lchan_fsm: add in_release_handler flag

If a release event is being handled, ignore other ricocheting release events
until that release handling has concluded.

For example, if an lchan is regularly released, it signals the lchan RTP FSM to
release, which then calls back to say "RTP is released" on termination -- this
should not trigger other state changes than the initial release intends.

Change-Id: Iec41e006b6ab9d0f618d36925341f9536353e5d8

2 files changed, 21 insertions, 7 deletions

diff --git a/include/osmocom/bsc/gsm_data.h b/include/osmocom/bsc/gsm_data.h
index 12bc5c354..448924c06 100644
--- a/include/osmocom/bsc/gsm_data.h
+++ b/include/osmocom/bsc/gsm_data.h
@@ -525,6 +525,10 @@ struct gsm_lchan {
 	/* RSL error code, RSL_ERR_* */
 	uint8_t rsl_error_cause;
 
+	/* If a release event is being handled, ignore other ricocheting release events until that
+	 * release handling has concluded. */
+	bool in_release_handler;
+
 	/* The logical channel type */
 	enum gsm_chan_t type;
 	/* RSL channel mode */
diff --git a/src/osmo-bsc/lchan_fsm.c b/src/osmo-bsc/lchan_fsm.c
index 1ecec7c3a..940afe8de 100644
--- a/src/osmo-bsc/lchan_fsm.c
+++ b/src/osmo-bsc/lchan_fsm.c
@@ -521,7 +521,7 @@ static void lchan_fsm_wait_ts_ready(struct osmo_fsm_inst *fi, uint32_t event, vo
 
 	case LCHAN_EV_RTP_RELEASED:
 	case LCHAN_EV_RTP_ERROR:
-		if (lchan->release_requested) {
+		if (lchan->in_release_handler) {
 			/* Already in release, the RTP is not the initial cause of failure.
 			 * Just ignore. */
 			return;
@@ -581,6 +581,7 @@ static void lchan_fsm_wait_activ_ack(struct osmo_fsm_inst *fi, uint32_t event, v
 		break;
 
 	case LCHAN_EV_RSL_CHAN_ACTIV_NACK:
+		lchan->in_release_handler = true;
 		if (data) {
 			uint32_t next_state;
 			lchan->rsl_error_cause = *(uint8_t*)data;
@@ -599,11 +600,12 @@ static void lchan_fsm_wait_activ_ack(struct osmo_fsm_inst *fi, uint32_t event, v
 			lchan->release_in_error = true;
 			lchan_fail_to(LCHAN_ST_BORKEN, "Chan Activ NACK without cause IE");
 		}
+		lchan->in_release_handler = false;
 		break;
 
 	case LCHAN_EV_RTP_RELEASED:
 	case LCHAN_EV_RTP_ERROR:
-		if (lchan->release_requested) {
+		if (lchan->in_release_handler) {
 			/* Already in release, the RTP is not the initial cause of failure.
 			 * Just ignore. */
 			return;
@@ -715,7 +717,7 @@ static void lchan_fsm_wait_rll_rtp_establish(struct osmo_fsm_inst *fi, uint32_t
 
 	case LCHAN_EV_RTP_RELEASED:
 	case LCHAN_EV_RTP_ERROR:
-		if (lchan->release_requested) {
+		if (lchan->in_release_handler) {
 			/* Already in release, the RTP is not the initial cause of failure.
 			 * Just ignore. */
 			return;
@@ -826,7 +828,7 @@ static void lchan_fsm_established(struct osmo_fsm_inst *fi, uint32_t event, void
 
 	case LCHAN_EV_RTP_RELEASED:
 	case LCHAN_EV_RTP_ERROR:
-		if (lchan->release_requested) {
+		if (lchan->in_release_handler) {
 			/* Already in release, the RTP is not the initial cause of failure.
 			 * Just ignore. */
 			return;
@@ -1201,6 +1203,11 @@ void lchan_release(struct gsm_lchan *lchan, bool sacch_deact,
 {
 	if (!lchan || !lchan->fi)
 		return;
+
+	if (lchan->in_release_handler)
+		return;
+	lchan->in_release_handler = true;
+
 	struct osmo_fsm_inst *fi = lchan->fi;
 	lchan->release_in_error = err;
 	lchan->rsl_error_cause = cause_rr;
@@ -1223,13 +1230,13 @@ void lchan_release(struct gsm_lchan *lchan, bool sacch_deact,
 			if (lchan->deact_sacch)
 				rsl_deact_sacch(lchan);
 			lchan_fsm_state_chg(LCHAN_ST_WAIT_RF_RELEASE_ACK);
-			return;
+			goto exit_release_handler;
 		case LCHAN_ST_WAIT_TS_READY:
 			lchan_fsm_state_chg(LCHAN_ST_WAIT_RLL_RTP_RELEASED);
-			return;
+			goto exit_release_handler;
 		case LCHAN_ST_WAIT_RF_RELEASE_ACK:
 		case LCHAN_ST_BORKEN:
-			return;
+			goto exit_release_handler;
 		}
 	}
 
@@ -1237,6 +1244,9 @@ void lchan_release(struct gsm_lchan *lchan, bool sacch_deact,
 	 * is: */
 	if (fi->state == LCHAN_ST_ESTABLISHED)
 		lchan_fsm_state_chg(LCHAN_ST_WAIT_RLL_RTP_RELEASED);
+
+exit_release_handler:
+	lchan->in_release_handler = false;
 }
 
 void lchan_fsm_cleanup(struct osmo_fsm_inst *fi, enum osmo_fsm_term_cause cause)