switch to smol instead of an internal runtime
dignifiedquire
5 years ago
parent
690ab16587
commit
1308fbdf55
@ -1,354 +0,0 @@
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use std::fmt;
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use std::sync::{Arc, Mutex};
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use std::time::Duration;
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use mio::{self, Evented};
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use slab::Slab;
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use crate::io;
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use crate::rt::RUNTIME;
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use crate::task::{Context, Poll, Waker};
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/// Data associated with a registered I/O handle.
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#[derive(Debug)]
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struct Entry {
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/// A unique identifier.
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token: mio::Token,
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/// Tasks that are blocked on reading from this I/O handle.
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readers: Mutex<Readers>,
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/// Tasks that are blocked on writing to this I/O handle.
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writers: Mutex<Writers>,
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}
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/// The state of a networking driver.
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pub struct Reactor {
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/// A mio instance that polls for new events.
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poller: mio::Poll,
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/// A list into which mio stores events.
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events: Mutex<mio::Events>,
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/// A collection of registered I/O handles.
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entries: Mutex<Slab<Arc<Entry>>>,
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/// Dummy I/O handle that is only used to wake up the polling thread.
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notify_reg: (mio::Registration, mio::SetReadiness),
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/// An identifier for the notification handle.
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notify_token: mio::Token,
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}
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/// The set of `Waker`s interested in read readiness.
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#[derive(Debug)]
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struct Readers {
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/// Flag indicating read readiness.
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/// (cf. `Watcher::poll_read_ready`)
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ready: bool,
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/// The `Waker`s blocked on reading.
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wakers: Vec<Waker>,
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}
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/// The set of `Waker`s interested in write readiness.
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#[derive(Debug)]
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struct Writers {
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/// Flag indicating write readiness.
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/// (cf. `Watcher::poll_write_ready`)
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ready: bool,
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/// The `Waker`s blocked on writing.
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wakers: Vec<Waker>,
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}
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impl Reactor {
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/// Creates a new reactor for polling I/O events.
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pub fn new() -> io::Result<Reactor> {
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let poller = mio::Poll::new()?;
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let notify_reg = mio::Registration::new2();
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let mut reactor = Reactor {
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poller,
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events: Mutex::new(mio::Events::with_capacity(1000)),
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entries: Mutex::new(Slab::new()),
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notify_reg,
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notify_token: mio::Token(0),
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};
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// Register a dummy I/O handle for waking up the polling thread.
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let entry = reactor.register(&reactor.notify_reg.0)?;
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reactor.notify_token = entry.token;
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Ok(reactor)
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}
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/// Registers an I/O event source and returns its associated entry.
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fn register(&self, source: &dyn Evented) -> io::Result<Arc<Entry>> {
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let mut entries = self.entries.lock().unwrap();
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// Reserve a vacant spot in the slab and use its key as the token value.
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let vacant = entries.vacant_entry();
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let token = mio::Token(vacant.key());
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// Allocate an entry and insert it into the slab.
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let entry = Arc::new(Entry {
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token,
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readers: Mutex::new(Readers {
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ready: false,
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wakers: Vec::new(),
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}),
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writers: Mutex::new(Writers {
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ready: false,
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wakers: Vec::new(),
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}),
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});
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vacant.insert(entry.clone());
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// Register the I/O event source in the poller.
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let interest = mio::Ready::all();
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let opts = mio::PollOpt::edge();
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self.poller.register(source, token, interest, opts)?;
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Ok(entry)
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}
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/// Deregisters an I/O event source associated with an entry.
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fn deregister(&self, source: &dyn Evented, entry: &Entry) -> io::Result<()> {
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// Deregister the I/O object from the mio instance.
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self.poller.deregister(source)?;
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// Remove the entry associated with the I/O object.
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self.entries.lock().unwrap().remove(entry.token.0);
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Ok(())
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}
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/// Notifies the reactor so that polling stops blocking.
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pub fn notify(&self) -> io::Result<()> {
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self.notify_reg.1.set_readiness(mio::Ready::readable())
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}
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/// Waits on the poller for new events and wakes up tasks blocked on I/O handles.
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///
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/// Returns `Ok(true)` if at least one new task was woken.
