Hi, > -----Original Message----- > From: Lennart Poettering [mailto:lenn...@poettering.net] > Sent: den 4 mars 2014 22:00 > To: Umut Tezduyar > Cc: Umut Tezduyar Lindskog; systemd-devel@lists.freedesktop.org > Subject: Re: [systemd-devel] StartupFinished signal is not sent on 210 > > On Tue, 04.03.14 21:40, Umut Tezduyar (u...@tezduyar.com) wrote: > > > >> To compare 208 and 210, I pretty much followed steps @ > > >> https://wiki.ubuntu.com/DebuggingDBus and by using $> dbus-monitor > > >> "type=signal,sender='org.freedesktop.systemd1'" --system > > > > > > You have to invoke "Subscribe()" first on the manager bus, to get > > > something. We only send out the messages as long as at least one > > > living client has issued this call. > > > > Don't you think this is something worth mentioning in the NEWS since > > we were able to retrieve signals without subscribing to them on 208. > > Excuse me if it is documented somewhere and I missed it. > > Subscribe() is actually around since day #1 of systemd. And it is documented > here: > > http://www.freedesktop.org/wiki/Software/systemd/dbus/ > > Of course, I must admit it is less than ideal that with logind around you > might > be able to get away with never calling it... That certainly hides bugs...
We don't have logind and we certainly weren't calling Subscribe(). Then I can't explain how come we were receiving the signal, can you? Could it be that one of systemd applications was subscribing and we were just lucky to get the signal? > > We changed a couple of times how systemd delivers those signals during the > history, but clients which called Subscribed() should always just have worked. > > Note that 211 actually changes things back to be more like < 209... > > The difference between < 209 + > 210 and 209+210 is the single subscriber > case. With < 209 + > 210 we have the following rule: > > 1. when there's no subscriber we don't send out any signals 2. when there's > one or more subscribers we broadcast signals to everybody > > In 209+210 we had this ruleset instead: > > 1. when there's no subscriber we don't send out any signals 2. when there's > one subscriber send all signals as unicast to it 3. when there's two or more > subscribers we broadcast signals to everybody > > I thought for a while that doing step #2 was smart, but then again, it's kinda > stupid, since it second guesses the dbus filter logic too much, and the > messages look different to the receiver depending on the number of other > subscribers. So I dropped this again... > > Lennart > > -- > Lennart Poettering, Red Hat _______________________________________________ systemd-devel mailing list systemd-devel@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/systemd-devel
