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.
Bug reported by Bruno Mongazon from Nokia.
"Without this line, the config file parameter is not properly stored and
the FH will always work with compression."
Prior to this commit, the following command failed to build dlsim:
./build_oai --phy_simulators -c
Choice has been made to define it in a .h file as a static inline
function.
The compilation line was:
./build_oai --eNB -w USRP
The file openairinterface5g/cmake_targets/log/lte-softmodem.Rel10.txt
has been checked and all LOG_X (and 'msg') warnings have been fixed.
- some cleanup
- thread names to include UE Mod_id
- arg of UE_thread_rxn_txnp4 to be struct rx_tx_thread_data again
- sync in UE_thread_rxn_txnp4 to use instance_cnt_rxtx again
- UE_thread to call itti_send_msg_to_task with UE->Mod_id + NB_eNB_INST
instead of INSTANCE_DEFAULT again
This may break the softmodem UE, to be tested.
The most problematic thing may be the synchronization.
I don't think it will impact the processing at all,
but I won't bet my shirt on it.
For whatever reason, lte-softmodem.c was totally messed up...
We took the version from the branch develop and added
abstraction_flag, which is needed in openair2/LAYER2/MAC/main.c
(this is not clean, previous commit added a comment for this).
This has to be cleaned at some point.
Cedric Roux