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pub fn poll(&self, timeout: Option<Duration>) -> io::Result<bool> {
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let mut events = self.events.lock().unwrap();
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// Block on the poller until at least one new event comes in.
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self.poller.poll(&mut events, timeout)?;
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// Lock the entire entry table while we're processing new events.
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let entries = self.entries.lock().unwrap();
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// The number of woken tasks.
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let mut progress = false;
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for event in events.iter() {
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let token = event.token();
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if token == self.notify_token {
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// If this is the notification token, we just need the notification state.
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self.notify_reg.1.set_readiness(mio::Ready::empty())?;
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} else {
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// Otherwise, look for the entry associated with this token.
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if let Some(entry) = entries.get(token.0) {
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// Set the readiness flags from this I/O event.
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let readiness = event.readiness();
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// Wake up reader tasks blocked on this I/O handle.
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let reader_interests = mio::Ready::all() - mio::Ready::writable();
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if !(readiness & reader_interests).is_empty() {
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let mut readers = entry.readers.lock().unwrap();
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readers.ready = true;
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for w in readers.wakers.drain(..) {
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w.wake();
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progress = true;
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}
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}
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// Wake up writer tasks blocked on this I/O handle.
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let writer_interests = mio::Ready::all() - mio::Ready::readable();
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if !(readiness & writer_interests).is_empty() {
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let mut writers = entry.writers.lock().unwrap();
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writers.ready = true;
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for w in writers.wakers.drain(..) {
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w.wake();
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progress = true;
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}
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}
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}
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}
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}
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Ok(progress)
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}
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}
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/// An I/O handle powered by the networking driver.
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///
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/// This handle wraps an I/O event source and exposes a "futurized" interface on top of it,
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/// implementing traits `AsyncRead` and `AsyncWrite`.
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pub struct Watcher<T: Evented> {
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/// Data associated with the I/O handle.
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entry: Arc<Entry>,
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/// The I/O event source.
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source: Option<T>,
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}
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impl<T: Evented> Watcher<T> {
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/// Creates a new I/O handle.
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///
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/// The provided I/O event source will be kept registered inside the reactor's poller for the
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/// lifetime of the returned I/O handle.
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pub fn new(source: T) -> Watcher<T> {
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Watcher {
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entry: RUNTIME
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.reactor()
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.register(&source)
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.expect("cannot register an I/O event source"),
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source: Some(source),
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}
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}
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/// Returns a reference to the inner I/O event source.
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pub fn get_ref(&self) -> &T {
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self.source.as_ref().unwrap()
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}
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/// Polls the inner I/O source for a non-blocking read operation.
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///
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/// If the operation returns an error of the `io::ErrorKind::WouldBlock` kind, the current task
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/// will be registered for wakeup when the I/O source becomes readable.
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pub fn poll_read_with<'a, F, R>(&'a self, cx: &mut Context<'_>, mut f: F) -> Poll<io::Result<R>>
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where
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F: FnMut(&'a T) -> io::Result<R>,
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{
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// If the operation isn't blocked, return its result.
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match f(self.source.as_ref().unwrap()) {
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Err(err) if err.kind() == io::ErrorKind::WouldBlock => {}
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res => return Poll::Ready(res),
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}
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// Lock the waker list.
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let mut readers = self.entry.readers.lock().unwrap();
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// Try running the operation again.
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match f(self.source.as_ref().unwrap()) {
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Err(err) if err.kind() == io::ErrorKind::WouldBlock => {}
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res => return Poll::Ready(res),
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}
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// Register the task if it isn't registered already.
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if readers.wakers.iter().all(|w| !w.will_wake(cx.waker())) {
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readers.wakers.push(cx.waker().clone());
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}
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Poll::Pending
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}
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/// Polls the inner I/O source for a non-blocking write operation.
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///
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/// If the operation returns an error of the `io::ErrorKind::WouldBlock` kind, the current task
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/// will be registered for wakeup when the I/O source becomes writable.
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pub fn poll_write_with<'a, F, R>(
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&'a self,
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cx: &mut Context<'_>,
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mut f: F,
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) -> Poll<io::Result<R>>
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where
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F: FnMut(&'a T) -> io::Result<R>,
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{
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// If the operation isn't blocked, return its result.
