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+# with all versions of Cargo and also rewrite `path` dependencies
+# to registry (e.g., crates.io) dependencies.
+#
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--- /dev/null
+ Apache License
+ Version 2.0, January 2004
+ http://www.apache.org/licenses/
+
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+ file or class name and description of purpose be included on the
+ same "printed page" as the copyright notice for easier
+ identification within third-party archives.
+
+Copyright [yyyy] [name of copyright owner]
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+ http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
--- /dev/null
+Permission is hereby granted, free of charge, to any
+person obtaining a copy of this software and associated
+documentation files (the "Software"), to deal in the
+Software without restriction, including without
+limitation the rights to use, copy, modify, merge,
+publish, distribute, sublicense, and/or sell copies of
+the Software, and to permit persons to whom the Software
+is furnished to do so, subject to the following
+conditions:
+
+The above copyright notice and this permission notice
+shall be included in all copies or substantial portions
+of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF
+ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED
+TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A
+PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT
+SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
+CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR
+IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+DEALINGS IN THE SOFTWARE.
--- /dev/null
+# async-executor
+
+[](
+https://github.com/smol-rs/async-executor/actions)
+[](
+https://github.com/smol-rs/async-executor)
+[](
+https://crates.io/crates/async-executor)
+[](
+https://docs.rs/async-executor)
+
+Async executors.
+
+## Examples
+
+```rust
+use async_executor::Executor;
+use futures_lite::future;
+
+// Create a new executor.
+let ex = Executor::new();
+
+// Spawn a task.
+let task = ex.spawn(async {
+ println!("Hello world");
+});
+
+// Run the executor until the task completes.
+future::block_on(ex.run(task));
+```
+
+## License
+
+Licensed under either of
+
+ * Apache License, Version 2.0 ([LICENSE-APACHE](LICENSE-APACHE) or http://www.apache.org/licenses/LICENSE-2.0)
+ * MIT license ([LICENSE-MIT](LICENSE-MIT) or http://opensource.org/licenses/MIT)
+
+at your option.
+
+#### Contribution
+
+Unless you explicitly state otherwise, any contribution intentionally submitted
+for inclusion in the work by you, as defined in the Apache-2.0 license, shall be
+dual licensed as above, without any additional terms or conditions.
--- /dev/null
+#![feature(test)]
+
+extern crate test;
+
+use std::future::Future;
+
+use async_executor::Executor;
+use futures_lite::{future, prelude::*};
+
+const TASKS: usize = 300;
+const STEPS: usize = 300;
+const LIGHT_TASKS: usize = 25_000;
+
+static EX: Executor<'_> = Executor::new();
+
+fn run(f: impl FnOnce()) {
+ let (s, r) = async_channel::bounded::<()>(1);
+ easy_parallel::Parallel::new()
+ .each(0..num_cpus::get(), |_| future::block_on(EX.run(r.recv())))
+ .finish(move || {
+ let _s = s;
+ f()
+ });
+}
+
+#[bench]
+fn create(b: &mut test::Bencher) {
+ b.iter(move || {
+ let ex = Executor::new();
+ let task = ex.spawn(async {});
+ future::block_on(ex.run(task));
+ });
+}
+
+#[bench]
+fn spawn_one(b: &mut test::Bencher) {
+ run(|| {
+ b.iter(move || {
+ future::block_on(async { EX.spawn(async {}).await });
+ });
+ });
+}
+
+#[bench]
+fn spawn_many(b: &mut test::Bencher) {
+ run(|| {
+ b.iter(move || {
+ future::block_on(async {
+ let mut tasks = Vec::new();
+ for _ in 0..LIGHT_TASKS {
+ tasks.push(EX.spawn(async {}));
+ }
+ for task in tasks {
+ task.await;
+ }
+ });
+ });
+ });
+}
+
+#[bench]
+fn spawn_recursively(b: &mut test::Bencher) {
+ fn go(i: usize) -> impl Future<Output = ()> + Send + 'static {
+ async move {
+ if i != 0 {
+ EX.spawn(async move {
+ let fut = go(i - 1).boxed();
+ fut.await;
+ })
+ .await;
+ }
+ }
+ }
+
+ run(|| {
+ b.iter(move || {
+ future::block_on(async {
+ let mut tasks = Vec::new();
+ for _ in 0..TASKS {
+ tasks.push(EX.spawn(go(STEPS)));
+ }
+ for task in tasks {
+ task.await;
+ }
+ });
+ });
+ });
+}
+
+#[bench]
+fn yield_now(b: &mut test::Bencher) {
+ run(|| {
+ b.iter(move || {
+ future::block_on(async {
+ let mut tasks = Vec::new();
+ for _ in 0..TASKS {
+ tasks.push(EX.spawn(async move {
+ for _ in 0..STEPS {
+ future::yield_now().await;
+ }
+ }));
+ }
+ for task in tasks {
+ task.await;
+ }
+ });
+ });
+ });
+}
--- /dev/null
+//! An executor with task priorities.
