Initial commit
This commit is contained in:
commit
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||||||
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github: stjepang
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|
||||||
|
name: Build and test
|
||||||
|
|
||||||
|
on:
|
||||||
|
push:
|
||||||
|
branches:
|
||||||
|
- master
|
||||||
|
pull_request:
|
||||||
|
|
||||||
|
jobs:
|
||||||
|
build_and_test:
|
||||||
|
runs-on: ${{ matrix.os }}
|
||||||
|
strategy:
|
||||||
|
fail-fast: false
|
||||||
|
matrix:
|
||||||
|
os: [ubuntu-latest]
|
||||||
|
rust: [nightly, beta, stable]
|
||||||
|
steps:
|
||||||
|
- uses: actions/checkout@v2
|
||||||
|
|
||||||
|
- name: Set current week of the year in environnement
|
||||||
|
if: startsWith(matrix.os, 'ubuntu') || startsWith(matrix.os, 'macOS')
|
||||||
|
run: echo "::set-env name=CURRENT_WEEK::$(date +%V)"
|
||||||
|
|
||||||
|
- name: Set current week of the year in environnement
|
||||||
|
if: startsWith(matrix.os, 'windows')
|
||||||
|
run: echo "::set-env name=CURRENT_WEEK::$(Get-Date -UFormat %V)"
|
||||||
|
|
||||||
|
- name: Install latest ${{ matrix.rust }}
|
||||||
|
uses: actions-rs/toolchain@v1
|
||||||
|
with:
|
||||||
|
toolchain: ${{ matrix.rust }}
|
||||||
|
profile: minimal
|
||||||
|
override: true
|
||||||
|
|
||||||
|
- name: Run cargo check
|
||||||
|
uses: actions-rs/cargo@v1
|
||||||
|
with:
|
||||||
|
command: check
|
||||||
|
args: --all --benches --bins --examples --tests --all-features
|
||||||
|
|
||||||
|
- name: Run cargo test
|
||||||
|
uses: actions-rs/cargo@v1
|
||||||
|
with:
|
||||||
|
command: test
|
|
@ -0,0 +1,26 @@
|
||||||
|
name: Lint
|
||||||
|
|
||||||
|
on:
|
||||||
|
push:
|
||||||
|
branches:
|
||||||
|
- master
|
||||||
|
pull_request:
|
||||||
|
|
||||||
|
jobs:
|
||||||
|
clippy:
|
||||||
|
runs-on: ubuntu-latest
|
||||||
|
steps:
|
||||||
|
- uses: actions/checkout@v2
|
||||||
|
|
||||||
|
- name: Set current week of the year in environnement
|
||||||
|
run: echo "::set-env name=CURRENT_WEEK::$(date +%V)"
|
||||||
|
|
||||||
|
- uses: actions-rs/toolchain@v1
|
||||||
|
with:
|
||||||
|
toolchain: stable
|
||||||
|
profile: minimal
|
||||||
|
components: clippy
|
||||||
|
- uses: actions-rs/clippy-check@v1
|
||||||
|
with:
|
||||||
|
token: ${{ secrets.GITHUB_TOKEN }}
|
||||||
|
args: --all-features -- -W clippy::all
|
|
@ -0,0 +1,20 @@
|
||||||
|
name: Security audit
|
||||||
|
|
||||||
|
on:
|
||||||
|
push:
|
||||||
|
branches:
|
||||||
|
- master
|
||||||
|
pull_request:
|
||||||
|
|
||||||
|
jobs:
|
||||||
|
security_audit:
|
||||||
|
runs-on: ubuntu-latest
|
||||||
|
steps:
|
||||||
|
- uses: actions/checkout@v2
|
||||||
|
|
||||||
|
- name: Set current week of the year in environnement
|
||||||
|
run: echo "::set-env name=CURRENT_WEEK::$(date +%V)"
|
||||||
|
|
||||||
|
- uses: actions-rs/audit-check@v1
|
||||||
|
with:
|
||||||
|
token: ${{ secrets.GITHUB_TOKEN }}
|
|
@ -0,0 +1 @@
|
||||||
|
/target
|
|
@ -0,0 +1,20 @@
|
||||||
|
# Version 0.3.2
|
||||||
|
|
||||||
|
- Make `Blocking` implement `Send` in more cases.
|
||||||
|
|
||||||
|
# Version 0.3.1
|
||||||
|
|
||||||
|
- Add `Blocking::with_mut()`.
|
||||||
|
|
||||||
|
# Version 0.3.0
|
||||||
|
|
||||||
|
- Remove `Blocking::spawn()`.
|
||||||
|
- Implement `Future` for `Blocking` only when the inner type is a `FnOnce`.
|
||||||
|
|
||||||
|
# Version 0.2.0
|
||||||
|
|
||||||
|
- Initial version
|
||||||
|
|
||||||
|
# Version 0.1.0
|
||||||
|
|
||||||
|
- Reserved crate name
|
|
@ -0,0 +1,6 @@
|
||||||
|
# This file is automatically @generated by Cargo.
|
||||||
|
# It is not intended for manual editing.
|
||||||
|
[[package]]
|
||||||
|
name = "event-listener"
|
||||||
|
version = "0.1.0"
|
||||||
|
|
|
@ -0,0 +1,13 @@
|
||||||
|
[package]
|
||||||
|
name = "event-listener"
|
||||||
|
version = "1.0.0"
|
||||||
|
authors = ["Stjepan Glavina <stjepang@gmail.com>"]
|
||||||
|
edition = "2018"
|
||||||
|
description = "Notify async tasks or threads"
|
||||||
|
license = "Apache-2.0 OR MIT"
|
||||||
|
repository = "https://github.com/stjepang/event-listener"
|
||||||
|
homepage = "https://github.com/stjepang/event-listener"
|
||||||
|
documentation = "https://docs.rs/event-listener"
|
||||||
|
keywords = ["condvar", "eventcount", "wake", "blocking", "park"]
|
||||||
|
categories = ["asynchronous", "concurrency"]
|
||||||
|
readme = "README.md"
|
|
@ -0,0 +1,201 @@
|
||||||
|
Apache License
|
||||||
|
Version 2.0, January 2004
|
||||||
|
http://www.apache.org/licenses/
|
||||||
|
|
||||||
|
TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION
|
||||||
|
|
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|
1. Definitions.
|
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|
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|
"License" shall mean the terms and conditions for use, reproduction,
|
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(d) If the Work includes a "NOTICE" text file as part of its
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APPENDIX: How to apply the Apache License to your work.
