Calling uv_close again for other handles within the uv_close callback will lead to a crash

[ghost]

libuv version: v1.44.2

Writing it this way would cause a crash:

void Socket::InternalCloseSocket() {
	if (uv_is_closing(reinterpret_cast<uv_handle_t*>(&stream)))
		return;
	OnInfo(std::string("Closing connection: ").append(GetPeerAddress(&stream)));
	uv_timer_stop(&read_timeout_req);
	uv_close(reinterpret_cast<uv_handle_t*>(&stream), [](uv_handle_t* handle) {
		auto socket = static_cast<Socket*>(handle->data);

		// I've done some counting here, this callback will never exceed one time

		// If uv_close is called here, it will often crash when closing a large number of connections.
		uv_close(reinterpret_cast<uv_handle_t*>(&socket->read_timeout_req), nullptr);
		uv_close(reinterpret_cast<uv_handle_t*>(&socket->async), nullptr); // The async handle is sometimes closed at this time

		socket->is_initialized = false;
		socket->m_send_queue = decltype(m_send_queue){};
		socket->is_sending = false;
		if (socket->OnClose) socket->OnClose();
	});
}

Here are several situations of crashes:

Thread 3 "easyrpg-player-" received signal SIGSEGV, Segmentation fault.
[Switching to Thread 0x7ffff6ffe640 (LWP 98764)]
0x00005555555bf645 in uv__finish_close (handle=0x7ffff00f32d8) at /home/easyrpg/EasyRPG-Multiplayer-Native/lib/libuv/src/unix/core.c:318
318       QUEUE_REMOVE(&handle->handle_queue);

easyrpg-player-server: /home/easyrpg/EasyRPG-Multiplayer-Native/lib/libuv/src/unix/core.c:116: uv_close: Assertion `!uv__is_closing(handle)' failed.
Thread 3 "easyrpg-player-" received signal SIGABRT, Aborted.

easyrpg-player-server: /home/easyrpg/EasyRPG-Multiplayer-Native/lib/libuv/src/unix/core.c:271: uv__finish_close: Assertion `handle->flags' failed.
Thread 3 "easyrpg-player-" received signal SIGABRT, Aborted.

easyrpg-player-server: /home/easyrpg/EasyRPG-Multiplayer-Native/lib/libuv/src/unix/core.c:273: uv__finish_close: Assertion `!(handle->flags & UV_HANDLE_CLOSED)' failed.
Thread 3 "easyrpg-player-" received signal SIGABRT, Aborted.

Thread 3 "easyrpg-player-" received signal SIGSEGV, Segmentation fault.
[Switching to Thread 0x7ffff6ffe640 (LWP 99387)]
0x00005555555c94e1 in uv__stream_destroy (stream=0x7ffff00c4858) at /home/easyrpg/EasyRPG-Multiplayer-Native/lib/libuv/src/unix/stream.c:450
450         uv__req_unregister(stream->loop, stream->connect_req);
#0  0x00005555555c94e1 in uv__stream_destroy (stream=0x7ffff00b16c8) at /home/easyrpg/EasyRPG-Multiplayer-Native/lib/libuv/src/unix/stream.c:450
#1  0x00005555555bf5ca in uv__finish_close (handle=0x7ffff00b16c8) at /home/easyrpg/EasyRPG-Multiplayer-Native/lib/libuv/src/unix/core.c:305
#2  0x00005555555bf6ca in uv__run_closing_handles (loop=0x5555556306a0) at /home/easyrpg/EasyRPG-Multiplayer-Native/lib/libuv/src/unix/core.c:335
#3  0x00005555555bf9a1 in uv_run (loop=0x5555556306a0, mode=UV_RUN_DEFAULT) at /home/easyrpg/EasyRPG-Multiplayer-Native/lib/libuv/src/unix/core.c:423

Writing it this way can prevent crashes, but I'm not sure why it works like this

void Socket::InternalCloseSocket() {
	if (uv_is_closing(reinterpret_cast<uv_handle_t*>(&stream)))
		return;
	OnInfo(std::string("Closing connection: ").append(GetPeerAddress(&stream)));

	// If uv_close is called here, it won't crash
	uv_close(reinterpret_cast<uv_handle_t*>(&read_timeout_req), nullptr);
	uv_close(reinterpret_cast<uv_handle_t*>(&async), nullptr);

	uv_timer_stop(&read_timeout_req);
	uv_close(reinterpret_cast<uv_handle_t*>(&stream), [](uv_handle_t* handle) {
		auto socket = static_cast<Socket*>(handle->data);
		socket->is_initialized = false;
		socket->m_send_queue = decltype(m_send_queue){};
		socket->is_sending = false;
		if (socket->OnClose) socket->OnClose();
	});
}

libuv version:

[saghul]

This is documented behavior, you can only call uv_close once.

[ghost]

https://docs.libuv.org/en/v1.x/handle.html#c.uv_close

I have only called uv_close once for each handle. However, I haven't found documentation stating that uv_close can only be called once. If that's the case, how should I close uv_tcp_t, uv_async_t, and uv_timer_t altogether?

[saghul]

Sorry for my terse response, I'd have sworn we had that documented :-/

You can call uv_close on all of them at once, with the same close callback, and have a counter, once it reaches 3 you'll know everything is ready to be disposed.