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match f(self.source.as_ref().unwrap()) {
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Err(err) if err.kind() == io::ErrorKind::WouldBlock => {}
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res => return Poll::Ready(res),
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}
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// Lock the waker list.
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let mut writers = self.entry.writers.lock().unwrap();
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// Try running the operation again.
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match f(self.source.as_ref().unwrap()) {
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Err(err) if err.kind() == io::ErrorKind::WouldBlock => {}
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res => return Poll::Ready(res),
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}
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// Register the task if it isn't registered already.
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if writers.wakers.iter().all(|w| !w.will_wake(cx.waker())) {
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writers.wakers.push(cx.waker().clone());
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}
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Poll::Pending
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}
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/// Polls the inner I/O source until a non-blocking read can be performed.
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///
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/// If non-blocking reads are currently not possible, the `Waker`
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/// will be saved and notified when it can read non-blocking
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/// again.
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#[allow(dead_code)]
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pub fn poll_read_ready(&self, cx: &mut Context<'_>) -> Poll<()> {
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// Lock the waker list.
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let mut readers = self.entry.readers.lock().unwrap();
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if readers.ready {
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return Poll::Ready(());
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}
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// Register the task if it isn't registered already.
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if readers.wakers.iter().all(|w| !w.will_wake(cx.waker())) {
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readers.wakers.push(cx.waker().clone());
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}
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Poll::Pending
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}
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/// Polls the inner I/O source until a non-blocking write can be performed.
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///
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/// If non-blocking writes are currently not possible, the `Waker`
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/// will be saved and notified when it can write non-blocking
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/// again.
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pub fn poll_write_ready(&self, cx: &mut Context<'_>) -> Poll<()> {
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// Lock the waker list.
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let mut writers = self.entry.writers.lock().unwrap();
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if writers.ready {
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return Poll::Ready(());
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}
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// Register the task if it isn't registered already.
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if writers.wakers.iter().all(|w| !w.will_wake(cx.waker())) {
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writers.wakers.push(cx.waker().clone());
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}
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Poll::Pending
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}
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/// Deregisters and returns the inner I/O source.
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///
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/// This method is typically used to convert `Watcher`s to raw file descriptors/handles.
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#[allow(dead_code)]
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pub fn into_inner(mut self) -> T {
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let source = self.source.take().unwrap();
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RUNTIME
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.reactor()
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.deregister(&source, &self.entry)
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.expect("cannot deregister I/O event source");
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source
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}
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}
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impl<T: Evented> Drop for Watcher<T> {
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fn drop(&mut self) {
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if let Some(ref source) = self.source {
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RUNTIME
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.reactor()
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.deregister(source, &self.entry)
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.expect("cannot deregister I/O event source");
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}
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}
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}
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impl<T: Evented + fmt::Debug> fmt::Debug for Watcher<T> {
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fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
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f.debug_struct("Watcher")
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.field("entry", &self.entry)
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.field("source", &self.source)
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.finish()
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}
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}
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@ -1,415 +0,0 @@
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use std::cell::Cell;
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use std::io;
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use std::iter;
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use std::ptr;
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use std::sync::atomic::{self, Ordering};
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use std::sync::{Arc, Mutex};
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use std::thread;
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use std::time::Duration;
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use crossbeam_deque::{Injector, Steal, Stealer, Worker};
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use crossbeam_utils::thread::scope;
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use once_cell::unsync::OnceCell;
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use crate::rt::Reactor;
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use crate::sync::Spinlock;
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use crate::task::Runnable;
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use crate::utils::{abort_on_panic, random};
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thread_local! {
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/// A reference to the current machine, if the current thread runs tasks.
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static MACHINE: OnceCell<Arc<Machine>> = OnceCell::new();
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/// This flag is set to true whenever `task::yield_now()` is invoked.
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static YIELD_NOW: Cell<bool> = Cell::new(false);
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}
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struct Scheduler {
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/// Set to `true` while a machine is polling the reactor.
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polling: bool,
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/// Idle processors.
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processors: Vec<Processor>,
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/// Running machines.
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machines: Vec<Arc<Machine>>,
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}
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/// An async runtime.
