Hello folks, we’re facing the following issue: An application does not receive DBUS signals via the DBUS file descriptor while waiting for a dbus-method response. The basic setup: Two applications are communicating via DBUS, using a select() loop waiting for events on the dbus-fd. The faulty procedure:
- Triggered by a timer event, Application A calls the dbus-method “transmit” of application B. - During processing of the “transmit”-method, application B broadcasts a dbus-signal on which application A is matched on. - Afterwards, application B sleeps for 5ms and then finishes its “transmit”-method by sending a response message towards application A. - The dbus-fd of Application A does not trigger the select() afterwards (same for epoll() if implemented so). Though … o … when triggering sd_bus_process() manually, the signal is being receved in application A, meaning that the signal was in fact received and queued, but the event was not signalled. o … other processes, not being “blocked” by waiting for a response-message, do also receive the signal. We saw this behavior on multiple platforms, e.g. Linux kubuntu 4.4.0-137-generic with 229-4ubuntu21.1 and Debian Buster 4.18.0-2-am64 with systemd 239-10. Attached you can find a simple example, including application A / B, a makefile and the correlating *.conf-files. Thanks in advance and best regards, Jan Mueller
<<attachment: mbsp_files.zip>>
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