mirror of
https://github.com/tokio-rs/tokio.git
synced 2025-09-25 12:00:35 +00:00
ec22fb9843
ATOMIC_BOOL_INIT is deprecated since 1.34 because the const fn AtomicUsize::new is now preferred. As deny(warnings) is set, tokio fails to build on latest nightly. This will fix it. Signed-off-by: Yilin Chen <sticnarf@gmail.com>
760 lines
23 KiB
Rust
760 lines
23 KiB
Rust
#![doc(html_root_url = "https://docs.rs/tokio-reactor/0.1.8")]
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#![deny(missing_docs, warnings, missing_debug_implementations)]
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//! Event loop that drives Tokio I/O resources.
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//!
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//! The reactor is the engine that drives asynchronous I/O resources (like TCP and
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//! UDP sockets). It is backed by [`mio`] and acts as a bridge between [`mio`] and
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//! [`futures`].
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//!
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//! The crate provides:
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//!
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//! * [`Reactor`] is the main type of this crate. It performs the event loop logic.
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//!
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//! * [`Handle`] provides a reference to a reactor instance.
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//!
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//! * [`Registration`] and [`PollEvented`] allow third parties to implement I/O
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//! resources that are driven by the reactor.
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//!
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//! Application authors will not use this crate directly. Instead, they will use the
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//! `tokio` crate. Library authors should only depend on `tokio-reactor` if they
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//! are building a custom I/O resource.
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//!
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//! For more details, see [reactor module] documentation in the Tokio crate.
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//!
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//! [`mio`]: http://github.com/carllerche/mio
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//! [`futures`]: http://github.com/rust-lang-nursery/futures-rs
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//! [`Reactor`]: struct.Reactor.html
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//! [`Handle`]: struct.Handle.html
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//! [`Registration`]: struct.Registration.html
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//! [`PollEvented`]: struct.PollEvented.html
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//! [reactor module]: https://docs.rs/tokio/0.1/tokio/reactor/index.html
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extern crate crossbeam_utils;
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#[macro_use]
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extern crate futures;
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#[macro_use]
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extern crate lazy_static;
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#[macro_use]
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extern crate log;
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extern crate mio;
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extern crate num_cpus;
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extern crate parking_lot;
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extern crate slab;
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extern crate tokio_executor;
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extern crate tokio_io;
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mod atomic_task;
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pub(crate) mod background;
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mod poll_evented;
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mod registration;
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mod sharded_rwlock;
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// ===== Public re-exports =====
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pub use self::background::{Background, Shutdown};
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pub use self::registration::Registration;
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pub use self::poll_evented::PollEvented;
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// ===== Private imports =====
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use atomic_task::AtomicTask;
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use sharded_rwlock::RwLock;
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use futures::task::Task;
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use tokio_executor::Enter;
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use tokio_executor::park::{Park, Unpark};
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use std::{fmt, usize};
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use std::error::Error;
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use std::io;
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use std::mem;
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use std::cell::RefCell;
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use std::sync::atomic::Ordering::{Relaxed, SeqCst};
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use std::sync::atomic::AtomicUsize;
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use std::sync::{Arc, Weak};
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use std::time::{Duration, Instant};
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use log::Level;
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use mio::event::Evented;
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use slab::Slab;
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/// The core reactor, or event loop.
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///
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/// The event loop is the main source of blocking in an application which drives
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/// all other I/O events and notifications happening. Each event loop can have
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/// multiple handles pointing to it, each of which can then be used to create
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/// various I/O objects to interact with the event loop in interesting ways.
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pub struct Reactor {
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/// Reuse the `mio::Events` value across calls to poll.
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events: mio::Events,
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/// State shared between the reactor and the handles.
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inner: Arc<Inner>,
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_wakeup_registration: mio::Registration,
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}
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/// A reference to a reactor.
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///
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/// A `Handle` is used for associating I/O objects with an event loop
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/// explicitly. Typically though you won't end up using a `Handle` that often
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/// and will instead use the default reactor for the execution context.
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///
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/// By default, most components bind lazily to reactors.
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/// To get this behavior when manually passing a `Handle`, use `default()`.
