[ResourceLoader] Do not wait for the main thread during initial reimport.

core/io/resource_loader.cpp

@@ -772,6 +772,10 @@ Ref<Resource> ResourceLoader::_load_complete(LoadToken &p_load_token, Error *r_e
 	return _load_complete_inner(p_load_token, r_error, thread_load_lock);
 }
 
+void ResourceLoader::set_is_import_thread(bool p_import_thread) {
+	import_thread = p_import_thread;
+}
+
 Ref<Resource> ResourceLoader::_load_complete_inner(LoadToken &p_load_token, Error *r_error, MutexLock<SafeBinaryMutex<BINARY_MUTEX_TAG>> &p_thread_load_lock) {
 	if (r_error) {
 		*r_error = OK;
@@ -886,9 +890,11 @@ Ref<Resource> ResourceLoader::_load_complete_inner(LoadToken &p_load_token, Erro
 							MessageQueue::get_main_singleton()->push_callable(callable_mp(rcc.source, &Resource::connect_changed).bind(rcc.callable, rcc.flags));
 						}
 					}
-					core_bind::Semaphore done;
-					MessageQueue::get_main_singleton()->push_callable(callable_mp(&done, &core_bind::Semaphore::post).bind(1));
-					done.wait();
+					if (!import_thread) { // Main thread is blocked by initial resource reimport, do not wait.
+						core_bind::Semaphore done;
+						MessageQueue::get_main_singleton()->push_callable(callable_mp(&done, &core_bind::Semaphore::post).bind(1));
+						done.wait();
+					}
 				}
 			}
 		}
@@ -1565,6 +1571,7 @@ bool ResourceLoader::create_missing_resources_if_class_unavailable = false;
 bool ResourceLoader::abort_on_missing_resource = true;
 bool ResourceLoader::timestamp_on_load = false;
 
+thread_local bool ResourceLoader::import_thread = false;
 thread_local int ResourceLoader::load_nesting = 0;
 thread_local Vector<String> ResourceLoader::load_paths_stack;
 thread_local HashMap<int, HashMap<String, Ref<Resource>>> ResourceLoader::res_ref_overrides;

core/io/resource_loader.h

@@ -204,6 +204,7 @@ private:
 
 	static void _run_load_task(void *p_userdata);
 
+	static thread_local bool import_thread;
 	static thread_local int load_nesting;
 	static thread_local HashMap<int, HashMap<String, Ref<Resource>>> res_ref_overrides; // Outermost key is nesting level.
 	static thread_local Vector<String> load_paths_stack;
@@ -253,6 +254,8 @@ public:
 	static bool is_imported(const String &p_path);
 	static int get_import_order(const String &p_path);
 
+	static void set_is_import_thread(bool p_import_thread);
+
 	static void set_timestamp_on_load(bool p_timestamp) { timestamp_on_load = p_timestamp; }
 	static bool get_timestamp_on_load() { return timestamp_on_load; }
 

editor/editor_file_system.cpp

@@ -3107,8 +3107,11 @@ void EditorFileSystem::_refresh_filesystem() {
 }
 
 void EditorFileSystem::_reimport_thread(uint32_t p_index, ImportThreadData *p_import_data) {
+	ResourceLoader::set_is_import_thread(true);
 	int file_idx = p_import_data->reimport_from + int(p_index);
 	_reimport_file(p_import_data->reimport_files[file_idx].path);
+	ResourceLoader::set_is_import_thread(false);
+
 	p_import_data->imported_sem->post();
 }