+
+use std::future::Future;
+use std::thread;
+
+use async_executor::{Executor, Task};
+use futures_lite::{future, prelude::*};
+
+/// Task priority.
+#[repr(usize)]
+#[derive(Debug, Clone, Copy)]
+enum Priority {
+ High = 0,
+ Medium = 1,
+ Low = 2,
+}
+
+/// An executor with task priorities.
+///
+/// Tasks with lower priorities only get polled when there are no tasks with higher priorities.
+struct PriorityExecutor<'a> {
+ ex: [Executor<'a>; 3],
+}
+
+impl<'a> PriorityExecutor<'a> {
+ /// Creates a new executor.
+ const fn new() -> PriorityExecutor<'a> {
+ PriorityExecutor {
+ ex: [Executor::new(), Executor::new(), Executor::new()],
+ }
+ }
+
+ /// Spawns a task with the given priority.
+ fn spawn<T: Send + 'a>(
+ &self,
+ priority: Priority,
+ future: impl Future<Output = T> + Send + 'a,
+ ) -> Task<T> {
+ self.ex[priority as usize].spawn(future)
+ }
+
+ /// Runs the executor forever.
+ async fn run(&self) {
+ loop {
+ for _ in 0..200 {
+ let t0 = self.ex[0].tick();
+ let t1 = self.ex[1].tick();
+ let t2 = self.ex[2].tick();
+
+ // Wait until one of the ticks completes, trying them in order from highest
+ // priority to lowest priority.
+ t0.or(t1).or(t2).await;
+ }
+
+ // Yield every now and then.
+ future::yield_now().await;
+ }
+ }
+}
+
+fn main() {
+ static EX: PriorityExecutor<'_> = PriorityExecutor::new();
+
+ // Spawn a thread running the executor forever.
+ thread::spawn(|| future::block_on(EX.run()));
+
+ let mut tasks = Vec::new();
+
+ for _ in 0..20 {
+ // Choose a random priority.
+ let choice = [Priority::High, Priority::Medium, Priority::Low];
+ let priority = choice[fastrand::usize(..choice.len())];
+
+ // Spawn a task with this priority.
+ tasks.push(EX.spawn(priority, async move {
+ println!("{:?}", priority);
+ future::yield_now().await;
+ println!("{:?}", priority);
+ }));
+ }
+
+ for task in tasks {
+ future::block_on(task);
+ }
+}
--- /dev/null
+//! Async executors.
+//!
+//! # Examples
+//!
+//! ```
+//! use async_executor::Executor;
+//! use futures_lite::future;
+//!
+//! // Create a new executor.
+//! let ex = Executor::new();
+//!
+//! // Spawn a task.
+//! let task = ex.spawn(async {
+//! println!("Hello world");
+//! });
+//!
+//! // Run the executor until the task completes.
+//! future::block_on(ex.run(task));
+//! ```
+
+#![warn(missing_docs, missing_debug_implementations, rust_2018_idioms)]
+
+use std::future::Future;
+use std::marker::PhantomData;
+use std::panic::{RefUnwindSafe, UnwindSafe};
+use std::rc::Rc;
+use std::sync::atomic::{AtomicBool, AtomicUsize, Ordering};
+use std::sync::{Arc, Mutex, RwLock};
+use std::task::{Poll, Waker};
+
+use async_lock::OnceCell;
+use async_task::Runnable;
+use concurrent_queue::ConcurrentQueue;
+use futures_lite::{future, prelude::*};
+use slab::Slab;
+
+#[doc(no_inline)]
+pub use async_task::Task;
+
+/// An async executor.
+///
+/// # Examples
+///
+/// A multi-threaded executor:
+///
+/// ```
+/// use async_channel::unbounded;
+/// use async_executor::Executor;
+/// use easy_parallel::Parallel;
+/// use futures_lite::future;
+///
+/// let ex = Executor::new();
+/// let (signal, shutdown) = unbounded::<()>();
+///
+/// Parallel::new()
+/// // Run four executor threads.