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#[derive(Clone)]
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pub struct Handle {
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inner: Option<HandlePriv>,
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}
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/// Like `Handle`, but never `None`.
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#[derive(Clone)]
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struct HandlePriv {
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inner: Weak<Inner>,
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}
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/// Return value from the `turn` method on `Reactor`.
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///
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/// Currently this value doesn't actually provide any functionality, but it may
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/// in the future give insight into what happened during `turn`.
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#[derive(Debug)]
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pub struct Turn {
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_priv: (),
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}
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/// Error returned from `Handle::set_fallback`.
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#[derive(Clone, Debug)]
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pub struct SetFallbackError(());
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#[deprecated(since = "0.1.2", note = "use SetFallbackError instead")]
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#[doc(hidden)]
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pub type SetDefaultError = SetFallbackError;
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#[test]
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fn test_handle_size() {
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use std::mem;
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assert_eq!(mem::size_of::<Handle>(), mem::size_of::<HandlePriv>());
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}
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struct Inner {
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/// The underlying system event queue.
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io: mio::Poll,
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/// ABA guard counter
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next_aba_guard: AtomicUsize,
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/// Dispatch slabs for I/O and futures events
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io_dispatch: RwLock<Slab<ScheduledIo>>,
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/// Used to wake up the reactor from a call to `turn`
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wakeup: mio::SetReadiness
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}
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struct ScheduledIo {
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aba_guard: usize,
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readiness: AtomicUsize,
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reader: AtomicTask,
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writer: AtomicTask,
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}
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#[derive(Debug, Eq, PartialEq, Clone, Copy)]
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pub(crate) enum Direction {
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Read,
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Write,
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}
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/// The global fallback reactor.
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static HANDLE_FALLBACK: AtomicUsize = AtomicUsize::new(0);
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/// Tracks the reactor for the current execution context.
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thread_local!(static CURRENT_REACTOR: RefCell<Option<HandlePriv>> = RefCell::new(None));
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const TOKEN_SHIFT: usize = 22;
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// Kind of arbitrary, but this reserves some token space for later usage.
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const MAX_SOURCES: usize = (1 << TOKEN_SHIFT) - 1;
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const TOKEN_WAKEUP: mio::Token = mio::Token(MAX_SOURCES);
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fn _assert_kinds() {
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fn _assert<T: Send + Sync>() {}
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_assert::<Handle>();
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}
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// ===== impl Reactor =====
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/// Set the default reactor for the duration of the closure
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///
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/// # Panics
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///
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/// This function panics if there already is a default reactor set.
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pub fn with_default<F, R>(handle: &Handle, enter: &mut Enter, f: F) -> R
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where F: FnOnce(&mut Enter) -> R
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{
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// Ensure that the executor is removed from the thread-local context
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// when leaving the scope. This handles cases that involve panicking.
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struct Reset;
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impl Drop for Reset {
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fn drop(&mut self) {
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CURRENT_REACTOR.with(|current| {
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let mut current = current.borrow_mut();
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*current = None;
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});
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}
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}
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// This ensures the value for the current reactor gets reset even if there
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// is a panic.
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let _r = Reset;
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CURRENT_REACTOR.with(|current| {
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{
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let mut current = current.borrow_mut();
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assert!(current.is_none(), "default Tokio reactor already set \
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for execution context");
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let handle = match handle.as_priv() {
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Some(handle) => handle,
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None => {
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panic!("`handle` does not reference a reactor");
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}
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};
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*current = Some(handle.clone());
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}
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f(enter)
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})
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}
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impl Reactor {
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/// Creates a new event loop, returning any error that happened during the
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/// creation.
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pub fn new() -> io::Result<Reactor> {
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let io = mio::Poll::new()?;
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let wakeup_pair = mio::Registration::new2();
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io.register(&wakeup_pair.0,
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TOKEN_WAKEUP,
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mio::Ready::readable(),
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mio::PollOpt::level())?;
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Ok(Reactor {
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events: mio::Events::with_capacity(1024),
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_wakeup_registration: wakeup_pair.0,
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inner: Arc::new(Inner {
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io: io,
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next_aba_guard: AtomicUsize::new(0),
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io_dispatch: RwLock::new(Slab::with_capacity(1)),
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wakeup: wakeup_pair.1,
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}),
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})
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}
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/// Returns a handle to this event loop which can be sent across threads
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/// and can be used as a proxy to the event loop itself.