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pub struct Runtime {
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/// The reactor.
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reactor: Reactor,
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/// The global queue of tasks.
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injector: Injector<Runnable>,
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/// Handles to local queues for stealing work.
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stealers: Vec<Stealer<Runnable>>,
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/// The scheduler state.
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sched: Mutex<Scheduler>,
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}
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impl Runtime {
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/// Creates a new runtime.
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pub fn new() -> Runtime {
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let cpus = num_cpus::get().max(1);
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let processors: Vec<_> = (0..cpus).map(|_| Processor::new()).collect();
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let stealers = processors.iter().map(|p| p.worker.stealer()).collect();
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Runtime {
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reactor: Reactor::new().unwrap(),
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injector: Injector::new(),
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stealers,
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sched: Mutex::new(Scheduler {
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processors,
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machines: Vec::new(),
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polling: false,
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}),
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}
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}
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/// Returns a reference to the reactor.
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pub fn reactor(&self) -> &Reactor {
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&self.reactor
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}
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/// Flushes the task slot so that tasks get run more fairly.
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pub fn yield_now(&self) {
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YIELD_NOW.with(|flag| flag.set(true));
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}
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/// Schedules a task.
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pub fn schedule(&self, task: Runnable) {
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MACHINE.with(|machine| {
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// If the current thread is a worker thread, schedule it onto the current machine.
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// Otherwise, push it into the global task queue.
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match machine.get() {
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None => {
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self.injector.push(task);
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self.notify();
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}
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Some(m) => m.schedule(&self, task),
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}
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});
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}
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/// Runs the runtime on the current thread.
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pub fn run(&self) {
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scope(|s| {
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let mut idle = 0;
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let mut delay = 0;
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loop {
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// Get a list of new machines to start, if any need to be started.
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for m in self.make_machines() {
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idle = 0;
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s.builder()
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.name("async-std/machine".to_string())
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.spawn(move |_| {
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abort_on_panic(|| {
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let _ = MACHINE.with(|machine| machine.set(m.clone()));
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m.run(self);
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})
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})
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.expect("cannot start a machine thread");
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}
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// Sleep for a bit longer if the scheduler state hasn't changed in a while.
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if idle > 10 {
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delay = (delay * 2).min(10_000);
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} else {
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idle += 1;
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delay = 1000;
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}
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thread::sleep(Duration::from_micros(delay));
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}
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})
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.unwrap();
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}
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/// Returns a list of machines that need to be started.
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fn make_machines(&self) -> Vec<Arc<Machine>> {
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let mut sched = self.sched.lock().unwrap();
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let mut to_start = Vec::new();
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// If no machine has been polling the reactor in a while, that means the runtime is
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// overloaded with work and we need to start another machine.
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if !sched.polling {
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if let Some(p) = sched.processors.pop() {
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let m = Arc::new(Machine::new(p));
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||||
to_start.push(m.clone());
|
||||
sched.machines.push(m);
|
||||
}
|
||||
}
|
||||
|
||||
to_start
|
||||
}
|
||||
|
||||
/// Unparks a thread polling the reactor.
|
||||
fn notify(&self) {
|
||||
atomic::fence(Ordering::SeqCst);
|
||||
self.reactor.notify().unwrap();
|
||||
}
|
||||
|
||||
/// Attempts to poll the reactor without blocking on it.
|
||||
///
|
||||
/// Returns `Ok(true)` if at least one new task was woken.
|
||||
///
|
||||
/// This function might not poll the reactor at all so do not rely on it doing anything. Only
|
||||
/// use for optimization.
|
||||
fn quick_poll(&self) -> io::Result<bool> {
|
||||
if let Ok(sched) = self.sched.try_lock() {
|
||||
if !sched.polling {
|
||||
return self.reactor.poll(Some(Duration::from_secs(0)));
|
||||
}
|
||||
}
|
||||
Ok(false)
|
||||
}
|
||||
}
|
||||
|
||||
/// A thread running a processor.
|
||||
struct Machine {
|
||||
/// Holds the processor until it gets stolen.
|
||||
processor: Spinlock<Option<Processor>>,
|
||||
}
|
||||
|
||||
impl Machine {
|
||||
/// Creates a new machine running a processor.
