The GTP module is common for 4G and 5G. It hardcodes the functions to
call when creating S1U and NGU tunnels. The S1U case is both applicable
for LTE and NR (NSA), which until now was not a problem as the PDCP data
forwarding functions where called pdcp_data_req. The issue is that in this
branch, the NR PDCP functions have changed to nr_pdcp_data_req_drb().
When setting up a GTP tunnel, we now pass the PDCP data forwarding
functions into GTP, since the caller knows whether it is in 4G or 5G,
but GTP itself does not.
nr_pdcp_entity_recv_sdu() processes PDCP SDUs, and forwards the PDU at the
end of the function, while having the PDCP lock. This can lead to
deadlocks, e.g., when another thread goes through RLC and tries to
access the PDCP while the PDCP tries to lock the RLC.
This commit changes the logic: instead of having recv_sdu() forward the
PDU directly, it fills a buffer with the PDU (thus the name change to
process_sdu()), and returns. We then unlock the PDCP, before forwarding
the PDU, thus eliminating potential deadlocks.
Creates function that have nr_pdcp_ prepended to their name, and change
the signature of some functions for the 5G PDCP:
- nr_pdcp_layer_init()
- nr_pdcp_data_req()
- nr_pdcp_remove_UE()
- nr_pdcp_config_set_security()
- nr_pdcp_remove_UE()
- Make separate functions for nr_pdcp_data_req_srb/drb()
The message is never sent to the RRC. And this message is to be
forwarded by the DU to the UE, hence it should not even be handled by
the RRC (as the RRC in the CU sends it).
During the Initial UL RRC Message, the CellGroup is created. Since the
CellGroup specifies the SRB1, the SRB1 should also be created (because
the DL RRC Messages is sent via SRB1). However, before this commit, the
CellGroup is created while having the RLC lock, so we cannot create
SRB1, as it results in a deadlock.
Therefore, we now first create CellGroup, SRB0, and SRB1, before giving
the UE message to the RLC.
Robert Schmidt