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///
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/// Handles are cloneable and clones always refer to the same event loop.
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/// This handle is typically passed into functions that create I/O objects
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/// to bind them to this event loop.
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pub fn handle(&self) -> Handle {
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Handle {
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inner: Some(HandlePriv {
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inner: Arc::downgrade(&self.inner),
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}),
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}
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}
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/// Configures the fallback handle to be returned from `Handle::default`.
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///
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/// The `Handle::default()` function will by default lazily spin up a global
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/// thread and run a reactor on this global thread. This behavior is not
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/// always desirable in all applications, however, and sometimes a different
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/// fallback reactor is desired.
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///
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/// This function will attempt to globally alter the return value of
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/// `Handle::default()` to return the `handle` specified rather than a
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/// lazily initialized global thread. If successful then all future calls to
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/// `Handle::default()` which would otherwise fall back to the global thread
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/// will instead return a clone of the handle specified.
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///
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/// # Errors
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///
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/// This function may not always succeed in configuring the fallback handle.
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/// If this function was previously called (or perhaps concurrently called
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/// on many threads) only the *first* invocation of this function will
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/// succeed. All other invocations will return an error.
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///
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/// Additionally if the global reactor thread has already been initialized
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/// then this function will also return an error. (aka if `Handle::default`
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/// has been called previously in this program).
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pub fn set_fallback(&self) -> Result<(), SetFallbackError> {
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set_fallback(self.handle().into_priv().unwrap())
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}
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/// Performs one iteration of the event loop, blocking on waiting for events
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/// for at most `max_wait` (forever if `None`).
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///
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/// This method is the primary method of running this reactor and processing
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/// I/O events that occur. This method executes one iteration of an event
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/// loop, blocking at most once waiting for events to happen.
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///
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/// If a `max_wait` is specified then the method should block no longer than
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/// the duration specified, but this shouldn't be used as a super-precise
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/// timer but rather a "ballpark approximation"
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///
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/// # Return value
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///
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/// This function returns an instance of `Turn`
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///
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/// `Turn` as of today has no extra information with it and can be safely
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/// discarded. In the future `Turn` may contain information about what
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/// happened while this reactor blocked.
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///
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/// # Errors
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///
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/// This function may also return any I/O error which occurs when polling
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/// for readiness of I/O objects with the OS. This is quite unlikely to
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/// arise and typically mean that things have gone horribly wrong at that
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/// point. Currently this is primarily only known to happen for internal
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/// bugs to `tokio` itself.
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pub fn turn(&mut self, max_wait: Option<Duration>) -> io::Result<Turn> {
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self.poll(max_wait)?;
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Ok(Turn { _priv: () })
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}
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/// Returns true if the reactor is currently idle.
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///
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/// Idle is defined as all tasks that have been spawned have completed,
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/// either successfully or with an error.
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pub fn is_idle(&self) -> bool {
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self.inner.io_dispatch
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.read()
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.is_empty()
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}
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/// Run this reactor on a background thread.
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///
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/// This function takes ownership, spawns a new thread, and moves the
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/// reactor to this new thread. It then runs the reactor, driving all
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/// associated I/O resources, until the `Background` handle is dropped or
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/// explicitly shutdown.
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pub fn background(self) -> io::Result<Background> {
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Background::new(self)
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}
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fn poll(&mut self, max_wait: Option<Duration>) -> io::Result<()> {
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// Block waiting for an event to happen, peeling out how many events
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// happened.