+/// .each(0..4, |_| future::block_on(ex.run(shutdown.recv())))
+/// // Run the main future on the current thread.
+/// .finish(|| future::block_on(async {
+/// println!("Hello world!");
+/// drop(signal);
+/// }));
+/// ```
+#[derive(Debug)]
+pub struct Executor<'a> {
+ /// The executor state.
+ state: OnceCell<Arc<State>>,
+
+ /// Makes the `'a` lifetime invariant.
+ _marker: PhantomData<std::cell::UnsafeCell<&'a ()>>,
+}
+
+unsafe impl Send for Executor<'_> {}
+unsafe impl Sync for Executor<'_> {}
+
+impl UnwindSafe for Executor<'_> {}
+impl RefUnwindSafe for Executor<'_> {}
+
+impl<'a> Executor<'a> {
+ /// Creates a new executor.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use async_executor::Executor;
+ ///
+ /// let ex = Executor::new();
+ /// ```
+ pub const fn new() -> Executor<'a> {
+ Executor {
+ state: OnceCell::new(),
+ _marker: PhantomData,
+ }
+ }
+
+ /// Returns `true` if there are no unfinished tasks.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use async_executor::Executor;
+ ///
+ /// let ex = Executor::new();
+ /// assert!(ex.is_empty());
+ ///
+ /// let task = ex.spawn(async {
+ /// println!("Hello world");
+ /// });
+ /// assert!(!ex.is_empty());
+ ///
+ /// assert!(ex.try_tick());
+ /// assert!(ex.is_empty());
+ /// ```
+ pub fn is_empty(&self) -> bool {
+ self.state().active.lock().unwrap().is_empty()
+ }
+
+ /// Spawns a task onto the executor.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use async_executor::Executor;
+ ///
+ /// let ex = Executor::new();
+ ///
+ /// let task = ex.spawn(async {
+ /// println!("Hello world");
+ /// });
+ /// ```
+ pub fn spawn<T: Send + 'a>(&self, future: impl Future<Output = T> + Send + 'a) -> Task<T> {
+ let mut active = self.state().active.lock().unwrap();
+
+ // Remove the task from the set of active tasks when the future finishes.
+ let index = active.vacant_entry().key();
+ let state = self.state().clone();
+ let future = async move {
+ let _guard = CallOnDrop(move || drop(state.active.lock().unwrap().try_remove(index)));
+ future.await
+ };
+
+ // Create the task and register it in the set of active tasks.
+ let (runnable, task) = unsafe { async_task::spawn_unchecked(future, self.schedule()) };
+ active.insert(runnable.waker());
+
+ runnable.schedule();
+ task
+ }
+
+ /// Attempts to run a task if at least one is scheduled.
+ ///
+ /// Running a scheduled task means simply polling its future once.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use async_executor::Executor;
+ ///
+ /// let ex = Executor::new();
+ /// assert!(!ex.try_tick()); // no tasks to run
+ ///
+ /// let task = ex.spawn(async {
+ /// println!("Hello world");
+ /// });
+ /// assert!(ex.try_tick()); // a task was found
+ /// ```
+ pub fn try_tick(&self) -> bool {
+ match self.state().queue.pop() {
+ Err(_) => false,
+ Ok(runnable) => {
+ // Notify another ticker now to pick up where this ticker left off, just in case
+ // running the task takes a long time.
+ self.state().notify();
+
+ // Run the task.
+ runnable.run();
+ true
+ }
+ }
+ }
+
+ /// Runs a single task.
+ ///
+ /// Running a task means simply polling its future once.
+ ///
+ /// If no tasks are scheduled when this method is called, it will wait until one is scheduled.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use async_executor::Executor;
+ /// use futures_lite::future;
+ ///
+ /// let ex = Executor::new();
+ ///
+ /// let task = ex.spawn(async {
+ /// println!("Hello world");
+ /// });
+ /// future::block_on(ex.tick()); // runs the task
+ /// ```
+ pub async fn tick(&self) {
+ let state = self.state();
+ let runnable = Ticker::new(state).runnable().await;
+ runnable.run();
+ }
+
+ /// Runs the executor until the given future completes.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use async_executor::Executor;
+ /// use futures_lite::future;
+ ///
+ /// let ex = Executor::new();
+ ///
+ /// let task = ex.spawn(async { 1 + 2 });
+ /// let res = future::block_on(ex.run(async { task.await * 2 }));
+ ///
+ /// assert_eq!(res, 6);
+ /// ```
+ pub async fn run<T>(&self, future: impl Future<Output = T>) -> T {
+ let runner = Runner::new(self.state());
+
+ // A future that runs tasks forever.
