RE: [libvirt] [RFC] making (newly public) EventImpl interface moreconsistent

Ugh. I see what you mean. It seems more complicated than that, though. For one thing, the AvahiWatch/AvahiPoll stuff is sufficiently abstract that it doesn't mention DBusConnection (or any other DBus type, AFAIK), so there's no indication that *any* DBusConnection is being used (though I trust that there is). Turning on AVAHI_DEBUG, I see both my (node_device_hal.c) callbacks and the avahi callbacks being called (but at different times, and with different fds and event sets). Makes me wonder whether the avahi library is using dbus_bus_get_private() to get its own DBusConnection that it doesn't have to worry about sharing with others. I tried changing the node_device_hal code to use a private dbus connection, and see exactly the same behavior (i.e., dbus immediately registers the same fd twice, with different event sets and enable state). Regardless, I like the idea of simply using this private connection (as you suggested but rejected), just for the sake of simplicity. (Also, what if Avahi's been configured out?) But ... back to the original problem. Immediately after calling dbus_set_watch_functions (and *before* initializing the Avahi stuff), I see two callbacks to watch_add with the same fd. Looking at the glib watch functions, I see watches on GIOChannels are added with g_io_add_watch(), which indeed doesn't specify what happens if the same GIOChannel is added twice. But GIOChannels aren't fds. Presumably, one could create two different GIOChannels with the same fd (via g_io_channel_unix_new) and then register watches on each of them. So I remain convinced that we need to support the registration of the same fd multiple times ...