Initialize notification queue pointer before switch create (sonic-net#411)

* Initialize notification queue pointer before switch create

* Fix spell mistake

* Move start ntf thread after switch create and init pointer directly

* Fix errors

Author: kcudnik

syncd/syncd.cpp

@@ -3630,6 +3630,10 @@ int syncd_main(int argc, char **argv)
         onSyncdStart(options.startType == SAI_WARM_BOOT);
         SWSS_LOG_NOTICE("after onSyncdStart");
 
+        // create notifications processing thread after we create_switch to
+        // make sure, we have switch_id translated to VID before we start
+        // processing possible quick fdb notifications, and pointer for
+        // notification queue is created before we create switch
         startNotificationsProcessingThread();
 
         SWSS_LOG_NOTICE("syncd listening for events");

syncd/syncd_notifications.cpp

@@ -458,6 +458,7 @@ std::condition_variable cv;
 class ntf_queue_t
 {
 public:
+    ntf_queue_t() { }
     bool enqueue(swss::KeyOpFieldsValuesTuple msg);
     bool tryDequeue(swss::KeyOpFieldsValuesTuple& msg);
     size_t queueStats()
@@ -480,7 +481,15 @@ class ntf_queue_t
     const size_t limit = 300000;
 };
 
-static std::unique_ptr<ntf_queue_t> ntf_queue_hdlr;
+
+/*
+ * Make sure that notification queue pointer is populated before we start
+ * thread, and before we create_switch, since at switch_create we can start
+ * receiving fdb_notifications which will arrive on different thread and
+ * will call queueStats() when queue pointer could be null (this=0x0).
+ */
+
+static std::unique_ptr<ntf_queue_t> ntf_queue_hdlr = std::unique_ptr<ntf_queue_t>(new ntf_queue_t);
 
 bool ntf_queue_t::tryDequeue(
         _Out_ swss::KeyOpFieldsValuesTuple &item)
@@ -641,8 +650,6 @@ void ntf_process_function()
 {
     SWSS_LOG_ENTER();
 
-    ntf_queue_hdlr = std::unique_ptr<ntf_queue_t>(new ntf_queue_t);
-
     while (runThread)
     {
         cv.wait(ulock);