here

2) this isn't shutdown, this is unregistering an object without shutting down
the bus

[satorux1, 2012/03/13 18:56:36]

re 2, i meant to just post tasks to d-bus thread from
UnregisterExportedObject(), and make sure all of these tasks
were run at the shutdown time.

+  virtual void UnregisterExportedObject(const ObjectPath& object_path);
+
   // Shuts down the bus and blocks until it's done. More specifically, this
   // function does the following:
   //
   // - Unregisters the object paths
   // - Releases the service names
   // - Closes the connection to dbus-daemon.
   //
   // BLOCKING CALL.
   virtual void ShutdownAndBlock();
 
@@ skipping 174 matching lines @@
   // Returns true if the bus is connected to D-Bus.
   bool is_connected() { return connection_ != NULL; }
 
  protected:
   // This is protected, so we can define sub classes.
   virtual ~Bus();
 
  private:
   friend class base::RefCountedThreadSafe<Bus>;
 
+  // Helper function used for UnregisterExportedObject(), |completion| is
+  // the waitable event that allows the caller to block until complete.
+  void UnregisterExportedObjectInternal(const ObjectPath& object_path,
+                                        base::WaitableEvent* completion);
+
   // Helper function used for ShutdownOnDBusThreadAndBlock().
   void ShutdownOnDBusThreadAndBlockInternal();
 
   // Helper function used for RequestOwnership().
   void RequestOwnershipInternal(const std::string& service_name,
                                 OnOwnershipCallback on_ownership_callback);
 
   // Called when the ownership request is completed.
   void OnOwnership(OnOwnershipCallback on_ownership_callback,
                    const std::string& service_name,
@@ skipping 79 matching lines @@
   // OnAddTimeout()/OnRemoveTimeou() are balanced.
   int num_pending_watches_;
   int num_pending_timeouts_;
 
   DISALLOW_COPY_AND_ASSIGN(Bus);
 };
 
 }  // namespace dbus
 
 #endif  // DBUS_BUS_H_