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To apply the Apache License to your work, attach the following
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@ -0,0 +1,23 @@
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Permission is hereby granted, free of charge, to any
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DEALINGS IN THE SOFTWARE.
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|
@ -0,0 +1,86 @@
|
||||||
|
# event-listener
|
||||||
|
|
||||||
|
[![Build](https://github.com/stjepang/event-listener/workflows/Build%20and%20test/badge.svg)](
|
||||||
|
https://github.com/stjepang/event-listener/actions)
|
||||||
|
[![License](https://img.shields.io/badge/license-MIT%2FApache--2.0-blue.svg)](
|
||||||
|
https://github.com/stjepang/event-listener)
|
||||||
|
[![Cargo](https://img.shields.io/crates/v/event-listener.svg)](
|
||||||
|
https://crates.io/crates/event-listener)
|
||||||
|
[![Documentation](https://docs.rs/event-listener/badge.svg)](
|
||||||
|
https://docs.rs/event-listener)
|
||||||
|
|
||||||
|
Notify async tasks or threads.
|
||||||
|
|
||||||
|
This is a synchronization primitive similar to [eventcounts] invented by Dmitry Vyukov.
|
||||||
|
|
||||||
|
You can use this crate to turn non-blocking data structures into async or blocking data
|
||||||
|
structures. See a [simple mutex] implementation that exposes an async and a blocking interface
|
||||||
|
for acquiring locks.
|
||||||
|
|
||||||
|
[eventcounts]: http://www.1024cores.net/home/lock-free-algorithms/eventcounts
|
||||||
|
[simple mutex]: TODO
|
||||||
|
|
||||||
|
## Examples
|
||||||
|
|
||||||
|
Wait until another thread sets a boolean flag:
|
||||||
|
|
||||||
|
```rust
|
||||||
|
use std::sync::atomic::{AtomicBool, Ordering};
|
||||||
|
use std::sync::Arc;
|
||||||
|
use std::thread;
|
||||||
|
use std::time::Duration;
|
||||||
|
use event_listener::Event;
|
||||||
|
|
||||||
|
let flag = Arc::new(AtomicBool::new(false));
|
||||||
|
let event = Arc::new(Event::new());
|
||||||
|
|
||||||
|
// Spawn a thread that will set the flag after 1 second.
|
||||||
|
thread::spawn({
|
||||||
|
let flag = flag.clone();
|
||||||
|
let event = event.clone();
|
||||||
|
move || {
|
||||||
|
// Wait for a second.
|
||||||
|
thread::sleep(Duration::from_secs(1));
|
||||||
|
|
||||||
|
// Set the flag.
|
||||||
|
flag.store(true, Ordering::SeqCst);
|
||||||
|
|
||||||
|
// Notify all listeners that the flag has been set.
|
||||||
|
event.notify_all();
|
||||||
|
}
|
||||||
|
});
|
||||||
|
|
||||||
|
// Wait until the flag is set.
|
||||||
|
loop {
|
||||||
|
// Check the flag.
|
||||||
|
if flag.load(Ordering::SeqCst) {
|
||||||
|
break;
|
||||||
|
}
|
||||||
|
|
||||||
|
// Start listening for events.
|
||||||
|
let listener = event.listen();
|
||||||
|
|
||||||
|
// Check the flag again after creating the listener.
|
||||||
|
if flag.load(Ordering::SeqCst) {
|
||||||
|
break;
|
||||||
|
}
|
||||||
|
|
||||||
|
// Wait for a notification and continue the loop.
|
||||||
|
listener.wait();
|
||||||
|
}
|
||||||
|
```
|
||||||
|
|
||||||
|
## 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.
|
|
@ -0,0 +1,178 @@
|
||||||
|
//! A simple mutex implementation.
|
||||||
|
//!
|
||||||
|
//! This mutex exposes both blocking and async methods for acquiring a lock.
|
||||||
|
|
||||||
|
#![allow(dead_code)]
|
||||||
|
|
||||||
|
use std::cell::UnsafeCell;
|
||||||
|
use std::ops::{Deref, DerefMut};
|
||||||
|
use std::sync::atomic::{AtomicBool, Ordering};
|
||||||
|
use std::sync::{mpsc, Arc};
|
||||||
|
use std::thread;
|
||||||
|
use std::time::{Duration, Instant};
|
||||||
|
|
||||||
|
use event_listener::Event;
|
||||||
|
|
||||||
|
/// A simple mutex.
|
||||||
|
struct Mutex<T> {
|
||||||
|
/// Set to `true` when the mutex is locked.
|
||||||
|
locked: AtomicBool,
|
||||||
|
|
||||||
|
/// Blocked lock operations.
|
||||||
|
lock_ops: Event,
|
||||||
|
|
||||||
|
/// The inner protected data.
