Merge branch 'fix_6286' into 'master'

Fix deadlock in Lua worker thread

Closes #6286

See merge request OpenMW/openmw!1228

apps/openmw/engine.cpp

@@ -875,7 +875,14 @@ public:
     void join()
     {
         if (mThread)
+        {
+            {
+                std::lock_guard<std::mutex> lk(mMutex);
+                mJoinRequest = true;
+            }
+            mCV.notify_one();
             mThread->join();
+        }
     }
 
 private:
@@ -891,10 +898,12 @@ private:
 
     void threadBody()
     {
-        while (!mEngine->mViewer->done() && !mEngine->mEnvironment.getStateManager()->hasQuitRequest())
+        while (true)
         {
             std::unique_lock<std::mutex> lk(mMutex);
-            mCV.wait(lk, [&]{ return mUpdateRequest; });
+            mCV.wait(lk, [&]{ return mUpdateRequest || mJoinRequest; });
+            if (mJoinRequest)
+                break;
 
             update();
 
@@ -908,6 +917,7 @@ private:
     std::mutex mMutex;
     std::condition_variable mCV;
     bool mUpdateRequest = false;
+    bool mJoinRequest = false;
     double mDt = 0;
     bool mIsGuiMode = false;
     std::optional<std::thread> mThread;