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match self.inner.io.poll(&mut self.events, max_wait) {
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Ok(_) => {}
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Err(e) => return Err(e),
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}
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let start = if log_enabled!(Level::Debug) {
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Some(Instant::now())
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} else {
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None
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};
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// Process all the events that came in, dispatching appropriately
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let mut events = 0;
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for event in self.events.iter() {
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events += 1;
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let token = event.token();
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trace!("event {:?} {:?}", event.readiness(), event.token());
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if token == TOKEN_WAKEUP {
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self.inner.wakeup.set_readiness(mio::Ready::empty()).unwrap();
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} else {
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self.dispatch(token, event.readiness());
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}
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}
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if let Some(start) = start {
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let dur = start.elapsed();
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trace!("loop process - {} events, {}.{:03}s",
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events,
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dur.as_secs(),
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dur.subsec_nanos() / 1_000_000);
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}
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Ok(())
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}
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fn dispatch(&self, token: mio::Token, ready: mio::Ready) {
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let aba_guard = token.0 & !MAX_SOURCES;
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let token = token.0 & MAX_SOURCES;
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let mut rd = None;
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let mut wr = None;
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// Create a scope to ensure that notifying the tasks stays out of the
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// lock's critical section.
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{
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let io_dispatch = self.inner.io_dispatch.read();
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let io = match io_dispatch.get(token) {
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Some(io) => io,
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None => return,
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};
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if aba_guard != io.aba_guard {
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return;
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}
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io.readiness.fetch_or(ready.as_usize(), Relaxed);
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if ready.is_writable() || platform::is_hup(&ready) {
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wr = io.writer.take_to_notify();
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}
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if !(ready & (!mio::Ready::writable())).is_empty() {
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rd = io.reader.take_to_notify();
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}
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}
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if let Some(task) = rd {
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task.notify();
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}
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if let Some(task) = wr {
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task.notify();
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}
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}
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}
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impl Park for Reactor {
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type Unpark = Handle;
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type Error = io::Error;
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fn unpark(&self) -> Self::Unpark {
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self.handle()
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}
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fn park(&mut self) -> io::Result<()> {
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self.turn(None)?;
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Ok(())
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}
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fn park_timeout(&mut self, duration: Duration) -> io::Result<()> {
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self.turn(Some(duration))?;
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Ok(())
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}
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}
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impl fmt::Debug for Reactor {
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fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
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write!(f, "Reactor")
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}
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}
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// ===== impl Handle =====
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impl Handle {
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#[doc(hidden)]
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#[deprecated(note = "semantics were sometimes surprising, use Handle::default()")]
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pub fn current() -> Handle {
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// TODO: Should this panic on error?
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HandlePriv::try_current()
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.map(|handle| Handle {
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inner: Some(handle),
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})
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.unwrap_or(Handle {
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inner: Some(HandlePriv {
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inner: Weak::new(),
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})
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})
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}
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fn as_priv(&self) -> Option<&HandlePriv> {
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self.inner.as_ref()
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}
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fn into_priv(self) -> Option<HandlePriv> {
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self.inner
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}
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fn wakeup(&self) {
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if let Some(handle) = self.as_priv() {
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handle.wakeup();
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}
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}
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}
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impl Unpark for Handle {
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fn unpark(&self) {
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if let Some(ref h) = self.inner {
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h.wakeup();
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}
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}
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}
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impl Default for Handle {
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/// Returns a "default" handle, i.e., a handle that lazily binds to a reactor.
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fn default() -> Handle {
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Handle { inner: None }
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}
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}
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impl fmt::Debug for Handle {
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fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
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write!(f, "Handle")
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}
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}
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fn set_fallback(handle: HandlePriv) -> Result<(), SetFallbackError> {
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unsafe {
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let val = handle.into_usize();
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match HANDLE_FALLBACK.compare_exchange(0, val, SeqCst, SeqCst) {
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Ok(_) => Ok(()),
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Err(_) => {
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drop(HandlePriv::from_usize(val));
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Err(SetFallbackError(()))
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}
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}
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}
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}
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|
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// ===== impl HandlePriv =====
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|
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impl HandlePriv {
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/// Try to get a handle to the current reactor.
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///
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/// Returns `Err` if no handle is found.
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pub(crate) fn try_current() -> io::Result<HandlePriv> {
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CURRENT_REACTOR.with(|current| {
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match *current.borrow() {
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Some(ref handle) => Ok(handle.clone()),
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None => HandlePriv::fallback(),
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}
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})
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}
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/// Returns a handle to the fallback reactor.