|
||||||
|
data: UnsafeCell<T>,
|
||||||
|
}
|
||||||
|
|
||||||
|
unsafe impl<T: Send> Send for Mutex<T> {}
|
||||||
|
unsafe impl<T: Send> Sync for Mutex<T> {}
|
||||||
|
|
||||||
|
impl<T> Mutex<T> {
|
||||||
|
/// Creates a mutex.
|
||||||
|
fn new(t: T) -> Mutex<T> {
|
||||||
|
Mutex {
|
||||||
|
locked: AtomicBool::new(false),
|
||||||
|
lock_ops: Event::new(),
|
||||||
|
data: UnsafeCell::new(t),
|
||||||
|
}
|
||||||
|
}
|
||||||
|
|
||||||
|
/// Attempts to acquire a lock.
|
||||||
|
fn try_lock(&self) -> Option<MutexGuard<'_, T>> {
|
||||||
|
if self.locked.swap(true, Ordering::Acquire) {
|
||||||
|
Some(MutexGuard(self))
|
||||||
|
} else {
|
||||||
|
None
|
||||||
|
}
|
||||||
|
}
|
||||||
|
|
||||||
|
/// Blocks until a lock is acquired.
|
||||||
|
fn lock(&self) -> MutexGuard<'_, T> {
|
||||||
|
let mut listener = None;
|
||||||
|
|
||||||
|
loop {
|
||||||
|
// Attempt grabbing a lock.
|
||||||
|
if let Some(guard) = self.try_lock() {
|
||||||
|
return guard;
|
||||||
|
}
|
||||||
|
|
||||||
|
// Set up an event listener or wait for a notification.
|
||||||
|
match listener.take() {
|
||||||
|
None => {
|
||||||
|
// Start listening and then try locking again.
|
||||||
|
listener = Some(self.lock_ops.listen());
|
||||||
|
}
|
||||||
|
Some(l) => {
|
||||||
|
// Wait until a notification is received.
|
||||||
|
l.wait();
|
||||||
|
}
|
||||||
|
}
|
||||||
|
}
|
||||||
|
}
|
||||||
|
|
||||||
|
/// Blocks until a lock is acquired or the timeout is reached.
|
||||||
|
fn lock_timeout(&self, timeout: Duration) -> Option<MutexGuard<'_, T>> {
|
||||||
|
let deadline = Instant::now() + timeout;
|
||||||
|
let mut listener = None;
|
||||||
|
|
||||||
|
loop {
|
||||||
|
// Attempt grabbing a lock.
|
||||||
|
if let Some(guard) = self.try_lock() {
|
||||||
|
return Some(guard);
|
||||||
|
}
|
||||||
|
|
||||||
|
// Set up an event listener or wait for an event.
|
||||||
|
match listener.take() {
|
||||||
|
None => {
|
||||||
|
// Start listening and then try locking again.
|
||||||
|
listener = Some(self.lock_ops.listen());
|
||||||
|
}
|
||||||
|
Some(l) => {
|
||||||
|
// Wait until a notification is received.
|
||||||
|
if !l.wait_deadline(deadline) {
|
||||||
|
return None;
|
||||||
|
}
|
||||||
|
}
|
||||||
|
}
|
||||||
|
}
|
||||||
|
}
|
||||||
|
|
||||||
|
/// Acquires a lock asynchronously.
|
||||||
|
async fn lock_async(&self) -> MutexGuard<'_, T> {
|
||||||
|
let mut listener = None;
|
||||||
|
|
||||||
|
loop {
|
||||||
|
// Attempt grabbing a lock.
|
||||||
|
if let Some(guard) = self.try_lock() {
|
||||||
|
return guard;
|
||||||
|
}
|
||||||
|
|
||||||
|
// Set up an event listener or wait for an event.
|
||||||
|
match listener.take() {
|
||||||
|
None => {
|
||||||
|
// Start listening and then try locking again.
|
||||||
|
listener = Some(self.lock_ops.listen());
|
||||||
|
}
|
||||||
|
Some(l) => {
|
||||||
|
// Wait until a notification is received.
|
||||||
|
l.await;
|
||||||
|
}
|
||||||
|
}
|
||||||
|
}
|
||||||
|
}
|
||||||
|
}
|
||||||
|
|
||||||
|
/// A guard holding a lock.
|
||||||
|
struct MutexGuard<'a, T>(&'a Mutex<T>);
|
||||||
|
|
||||||
|
unsafe impl<T: Send> Send for MutexGuard<'_, T> {}
|
||||||
|
unsafe impl<T: Sync> Sync for MutexGuard<'_, T> {}
|
||||||
|
|
||||||
|
impl<T> Deref for MutexGuard<'_, T> {
|
||||||
|
type Target = T;
|
||||||
|
|
||||||
|
fn deref(&self) -> &T {
|
||||||
|
unsafe { &*self.0.data.get() }
|
||||||
|
}
|
||||||
|
}
|
||||||
|
|
||||||
|
impl<T> DerefMut for MutexGuard<'_, T> {
|
||||||
|
fn deref_mut(&mut self) -> &mut T {
|
||||||
|
unsafe { &mut *self.0.data.get() }
|
||||||
|
}
|
||||||
|
}
|
||||||
|
|
||||||
|
fn main() {
|
||||||
|
const N: usize = 10;
|
||||||
|
|
||||||
|
// A shared counter.
|
||||||
|
let counter = Arc::new(Mutex::new(0));
|
||||||
|
|
||||||
|
// A channel that signals when all threads are done.
|
||||||
|
let (tx, rx) = mpsc::channel();
|
||||||
|
|
||||||
|
// Spawn a bunch of threads incrementing the counter.
