From a0557840eb424e174bf81a0175c40f9e176a2cc2 Mon Sep 17 00:00:00 2001 From: Sean McArthur Date: Wed, 23 Sep 2020 13:02:15 -0700 Subject: io: use intrusive wait list for I/O driver (#2828) This refactors I/O registration in a few ways: - Cleans up the cached readiness in `PollEvented`. This cache used to be helpful when readiness was a linked list of `*mut Node`s in `Registration`. Previous refactors have turned `Registration` into just an `AtomicUsize` holding the current readiness, so the cache is just extra work and complexity. Gone. - Polling the `Registration` for readiness now gives a `ReadyEvent`, which includes the driver tick. This event must be passed back into `clear_readiness`, so that the readiness is only cleared from `Registration` if the tick hasn't changed. Previously, it was possible to clear the readiness even though another thread had *just* polled the driver and found the socket ready again. - Registration now also contains an `async fn readiness`, which stores wakers in an instrusive linked list. This allows an unbounded number of tasks to register for readiness (previously, only 1 per direction (read and write)). By using the intrusive linked list, there is no concern of leaking the storage of the wakers, since they are stored inside the `async fn` and released when the future is dropped. - Registration retains a `poll_readiness(Direction)` method, to support `AsyncRead` and `AsyncWrite`. They aren't able to use `async fn`s, and so there are 2 reserved slots for those methods. - IO types where it makes sense to have multiple tasks waiting on them now take advantage of this new `async fn readiness`, such as `UdpSocket` and `UnixDatagram`. Additionally, this makes the `io-driver` "feature" internal-only (no longer documented, not part of public API), and adds a second internal-only feature, `io-readiness`, to group together linked list part of registration that is only used by some of the IO types. After a bit of discussion, changing stream-based transports (like `TcpStream`) to have `async fn read(&self)` is punted, since that is likely too easy of a footgun to activate. Refs: #2779, #2728 --- examples/udp-codec.rs | 6 ++++++ 1 file changed, 6 insertions(+) (limited to 'examples/udp-codec.rs') diff --git a/examples/udp-codec.rs b/examples/udp-codec.rs index 8b64cbc3..f338bd84 100644 --- a/examples/udp-codec.rs +++ b/examples/udp-codec.rs @@ -1,3 +1,8 @@ +fn main() {} + +// Disabled while future of UdpFramed is decided on. +// See https://github.com/tokio-rs/tokio/issues/2830 +/* //! This example leverages `BytesCodec` to create a UDP client and server which //! speak a custom protocol. //! @@ -78,3 +83,4 @@ async fn pong(socket: &mut UdpFramed) -> Result<(), io::Error> { Ok(()) } +*/ -- cgit v1.2.3