avoid gnb stalling on retransmissions

openair2/LAYER2/NR_MAC_gNB/gNB_scheduler_RA.c

@@ -1401,14 +1401,10 @@ void nr_generate_Msg4(module_id_t module_idP, int CC_id, frame_t frameP, sub_fra
 
     uint16_t mac_sdu_length = 0;
 
-    rnti_t tc_rnti = ra->rnti;
     // If UE is known by the network, C-RNTI to be used instead of TC-RNTI
+    rnti_t tc_rnti = ra->rnti;
     if (ra->msg3_dcch_dtch) {
       ra->rnti = ra->crnti;
-    } else {
-      mac_sdu_length = mac_rrc_nr_data_req(module_idP, CC_id, frameP, CCCH, ra->rnti, 1, NULL);
-      if (mac_sdu_length <= 0)
-        return; // need to wait until RRCSetup is encoded
     }
 
     NR_UE_info_t * UE = find_nr_UE(&nr_mac->UE_info, ra->rnti);
@@ -1417,6 +1413,16 @@ void nr_generate_Msg4(module_id_t module_idP, int CC_id, frame_t frameP, sub_fra
       return;
     }
 
+    NR_UE_sched_ctrl_t *sched_ctrl = &UE->UE_sched_ctrl;
+    /* get the PID of a HARQ process awaiting retrnasmission, or -1 otherwise */
+    int current_harq_pid = sched_ctrl->retrans_dl_harq.head;
+
+    if (ra->msg3_dcch_dtch == false && current_harq_pid < 0) {
+      mac_sdu_length = mac_rrc_nr_data_req(module_idP, CC_id, frameP, CCCH, ra->rnti, 1, NULL);
+      if (mac_sdu_length <= 0)
+        return; // need to wait until RRCSetup is encoded
+    }
+
     long BWPStart = 0;
     long BWPSize = 0;
     NR_Type0_PDCCH_CSS_config_t *type0_PDCCH_CSS_config = NULL;
@@ -1509,9 +1515,6 @@ void nr_generate_Msg4(module_id_t module_idP, int CC_id, frame_t frameP, sub_fra
 
     LOG_I(NR_MAC,"Generate msg4, rnti: %04x\n", ra->rnti);
 
-    NR_UE_sched_ctrl_t *sched_ctrl = &UE->UE_sched_ctrl;
-    /* get the PID of a HARQ process awaiting retrnasmission, or -1 otherwise */
-    int current_harq_pid = sched_ctrl->retrans_dl_harq.head;
     // HARQ management
     if (current_harq_pid < 0) {
       AssertFatal(sched_ctrl->available_dl_harq.head >= 0,