|
||||||
|
for _ in 0..N {
|
||||||
|
let counter = counter.clone();
|
||||||
|
let tx = tx.clone();
|
||||||
|
|
||||||
|
thread::spawn(move || {
|
||||||
|
let mut counter = counter.lock();
|
||||||
|
*counter += 1;
|
||||||
|
|
||||||
|
// If this is the last increment, signal that we're done.
|
||||||
|
if *counter == N {
|
||||||
|
tx.send(()).unwrap();
|
||||||
|
}
|
||||||
|
});
|
||||||
|
}
|
||||||
|
|
||||||
|
// Wait until the last thread increments the counter.
|
||||||
|
rx.recv().unwrap();
|
||||||
|
|
||||||
|
// The counter must equal the number of threads.
|
||||||
|
assert_eq!(*counter.lock(), N);
|
||||||
|
|
||||||
|
println!("Done!");
|
||||||
|
}
|
|
@ -0,0 +1,722 @@
|
||||||
|
//! Notify async tasks or threads.
|
||||||
|
//!
|
||||||
|
//! This is a synchronization primitive similar to [eventcounts] invented by Dmitry Vyukov.
|
||||||
|
//!
|
||||||
|
//! You can use this crate to turn non-blocking data structures into async or blocking data
|
||||||
|
//! structures. See a [simple mutex] implementation that exposes an async and a blocking interface
|
||||||
|
//! for acquiring locks.
|
||||||
|
//!
|
||||||
|
//! [eventcounts]: http://www.1024cores.net/home/lock-free-algorithms/eventcounts
|
||||||
|
//! [simple mutex]: TODO
|
||||||
|
//!
|
||||||
|
//! # Examples
|
||||||
|
//!
|
||||||
|
//! Wait until another thread sets a boolean flag:
|
||||||
|
//!
|
||||||
|
//! ```
|
||||||
|
//! use std::sync::atomic::{AtomicBool, Ordering};
|
||||||
|
//! use std::sync::Arc;
|
||||||
|
//! use std::thread;
|
||||||
|
//! use std::time::Duration;
|
||||||
|
//! use event_listener::Event;
|
||||||
|
//!
|
||||||
|
//! let flag = Arc::new(AtomicBool::new(false));
|
||||||
|
//! let event = Arc::new(Event::new());
|
||||||
|
//!
|
||||||
|
//! // Spawn a thread that will set the flag after 1 second.
|
||||||
|
//! thread::spawn({
|
||||||
|
//! let flag = flag.clone();
|
||||||
|
//! let event = event.clone();
|
||||||
|
//! move || {
|
||||||
|
//! // Wait for a second.
|
||||||
|
//! thread::sleep(Duration::from_secs(1));
|
||||||
|
//!
|
||||||
|
//! // Set the flag.
|
||||||
|
//! flag.store(true, Ordering::SeqCst);
|
||||||
|
//!
|
||||||
|
//! // Notify all listeners that the flag has been set.
|
||||||
|
//! event.notify_all();
|
||||||
|
//! }
|
||||||
|
//! });
|
||||||
|
//!
|
||||||
|
//! // Wait until the flag is set.
|
||||||
|
//! loop {
|
||||||
|
//! // Check the flag.
|
||||||
|
//! if flag.load(Ordering::SeqCst) {
|
||||||
|
//! break;
|
||||||
|
//! }
|
||||||
|
//!
|
||||||
|
//! // Start listening for events.
|
||||||
|
//! let listener = event.listen();
|
||||||
|
//!
|
||||||
|
//! // Check the flag again after creating the listener.
|
||||||
|
//! if flag.load(Ordering::SeqCst) {
|
||||||
|
//! break;
|
||||||
|
//! }
|
||||||
|
//!
|
||||||
|
//! // Wait for a notification and continue the loop.
|
||||||
|
//! listener.wait();
|
||||||
|
//! }
|
||||||
|
//! ```
|
||||||
|
|
||||||
|
#![warn(missing_docs, missing_debug_implementations, rust_2018_idioms)]
|
||||||
|
|
||||||
|
use std::cell::Cell;
|
||||||
|
use std::fmt;
|
||||||
|
use std::future::Future;
|
||||||
|
use std::mem::{self, ManuallyDrop};
|
||||||
|
use std::ops::{Deref, DerefMut};
|
||||||
|
use std::pin::Pin;
|
||||||
|
use std::ptr::NonNull;
|
||||||
|
use std::sync::atomic::{self, AtomicPtr, AtomicUsize, Ordering};
|
||||||
|
use std::sync::{Arc, Mutex, MutexGuard};
|
||||||
|
use std::task::{Context, Poll, Waker};
|
||||||
|
use std::thread::{self, Thread};
|
||||||
|
use std::time::{Duration, Instant};
|
||||||
|
|
||||||
|
/// A bit set inside [`Event`] when there is at least one listener that has already been notified.
|
||||||
|
const NOTIFIED: usize = 1 << 0;
|
||||||
|
|
||||||
|
/// A bit set inside [`Event`] when there is at least one notifiable listener.
|
||||||
|
const NOTIFIABLE: usize = 1 << 1;
|
||||||
|
|
||||||
|
/// Inner state of [`Event`].
|
||||||
|
struct Inner {
|
||||||
|
/// Holds bits [`NOTIFIED`] and [`NOTIFIABLE`].
|
||||||
|
flags: AtomicUsize,
|
||||||
|
|
||||||
|
/// A linked list holding registered listeners.
|
||||||
|
list: Mutex<List>,
|
||||||
|
}
|
||||||
|
|
||||||
|
impl Inner {
|
||||||
|
/// Locks the list.
|
||||||
|
fn lock(&self) -> ListGuard<'_> {
|
||||||
|
ListGuard {
|
||||||
|
inner: self,
|
||||||
|
guard: self.list.lock().unwrap(),
|
||||||
|
}
|
||||||
|
}
|
||||||
|
}
|
||||||
|
|
||||||
|
/// A synchronization primitive for notifying async tasks and threads.
