With the current implementation of oaisim
(rxdata and channel simulation), we cannot
call trx_read_func on a dummy buffer. The
code will actually modify the rxdata buffers
of the UE.
This is has to be rewritten properly. In the
meantime, let's introduce a simple hack. The
idea of the read at this point is to wait for
the synch to finish and not lose samples from
the hardware in the real UE. In the simulator,
as it is today, we can simply sleep until the
synch code has finished its work.
- rename UE_NO_LOG to DISABLE_LOG_X
because the name is misleading. The full software
is impacted, not only the UE part
- same for compilation option ---ue-no-log
that becomes --disable-log
- keep LOG_X for the standard case, that is the
case without DISABLE_LOG_X where printf has been
put. Two reasons:
* printf is not realtime friendly
* keep behavior similar for other users who may
be troubled by different logs that don't add
any benefit to previous logs
Using "system" to call "git log" is too error-prone.
In the test setup, lte-softmodem was blocked because
"git log" uses a pager ("less") and the pager was
waiting for the user to press enter.
We could pass "--no-pager" to "git log" but then
what if someone runs the softmodem out of the source
tree?
cmake defines PACKAGE_VERSION, we can use that instead,
as is done in openair-cn.
see https://gitlab.eurecom.fr/oai/openairinterface5g/issues/227
When the UE connects to the eNodeB and receives its IP address from the
network, it calls system() to set it in the linux kernel world. This call
is not done in a realtime thread, but in the NAS, which uses its own thread,
independent of the realtime processing.
In some situations this totally disrupts realtime processing.
It is difficult to know precisely why that happens, but it seems that calling
fork(), as system() does, in a multi-threaded program is not a good idea. (So
say several people on the internet.) It is not clear why the softmodem is
impacted, but it seems that fork() is really what triggers the disruption.
Several tests lead to that conclusion.
To fix the problem, we create a child background process very early in main()
(before anything else basically). Then instead of calling system(), the main
process sends the string to the background process. The background process
gets the string, passes it to system() and reports the success/failure back
to the main process.
This solution involves a lot of system calls, but calling system() in the
first place is not cheap either. As long as no realtime thread uses this
mechanism, things should be fine. Time will tell.
Florian Kaltenberger