+ let run_forever = async {
+ loop {
+ for _ in 0..200 {
+ let runnable = runner.runnable().await;
+ runnable.run();
+ }
+ future::yield_now().await;
+ }
+ };
+
+ // Run `future` and `run_forever` concurrently until `future` completes.
+ future.or(run_forever).await
+ }
+
+ /// Returns a function that schedules a runnable task when it gets woken up.
+ fn schedule(&self) -> impl Fn(Runnable) + Send + Sync + 'static {
+ let state = self.state().clone();
+
+ // TODO(stjepang): If possible, push into the current local queue and notify the ticker.
+ move |runnable| {
+ state.queue.push(runnable).unwrap();
+ state.notify();
+ }
+ }
+
+ /// Returns a reference to the inner state.
+ fn state(&self) -> &Arc<State> {
+ self.state.get_or_init_blocking(|| Arc::new(State::new()))
+ }
+}
+
+impl Drop for Executor<'_> {
+ fn drop(&mut self) {
+ if let Some(state) = self.state.get() {
+ let mut active = state.active.lock().unwrap();
+ for w in active.drain() {
+ w.wake();
+ }
+ drop(active);
+
+ while state.queue.pop().is_ok() {}
+ }
+ }
+}
+
+impl<'a> Default for Executor<'a> {
+ fn default() -> Executor<'a> {
+ Executor::new()
+ }
+}
+
+/// A thread-local executor.
+///
+/// The executor can only be run on the thread that created it.
+///
+/// # Examples
+///
+/// ```
+/// use async_executor::LocalExecutor;
+/// use futures_lite::future;
+///
+/// let local_ex = LocalExecutor::new();
+///
+/// future::block_on(local_ex.run(async {
+/// println!("Hello world!");
+/// }));
+/// ```
+#[derive(Debug)]
+pub struct LocalExecutor<'a> {
+ /// The inner executor.
+ inner: Executor<'a>,
+
+ /// Makes the type `!Send` and `!Sync`.
+ _marker: PhantomData<Rc<()>>,
+}
+
+impl UnwindSafe for LocalExecutor<'_> {}
+impl RefUnwindSafe for LocalExecutor<'_> {}
+
+impl<'a> LocalExecutor<'a> {
+ /// Creates a single-threaded executor.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use async_executor::LocalExecutor;
+ ///
+ /// let local_ex = LocalExecutor::new();
+ /// ```
+ pub const fn new() -> LocalExecutor<'a> {
+ LocalExecutor {
+ inner: Executor::new(),
+ _marker: PhantomData,
+ }
+ }
+
+ /// Returns `true` if there are no unfinished tasks.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use async_executor::LocalExecutor;
+ ///
+ /// let local_ex = LocalExecutor::new();
+ /// assert!(local_ex.is_empty());
+ ///
+ /// let task = local_ex.spawn(async {
+ /// println!("Hello world");
+ /// });
+ /// assert!(!local_ex.is_empty());
+ ///
+ /// assert!(local_ex.try_tick());
+ /// assert!(local_ex.is_empty());
+ /// ```
+ pub fn is_empty(&self) -> bool {
+ self.inner().is_empty()
+ }
+
+ /// Spawns a task onto the executor.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use async_executor::LocalExecutor;
+ ///
+ /// let local_ex = LocalExecutor::new();
+ ///
+ /// let task = local_ex.spawn(async {
+ /// println!("Hello world");
+ /// });
+ /// ```
+ pub fn spawn<T: 'a>(&self, future: impl Future<Output = T> + 'a) -> Task<T> {
+ let mut active = self.inner().state().active.lock().unwrap();
+
+ // Remove the task from the set of active tasks when the future finishes.
+ let index = active.vacant_entry().key();
+ let state = self.inner().state().clone();
+ let future = async move {
+ let _guard = CallOnDrop(move || drop(state.active.lock().unwrap().try_remove(index)));
+ future.await
+ };
+
+ // Create the task and register it in the set of active tasks.
+ let (runnable, task) = unsafe { async_task::spawn_unchecked(future, self.schedule()) };
+ active.insert(runnable.waker());
+
+ runnable.schedule();
+ task
+ }
+
+ /// Attempts to run a task if at least one is scheduled.
