paging: start/stop credit_timer based on C0 running

This way we avoid triggering timers and doing extra poll loops for each
BTS which is configured but not up. It also has the effect of removing
logging about estimating paging buffers for BTS which are down, which
can be confusing.
Furthermore, since work is delayed until the TRX and cell in general is
configured, the first estimation is properly done now since the correct
configuration is in place at that time.

Related: SYS#5922
Change-Id: I1b5b1a98115b4e9d821eb3330fc5b970a0e78a44

2 files changed, 67 insertions, 11 deletions

diff --git a/src/osmo-bsc/osmo_bsc_main.c b/src/osmo-bsc/osmo_bsc_main.c
index c6f8b13f9..c78bb45ef 100644
--- a/src/osmo-bsc/osmo_bsc_main.c
+++ b/src/osmo-bsc/osmo_bsc_main.c
@@ -934,6 +934,7 @@ int main(int argc, char **argv)
 	handover_fsm_init();
 	lb_init();
 	acc_ramp_global_init();
+	paging_global_init();
 
 	/* Read the config */
 	rc = bsc_network_configure(config_file);
diff --git a/src/osmo-bsc/paging.c b/src/osmo-bsc/paging.c
index 11071ecad..a0e306764 100644
--- a/src/osmo-bsc/paging.c
+++ b/src/osmo-bsc/paging.c
@@ -223,10 +223,6 @@ static void paging_handle_pending_requests(struct gsm_bts_paging_state *paging_b
 		return;
 	}
 
-	/* Skip paging if the bts is down. */
-	if (!bts->c0->rsl_link_primary)
-		goto sched_next_iter;
-
 	osmo_clock_gettime(CLOCK_MONOTONIC, &now);
 	paging_bts->last_sched_ts = now;
 
@@ -307,12 +303,10 @@ void paging_init(struct gsm_bts *bts)
 {
 	bts->paging.bts = bts;
 	bts->paging.free_chans_need = -1;
-	unsigned int load_ind_timeout = bts_no_ccch_load_ind_timeout_sec(bts);
-	bts->paging.available_slots = paging_estimate_available_slots(bts, load_ind_timeout);
+	bts->paging.available_slots = 0;
 	INIT_LLIST_HEAD(&bts->paging.pending_requests);
 	osmo_timer_setup(&bts->paging.work_timer, paging_worker, &bts->paging);
 	osmo_timer_setup(&bts->paging.credit_timer, paging_give_credit, &bts->paging);
-	osmo_timer_schedule(&bts->paging.credit_timer, load_ind_timeout, 0);
 }
 
 /* Called upon the bts struct being freed */
@@ -625,10 +619,12 @@ void paging_update_buffer_space(struct gsm_bts *bts, uint16_t free_slots)
 	LOG_BTS(bts, DPAG, LOGL_DEBUG, "Rx CCCH Load Indication from BTS (available_slots %u -> %u)\n",
 		bts->paging.available_slots, free_slots);
 	bts->paging.available_slots = free_slots;
-	paging_schedule_if_needed(&bts->paging);
-	/* Re-arm credit_timer */
-	osmo_timer_schedule(&bts->paging.credit_timer,
-			    bts_no_ccch_load_ind_timeout_sec(bts), 0);
+	/* Re-arm credit_timer if needed */
+	if (trx_is_usable(bts->c0)) {
+		paging_schedule_if_needed(&bts->paging);
+		osmo_timer_schedule(&bts->paging.credit_timer,
+				    bts_no_ccch_load_ind_timeout_sec(bts), 0);
+	}
 }
 
 /*! Count the number of pending paging requests on given BTS */
@@ -706,3 +702,62 @@ static unsigned int paging_estimate_delay_us(struct gsm_bts *bts, unsigned int n
 	}
 	return time_us;
 }
+
+/* Callback function to be called every time we receive a signal from NM */
+static int nm_sig_cb(unsigned int subsys, unsigned int signal,
+		     void *handler_data, void *signal_data)
+{
+	struct nm_running_chg_signal_data *nsd;
+	struct gsm_bts *bts;
+	struct gsm_bts_trx *trx;
+	unsigned int load_ind_timeout;
+
+	if (signal != S_NM_RUNNING_CHG)
+		return 0;
+
+	nsd = signal_data;
+	bts = nsd->bts;
+
+	switch (nsd->obj_class) {
+	case NM_OC_RADIO_CARRIER:
+		trx = (struct gsm_bts_trx *)nsd->obj;
+		break;
+	case NM_OC_BASEB_TRANSC:
+		trx = gsm_bts_bb_trx_get_trx((struct gsm_bts_bb_trx *)nsd->obj);
+		break;
+	default:
+		return 0;
+	}
+
+	/* We only care about state changes of C0. */
+	if (trx != trx->bts->c0)
+		return 0;
+
+	if (nsd->running) {
+		if (trx_is_usable(trx)) {
+			LOG_BTS(bts, DPAG, LOGL_INFO, "C0 becomes available for paging\n");
+			/* Fill in initial credit */
+			load_ind_timeout = bts_no_ccch_load_ind_timeout_sec(bts);
+			bts->paging.available_slots = paging_estimate_available_slots(bts, load_ind_timeout);
+			/* Start scheduling credit_timer */
+			osmo_timer_schedule(&bts->paging.credit_timer,
+					    bts_no_ccch_load_ind_timeout_sec(bts), 0);
+			/* work_timer will be started when new paging requests arrive. */
+		}
+	} else {
+		/* If credit timer was not pending it means C0 was already unavailable before (rcarrier||bbtransc) */
+		if (osmo_timer_pending(&bts->paging.credit_timer)) {
+			LOG_BTS(bts, DPAG, LOGL_INFO, "C0 becomes unavailable for paging\n");
+			/* Note: flushing will osmo_timer_del(&bts->paging.work_timer) when queue becomes empty */
+			paging_flush_bts(bts, NULL);
+			osmo_timer_del(&bts->paging.credit_timer);
+		}
+	}
+	return 0;
+}
+
+/* To be called once at startup of the process: */
+void paging_global_init(void)
+{
+	osmo_signal_register_handler(SS_NM, nm_sig_cb, NULL);
+}