bts_shutdown_fsm: Make sure pending power ramping are aborted before closing TRX

It can happen when using several TRX that all of them go alreadyunder
shutdown target tx power level, but that due to configuration the BTS
still may want to keep pushing the tx power level even lower. Hence, we
end up in a situation where the FSM is trying to close all the TRX while the
power ramp procedure is ongoing for some of them. As a result, race
conditions can happen where for instance the power ramping procedure for
one TRX ends and calls the cb to send SETPOWER after the TRX PHY has
been closed (and hence TRXC link is unavaialble).
If that happens, the trx_if lower layers store the SETPOWER and attempt
a later retransmit, which may take up to 2 seconds after TRX becomes
active if BTS reconnects immediatelly.
Hence, we end up in some test cases where BTS reconnects and configures
some TRX while others are kep unconfigured for a while due to the
mentioned delay, hence the test attempting to use the TS while it hasn't
been yet configured.

The solution is to avoid this kind of unexpected events with ongoing
powe ramp once we have decided tx power is lower enough to shutdown the
TRX completely. Hence we abort the pending power ramp procedure.

Change-Id: Ibca581131eb142d7c38c917a0d6990efec03123c

1 files changed, 8 insertions, 1 deletions

diff --git a/src/common/bts_shutdown_fsm.c b/src/common/bts_shutdown_fsm.c
index a663f5bf..0c6d80c1 100644
--- a/src/common/bts_shutdown_fsm.c
+++ b/src/common/bts_shutdown_fsm.c
@@ -112,8 +112,15 @@ static void st_wait_ramp_down_compl(struct osmo_fsm_inst *fi, uint32_t event, vo
 
 		LOGPFSML(fi, LOGL_INFO, "%s Ramping down complete, %u TRX remaining\n",
 			 gsm_trx_name(src_trx), remaining);
-		if (remaining == 0)
+		if (remaining == 0) {
+			/* Make sure we end up any remaining ongoing power ramp
+			 * down under target shutdown tx power level, then
+			 * finally transit to next state:
+			 */
+			llist_for_each_entry(trx, &bts->trx_list, list)
+				power_ramp_abort(trx);
 			bts_shutdown_fsm_state_chg(fi, BTS_SHUTDOWN_ST_WAIT_TRX_CLOSED);
+		}
 		break;
 	}
 }