Prevent race conditions from simultaneous dispatch calls

src/plugin/host-bridge.cpp

@@ -269,8 +269,20 @@ intptr_t HostBridge::dispatch(AEffect* /*plugin*/,
     }
 
     // TODO: Maybe reuse buffers here when dealing with chunk data
-    return send_event(host_vst_dispatch, converter, opcode, index, value, data,
-                      option, std::pair<Logger&, bool>(logger, true));
+
+    // Finish message Bitwig's plugin host sometimes calls the dispatch function
+    // for opcode 52 from an off thread. This shouldn't be happening, but it
+    // does. To prevent race conditions from multiple writes over the same
+    // socket at once we'll make sure that only one thread can send sockets at
+    // once. These locks are actually only needed around the `write_object()`
+    // part of `send_event()`.
+    dispatch_semaphore.lock();
+    const auto return_value =
+        send_event(host_vst_dispatch, converter, opcode, index, value, data,
+                   option, std::pair<Logger&, bool>(logger, true));
+    dispatch_semaphore.unlock();
+
+    return return_value;
 }
 
 void HostBridge::process_replacing(AEffect* /*plugin*/,