NativeThreadSet is a supporting class used by FileChannel to track the threads doing I/O on the channel. It supports the signalling of native threads that are blocked in file I/O and also supports waiting for all threads to finish I/O operations. NativeThreadSet should be re-examined. On Windows it doesn't need to use the threads array as threads aren't signalled. For virtual threads then it we need to move away from tracking the carrier thread handle.