Suppress storm detect counter increment for ongoing pfc storm case du…

…ring a warm reboot (sonic-net#869)

* Suppress storm detect counter increment for ongoing pfc storm case during
a warm reboot

Signed-off-by: Wenda Ni <wenni@microsoft.com>

* Comment touch-up

Signed-off-by: Wenda Ni <wenni@microsoft.com>

orchagent/pfcactionhandler.cpp

@@ -55,14 +55,23 @@ void PfcWdActionHandler::initCounters(void)
     }
 
     auto wdQueueStats = getQueueStats(m_countersTable, sai_serialize_object_id(m_queue));
-    wdQueueStats.detectCount++;
+    // initCounters() is called when the event channel receives
+    // a storm signal. This can happen when there is a true new storm or
+    // when there is an existing storm ongoing before warm-reboot. In the latter case,
+    // we treat the storm as an old storm. In particular,
+    // we do not increment the detectCount so as to clamp the
+    // gap between detectCount and restoreCount by 1 at maximum
+    if (!(wdQueueStats.detectCount > wdQueueStats.restoreCount))
+    {
+        wdQueueStats.detectCount++;
+
+        wdQueueStats.txPktLast = 0;
+        wdQueueStats.txDropPktLast = 0;
+        wdQueueStats.rxPktLast = 0;
+        wdQueueStats.rxDropPktLast = 0;
+    }
     wdQueueStats.operational = false;
 
-    wdQueueStats.txPktLast = 0;
-    wdQueueStats.txDropPktLast = 0;
-    wdQueueStats.rxPktLast = 0;
-    wdQueueStats.rxDropPktLast = 0;
-
     updateWdCounters(sai_serialize_object_id(m_queue), wdQueueStats);
 }