|
||||||
|
///
|
||||||
|
/// Listeners can be registered using [`Event::listen()`]. There are two ways of notifying
|
||||||
|
/// listeners:
|
||||||
|
///
|
||||||
|
/// 1. [`Event::notify_one()`] notifies one listener.
|
||||||
|
/// 2. [`Event::notify_all()`] notifies all listeners.
|
||||||
|
///
|
||||||
|
/// If there are no active listeners at the time a notification is sent, it simply gets lost.
|
||||||
|
///
|
||||||
|
/// Note that [`Event::notify_one()`] does not notify one *additional* listener - it only makes
|
||||||
|
/// sure *at least* one listener among the active ones is notified.
|
||||||
|
///
|
||||||
|
/// There are two ways for a listener to wait for a notification:
|
||||||
|
///
|
||||||
|
/// 1. In an asynchronous manner using `.await`.
|
||||||
|
/// 2. In a blocking manner by calling [`EventListener::wait()`] on it.
|
||||||
|
///
|
||||||
|
/// If a notified listener is dropped without receiving a notification, dropping will notify
|
||||||
|
/// another active listener.
|
||||||
|
///
|
||||||
|
/// Listeners are registered and notified in the first-in first-out fashion, ensuring fairness.
|
||||||
|
pub struct Event {
|
||||||
|
/// A pointer to heap-allocated inner state.
|
||||||
|
///
|
||||||
|
/// This pointer is initially null and gets lazily initialized on first use. Semantically, it
|
||||||
|
/// is an `Arc<Inner>` so it's important to keep in mind that it contributes to the [`Arc`]'s
|
||||||
|
/// reference count.
|
||||||
|
inner: AtomicPtr<Inner>,
|
||||||
|
}
|
||||||
|
|
||||||
|
unsafe impl Send for Event {}
|
||||||
|
unsafe impl Sync for Event {}
|
||||||
|
|
||||||
|
impl Event {
|
||||||
|
/// Creates a new [`Event`].
|
||||||
|
///
|
||||||
|
/// # Examples
|
||||||
|
///
|
||||||
|
/// ```
|
||||||
|
/// use event_listener::Event;
|
||||||
|
///
|
||||||
|
/// let event = Event::new();
|
||||||
|
/// ```
|
||||||
|
#[inline]
|
||||||
|
pub fn new() -> Event {
|
||||||
|
Event {
|
||||||
|
inner: AtomicPtr::default(),
|
||||||
|
}
|
||||||
|
}
|
||||||
|
|
||||||
|
/// Returns a guard listening for a notification.
|
||||||
|
///
|
||||||
|
/// # Examples
|
||||||
|
///
|
||||||
|
/// ```
|
||||||
|
/// use event_listener::Event;
|
||||||
|
///
|
||||||
|
/// let event = Event::new();
|
||||||
|
/// let listener = event.listen();
|
||||||
|
/// ```
|
||||||
|
#[cold]
|
||||||
|
pub fn listen(&self) -> EventListener {
|
||||||
|
let inner = self.inner();
|
||||||
|
let listener = EventListener {
|
||||||
|
inner: unsafe { Arc::clone(&ManuallyDrop::new(Arc::from_raw(inner))) },
|
||||||
|
entry: Some(inner.lock().insert()),
|
||||||
|
};
|
||||||
|
|
||||||
|
// Make sure the listener is registered before whatever happens next.
|
||||||
|
full_fence();
|
||||||
|
listener
|
||||||
|
}
|
||||||
|
|
||||||
|
/// Notifies a single active listener.
|
||||||
|
///
|
||||||
|
/// Note that this does not notify one *additional* listener - it only makes sure *at least*
|
||||||
|
/// one listener among the active ones is notified.
|
||||||
|
///
|
||||||
|
/// # Examples
|
||||||
|
///
|
||||||
|
/// ```
|
||||||
|
/// use event_listener::Event;
|
||||||
|
///
|
||||||
|
/// let event = Event::new();
|
||||||
|
///
|
||||||
|
/// // This notification gets lost because there are no listeners.
|
||||||
|
/// event.notify_one();
|
||||||
|
///
|
||||||
|
/// let listener1 = event.listen();
|
||||||
|
/// let listener2 = event.listen();
|
||||||
|
///
|
||||||
|
/// // Notifies just one of `listener1` and `listener2`.
|
||||||
|
/// //
|
||||||
|
/// // Listener queueing is fair, which means `listener1` gets notified
|
||||||
|
/// // here since it was the first to start listening.
|
||||||
|
/// event.notify_one();
|
||||||
|
/// ```
|
||||||
|
#[inline]
|
||||||
|
pub fn notify_one(&self) {
|
||||||
|
let inner = self.inner();
|
||||||
|
|
||||||
|
// Make sure the notification comes after whatever triggered it.
|
||||||
|
full_fence();
|
||||||
|
|
||||||
|
// Notify if no active listeners have been notified and there is at least one listener.
|
||||||
|
let flags = inner.flags.load(Ordering::Relaxed);
|
||||||
|
if flags & NOTIFIED == 0 && flags & NOTIFIABLE != 0 {
|
||||||
|
inner.lock().notify(false);
|
||||||
|
}
|
||||||
|
}
|
||||||
|
|
||||||
|
/// Notifies all active listeners.
|
||||||
|
///
|
||||||
|
/// # Examples
|
||||||
|
///
|
||||||
|
/// ```
|
||||||
|
/// use event_listener::Event;
|
||||||
|
///
|
||||||
|
/// let event = Event::new();
|
||||||
|
///
|
||||||
|
/// // This notification gets lost because there are no listeners.
