2012/3/15 Patrick Ohly <[email protected]>:
> On Thu, 2012-03-15 at 16:03 +0100, Patrick Ohly wrote:
>> On Thu, 2012-03-15 at 15:43 +0100, Krzesimir Nowak wrote:
>> > W dniu 15 marca 2012 10:58 użytkownik Krzesimir Nowak
>> > <[email protected]> napisał:
>> > > 2012/3/15 Patrick Ohly <[email protected]>:
>> > >> On Thu, 2012-03-15 at 10:21 +0100, Krzesimir Nowak wrote:
>> > >>> W dniu 14 marca 2012 15:30 użytkownik Patrick Ohly
>> > >>> <[email protected]> napisał:
>> > >>> > Hello Krzesimir!
>> > >>> >
>> > >>> > You added the add/remove_filter() methods to DBusConnectionPtr, with 
>> > >>> > the
>> > >>> > comment "those additions will be needed for ForkExec ready message
>> > >>> > handling" in the commit message.
>> > >>> >
>> > >>> > The methods themselves are not documented. Can you explain a bit how
>> > >>> > this is meant to work?
>> > >>>
>> > >>> The history is that I needed to add a new signal to ForkExec, because
>> > >>> activation of DBus interface on child side was racing with using this
>> > >>> interface on parent side.
>> > >>
>> > >> Wouldn't it be easier to delay message processing on the child side
>> > >> until the child is set up, then enable the message processing?
>> > >>
>> > >> http://developer.gnome.org/gio/unstable/GDBusConnection.html#GDBusConnectionFlags
>> > >> mentions G_DBUS_CONNECTION_FLAGS_DELAY_MESSAGE_PROCESSING and
>> > >> g_dbus_connection_start_message_processing() for this purpose.
>> > >>
>> > >> Then the parent can start making method calls right away. They simply
>> > >> will not be processed before the child is really ready to handle them.
>> > >
>> > > I have not noticed that before - I will check it.
>> >
>> > Nope, still racy. I tested that by running a loop with 100 iterations
>> > of TestDBusServerPresence and breaking it after first failure. It got
>> > me as far as 34 iterations. Usually first 15-20 iteration succeeded.
>> > Failures on 1 iteration weren't all that rare. I have created two
>> > quick-and-dirty branches with my two attempts to solve the problem
>> > with g_dbus_connection_start_message_processing():
>> > 1. with running said function directly:
>> > https://meego.gitorious.org/~krnowak/meego-middleware/krnowaks-syncevolution/commits/css-with-direct-msg-proc
>> > 2. with running said function in idle callback:
>> > https://meego.gitorious.org/~krnowak/meego-middleware/krnowaks-syncevolution/commits/css-with-idle-msg-proc
>>
>> Is the logic of the if() check accidentally reverted here?
>>
>> void ForkExecChild::connect(bool delayed /* = false */)
>>
>> +    if (delayed) {
>> +        m_conn = 
>> GDBusCXX::DBusConnectionPtr(dbus_get_bus_connection(address,
>> +                                                                     
>> &dbusError));
>> +    } else {
>> +        m_conn = 
>> GDBusCXX::DBusConnectionPtr(dbus_get_bus_connection_delayed(address,
>> +                                                                            
>>  &dbusError));
>> +    }
>
> Inverting that logic so that message processing really gets delayed as
> intended leads makes your test succeed. It passed all 100 rounds without
> problems, whereas it failed quickly with the unchanged if().
>
> So it seems to me that this is the right way to go. Regarding the code,
> can we introduce flags for dbus_get_bus_connection() instead of creating
> multiple copies of it? That'll scale better in case that we find a need
> for other variations.

That is almost exactly what I did - but instead of adding flags I just
added a bool parameter. Right now I am creating some commits. I will
let you know when I push this.

> --
> Best Regards, Patrick Ohly
>
> The content of this message is my personal opinion only and although
> I am an employee of Intel, the statements I make here in no way
> represent Intel's position on the issue, nor am I authorized to speak
> on behalf of Intel on this matter.
>
>
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