introduce dedicated nr pdcp tick thread for F1 split

Currently, NR PDCP ticks are active only with monolithic gNB, triggered by the MAC scheduler in gNB_scheduler.c.
In F1 split mode, as there is no MAC, there’s no source to advance the NR PDCP timer via "nr_pdcp_wakeup_timer_thread()".
This commit introduces a dedicated thread for NR PDCP ticks in gNB-CU and CU-UP mode.
Without it, packet losses at the F1 uplink would cause indefinite buffering, as t-Reordering won't expire due to the lack of NR PDCP timer ticks.

openair2/LAYER2/NR_MAC_gNB/main.c

@@ -277,7 +277,7 @@ void mac_top_init_gNB(ngran_node_t node_type,
     AssertFatal(rlc_module_init(1) == 0,"Could not initialize RLC layer\n");
 
     // These should be out of here later
-    if (get_softmodem_params()->usim_test == 0 ) nr_pdcp_layer_init(false);
+    if (get_softmodem_params()->usim_test == 0 ) nr_pdcp_layer_init();
 
     if(IS_SOFTMODEM_NOS1 && get_softmodem_params()->phy_test) {
       // get default noS1 configuration

openair2/LAYER2/nr_pdcp/nr_pdcp_oai_api.c

@@ -566,7 +566,7 @@ void pdcp_layer_init(void)
   abort();
 }
 
-void nr_pdcp_layer_init(bool uses_e1)
+void nr_pdcp_layer_init(void)
 {
   /* hack: be sure to initialize only once */
   static pthread_mutex_t m = PTHREAD_MUTEX_INITIALIZER;
@@ -586,10 +586,12 @@ void nr_pdcp_layer_init(bool uses_e1)
   if ((RC.nrrrc == NULL) || (!NODE_IS_CU(node_type))) {
     init_nr_rlc_data_req_queue();
   }
-
-  nr_pdcp_e1_if_init(uses_e1);
+  nr_pdcp_e1_if_init(node_type == ngran_gNB_CUUP || node_type == ngran_gNB_CUCP);
   init_nr_pdcp_data_ind_queue();
   nr_pdcp_init_timer_thread(nr_pdcp_ue_manager);
+  if (NODE_IS_CU(node_type)) {
+    nr_pdcp_init_tick_thread();
+  }
 }
 
 #include "nfapi/oai_integration/vendor_ext.h"

openair2/LAYER2/nr_pdcp/nr_pdcp_oai_api.h

@@ -25,7 +25,7 @@
 #include "pdcp.h"
 #include "nr_pdcp_ue_manager.h"
 
-void nr_pdcp_layer_init(bool uses_e1);
+void nr_pdcp_layer_init(void);
 uint64_t nr_pdcp_module_init(uint64_t _pdcp_optmask, int id);
 
 void du_rlc_data_req(const protocol_ctxt_t *const ctxt_pP,

openair2/LAYER2/nr_pdcp/nr_pdcp_timer_thread.c

@@ -70,6 +70,26 @@ static void *nr_pdcp_timer_thread(void *_nr_pdcp_ue_manager)
   return NULL;
 }
 
+static void *nr_pdcp_tick_thread() {
+  pthread_setname_np(pthread_self(),"nr_pdcp_tick_thread");
+  uint64_t curr_time = 0;
+  while (1) {
+    usleep(1000);
+    curr_time++;
+    nr_pdcp_wakeup_timer_thread(curr_time);
+  }
+  return NULL;
+}
+
+void nr_pdcp_init_tick_thread() 
+{
+  pthread_t t;
+  if (pthread_create(&t, NULL, nr_pdcp_tick_thread, NULL) != 0) {
+    LOG_E(PDCP, "%s:%d:%s: fatal\n", __FILE__, __LINE__, __FUNCTION__);
+    exit(1);
+  }
+}
+
 void nr_pdcp_init_timer_thread(nr_pdcp_ue_manager_t *nr_pdcp_ue_manager)
 {
   pthread_t t;

openair2/LAYER2/nr_pdcp/nr_pdcp_timer_thread.h

@@ -26,6 +26,7 @@
 
 #include <stdint.h>
 
+void nr_pdcp_init_tick_thread();
 void nr_pdcp_init_timer_thread(nr_pdcp_ue_manager_t *nr_pdcp_ue_manager);
 void nr_pdcp_wakeup_timer_thread(uint64_t time);