Prevent race condition when sync req received

Added a flush mechanism to actor thread. This is used to wait for all
waiting jobs in the queue to be completed.

common/utils/actor/actor.c

@@ -50,7 +50,8 @@ void *actor_thread(void *arg)
       break;
     }
 
-    elt->processingFunc(NotifiedFifoData(elt));
+    if (elt->processingFunc) // processing function can be NULL
+      elt->processingFunc(NotifiedFifoData(elt));
     if (elt->reponseFifo) {
       pushNotifiedFIFO(elt->reponseFifo, elt);
     } else
@@ -85,3 +86,14 @@ void shutdown_actor(Actor_t *actor)
   abortNotifiedFIFO(&response_fifo);
   pthread_join(actor->thread, NULL);
 }
+
+void flush_actor(Actor_t *actor)
+{
+  notifiedFIFO_t response_fifo;
+  initNotifiedFIFO(&response_fifo);
+  notifiedFIFO_elt_t *elt = newNotifiedFIFO_elt(0, 0, &response_fifo, NULL);
+  pushNotifiedFIFO(&actor->fifo, elt);
+  elt = pullNotifiedFIFO(&response_fifo);
+  delNotifiedFIFO_elt(elt);
+  abortNotifiedFIFO(&response_fifo);
+}

common/utils/actor/actor.h

@@ -49,4 +49,9 @@ void destroy_actor(Actor_t *actor);
 /// @param actor
 void shutdown_actor(Actor_t *actor);
 
+/// @brief This function will return when all current jobs in the queue are finished.
+/// The caller should make sure no new jobs are added to the queue between this function call and return.
+/// @param actor
+void flush_actor(Actor_t *actor);
+
 #endif

executables/nr-ue.c

@@ -570,7 +570,6 @@ static int handle_sync_req_from_mac(PHY_VARS_NR_UE *UE)
   NR_DL_FRAME_PARMS *fp = &UE->frame_parms;
   // Start synchronization with a target gNB
   if (UE->synch_request.received_synch_request == 1) {
-    UE->is_synchronized = 0;
     // if upper layers signal BW scan we do as instructed by command line parameter
     // if upper layers disable BW scan we set it to false
     if (UE->synch_request.synch_req.ssb_bw_scan)
@@ -590,7 +589,15 @@ static int handle_sync_req_from_mac(PHY_VARS_NR_UE *UE)
       init_symbol_rotation(fp);
     }
 
+    /* Clearing UE harq while DL actors are active causes race condition.
+        So we let the current execution to complete here.*/
+    for (int i = 0; i < NUM_DL_ACTORS; i++) {
+      flush_actor(UE->dl_actors + i);
+    }
+    /*TODO: Flush UL jobs */
+
     clean_UE_harq(UE);
+    UE->is_synchronized = 0;
     UE->synch_request.received_synch_request = 0;
     return 0;
   }