Flush stuff pending on visual server thread when exiting, fixes #24669

editor/editor_resource_preview.cpp

@@ -313,6 +313,8 @@ void EditorResourcePreview::_thread() {
 			preview_mutex->unlock();
 		}
 	}
+
+	exited = true;
 }
 
 void EditorResourcePreview::queue_edited_resource_preview(const Ref<Resource> &p_res, Object *p_receiver, const StringName &p_receiver_func, const Variant &p_userdata) {
@@ -420,11 +422,16 @@ void EditorResourcePreview::check_for_invalidation(const String &p_path) {
 void EditorResourcePreview::start() {
 	ERR_FAIL_COND(thread);
 	thread = Thread::create(_thread_func, this);
+	exited = false;
 }
 void EditorResourcePreview::stop() {
 	if (thread) {
 		exit = true;
 		preview_sem->post();
+		while (!exited) {
+			OS::get_singleton()->delay_usec(10000);
+			VisualServer::get_singleton()->sync(); //sync pending stuff, as thread may be blocked on visual server
+		}
 		Thread::wait_to_finish(thread);
 		memdelete(thread);
 		thread = NULL;
@@ -438,6 +445,7 @@ EditorResourcePreview::EditorResourcePreview() {
 	preview_sem = Semaphore::create();
 	order = 0;
 	exit = false;
+	exited = false;
 }
 
 EditorResourcePreview::~EditorResourcePreview() {

editor/editor_resource_preview.h

@@ -90,7 +90,8 @@ class EditorResourcePreview : public Node {
 	Mutex *preview_mutex;
 	Semaphore *preview_sem;
 	Thread *thread;
-	bool exit;
+	volatile bool exit;
+	volatile bool exited;
 
 	struct Item {
 		Ref<Texture> preview;