Kroah-Hartman: AF_BUS, D-Bus, and the Linux kernel

Unless you have an infinite amount of resources, all reliable multicast systems are partially reliable. The only question is when you resort to the expedient of dropping non-responsive recipients, dropping messages to non-responsive recipients, or blocking indefinitely.

I suspect the DBUS developers did not intend to set up an electronic mail system, but rather intended the service for messages only useful if they are delivered in a bounded time. DBUS doesn't preserve messages across reboots does it?

No sane kernel implementation of reliable multicast would either. It seems pretty obvious that you must either kick out or drop messages to non-responsive recipients, with some appropriate definition of non-responsiveness, or you can't do anything useful. Blocking the sender is not a realistic option.

There is no need to kill any processes - each receiver should have a receive buffer limit, and be sent a control message when one or more messages were dropped because that limit would be exceeded.