|
||||
fn new(p: Processor) -> Machine {
|
||||
Machine {
|
||||
processor: Spinlock::new(Some(p)),
|
||||
}
|
||||
}
|
||||
|
||||
/// Schedules a task onto the machine.
|
||||
fn schedule(&self, rt: &Runtime, task: Runnable) {
|
||||
match self.processor.lock().as_mut() {
|
||||
None => {
|
||||
rt.injector.push(task);
|
||||
rt.notify();
|
||||
}
|
||||
Some(p) => p.schedule(rt, task),
|
||||
}
|
||||
}
|
||||
|
||||
/// Finds the next runnable task.
|
||||
fn find_task(&self, rt: &Runtime) -> Steal<Runnable> {
|
||||
let mut retry = false;
|
||||
|
||||
// First try finding a task in the local queue or in the global queue.
|
||||
if let Some(p) = self.processor.lock().as_mut() {
|
||||
if let Some(task) = p.pop_task() {
|
||||
return Steal::Success(task);
|
||||
}
|
||||
|
||||
match p.steal_from_global(rt) {
|
||||
Steal::Empty => {}
|
||||
Steal::Retry => retry = true,
|
||||
Steal::Success(task) => return Steal::Success(task),
|
||||
}
|
||||
}
|
||||
|
||||
// Try polling the reactor, but don't block on it.
|
||||
let progress = rt.quick_poll().unwrap();
|
||||
|
||||
// Try finding a task in the local queue, which might hold tasks woken by the reactor. If
|
||||
// the local queue is still empty, try stealing from other processors.
|
||||
if let Some(p) = self.processor.lock().as_mut() {
|
||||
if progress {
|
||||
if let Some(task) = p.pop_task() {
|
||||
return Steal::Success(task);
|
||||
}
|
||||
}
|
||||
|
||||
match p.steal_from_others(rt) {
|
||||
Steal::Empty => {}
|
||||
Steal::Retry => retry = true,
|
||||
Steal::Success(task) => return Steal::Success(task),
|
||||
}
|
||||
}
|
||||
|
||||
if retry { Steal::Retry } else { Steal::Empty }
|
||||
}
|
||||
|
||||
/// Runs the machine on the current thread.
|
||||
fn run(&self, rt: &Runtime) {
|
||||
/// Number of yields when no runnable task is found.
|
||||
const YIELDS: u32 = 3;
|
||||
/// Number of short sleeps when no runnable task in found.
|
||||
const SLEEPS: u32 = 10;
|
||||
/// Number of runs in a row before the global queue is inspected.
|
||||
const RUNS: u32 = 64;
|
||||
|
||||
// The number of times the thread found work in a row.
|
||||
let mut runs = 0;
|
||||
// The number of times the thread didn't find work in a row.
|
||||
let mut fails = 0;
|
||||
|
||||
loop {
|
||||
// Check if `task::yield_now()` was invoked and flush the slot if so.
|
||||
YIELD_NOW.with(|flag| {
|
||||
if flag.replace(false) {
|
||||
if let Some(p) = self.processor.lock().as_mut() {
|
||||
p.flush_slot(rt);
|
||||
}
|
||||
}
|
||||
});
|
||||
|
||||
// After a number of runs in a row, do some work to ensure no task is left behind
|
||||
// indefinitely. Poll the reactor, steal tasks from the global queue, and flush the
|
||||
// task slot.
|
||||
if runs >= RUNS {
|
||||
runs = 0;
|
||||
rt.quick_poll().unwrap();
|
||||
|
||||
if let Some(p) = self.processor.lock().as_mut() {
|
||||
if let Steal::Success(task) = p.steal_from_global(rt) {
|
||||
p.schedule(rt, task);
|
||||
}
|
||||
|
||||
p.flush_slot(rt);
|
||||
}
|
||||
}
|
||||
|
||||
// Try to find a runnable task.
|
||||
if let Steal::Success(task) = self.find_task(rt) {
|
||||
task.run();
|
||||
runs += 1;
|
||||
fails = 0;
|
||||
continue;
|
||||
}
|
||||
|
||||
fails += 1;
|
||||
|
||||
// Yield the current thread a few times.