+ ///
+ /// Running a scheduled task means simply polling its future once.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use async_executor::LocalExecutor;
+ ///
+ /// let ex = LocalExecutor::new();
+ /// assert!(!ex.try_tick()); // no tasks to run
+ ///
+ /// let task = ex.spawn(async {
+ /// println!("Hello world");
+ /// });
+ /// assert!(ex.try_tick()); // a task was found
+ /// ```
+ pub fn try_tick(&self) -> bool {
+ self.inner().try_tick()
+ }
+
+ /// Runs a single task.
+ ///
+ /// Running a task means simply polling its future once.
+ ///
+ /// If no tasks are scheduled when this method is called, it will wait until one is scheduled.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use async_executor::LocalExecutor;
+ /// use futures_lite::future;
+ ///
+ /// let ex = LocalExecutor::new();
+ ///
+ /// let task = ex.spawn(async {
+ /// println!("Hello world");
+ /// });
+ /// future::block_on(ex.tick()); // runs the task
+ /// ```
+ pub async fn tick(&self) {
+ self.inner().tick().await
+ }
+
+ /// Runs the executor until the given future completes.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use async_executor::LocalExecutor;
+ /// use futures_lite::future;
+ ///
+ /// let local_ex = LocalExecutor::new();
+ ///
+ /// let task = local_ex.spawn(async { 1 + 2 });
+ /// let res = future::block_on(local_ex.run(async { task.await * 2 }));
+ ///
+ /// assert_eq!(res, 6);
+ /// ```
+ pub async fn run<T>(&self, future: impl Future<Output = T>) -> T {
+ self.inner().run(future).await
+ }
+
+ /// Returns a function that schedules a runnable task when it gets woken up.
+ fn schedule(&self) -> impl Fn(Runnable) + Send + Sync + 'static {
+ let state = self.inner().state().clone();
+
+ move |runnable| {
+ state.queue.push(runnable).unwrap();
+ state.notify();
+ }
+ }
+
+ /// Returns a reference to the inner executor.
+ fn inner(&self) -> &Executor<'a> {
+ &self.inner
+ }
+}
+
+impl<'a> Default for LocalExecutor<'a> {
+ fn default() -> LocalExecutor<'a> {
+ LocalExecutor::new()
+ }
+}
+
+/// The state of a executor.
+#[derive(Debug)]
+struct State {
+ /// The global queue.
+ queue: ConcurrentQueue<Runnable>,
+
+ /// Local queues created by runners.
+ local_queues: RwLock<Vec<Arc<ConcurrentQueue<Runnable>>>>,
+
+ /// Set to `true` when a sleeping ticker is notified or no tickers are sleeping.
+ notified: AtomicBool,
+
+ /// A list of sleeping tickers.
+ sleepers: Mutex<Sleepers>,
+
+ /// Currently active tasks.
+ active: Mutex<Slab<Waker>>,
+}
+
+impl State {
+ /// Creates state for a new executor.
+ fn new() -> State {
+ State {
+ queue: ConcurrentQueue::unbounded(),
+ local_queues: RwLock::new(Vec::new()),
+ notified: AtomicBool::new(true),
+ sleepers: Mutex::new(Sleepers {
+ count: 0,
+ wakers: Vec::new(),
+ free_ids: Vec::new(),
+ }),
+ active: Mutex::new(Slab::new()),
+ }
+ }
+
+ /// Notifies a sleeping ticker.
+ #[inline]
+ fn notify(&self) {
+ if self
+ .notified
+ .compare_exchange(false, true, Ordering::SeqCst, Ordering::SeqCst)
+ .is_ok()
+ {
+ let waker = self.sleepers.lock().unwrap().notify();
+ if let Some(w) = waker {
+ w.wake();
+ }
+ }
+ }
+}
+
+/// A list of sleeping tickers.
+#[derive(Debug)]
+struct Sleepers {
+ /// Number of sleeping tickers (both notified and unnotified).
+ count: usize,
+
+ /// IDs and wakers of sleeping unnotified tickers.
+ ///
+ /// A sleeping ticker is notified when its waker is missing from this list.
+ wakers: Vec<(usize, Waker)>,
+
+ /// Reclaimed IDs.
+ free_ids: Vec<usize>,
+}
+
+impl Sleepers {
+ /// Inserts a new sleeping ticker.
