dbus glib + pthreads

[John Palmieri]

You always need to use private connections in different threads otherwise one thread can starve the buffer or make calls to code across the thread boundary.
  
----- "Kees Jongenburger" <kees.jongenburger at gmail.com> wrote:

> Hello I am having difficulties using dbus in combination with a
> threaded program.
> 
> Basically I have two threads one where I want to listen to incoming
> dbus calls and one thread that will call other dbus services. This
> second thread
> will for example also perform a long running download or call other
> dbus services (also using glib). My main thread uses the glib main
> loop while my second thread
> simply performs his tasks end then dies.
> 
> I am experiencing random crashes when in the seconds thread I start
> performing dbus glib method calls.I am  dbus_threads_init_default but
> clearly this is not enough
> What else am I missing?
> 
> -Do I have to use the same dbus connection for booth threads or not?
> -Do I have to use a private dbus connection?
> -Should I run two mainloops?
> 
> I am currently quite clueless. Here is such a backtrace for example
> 0x00007f91c0a85b6f in g_main_context_query () from
> /usr/lib/libglib-2.0.so.0
> (gdb) bt
> #0  0x00007f91c0a85b6f in g_main_context_query () from
> /usr/lib/libglib-2.0.so.0
> #1  0x00007f91c0a8a627 in ?? () from /usr/lib/libglib-2.0.so.0
> #2  0x00007f91c0a8adad in g_main_loop_run () from
> /usr/lib/libglib-2.0.so.0
> #3  0x0000000000402a13 in run_main_loop () at
> echo_calling_service_threaded.c:202
> #4  0x0000000000402aee in main (argc=2, argv=0x7fffc95d6738) at
> echo_calling_service_threaded.c:234
> 
> 
> I created sample code and "demo" that shows the problem I am
> experiencing you can get it from
> http://github.com/keesj/dbus_glib_pthread
> 
> We have a EchoService that can echo strings. We also have a
> EchoCallingService that can be called to call the
> EchoService a certain number of time. The EchoCallingService on one
> side accepts incomming requests to call the
> EchoService a given number of times.
> At the same time it will be calling the EchoService itself. We want
> to
> use thread to model this and want one thread that
> listens for incoming dbus messages(this is the main thread)
> and one thread that performs the calls to the EchoService.
> 
> 
> 
> The flow of the calls should look something like this.
> test/test_echo_calling_service test 1200
>   |
>   |
>   |--callEcho(test,1200)->echo_calling_service_threaded(incomming
> end)
>                            |
>                            |
>                            |- start or
> notify--->echo_calling_service_threaded(sending end)
>   |<-----------------------|                     |
>                                                  |
>                                                  |--1200 times
> echo(test)-->echo_service
>                                                                       
>       |
>                                                 
> |<--------------------------|
> 
> 
> How to test the current code:
> 0) compile the code run make
> 1) modify and copy the configuration file in data/
> (echo_calling_service.conf and echo_service.conf) to
> /etc/dbus/system.d the user name needs changing.
> 2) run export LD_LIBRARY_PATH=alib
> 3) start the echo_service ./echo_service -v &
> 4) run ./echo_client and see it is possible to call the echo service
> 10000 times witout problem
> 5) start the echo calling service ./echo_calling_service_threaded -v
> &
> (possibly running this under gdb)
> 6) start the test -> execute ./test/test_echo_calling_service test
> 1200 a number of times
> 
> Expected outcome the service works like charm and doesn't eat memory
> or crash
> 
> Actual outcome:
> the echo_calling_service_threaded crashed in unpredictable ways
> _______________________________________________
> dbus mailing list
> dbus at lists.freedesktop.org
> http://lists.freedesktop.org/mailman/listinfo/dbus

-- 
--
John (J5) Palmieri
Software Engineer
Red Hat, Inc.