Synchronous method in asynchronous signal callback

[Marco Bascetta]

Hello,

I'm using libdbus with a poll mainloop. I monitor the DBusWatch file 
descriptor to call "dbus_watch_handle" and "dbus_connection_dispatch".
Also, I add a connection filter to handle asynchronous signals (only 
DBUS_MESSAGE_TYPE_SIGNAL messages).

When an event occurs, a callback is called and a specified method is 
performed throught "dbus_connection_send_with_reply_and_block" and a 
flag is set in order to indicates that the dispatch function must run 
another time.

This is an example of the code
[pseudocode]
init_func()
{
     dbus_threads_init_default()
     conn = dbus_bus_get(...)
     dbus_connection_set_watch_functions(conn, ...)               # This 
store watch_fd in poll
     dbus_connection_add_filter(conn, filter_func, ...)
}

invoke_method()
{
     dbus_connection_send_with_reply_and_block(conn, ...)
     use_reply()
     flag_set(force_dispatch)
}

filter_func()
{
     if( dbus_message_get_type(...) == DBUS_MESSAGE_TYPE_SIGNAL ) {
         if( is(signal_A) ) {
             invoke_method()
         } else {
             do_other_things()
         }
     }
}

# This is called when watch_fd
dispach_func()
{
         do {
             flag_unset(force_dispatch)

             dbus_watch_handle(dbus_watch, 
dbus_watch_get_flags(dbus_watch));

             while (dbus_connection_get_dispatch_status(conn) == 
DBUS_DISPATCH_DATA_REMAINS) {
                 dbus_connection_dispatch(conn);
             }

         } while( flag_is_set(force_dispatch) );
}
[pseudocode]

It works without deadlock or message missing, but the signals received 
during the "invoke_method" are delayed until another signal is received 
(watch fd unlocks the poll) (and this could occurs much later...)

Could you suggest me how to resolve this issue without using the 
asynchronous calls only?

Thanks

Best regards

-- 
Marco Bascetta - Sadel SpA
Software Development
Via Serenari 1, Castel Maggiore (BO)