+ fn insert(&mut self, waker: &Waker) -> usize {
+ let id = match self.free_ids.pop() {
+ Some(id) => id,
+ None => self.count + 1,
+ };
+ self.count += 1;
+ self.wakers.push((id, waker.clone()));
+ id
+ }
+
+ /// Re-inserts a sleeping ticker's waker if it was notified.
+ ///
+ /// Returns `true` if the ticker was notified.
+ fn update(&mut self, id: usize, waker: &Waker) -> bool {
+ for item in &mut self.wakers {
+ if item.0 == id {
+ if !item.1.will_wake(waker) {
+ item.1 = waker.clone();
+ }
+ return false;
+ }
+ }
+
+ self.wakers.push((id, waker.clone()));
+ true
+ }
+
+ /// Removes a previously inserted sleeping ticker.
+ ///
+ /// Returns `true` if the ticker was notified.
+ fn remove(&mut self, id: usize) -> bool {
+ self.count -= 1;
+ self.free_ids.push(id);
+
+ for i in (0..self.wakers.len()).rev() {
+ if self.wakers[i].0 == id {
+ self.wakers.remove(i);
+ return false;
+ }
+ }
+ true
+ }
+
+ /// Returns `true` if a sleeping ticker is notified or no tickers are sleeping.
+ fn is_notified(&self) -> bool {
+ self.count == 0 || self.count > self.wakers.len()
+ }
+
+ /// Returns notification waker for a sleeping ticker.
+ ///
+ /// If a ticker was notified already or there are no tickers, `None` will be returned.
+ fn notify(&mut self) -> Option<Waker> {
+ if self.wakers.len() == self.count {
+ self.wakers.pop().map(|item| item.1)
+ } else {
+ None
+ }
+ }
+}
+
+/// Runs task one by one.
+#[derive(Debug)]
+struct Ticker<'a> {
+ /// The executor state.
+ state: &'a State,
+
+ /// Set to a non-zero sleeper ID when in sleeping state.
+ ///
+ /// States a ticker can be in:
+ /// 1) Woken.
+ /// 2a) Sleeping and unnotified.
+ /// 2b) Sleeping and notified.
+ sleeping: AtomicUsize,
+}
+
+impl Ticker<'_> {
+ /// Creates a ticker.
+ fn new(state: &State) -> Ticker<'_> {
+ Ticker {
+ state,
+ sleeping: AtomicUsize::new(0),
+ }
+ }
+
+ /// Moves the ticker into sleeping and unnotified state.
+ ///
+ /// Returns `false` if the ticker was already sleeping and unnotified.
+ fn sleep(&self, waker: &Waker) -> bool {
+ let mut sleepers = self.state.sleepers.lock().unwrap();
+
+ match self.sleeping.load(Ordering::SeqCst) {
+ // Move to sleeping state.
+ 0 => self
+ .sleeping
+ .store(sleepers.insert(waker), Ordering::SeqCst),
+
+ // Already sleeping, check if notified.
+ id => {
+ if !sleepers.update(id, waker) {
+ return false;
+ }
+ }
+ }
+
+ self.state
+ .notified
+ .swap(sleepers.is_notified(), Ordering::SeqCst);
+
+ true
+ }
+
+ /// Moves the ticker into woken state.
+ fn wake(&self) {
+ let id = self.sleeping.swap(0, Ordering::SeqCst);
+ if id != 0 {
+ let mut sleepers = self.state.sleepers.lock().unwrap();
+ sleepers.remove(id);
+
+ self.state
+ .notified
+ .swap(sleepers.is_notified(), Ordering::SeqCst);
+ }
+ }
+
+ /// Waits for the next runnable task to run.
+ async fn runnable(&self) -> Runnable {
+ self.runnable_with(|| self.state.queue.pop().ok()).await
+ }
+
+ /// Waits for the next runnable task to run, given a function that searches for a task.
+ async fn runnable_with(&self, mut search: impl FnMut() -> Option<Runnable>) -> Runnable {
+ future::poll_fn(|cx| {
+ loop {
+ match search() {
+ None => {
+ // Move to sleeping and unnotified state.
+ if !self.sleep(cx.waker()) {
+ // If already sleeping and unnotified, return.
+ return Poll::Pending;
+ }
+ }
+ Some(r) => {
+ // Wake up.
+ self.wake();
+
+ // Notify another ticker now to pick up where this ticker left off, just in
+ // case running the task takes a long time.
