RU: stop RF after all threads finished

If we do not stop RF after all threads, it can happen that the RF is
finished, but another thread of the RU (e.g., reorder thread) tries to
send out a package to the RF. This can lead to a segfault, as observed
in UHD, because we free all resources before reusing them.

This commit fixes this behavior.

executables/nr-ru.c

@@ -1295,12 +1295,6 @@ void *ru_thread( void *param ) {
 
   printf( "Exiting ru_thread \n");
 
-  if (ru->stop_rf != NULL) {
-    if (ru->stop_rf(ru) != 0)
-      LOG_E(HW,"Could not stop the RF device\n");
-    else LOG_I(PHY,"RU %d rf device stopped\n",ru->idx);
-  }
-
   ru_thread_status = 0;
   return &ru_thread_status;
 }
@@ -1378,6 +1372,18 @@ void kill_NR_RU_proc(int inst) {
     LOG_D(PHY, "Joining ru_stats_thread\n");
     pthread_join(ru->ru_stats_thread, NULL);
   }
+
+  // everything should be stopped now, we can safely stop the RF device
+  if (ru->stop_rf == NULL) {
+    LOG_W(PHY, "No stop_rf() for RU %d defined, cannot stop RF!\n", ru->idx);
+    return;
+  }
+  int rc = ru->stop_rf(ru);
+  if (rc != 0) {
+    LOG_W(PHY, "stop_rf() returned %d, RU %d RF device did not stop properly!\n", rc, ru->idx);
+    return;
+  }
+  LOG_I(PHY, "RU %d RF device stopped\n",ru->idx);
 }
 
 int check_capabilities(RU_t *ru,RRU_capabilities_t *cap) {