Add a thread safe way to clear game protocols when deleting world

src/network/protocols/client_lobby.cpp

@@ -960,6 +960,19 @@ void ClientLobby::backToLobby(Event *event)
     setup();
     m_auto_started = false;
     m_state.store(CONNECTED);
+
+    RaceEventManager::getInstance()->stop();
+    auto gep = RaceEventManager::getInstance()->getProtocol();
+    if (gep)
+        gep->requestTerminate();
+    auto gp = GameProtocol::lock();
+    if (gp)
+    {
+        auto lock = gp->acquireWorldDeletingMutex();
+        gp->requestTerminate();
+        RaceResultGUI::getInstance()->backToLobby();
+    }
+    else
         RaceResultGUI::getInstance()->backToLobby();
 
     NetworkString &data = event->data();

src/network/protocols/game_protocol.cpp

@@ -115,6 +115,11 @@ bool GameProtocol::notifyEventAsynchronous(Event* event)
 {
     if(!checkDataSize(event, 1)) return true;
 
+    // Ignore events arriving when client has already exited
+    auto lock = acquireWorldDeletingMutex();
+    if (!World::getWorld())
+        return true;
+
     NetworkString &data = event->data();
     uint8_t message_type = data.getUInt8();
     switch (message_type)
@@ -398,10 +403,6 @@ void GameProtocol::sendState()
  */
 void GameProtocol::handleState(Event *event)
 {
-    // Ignore events arriving when client has already exited
-    if (!World::getWorld())
-        return;
-
     assert(NetworkConfig::get()->isClient());
     NetworkString &data = event->data();
     int ticks          = data.getUInt32();

src/network/protocols/game_protocol.hpp

@@ -28,6 +28,7 @@
 
 #include <cstdlib>
 #include <map>
+#include <mutex>
 #include <vector>
 #include <tuple>
 
@@ -39,6 +40,9 @@ class GameProtocol : public Protocol
                    , public EventRewinder
 {
 private:
+    /* Used to check if deleting world is doing at the same the for
+     * asynchronous event update. */
+    mutable std::mutex m_world_deleting_mutex;
 
     /** The type of game events to be forwarded to the server. */
     enum { GP_CONTROLLER_ACTION,
@@ -138,6 +142,9 @@ public:
     NetworkString* getState() const { return m_data_to_send;  }
     // ------------------------------------------------------------------------
     void addInitialTicks(STKPeer* p, int ticks);
+    // ------------------------------------------------------------------------
+    std::unique_lock<std::mutex> acquireWorldDeletingMutex() const
+               { return std::unique_lock<std::mutex>(m_world_deleting_mutex); }
 
 };   // class GameProtocol