+ self.state.notify();
+
+ return Poll::Ready(r);
+ }
+ }
+ }
+ })
+ .await
+ }
+}
+
+impl Drop for Ticker<'_> {
+ fn drop(&mut self) {
+ // If this ticker is in sleeping state, it must be removed from the sleepers list.
+ let id = self.sleeping.swap(0, Ordering::SeqCst);
+ if id != 0 {
+ let mut sleepers = self.state.sleepers.lock().unwrap();
+ let notified = sleepers.remove(id);
+
+ self.state
+ .notified
+ .swap(sleepers.is_notified(), Ordering::SeqCst);
+
+ // If this ticker was notified, then notify another ticker.
+ if notified {
+ drop(sleepers);
+ self.state.notify();
+ }
+ }
+ }
+}
+
+/// A worker in a work-stealing executor.
+///
+/// This is just a ticker that also has an associated local queue for improved cache locality.
+#[derive(Debug)]
+struct Runner<'a> {
+ /// The executor state.
+ state: &'a State,
+
+ /// Inner ticker.
+ ticker: Ticker<'a>,
+
+ /// The local queue.
+ local: Arc<ConcurrentQueue<Runnable>>,
+
+ /// Bumped every time a runnable task is found.
+ ticks: AtomicUsize,
+}
+
+impl Runner<'_> {
+ /// Creates a runner and registers it in the executor state.
+ fn new(state: &State) -> Runner<'_> {
+ let runner = Runner {
+ state,
+ ticker: Ticker::new(state),
+ local: Arc::new(ConcurrentQueue::bounded(512)),
+ ticks: AtomicUsize::new(0),
+ };
+ state
+ .local_queues
+ .write()
+ .unwrap()
+ .push(runner.local.clone());
+ runner
+ }
+
+ /// Waits for the next runnable task to run.
+ async fn runnable(&self) -> Runnable {
+ let runnable = self
+ .ticker
+ .runnable_with(|| {
+ // Try the local queue.
+ if let Ok(r) = self.local.pop() {
+ return Some(r);
+ }
+
+ // Try stealing from the global queue.
+ if let Ok(r) = self.state.queue.pop() {
+ steal(&self.state.queue, &self.local);
+ return Some(r);
+ }
+
+ // Try stealing from other runners.
+ let local_queues = self.state.local_queues.read().unwrap();
+
+ // Pick a random starting point in the iterator list and rotate the list.
+ let n = local_queues.len();
+ let start = fastrand::usize(..n);
+ let iter = local_queues
+ .iter()
+ .chain(local_queues.iter())
+ .skip(start)
+ .take(n);
+
+ // Remove this runner's local queue.
+ let iter = iter.filter(|local| !Arc::ptr_eq(local, &self.local));
+
+ // Try stealing from each local queue in the list.
+ for local in iter {
+ steal(local, &self.local);
+ if let Ok(r) = self.local.pop() {
+ return Some(r);
+ }
+ }
+
+ None
+ })
+ .await;
+
+ // Bump the tick counter.
+ let ticks = self.ticks.fetch_add(1, Ordering::SeqCst);
+
+ if ticks % 64 == 0 {
+ // Steal tasks from the global queue to ensure fair task scheduling.
+ steal(&self.state.queue, &self.local);
+ }
+
+ runnable
+ }
+}
+
+impl Drop for Runner<'_> {
+ fn drop(&mut self) {
+ // Remove the local queue.
+ self.state
+ .local_queues
+ .write()
+ .unwrap()
+ .retain(|local| !Arc::ptr_eq(local, &self.local));
+
+ // Re-schedule remaining tasks in the local queue.
+ while let Ok(r) = self.local.pop() {
+ r.schedule();
+ }
+ }
+}
+
+/// Steals some items from one queue into another.
+fn steal<T>(src: &ConcurrentQueue<T>, dest: &ConcurrentQueue<T>) {
+ // Half of `src`'s length rounded up.
+ let mut count = (src.len() + 1) / 2;
+
+ if count > 0 {
+ // Don't steal more than fits into the queue.
+ if let Some(cap) = dest.capacity() {
+ count = count.min(cap - dest.len());
+ }
+
+ // Steal tasks.
+ for _ in 0..count {
+ if let Ok(t) = src.pop() {
+ assert!(dest.push(t).is_ok());
+ } else {
+ break;
+ }
+ }
+ }
+}
+
+/// Runs a closure when dropped.
