Do not change _state value in message handler to avoid race conditions

Author: pennam

src/ArduinoIoTCloudTCP.cpp

@@ -80,6 +80,7 @@ extern "C" void setThingIdOutdated()
 
 ArduinoIoTCloudTCP::ArduinoIoTCloudTCP()
 : _state{State::ConnectPhy}
+, _next_state{State::Invalid}
 , _next_connection_attempt_tick{0}
 , _last_connection_attempt_cnt{0}
 , _next_device_subscribe_attempt_tick{0}
@@ -325,6 +326,12 @@ void ArduinoIoTCloudTCP::update()
   watchdog_reset();
 #endif
 
+  /* Check if the state has changed in message handler */
+  if(_next_state != State::Invalid)
+  {
+    _state = _next_state;
+    _next_state = State::Invalid;
+  }
 
   /* Run through the state machine. */
   State next_state = _state;
@@ -716,7 +723,7 @@ void ArduinoIoTCloudTCP::handleMessage(int length)
     CBORDecoder::decode(_device_property_container, (uint8_t*)bytes, length);
     _last_device_subscribe_cnt = 0;
     _next_device_subscribe_attempt_tick = 0;
-    _state = State::CheckDeviceConfig;
+    _next_state = State::CheckDeviceConfig;
   }
 
   /* Topic for user input data */
@@ -734,7 +741,7 @@ void ArduinoIoTCloudTCP::handleMessage(int length)
     execCloudEventCallback(ArduinoIoTCloudEvent::SYNC);
     _last_sync_request_cnt = 0;
     _last_sync_request_tick = 0;
-    _state = State::Connected;
+    _next_state = State::Connected;
   }
 }
 

src/ArduinoIoTCloudTCP.h

@@ -112,9 +112,11 @@ class ArduinoIoTCloudTCP: public ArduinoIoTCloudClass
       SubscribeThingTopics,
       RequestLastValues,
       Connected,
+      Invalid
     };
 
     State _state;
+    State _next_state;
 
     unsigned long _next_connection_attempt_tick;
     unsigned int _last_connection_attempt_cnt;