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
<>
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