+struct CallOnDrop<F: Fn()>(F);
+
+impl<F: Fn()> Drop for CallOnDrop<F> {
+ fn drop(&mut self) {
+ (self.0)();
+ }
+}
--- /dev/null
+use std::mem;
+use std::panic::catch_unwind;
+use std::sync::atomic::{AtomicUsize, Ordering};
+use std::sync::Mutex;
+use std::task::{Poll, Waker};
+
+use async_executor::{Executor, Task};
+use futures_lite::future;
+use once_cell::sync::Lazy;
+
+#[test]
+fn executor_cancels_everything() {
+ static DROP: AtomicUsize = AtomicUsize::new(0);
+ static WAKER: Lazy<Mutex<Option<Waker>>> = Lazy::new(Default::default);
+
+ let ex = Executor::new();
+
+ let task = ex.spawn(async {
+ let _guard = CallOnDrop(|| {
+ DROP.fetch_add(1, Ordering::SeqCst);
+ });
+
+ future::poll_fn(|cx| {
+ *WAKER.lock().unwrap() = Some(cx.waker().clone());
+ Poll::Pending::<()>
+ })
+ .await;
+ });
+
+ future::block_on(ex.tick());
+ assert!(WAKER.lock().unwrap().is_some());
+ assert_eq!(DROP.load(Ordering::SeqCst), 0);
+
+ drop(ex);
+ assert_eq!(DROP.load(Ordering::SeqCst), 1);
+
+ assert!(catch_unwind(|| future::block_on(task)).is_err());
+ assert_eq!(DROP.load(Ordering::SeqCst), 1);
+}
+
+#[test]
+fn leaked_executor_leaks_everything() {
+ static DROP: AtomicUsize = AtomicUsize::new(0);
+ static WAKER: Lazy<Mutex<Option<Waker>>> = Lazy::new(Default::default);
+
+ let ex = Executor::new();
+
+ let task = ex.spawn(async {
+ let _guard = CallOnDrop(|| {
+ DROP.fetch_add(1, Ordering::SeqCst);
+ });
+
+ future::poll_fn(|cx| {
+ *WAKER.lock().unwrap() = Some(cx.waker().clone());
+ Poll::Pending::<()>
+ })
+ .await;
+ });
+
+ future::block_on(ex.tick());
+ assert!(WAKER.lock().unwrap().is_some());
+ assert_eq!(DROP.load(Ordering::SeqCst), 0);
+
+ mem::forget(ex);
+ assert_eq!(DROP.load(Ordering::SeqCst), 0);
+
+ assert!(future::block_on(future::poll_once(task)).is_none());
+ assert_eq!(DROP.load(Ordering::SeqCst), 0);
+}
+
+#[test]
+fn await_task_after_dropping_executor() {
+ let s: String = "hello".into();
+
+ let ex = Executor::new();
+ let task: Task<&str> = ex.spawn(async { &*s });
+ assert!(ex.try_tick());
+
+ drop(ex);
+ assert_eq!(future::block_on(task), "hello");
+ drop(s);
+}
+
+#[test]
+fn drop_executor_and_then_drop_finished_task() {
+ static DROP: AtomicUsize = AtomicUsize::new(0);
+
+ let ex = Executor::new();
+ let task = ex.spawn(async {
+ CallOnDrop(|| {
+ DROP.fetch_add(1, Ordering::SeqCst);
+ })
+ });
+ assert!(ex.try_tick());
+
+ assert_eq!(DROP.load(Ordering::SeqCst), 0);
+ drop(ex);
+ assert_eq!(DROP.load(Ordering::SeqCst), 0);
+ drop(task);
+ assert_eq!(DROP.load(Ordering::SeqCst), 1);
+}
+
+#[test]
+fn drop_finished_task_and_then_drop_executor() {
+ static DROP: AtomicUsize = AtomicUsize::new(0);
+
+ let ex = Executor::new();
+ let task = ex.spawn(async {
+ CallOnDrop(|| {
+ DROP.fetch_add(1, Ordering::SeqCst);
+ })
+ });
+ assert!(ex.try_tick());
+
+ assert_eq!(DROP.load(Ordering::SeqCst), 0);
+ drop(task);
+ assert_eq!(DROP.load(Ordering::SeqCst), 1);
+ drop(ex);
+ assert_eq!(DROP.load(Ordering::SeqCst), 1);
+}
+
+struct CallOnDrop<F: Fn()>(F);
+
+impl<F: Fn()> Drop for CallOnDrop<F> {
+ fn drop(&mut self) {
+ (self.0)();
+ }
+}
projects / platform / upstream / rust-async-executor.git / commitdiff