|
||||
if fails <= YIELDS {
|
||||
thread::yield_now();
|
||||
continue;
|
||||
}
|
||||
|
||||
// Put the current thread to sleep a few times.
|
||||
if fails <= YIELDS + SLEEPS {
|
||||
let opt_p = self.processor.lock().take();
|
||||
thread::sleep(Duration::from_micros(10));
|
||||
*self.processor.lock() = opt_p;
|
||||
continue;
|
||||
}
|
||||
|
||||
let mut sched = rt.sched.lock().unwrap();
|
||||
|
||||
// One final check for available tasks while the scheduler is locked.
|
||||
if let Some(task) = iter::repeat_with(|| self.find_task(rt))
|
||||
.find(|s| !s.is_retry())
|
||||
.and_then(|s| s.success())
|
||||
{
|
||||
self.schedule(rt, task);
|
||||
continue;
|
||||
}
|
||||
|
||||
// If another thread is already blocked on the reactor, there is no point in keeping
|
||||
// the current thread around since there is too little work to do.
|
||||
if sched.polling {
|
||||
break;
|
||||
}
|
||||
|
||||
// Take out the machine associated with the current thread.
|
||||
let m = match sched
|
||||
.machines
|
||||
.iter()
|
||||
.position(|elem| ptr::eq(&**elem, self))
|
||||
{
|
||||
None => break, // The processor was stolen.
|
||||
Some(pos) => sched.machines.swap_remove(pos),
|
||||
};
|
||||
|
||||
// Unlock the schedule poll the reactor until new I/O events arrive.
|
||||
sched.polling = true;
|
||||
drop(sched);
|
||||
rt.reactor.poll(None).unwrap();
|
||||
|
||||
// Lock the scheduler again and re-register the machine.
|
||||
sched = rt.sched.lock().unwrap();
|
||||
sched.polling = false;
|
||||
sched.machines.push(m);
|
||||
|
||||
runs = 0;
|
||||
fails = 0;
|
||||
}
|
||||
|
||||
// When shutting down the thread, take the processor out if still available.
|
||||
let opt_p = self.processor.lock().take();
|
||||
|
||||
// Return the processor to the scheduler and remove the machine.
|
||||
if let Some(p) = opt_p {
|
||||
let mut sched = rt.sched.lock().unwrap();
|
||||
sched.processors.push(p);
|
||||
sched.machines.retain(|elem| !ptr::eq(&**elem, self));
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
struct Processor {
|
||||
/// The local task queue.
|
||||
worker: Worker<Runnable>,
|
||||
|
||||
/// Contains the next task to run as an optimization that skips the queue.
|
||||
slot: Option<Runnable>,
|
||||
}
|
||||
|
||||
impl Processor {
|
||||
/// Creates a new processor.
|
||||
fn new() -> Processor {
|
||||
Processor {
|
||||
worker: Worker::new_fifo(),
|
||||
slot: None,
|
||||
}
|
||||
}
|
||||
|
||||
/// Schedules a task to run on this processor.
|
||||
fn schedule(&mut self, rt: &Runtime, task: Runnable) {
|
||||
match self.slot.replace(task) {
|
||||
None => {}
|
||||
Some(task) => {
|
||||
self.worker.push(task);
|
||||
rt.notify();
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
/// Flushes a task from the slot into the local queue.
|
||||
fn flush_slot(&mut self, rt: &Runtime) {
|
||||
if let Some(task) = self.slot.take() {
|
||||
self.worker.push(task);
|
||||
rt.notify();
|
||||
}
|
||||
}
|
||||
|
||||
/// Pops a task from this processor.
|
||||
fn pop_task(&mut self) -> Option<Runnable> {
|
||||
self.slot.take().or_else(|| self.worker.pop())
|
||||
}
|
||||
|
||||
/// Steals a task from the global queue.
|
||||
fn steal_from_global(&self, rt: &Runtime) -> Steal<Runnable> {
|
||||
rt.injector.steal_batch_and_pop(&self.worker)
|
||||
}
|
||||
|
||||
/// Steals a task from other processors.
