tree 4740d41791861dcfdca574f142c8d3a737f350e8
parent e2b20c4aa855fd295b72e090bd1df6cc12bd5993
author Philipp Maier <pmaier@sysmocom.de> 1598042423 +0200
committer Philipp Maier <pmaier@sysmocom.de> 1599475481 +0200

abis_rsl: prioritize emergency calls over regular calls

when an emergency call arrives while all TCH are busy, the BSC should
pick an arbitrary (preferably the longest lasting) call / lchan and
release it in favor of the incoming emergancy call.

The release of the existing call is a process that can not be done
synchronously while the ChanRQD is handled sonce multiple messages are
exchanged between BTS and MSC and multiple FSMs need to do their work.

To be able to release one lchan while handling a ChanRQD a queue is
implemented in which the incomming channel requests are collected. If
an emergency call is established while all channels are busy, an
arbitrary lchan is picked and freed. When freeing the lchan is done,
the queue is checked again and the emergency call is put on the free
lchan (TCH/H or TCH/F).

Change-Id: If8651265928797dbda9f528b544931dcfa4a0b36
Related: OS#4549