stack,nr: isolate calls between LTE and NR stacks via the task multiqueue

lib/include/srsran/interfaces/enb_x2_interfaces.h

@@ -90,17 +90,9 @@ public:
   virtual void set_activity_user(uint16_t eutra_rnti) = 0;
 };
 
-class stack_nr_interface_stack_eutra
-{
-public:
-  /// Helper method to provide time signal to NR-RRC (PHY only sends TTI ticks to EUTRA stack)
-  virtual void tti_clock() = 0;
-};
-
 // combined interface used by X2 adapter
 class x2_interface : public rrc_nr_interface_rrc,
                      public rrc_eutra_interface_rrc_nr,
-                     public stack_nr_interface_stack_eutra,
                      public pdcp_interface_gtpu, // allow GTPU to access PDCP in DL direction
                      public gtpu_interface_pdcp  // allow PDCP to access GTPU in UL direction
 {};

srsenb/hdr/stack/enb_stack_lte.h

@@ -111,14 +111,21 @@ public:
   // rrc_eutra_interface_rrc_nr
   void sgnb_addition_ack(uint16_t eutra_rnti, sgnb_addition_ack_params_t params) final
   {
-    rrc.sgnb_addition_ack(eutra_rnti, params);
+    x2_task_queue.push([this, eutra_rnti, params]() { rrc.sgnb_addition_ack(eutra_rnti, params); });
+  }
+  void sgnb_addition_reject(uint16_t eutra_rnti) final
+  {
+    x2_task_queue.push([this, eutra_rnti]() { rrc.sgnb_addition_reject(eutra_rnti); });
   }
-  void sgnb_addition_reject(uint16_t eutra_rnti) final { rrc.sgnb_addition_reject(eutra_rnti); }
   void sgnb_addition_complete(uint16_t eutra_rnti, uint16_t nr_rnti) final
   {
-    rrc.sgnb_addition_complete(eutra_rnti, nr_rnti);
+    x2_task_queue.push([this, eutra_rnti, nr_rnti]() { rrc.sgnb_addition_complete(eutra_rnti, nr_rnti); });
+  }
+  void set_activity_user(uint16_t eutra_rnti) final
+  {
+    // Note: RRC processes activity asynchronously, so there is no need to use x2_task_queue
+    rrc.set_activity_user(eutra_rnti);
   }
-  void set_activity_user(uint16_t eutra_rnti) final { rrc.set_activity_user(eutra_rnti); }
 
   // gtpu_interface_pdcp
   void write_pdu(uint16_t rnti, uint32_t lcid, srsran::unique_byte_buffer_t pdu);
@@ -151,7 +158,7 @@ private:
 
   // task handling
   srsran::task_scheduler    task_sched;
-  srsran::task_queue_handle enb_task_queue, sync_task_queue, metrics_task_queue;
+  srsran::task_queue_handle enb_task_queue, sync_task_queue, metrics_task_queue, x2_task_queue;
 
   // bearer management
   enb_bearer_manager                 bearers; // helper to manage mapping between EPS and radio bearers

srsenb/hdr/stack/gnb_stack_nr.h

@@ -87,10 +87,14 @@ public:
   // X2 data interface
   void write_sdu(uint16_t rnti, uint32_t lcid, srsran::unique_byte_buffer_t sdu, int pdcp_sn = -1) final
   {
+    auto task = [this, rnti, lcid, pdcp_sn](srsran::unique_byte_buffer_t& sdu) {
       pdcp.write_sdu(rnti, lcid, std::move(sdu), pdcp_sn);
+    };
+    gtpu_task_queue.push(std::bind(task, std::move(sdu)));
   }
   std::map<uint32_t, srsran::unique_byte_buffer_t> get_buffered_pdus(uint16_t rnti, uint32_t lcid) final
   {
+    // TODO: make it thread-safe. For now, this function is unused
     return pdcp.get_buffered_pdus(rnti, lcid);
   }
 
@@ -111,7 +115,7 @@ private:
   // task scheduling
   static const int                      STACK_MAIN_THREAD_PRIO = 4;
   srsran::task_scheduler                task_sched;
-  srsran::task_multiqueue::queue_handle sync_task_queue, ue_task_queue, gw_task_queue, mac_task_queue;
+  srsran::task_multiqueue::queue_handle sync_task_queue, ue_task_queue, gtpu_task_queue, mac_task_queue;
 
   // derived
   srsenb::mac_nr mac;

srsenb/hdr/x2_adapter.h

@@ -93,15 +93,6 @@ public:
     eutra_stack->set_activity_user(eutra_rnti);
   }
 
-  // stack_nr_interface_stack_eutra
-  void tti_clock()
-  {
-    if (nr_stack == nullptr) {
-      return;
-    }
-    nr_stack->tti_clock();
-  }
-
   // pdcp_interface_gtpu
   void write_sdu(uint16_t rnti, uint32_t lcid, srsran::unique_byte_buffer_t sdu, int pdcp_sn = -1)
   {

srsenb/src/stack/enb_stack_lte.cc

@@ -164,6 +164,11 @@ int enb_stack_lte::init(const stack_args_t&      args_,
   // add sync queue
   sync_task_queue = task_sched.make_task_queue(args.sync_queue_size);
 
+  // add x2 queue
+  if (x2_ != nullptr) {
+    x2_task_queue = task_sched.make_task_queue();
+  }
+
   // setup bearer managers
   gtpu_adapter.reset(new gtpu_pdcp_adapter(stack_logger, &pdcp, x2_, &gtpu, bearers));
 
@@ -286,7 +291,10 @@ void enb_stack_lte::run_thread()
 void enb_stack_lte::write_pdu(uint16_t rnti, uint32_t lcid, srsran::unique_byte_buffer_t pdu)
 {
   // call GTPU adapter to map to EPS bearer
+  auto task = [this, rnti, lcid](srsran::unique_byte_buffer_t& pdu) {
     gtpu_adapter->write_pdu(rnti, lcid, std::move(pdu));
+  };
+  x2_task_queue.push(std::bind(task, std::move(pdu)));
 }
 
 } // namespace srsenb

srsenb/src/stack/gnb_stack_nr.cc

@@ -32,7 +32,7 @@ gnb_stack_nr::gnb_stack_nr(srslog::sink& log_sink) :
 {
   ue_task_queue   = task_sched.make_task_queue();
   sync_task_queue = task_sched.make_task_queue();
-  gw_task_queue   = task_sched.make_task_queue();
+  gtpu_task_queue = task_sched.make_task_queue();
   mac_task_queue  = task_sched.make_task_queue();
 }