>>>>> Gabriel Rossetti <gabriel.rosse...@arimaz.com> (GR) wrote:
>GR> Piet van Oostrum wrote: ... >GR> I wrote a small example that listens for xmpp msgs in a thread. The main >GR> program calls a function that blocks (using Condition.wait) until a msg >GR> has been received and then returns the msg. When a msg arrives, it is >GR> put in a variable in the thread's object, it then calls the notify() >GR> attr on the Condition object. For some reason, this doesn't work, the >GR> thread gets the msg, tries to notify the Condition object, fails because >GR> the lock has not been acquired yet and blocks. I tried ignoring the >GR> failure, thinking that since it has not been acquired yet then when it >GR> is, it will get the msg right away and never call Condition.wait, thus >GR> not causing any problems, but this does not work either. Does someone >GR> know what I am doing wrong? I attached the code to this msg. >>>> >>> >>> The code that puts the message in the variable should also acquire the >>> lock: >>> >>> >>> def onMessage(self, conn, msg): >>> with self._cv: >>> self.message = msg >>> self._cv.notify() >>> >GR> Thank you, that was the problem, I eventually found that >>> A couple of remarks: >>> >>> 1. I think the code is neater if all manipulation with the condition is >>> done in the same class (actually in the same instance -- making this >>> instance into a monitor). >>> >GR> The reason I didn't do that is that I don' t want the Listener to sleep, I >GR> maybe over simplified the example, I actually put them in a dictionary as >GR> they come in, so in your example, if I have several threads waiting on msgs >GR> it wouldn't work. I'm trying to make a webservice api thay will also be >GR> turned into a java .jar for people that need java. Now that I think about >GR> it, each session will have an instance of the object so msgs shouldn' t get >GR> mixed up (one connection per user), so I could block in the thread. I'll >GR> try your suggestion as I think it is cleaner. Sleeping as you call it is better than busy waiting. You must have some synchronisation to make it efficient. If you put the messages in a dictionary access to the dictionary must be protected. Having several threads waiting for the messages doesn't prevent you from using proper synchronisation. Maybe you must use notify_all instead of notify. -- Piet van Oostrum <p...@cs.uu.nl> URL: http://pietvanoostrum.com [PGP 8DAE142BE17999C4] Private email: p...@vanoostrum.org -- http://mail.python.org/mailman/listinfo/python-list