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fn fallback() -> io::Result<HandlePriv> {
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let mut fallback = HANDLE_FALLBACK.load(SeqCst);
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|
// If the fallback hasn't been previously initialized then let's spin
|
|
// up a helper thread and try to initialize with that. If we can't
|
|
// actually create a helper thread then we'll just return a "defunct"
|
|
// handle which will return errors when I/O objects are attempted to be
|
|
// associated.
|
|
if fallback == 0 {
|
|
let reactor = match Reactor::new() {
|
|
Ok(reactor) => reactor,
|
|
Err(_) => return Err(io::Error::new(io::ErrorKind::Other,
|
|
"failed to create reactor")),
|
|
};
|
|
|
|
// If we successfully set ourselves as the actual fallback then we
|
|
// want to `forget` the helper thread to ensure that it persists
|
|
// globally. If we fail to set ourselves as the fallback that means
|
|
// that someone was racing with this call to `Handle::default`.
|
|
// They ended up winning so we'll destroy our helper thread (which
|
|
// shuts down the thread) and reload the fallback.
|
|
if set_fallback(reactor.handle().into_priv().unwrap()).is_ok() {
|
|
let ret = reactor.handle().into_priv().unwrap();
|
|
|
|
match reactor.background() {
|
|
Ok(bg) => bg.forget(),
|
|
// The global handle is fubar, but y'all probably got bigger
|
|
// problems if a thread can't spawn.
|
|
Err(_) => {}
|
|
}
|
|
|
|
return Ok(ret);
|
|
}
|
|
|
|
fallback = HANDLE_FALLBACK.load(SeqCst);
|
|
}
|
|
|
|
// At this point our fallback handle global was configured so we use
|
|
// its value to reify a handle, clone it, and then forget our reified
|
|
// handle as we don't actually have an owning reference to it.
|
|
assert!(fallback != 0);
|
|
|
|
let ret = unsafe {
|
|
let handle = HandlePriv::from_usize(fallback);
|
|
let ret = handle.clone();
|
|
|
|
// This prevents `handle` from being dropped and having the ref
|
|
// count decremented.
|
|
drop(handle.into_usize());
|
|
|
|
ret
|
|
};
|
|
|
|
Ok(ret)
|
|
}
|
|
|
|
/// Forces a reactor blocked in a call to `turn` to wakeup, or otherwise
|
|
/// makes the next call to `turn` return immediately.
|
|
///
|
|
/// This method is intended to be used in situations where a notification
|
|
/// needs to otherwise be sent to the main reactor. If the reactor is
|
|
/// currently blocked inside of `turn` then it will wake up and soon return
|
|
/// after this method has been called. If the reactor is not currently
|
|
/// blocked in `turn`, then the next call to `turn` will not block and
|
|
/// return immediately.
|
|
fn wakeup(&self) {
|
|
if let Some(inner) = self.inner() {
|
|
inner.wakeup.set_readiness(mio::Ready::readable()).unwrap();
|
|
}
|
|
}
|
|
|
|
fn into_usize(self) -> usize {
|
|
unsafe {
|
|
mem::transmute::<Weak<Inner>, usize>(self.inner)
|
|
}
|
|
}
|
|
|
|
unsafe fn from_usize(val: usize) -> HandlePriv {
|
|
let inner = mem::transmute::<usize, Weak<Inner>>(val);;
|
|
HandlePriv { inner }
|
|
}
|
|
|
|
fn inner(&self) -> Option<Arc<Inner>> {
|
|
self.inner.upgrade()
|
|
}
|
|
}
|
|
|
|
impl fmt::Debug for HandlePriv {
|
|
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
|
|
write!(f, "HandlePriv")
|
|
}
|
|
}
|
|
|
|
// ===== impl Inner =====
|
|
|
|
impl Inner {
|
|
/// Register an I/O resource with the reactor.
|
|
///
|
|
/// The registration token is returned.