|
||||
fn steal_from_others(&self, rt: &Runtime) -> Steal<Runnable> {
|
||||
// Pick a random starting point in the list of queues.
|
||||
let len = rt.stealers.len();
|
||||
let start = random(len as u32) as usize;
|
||||
|
||||
// Create an iterator over stealers that starts from the chosen point.
|
||||
let (l, r) = rt.stealers.split_at(start);
|
||||
let stealers = r.iter().chain(l.iter());
|
||||
|
||||
// Try stealing a batch of tasks from each queue.
|
||||
stealers
|
||||
.map(|s| s.steal_batch_and_pop(&self.worker))
|
||||
.collect()
|
||||
}
|
||||
}
|
||||
@ -1,89 +0,0 @@
|
||||
use std::cell::UnsafeCell;
|
||||
use std::ops::{Deref, DerefMut};
|
||||
use std::sync::atomic::{AtomicBool, Ordering};
|
||||
|
||||
use crossbeam_utils::Backoff;
|
||||
|
||||
/// A simple spinlock.
|
||||
#[derive(Debug)]
|
||||
pub struct Spinlock<T> {
|
||||
locked: AtomicBool,
|
||||
value: UnsafeCell<T>,
|
||||
}
|
||||
|
||||
unsafe impl<T: Send> Send for Spinlock<T> {}
|
||||
unsafe impl<T: Send> Sync for Spinlock<T> {}
|
||||
|
||||
impl<T> Spinlock<T> {
|
||||
/// Returns a new spinlock initialized with `value`.
|
||||
pub const fn new(value: T) -> Spinlock<T> {
|
||||
Spinlock {
|
||||
locked: AtomicBool::new(false),
|
||||
value: UnsafeCell::new(value),
|
||||
}
|
||||
}
|
||||
|
||||
/// Locks the spinlock.
|
||||
pub fn lock(&self) -> SpinlockGuard<'_, T> {
|
||||
let backoff = Backoff::new();
|
||||
while self.locked.compare_and_swap(false, true, Ordering::Acquire) {
|
||||
backoff.snooze();
|
||||
}
|
||||
SpinlockGuard { parent: self }
|
||||
}
|
||||
}
|
||||
|
||||
/// A guard holding a spinlock locked.
|
||||
#[derive(Debug)]
|
||||
pub struct SpinlockGuard<'a, T> {
|
||||
parent: &'a Spinlock<T>,
|
||||
}
|
||||
|
||||
unsafe impl<T: Send> Send for SpinlockGuard<'_, T> {}
|
||||
unsafe impl<T: Sync> Sync for SpinlockGuard<'_, T> {}
|
||||
|
||||
impl<'a, T> Drop for SpinlockGuard<'a, T> {
|
||||
fn drop(&mut self) {
|
||||
self.parent.locked.store(false, Ordering::Release);
|
||||
}
|
||||
}
|
||||
|
||||
impl<'a, T> Deref for SpinlockGuard<'a, T> {
|
||||
type Target = T;
|
||||
|
||||
fn deref(&self) -> &T {
|
||||
unsafe { &*self.parent.value.get() }
|
||||
}
|
||||
}
|
||||
|
||||
impl<'a, T> DerefMut for SpinlockGuard<'a, T> {
|
||||
fn deref_mut(&mut self) -> &mut T {
|
||||
unsafe { &mut *self.parent.value.get() }
|
||||
}
|
||||
}
|
||||
|
||||
#[test]
|
||||
fn spinlock() {
|
||||
use std::sync::Arc;
|
||||
|
||||
use crate::sync::{Spinlock};
|
||||
use crate::task;
|
||||
|
||||
task::block_on(async {
|
||||
|
||||
let m = Arc::new(Spinlock::new(0));
|
||||
let mut tasks = vec![];
|
||||
|
||||
for _ in 0..10 {
|
||||
let m = m.clone();
|
||||
tasks.push(task::spawn(async move {
|
||||
*m.lock() += 1;
|
||||
}));
|
||||
}
|
||||
|
||||
for t in tasks {
|
||||
t.await;
|
||||
}
|
||||
assert_eq!(*m.lock(), 10);
|
||||
})
|
||||
}
|
||||
Loading…
Reference in New Issue