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

3 files changed, 16 insertions, 2 deletions

diff --git a/include/osmo-bts/tx_power.h b/include/osmo-bts/tx_power.h
index 8f68d8a5..a7f846e8 100644
--- a/include/osmo-bts/tx_power.h
+++ b/include/osmo-bts/tx_power.h
@@ -78,6 +78,7 @@ int get_p_trxout_actual_mdBm(const struct gsm_bts_trx *trx, uint8_t bs_power_red
 int get_p_trxout_actual_mdBm_lchan(const struct gsm_lchan *lchan);
 
 int power_ramp_start(struct gsm_bts_trx *trx, int p_total_tgt_mdBm, int bypass, ramp_compl_cb_t ramp_compl_cb);
+void power_ramp_abort(struct gsm_bts_trx *trx);
 
 void power_trx_change_compl(struct gsm_bts_trx *trx, int p_trxout_cur_mdBm);
 
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;
 	}
 }
diff --git a/src/common/tx_power.c b/src/common/tx_power.c
index 348aba5c..03074221 100644
--- a/src/common/tx_power.c
+++ b/src/common/tx_power.c
@@ -259,7 +259,7 @@ int power_ramp_start(struct gsm_bts_trx *trx, int p_total_tgt_mdBm, int bypass,
 	}
 
 	/* Cancel any pending request */
-	osmo_timer_del(&tpp->ramp.step_timer);
+	power_ramp_abort(trx);
 
 	/* set the new target */
 	tpp->p_total_tgt_mdBm = p_total_tgt_mdBm;
@@ -297,6 +297,12 @@ int power_ramp_start(struct gsm_bts_trx *trx, int p_total_tgt_mdBm, int bypass,
 	return 0;
 }
 
+/* Cancel any pending request */
+void power_ramp_abort(struct gsm_bts_trx *trx)
+{
+	osmo_timer_del(&trx->power_params.ramp.step_timer);
+}
+
 /* determine the initial transceiver output power at start-up time */
 int power_ramp_initial_power_mdBm(const struct gsm_bts_trx *trx)
 {