|
|
fn add_source(&self, source: &Evented)
|
|
-> io::Result<usize>
|
|
{
|
|
// Get an ABA guard value
|
|
let aba_guard = self.next_aba_guard.fetch_add(1 << TOKEN_SHIFT, Relaxed);
|
|
|
|
let mut io_dispatch = self.io_dispatch.write();
|
|
|
|
if io_dispatch.len() == MAX_SOURCES {
|
|
return Err(io::Error::new(io::ErrorKind::Other, "reactor at max \
|
|
registered I/O resources"));
|
|
}
|
|
|
|
// Acquire a write lock
|
|
let key = io_dispatch.insert(ScheduledIo {
|
|
aba_guard,
|
|
readiness: AtomicUsize::new(0),
|
|
reader: AtomicTask::new(),
|
|
writer: AtomicTask::new(),
|
|
});
|
|
|
|
try!(self.io.register(source,
|
|
mio::Token(aba_guard | key),
|
|
mio::Ready::all(),
|
|
mio::PollOpt::edge()));
|
|
|
|
Ok(key)
|
|
}
|
|
|
|
/// Deregisters an I/O resource from the reactor.
|
|
fn deregister_source(&self, source: &Evented) -> io::Result<()> {
|
|
self.io.deregister(source)
|
|
}
|
|
|
|
fn drop_source(&self, token: usize) {
|
|
debug!("dropping I/O source: {}", token);
|
|
self.io_dispatch.write().remove(token);
|
|
}
|
|
|
|
/// Registers interest in the I/O resource associated with `token`.
|
|
fn register(&self, token: usize, dir: Direction, t: Task) {
|
|
debug!("scheduling direction for: {}", token);
|
|
let io_dispatch = self.io_dispatch.read();
|
|
let sched = io_dispatch.get(token).unwrap();
|
|
|
|
let (task, ready) = match dir {
|
|
Direction::Read => (&sched.reader, !mio::Ready::writable()),
|
|
Direction::Write => (&sched.writer, mio::Ready::writable()),
|
|
};
|
|
|
|
task.register_task(t);
|
|
|
|
if sched.readiness.load(SeqCst) & ready.as_usize() != 0 {
|
|
task.notify();
|
|
}
|
|
}
|
|
}
|
|
|
|
impl Drop for Inner {
|
|
fn drop(&mut self) {
|
|
// When a reactor is dropped it needs to wake up all blocked tasks as
|
|
// they'll never receive a notification, and all connected I/O objects
|
|
// will start returning errors pretty quickly.
|
|
let io = self.io_dispatch.read();
|
|
for (_, io) in io.iter() {
|
|
io.writer.notify();
|
|
io.reader.notify();
|
|
}
|
|
}
|
|
}
|
|
|
|
impl Direction {
|
|
fn mask(&self) -> mio::Ready {
|
|
match *self {
|
|
Direction::Read => {
|
|
// Everything except writable is signaled through read.
|
|
mio::Ready::all() - mio::Ready::writable()
|
|
}
|
|
Direction::Write => mio::Ready::writable() | platform::hup(),
|
|
}
|
|
}
|
|
}
|
|
|
|
#[cfg(unix)]
|
|
mod platform {
|
|
use mio::Ready;
|
|
use mio::unix::UnixReady;
|
|
|
|
pub fn hup() -> Ready {
|
|
UnixReady::hup().into()
|
|
}
|
|
|
|
pub fn is_hup(ready: &Ready) -> bool {
|
|
UnixReady::from(*ready).is_hup()
|
|
}
|
|
}
|
|
|
|
#[cfg(windows)]
|
|
mod platform {
|
|
use mio::Ready;
|
|
|
|
pub fn hup() -> Ready {
|
|
Ready::empty()
|
|
}
|
|
|
|
pub fn is_hup(_: &Ready) -> bool {
|
|
false
|
|
}
|
|
}
|
|
|
|
// ===== impl SetFallbackError =====
|
|
|
|
impl fmt::Display for SetFallbackError {
|
|
fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
|
|
write!(fmt, "{}", self.description())
|
|
}
|
|
}
|
|
|
|
impl Error for SetFallbackError {
|
|
fn description(&self) -> &str {
|
|
"attempted to set fallback reactor while already configured"
|
|
}
|
|
}
|