[signal] Differentiate paging success from expiration in SS_PAGING

This is useful information to know and actually fixes a segfault
in rllp.c where lchan is accessed even tough it could be NULL in
case of failure.

Signed-off-by: Sylvain Munaut <tnt@246tNt.com>
diff --git a/openbsc/include/openbsc/signal.h b/openbsc/include/openbsc/signal.h
index 23551f7..07b4e39 100644
--- a/openbsc/include/openbsc/signal.h
+++ b/openbsc/include/openbsc/signal.h
@@ -45,7 +45,8 @@
 
 /* SS_PAGING signals */
 enum signal_paging {
-	S_PAGING_COMPLETED,
+	S_PAGING_SUCCEEDED,
+	S_PAGING_EXPIRED,
 };
 
 /* SS_SMS signals */
diff --git a/openbsc/src/gsm_04_08_utils.c b/openbsc/src/gsm_04_08_utils.c
index a184277..d5785f9 100644
--- a/openbsc/src/gsm_04_08_utils.c
+++ b/openbsc/src/gsm_04_08_utils.c
@@ -490,7 +490,7 @@
 
 	bts->network->stats.paging.completed++;
 
-	dispatch_signal(SS_PAGING, S_PAGING_COMPLETED, &sig_data);
+	dispatch_signal(SS_PAGING, S_PAGING_SUCCEEDED, &sig_data);
 
 	/* Stop paging on the bts we received the paging response */
 	paging_request_stop(msg->trx->bts, subscr, msg->lchan);
diff --git a/openbsc/src/paging.c b/openbsc/src/paging.c
index b5dc2d0..91de702 100644
--- a/openbsc/src/paging.c
+++ b/openbsc/src/paging.c
@@ -214,7 +214,7 @@
 
 	counter_inc(req->bts->network->stats.paging.expired);
 
-	dispatch_signal(SS_PAGING, S_PAGING_COMPLETED, &sig_data);
+	dispatch_signal(SS_PAGING, S_PAGING_EXPIRED, &sig_data);
 	if (cbfn)
 		cbfn(GSM_HOOK_RR_PAGING, GSM_PAGING_EXPIRED, NULL, NULL,
 			  cbfn_param);
diff --git a/openbsc/src/rrlp.c b/openbsc/src/rrlp.c
index d4665d5..3504451 100644
--- a/openbsc/src/rrlp.c
+++ b/openbsc/src/rrlp.c
@@ -89,14 +89,12 @@
 	struct paging_signal_data *psig_data = signal_data;
 
 	switch (signal) {
-	case S_PAGING_COMPLETED:
-		/* paging might have "completed' unsucessfully,
-		 * in this case we don't have a lchan */
-		if (!psig_data->lchan)
-			break;
+	case S_PAGING_SUCCEEDED:
 		/* A subscriber has attached. */
 		send_rrlp_req(psig_data->lchan);
 		break;
+	case S_PAGING_EXPIRED:
+		break;
 	}
 	return 0;
 }