FWICS D-Bus is behaving as designed: since the client has not called
dbus_connection_set_wakeup_main_function(), and since D-Bus messaging is
reliable, all libdbus is able to do when a signal is sent to a
connection is cache any messages the client has not yet processed in the
hope that at some future point it might consume them.
The key part of the D-Bus code that explains this is
dbus_connection_send_preallocated_unlocked_no_update():
------------------------------
/* Now we need to run an iteration to hopefully just write the messages
* out immediately, and otherwise get them queued up
*/
_dbus_connection_do_iteration_unlocked (connection,
NULL,
DBUS_ITERATION_DO_WRITING,
-1);
/* If stuff is still queued up, be sure we wake up the main loop */
if (connection->n_outgoing > 0)
_dbus_connection_wakeup_mainloop (connection);
------------------------------
As shown, the messages (signals in the case of Upstart) are added to the client
connection queue, but since the client called
dbus_connection_open() rather than nih_dbus_connect(), no mainloop handler is
registered to allow the client to deal with the signals sent to it.
>From the upstart perspective, a fix is to call
>dbus_connection_has_messages_to_send() and ignore that connection if the
client still has unprocessed messages (patch attached).
>From the D-Bus perspective, it would be useful to introduce a new public
API:
dbus_bool_t
dbus_connection_has_wakeup_main_function (DBusConnection *connection);
This would allow Upstart and other D-Bus server applications to detect
erroneous client connections.
** Patch added: "bug-1235649.diff"
https://bugs.launchpad.net/ubuntu/+source/unity/+bug/1235649/+attachment/3879222/+files/bug-1235649.diff
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https://bugs.launchpad.net/bugs/1235649
Title:
uevent spam causes libdbus client code in session upstart to consume
massive amounts of memory on Ubuntu Touch
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