Decouple UEContextReleaseComplete message generation from MAC UE release

The next commit implements the release of all UEs following the F1 Reset
message. It uses nr_mac_release_ue(), which as of now, triggered a
release complete message automatically, which we don't want in the case
of F1 Reset.

This commit refactors the code to split UE release at MAC/RLC and
release complete message sending to allow to release UEs without sending
the complete. Corresponding users are updated.

openair2/LAYER2/NR_MAC_gNB/gNB_scheduler_RA.c

@@ -2190,6 +2190,7 @@ void nr_schedule_RA(module_id_t module_idP,
         if (ra->contention_resolution_timer < 0) {
           LOG_W(NR_MAC, "(%d.%d) RA Contention Resolution timer expired for UE 0x%04x, RA procedure failed...\n", frameP, slotP, ra->rnti);
           nr_mac_release_ue(mac, ra->rnti);
+          nr_mac_trigger_release_complete(mac, ra->rnti);
           nr_clear_ra_proc(ra);
           continue;
         }

openair2/LAYER2/NR_MAC_gNB/gNB_scheduler_primitives.c

@@ -3013,32 +3013,36 @@ int nr_mac_enable_ue_rrc_processing_timer(gNB_MAC_INST *mac, NR_UE_info_t *UE, b
   return 0;
 }
 
-void nr_mac_release_ue(gNB_MAC_INST *mac, int rnti)
+void nr_mac_trigger_release_complete(gNB_MAC_INST *mac, int rnti)
 {
-  NR_SCHED_ENSURE_LOCKED(&mac->sched_lock);
-
-  nr_rlc_remove_ue(rnti);
-  mac_remove_nr_ue(mac, rnti);
-
   // the CU might not know such UE, e.g., because we never sent a message to
   // it, so there might not be a corresponding entry for such UE in the look up
   // table. This can happen, e.g., on Msg.3 with C-RNTI, where we create a UE
   // MAC context, decode the PDU, find the C-RNTI MAC CE, and then throw the
   // newly created context away. See also in _nr_rx_sdu() and commit 93f59a3c6e56f
-  if (du_exists_f1_ue_data(rnti)) {
-    // unlock the scheduler temporarily to prevent possible deadlocks with
-    // du_remove_f1_ue_data() (and also while sending the message to RRC)
-    NR_SCHED_UNLOCK(&mac->sched_lock);
-    f1_ue_data_t ue_data = du_get_f1_ue_data(rnti);
-    f1ap_ue_context_release_complete_t complete = {
-      .gNB_CU_ue_id = ue_data.secondary_ue,
-      .gNB_DU_ue_id = rnti,
-    };
-    mac->mac_rrc.ue_context_release_complete(&complete);
+  if (!du_exists_f1_ue_data(rnti)) 
+    return;
 
-    du_remove_f1_ue_data(rnti);
-    NR_SCHED_LOCK(&mac->sched_lock);
-  }
+  // unlock the scheduler temporarily to prevent possible deadlocks with
+  // du_remove_f1_ue_data() (and also while sending the message to RRC)
+  NR_SCHED_UNLOCK(&mac->sched_lock);
+  f1_ue_data_t ue_data = du_get_f1_ue_data(rnti);
+  f1ap_ue_context_release_complete_t complete = {
+    .gNB_CU_ue_id = ue_data.secondary_ue,
+    .gNB_DU_ue_id = rnti,
+  };
+  mac->mac_rrc.ue_context_release_complete(&complete);
+
+  du_remove_f1_ue_data(rnti);
+  NR_SCHED_LOCK(&mac->sched_lock);
+}
+
+void nr_mac_release_ue(gNB_MAC_INST *mac, int rnti)
+{
+  NR_SCHED_ENSURE_LOCKED(&mac->sched_lock);
+
+  nr_rlc_remove_ue(rnti);
+  mac_remove_nr_ue(mac, rnti);
 }
 
 void nr_mac_update_timers(module_id_t module_id,
@@ -3055,6 +3059,8 @@ void nr_mac_update_timers(module_id_t module_id,
     NR_UE_sched_ctrl_t *sched_ctrl = &UE->UE_sched_ctrl;
 
     if (nr_mac_check_release(sched_ctrl, UE->rnti)) {
+      // trigger release first as nr_mac_release_ue() invalidates UE ptr
+      nr_mac_trigger_release_complete(mac, UE->rnti);
       nr_mac_release_ue(mac, UE->rnti);
       // go back to examine the next UE, which is at the position the
       // current UE was

openair2/LAYER2/NR_MAC_gNB/mac_proto.h

@@ -438,6 +438,7 @@ void abort_nr_dl_harq(NR_UE_info_t* UE, int8_t harq_pid);
 
 void nr_mac_trigger_release_timer(NR_UE_sched_ctrl_t *sched_ctrl, NR_SubcarrierSpacing_t subcarrier_spacing);
 bool nr_mac_check_release(NR_UE_sched_ctrl_t *sched_ctrl, int rnti);
+void nr_mac_trigger_release_complete(gNB_MAC_INST *mac, int rnti);
 void nr_mac_release_ue(gNB_MAC_INST *mac, int rnti);
 
 void nr_mac_trigger_ul_failure(NR_UE_sched_ctrl_t *sched_ctrl, NR_SubcarrierSpacing_t subcarrier_spacing);

openair2/LAYER2/NR_MAC_gNB/mac_rrc_dl_handler.c

@@ -627,6 +627,7 @@ void ue_context_release_command(const f1ap_ue_context_release_cmd_t *cmd)
   if (UE->UE_sched_ctrl.ul_failure || cmd->rrc_container_length == 0) {
     /* The UE is already not connected anymore or we have nothing to forward*/
     nr_mac_release_ue(mac, cmd->gNB_DU_ue_id);
+    nr_mac_trigger_release_complete(mac, cmd->gNB_DU_ue_id);
   } else {
     /* UE is in sync: forward release message and mark to be deleted
      * after UL failure */