race condition fix (win tun)

lib/u_async.c

@@ -1426,6 +1426,19 @@ void uasync_get_stats(struct UASYNC* ua, size_t* timer_alloc, size_t* timer_u_fr
     if (socket_u_free) *socket_u_free = ua->socket_free_count;
 }
 
+void uasync_memsync(struct UASYNC* ua) {
+#ifdef _WIN32
+    EnterCriticalSection(&ua->posted_lock);
+#else
+    pthread_mutex_lock(&ua->posted_lock);
+#endif
+#ifdef _WIN32
+    LeaveCriticalSection(&ua->posted_lock);
+#else
+    pthread_mutex_unlock(&ua->posted_lock);
+#endif
+}
+
 void uasync_post(struct UASYNC* ua, uasync_post_callback_t callback, void* arg) {
     if (!ua || !callback) return;