|
||||||
|
/// event.notify_all();
|
||||||
|
///
|
||||||
|
/// let listener1 = event.listen();
|
||||||
|
/// let listener2 = event.listen();
|
||||||
|
///
|
||||||
|
/// // Both `listener1` and `listener2` get notified.
|
||||||
|
/// event.notify_all();
|
||||||
|
/// ```
|
||||||
|
#[inline]
|
||||||
|
pub fn notify_all(&self) {
|
||||||
|
let inner = self.inner();
|
||||||
|
|
||||||
|
// Make sure the notification comes after whatever triggered it.
|
||||||
|
full_fence();
|
||||||
|
|
||||||
|
// Notify if there is at least one listener.
|
||||||
|
if inner.flags.load(Ordering::Relaxed) & NOTIFIABLE != 0 {
|
||||||
|
inner.lock().notify(true);
|
||||||
|
}
|
||||||
|
}
|
||||||
|
|
||||||
|
/// Returns a reference to the inner state.
|
||||||
|
fn inner(&self) -> &Inner {
|
||||||
|
let mut inner = self.inner.load(Ordering::Acquire);
|
||||||
|
|
||||||
|
// Initialize the state if this is its first use.
|
||||||
|
if inner.is_null() {
|
||||||
|
// Allocate on the heap.
|
||||||
|
let new = Arc::new(Inner {
|
||||||
|
flags: AtomicUsize::new(0),
|
||||||
|
list: Mutex::new(List {
|
||||||
|
head: None,
|
||||||
|
tail: None,
|
||||||
|
len: 0,
|
||||||
|
notifiable: 0,
|
||||||
|
}),
|
||||||
|
});
|
||||||
|
// Convert the heap-allocated state into a raw pointer.
|
||||||
|
let new = Arc::into_raw(new) as *mut Inner;
|
||||||
|
|
||||||
|
// Attempt to replace the null-pointer with the new state pointer.
|
||||||
|
inner = self.inner.compare_and_swap(inner, new, Ordering::AcqRel);
|
||||||
|
|
||||||
|
// Check if the old pointer value was indeed null.
|
||||||
|
if inner.is_null() {
|
||||||
|
// If yes, then use the new state pointer.
|
||||||
|
inner = new;
|
||||||
|
} else {
|
||||||
|
// If not, that means a concurrent operation has initialized the state.
|
||||||
|
// In that case, use the old pointer and deallocate the new one.
|
||||||
|
unsafe {
|
||||||
|
drop(Arc::from_raw(new));
|
||||||
|
}
|
||||||
|
}
|
||||||
|
}
|
||||||
|
|
||||||
|
unsafe { &*inner }
|
||||||
|
}
|
||||||
|
}
|
||||||
|
|
||||||
|
impl Drop for Event {
|
||||||
|
#[inline]
|
||||||
|
fn drop(&mut self) {
|
||||||
|
let inner: *mut Inner = *self.inner.get_mut();
|
||||||
|
|
||||||
|
// If the state pointer has been initialized, deallocate it.
|
||||||
|
if !inner.is_null() {
|
||||||
|
unsafe {
|
||||||
|
drop(Arc::from_raw(inner));
|
||||||
|
}
|
||||||
|
}
|
||||||
|
}
|
||||||
|
}
|
||||||
|
|
||||||
|
impl fmt::Debug for Event {
|
||||||
|
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
|
||||||
|
f.pad("Event { .. }")
|
||||||
|
}
|
||||||
|
}
|
||||||
|
|
||||||
|
impl Default for Event {
|
||||||
|
fn default() -> Event {
|
||||||
|
Event::new()
|
||||||
|
}
|
||||||
|
}
|
||||||
|
|
||||||
|
/// A guard waiting for a notification from an [`Event`].
|
||||||
|
///
|
||||||
|
/// There are two ways for a listener to wait for a notification:
|
||||||
|
///
|
||||||
|
/// 1. In an asynchronous manner using `.await`.
|
||||||
|
/// 2. In a blocking manner by calling [`EventListener::wait()`] on it.
|
||||||
|
///
|
||||||
|
/// If a notified listener is dropped without receiving a notification, dropping will notify
|
||||||
|
/// another active listener.
|
||||||
|
pub struct EventListener {
|
||||||
|
/// A reference to [`Event`]'s inner state.
|
||||||
|
inner: Arc<Inner>,
|
||||||
|
|
||||||
|
/// A pointer to this listener's entry in the linked list.
|
||||||
|
entry: Option<NonNull<Entry>>,
|
||||||
|
}
|
||||||
|
|
||||||
|
unsafe impl Send for EventListener {}
|
||||||
|
unsafe impl Sync for EventListener {}
|
||||||
|
|
||||||
|
impl EventListener {
|
||||||
|
/// Blocks until a notification is received.
|
||||||
|
///
|
||||||
|
/// # Examples
|
||||||
|
///
|
||||||
|
/// ```
|
||||||
|
/// use event_listener::Event;
|
||||||
|
///
|
||||||
|
/// let event = Event::new();
|
||||||
|
/// let listener = event.listen();
|
||||||
|
///
|
||||||
|
/// // Notify `listener`.
|
||||||
|
/// event.notify_one();
|
||||||
|
///
|
||||||
|
/// // Receive the notification.
|
||||||
|
/// listener.wait();
|
||||||
|
/// ```
|
||||||
|
pub fn wait(self) {
|
||||||
|
self.wait_internal(None);
|
||||||
|
}
|
||||||
|
|
||||||
|
/// Blocks until a notification is received or a timeout is reached.
|
||||||
|
///
|
||||||
|
/// Returns `true` if a notification was received.
