dbus glib + pthreads

[Kees Jongenburger]

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