|
||||||
|
///
|
||||||
|
/// # Examples
|
||||||
|
///
|
||||||
|
/// ```
|
||||||
|
/// use std::time::Duration;
|
||||||
|
/// use event_listener::Event;
|
||||||
|
///
|
||||||
|
/// let event = Event::new();
|
||||||
|
/// let listener = event.listen();
|
||||||
|
///
|
||||||
|
/// // There are no notification so this times out.
|
||||||
|
/// assert!(!listener.wait_timeout(Duration::from_secs(1)));
|
||||||
|
/// ```
|
||||||
|
pub fn wait_timeout(self, timeout: Duration) -> bool {
|
||||||
|
self.wait_internal(Some(Instant::now() + timeout))
|
||||||
|
}
|
||||||
|
|
||||||
|
/// Blocks until a notification is received or a deadline is reached.
|
||||||
|
///
|
||||||
|
/// Returns `true` if a notification was received.
|
||||||
|
///
|
||||||
|
/// # Examples
|
||||||
|
///
|
||||||
|
/// ```
|
||||||
|
/// use std::time::{Duration, Instant};
|
||||||
|
/// use event_listener::Event;
|
||||||
|
///
|
||||||
|
/// let event = Event::new();
|
||||||
|
/// let listener = event.listen();
|
||||||
|
///
|
||||||
|
/// // There are no notification so this times out.
|
||||||
|
/// assert!(!listener.wait_deadline(Instant::now() + Duration::from_secs(1)));
|
||||||
|
/// ```
|
||||||
|
pub fn wait_deadline(self, deadline: Instant) -> bool {
|
||||||
|
self.wait_internal(Some(deadline))
|
||||||
|
}
|
||||||
|
|
||||||
|
fn wait_internal(mut self, deadline: Option<Instant>) -> bool {
|
||||||
|
// Take out the entry pointer and set it to `None`.
|
||||||
|
let entry = match self.entry.take() {
|
||||||
|
None => unreachable!("cannot wait twice on an `EventListener`"),
|
||||||
|
Some(entry) => entry,
|
||||||
|
};
|
||||||
|
|
||||||
|
// Set this listener's state to `Waiting`.
|
||||||
|
{
|
||||||
|
let mut list = self.inner.lock();
|
||||||
|
let e = unsafe { entry.as_ref() };
|
||||||
|
|
||||||
|
// Do a dummy replace operation in order to take out the state.
|
||||||
|
match e.state.replace(State::Notified) {
|
||||||
|
State::Notified => {
|
||||||
|
// If this listener has been notified, remove it from the list and return.
|
||||||
|
list.remove(entry);
|
||||||
|
return true;
|
||||||
|
}
|
||||||
|
// Otherwise, set the state to `Waiting`.
|
||||||
|
_ => e.state.set(State::Waiting(thread::current())),
|
||||||
|
}
|
||||||
|
}
|
||||||
|
|
||||||
|
// Wait until a notification is received or the timeout is reached.
|
||||||
|
loop {
|
||||||
|
match deadline {
|
||||||
|
None => thread::park(),
|
||||||
|
|
||||||
|
Some(deadline) => {
|
||||||
|
// Check for timeout.
|
||||||
|
let now = Instant::now();
|
||||||
|
if now >= deadline {
|
||||||
|
return false;
|
||||||
|
}
|
||||||
|
|
||||||
|
// Park until the deadline.
|
||||||
|
thread::park_timeout(deadline - now);
|
||||||
|
}
|
||||||
|
}
|
||||||
|
|
||||||
|
let mut list = self.inner.lock();
|
||||||
|
let e = unsafe { entry.as_ref() };
|
||||||
|
|
||||||
|
// Do a dummy replace operation in order to take out the state.
|
||||||
|
match e.state.replace(State::Notified) {
|
||||||
|
State::Notified => {
|
||||||
|
// If this listener has been notified, remove it from the list and return.
|
||||||
|
list.remove(entry);
|
||||||
|
return true;
|
||||||
|
}
|
||||||
|
// Otherwise, set the state back to `Waiting`.
|
||||||
|
state => e.state.set(state),
|
||||||
|
}
|
||||||
|
}
|
||||||
|
}
|
||||||
|
}
|
||||||
|
|
||||||
|
impl fmt::Debug for EventListener {
|
||||||
|
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
|
||||||
|
f.pad("EventListener { .. }")
|
||||||
|
}
|
||||||
|
}
|
||||||
|
|
||||||
|
impl Future for EventListener {
|
||||||
|
type Output = ();
|
||||||
|
|
||||||
|
fn poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
|
||||||
|
let mut list = self.inner.lock();
|
||||||
|
|
||||||
|
let entry = match self.entry {
|
||||||
|
None => unreachable!("cannot poll a completed `EventListener` future"),
|
||||||
|
Some(entry) => entry,
|
||||||
|
};
|
||||||
|
let state = unsafe { &entry.as_ref().state };
|
||||||
|
|
||||||
|
// Do a dummy replace operation in order to take out the state.
|
||||||
|
match state.replace(State::Notified) {
|
||||||
|
State::Notified => {
|
||||||
|
// If this listener has been notified, remove it from the list and return.
|
||||||
|
list.remove(entry);
|
||||||
|
drop(list);
|
||||||
|
self.entry = None;
|
||||||
|
return Poll::Ready(());
|
||||||
|
}
|
||||||
|
State::Created => {
|
||||||
|
// If the listener was just created, put it in the `Polling` state.
|
||||||
|
state.set(State::Polling(cx.waker().clone()));
|
||||||
|
}
|
||||||
|
State::Polling(w) => {
|
||||||
|
// If the listener was in the `Pooling` state, keep it.
|
||||||
|
state.set(State::Polling(w));
|
||||||
|
}
|
||||||
|
State::Waiting(_) => {
|
||||||
|
unreachable!("cannot poll and wait on `EventListener` at the same time")
|
||||||
|
}
|
||||||
|
}
|
||||||
|
|
||||||
|
Poll::Pending
|
||||||
|
}
|
||||||
|
}
|
||||||
|
|
||||||
|
impl Drop for EventListener {
|
||||||
|
fn drop(&mut self) {
|
||||||
|
// If this listener has never picked up a notification...
|
||||||
|
if let Some(entry) = self.entry.take() {
|
||||||
|
let mut list = self.inner.lock();
|
||||||
|
|
||||||
|
// But if a notification was delivered to it...
|
||||||
|
if list.remove(entry).is_notified() {
|
||||||
|
// Then pass it on to another active listener.
|
||||||
|
list.notify(false);
|
||||||
|
}
|
||||||
|
}
|
||||||
|
}
|
||||||
|
}
|
||||||
|
|
||||||
|
/// A guard holding the linked list locked.
|
||||||
|
struct ListGuard<'a> {
|
||||||
|
/// A reference to [`Event`]'s inner state.
|
||||||
|
inner: &'a Inner,
|
||||||
|
|
||||||
|
/// The actual guard that acquired the linked list.
|
||||||
|
guard: MutexGuard<'a, List>,
|
||||||
|
}
|
||||||
|
|
||||||
|
impl Drop for ListGuard<'_> {
|
||||||
|
#[inline]
|
||||||
|
fn drop(&mut self) {
|
||||||
|
let list = &mut **self;
|
||||||
|
let mut flags = 0;
|
||||||
|
|
||||||
|
// Set the `NOTIFIED` flag if there is at least one notified listener.
|
||||||
|
if list.len - list.notifiable > 0 {
|
||||||
|
flags |= NOTIFIED;
|
||||||
|
}
|
||||||
|
|
||||||
|
// Set the `NOTIFIABLE` flag if there is at least one notifiable listener.
|
||||||
|
if list.notifiable > 0 {
|
||||||
|
flags |= NOTIFIABLE;
|
||||||
|
}
|
||||||
|
|
||||||
|
self.inner.flags.store(flags, Ordering::Release);
|
||||||
|
}
|
||||||
|
}
|
||||||
|
|
||||||
|
impl Deref for ListGuard<'_> {
|
||||||
|
type Target = List;
|
||||||
|
|
||||||
|
#[inline]
|
||||||
|
fn deref(&self) -> &List {
|
||||||
|
&*self.guard
|
||||||
|
}
|
||||||
|
}
|
||||||
|
|
||||||
|
impl DerefMut for ListGuard<'_> {
|
||||||
|
#[inline]
|
||||||
|
fn deref_mut(&mut self) -> &mut List {
|
||||||
|
&mut *self.guard
|
||||||
|
}
|
||||||
|
}
|
||||||
|
|
||||||
|
/// The state of a listener.
|
||||||
|
enum State {
|
||||||
|
/// It has just been created.
|
||||||
|
Created,
|
||||||
|
|
||||||
|
/// It has received a notification.
|
||||||
|
Notified,
|
||||||
|
|
||||||
|
/// An async task is polling it.
|
||||||
|
Polling(Waker),
|
||||||
|
|
||||||
|
/// A thread is blocked on it.
|
||||||
|
Waiting(Thread),
|
||||||
|
}
|
||||||
|
|
||||||
|
impl State {
|
||||||
|
/// Returns `true` if this is the `Notified` state.
|
||||||
|
#[inline]
|
||||||
|
fn is_notified(&self) -> bool {
|
||||||
|
match self {
|
||||||
|
State::Notified => true,
|
||||||
|
State::Created | State::Polling(_) | State::Waiting(_) => false,
|
||||||
|
}
|
||||||
|
}
|
||||||
|
}
|
||||||
|
|
||||||
|
/// An entry representing a registered listener.
|
||||||
|
struct Entry {
|
||||||
|
/// THe state of this listener.
|
||||||
|
state: Cell<State>,
|
||||||
|
|
||||||
|
/// Previous entry in the linked list.
|
||||||
|
prev: Cell<Option<NonNull<Entry>>>,
|
||||||
|
|
||||||
|
/// Next entry in the linked list.
|
||||||
|
next: Cell<Option<NonNull<Entry>>>,
|
||||||
|
}
|
||||||
|
|
||||||
|
/// A linked list of entries.
|
||||||
|
struct List {
|
||||||
|
/// First entry in the list.
|
||||||
|
head: Option<NonNull<Entry>>,
|
||||||
|
|
||||||
|
/// Last entry in the list.
|
||||||
|
tail: Option<NonNull<Entry>>,
|
||||||
|
|
||||||
|
/// Total number of entries in the list.
|
||||||
|
len: usize,
|
||||||
|
|
||||||
|
/// Number of notifiable entries in the list.
|
||||||
|
///
|
||||||
|
/// Notifiable entries are those that haven't been notified yet.
|
||||||
|
notifiable: usize,
|
||||||
|
}
|
||||||
|
|
||||||
|
impl List {
|
||||||
|
/// Inserts a new entry into the list.
|
||||||
|
fn insert(&mut self) -> NonNull<Entry> {
|
||||||
|
unsafe {
|
||||||
|
// Allocate an entry that is going to become the new tail.
|
||||||
|
let entry = NonNull::new_unchecked(Box::into_raw(Box::new(Entry {
|
||||||
|
state: Cell::new(State::Created),
|
||||||
|
prev: Cell::new(self.tail),
|
||||||
|
next: Cell::new(None),
|
||||||
|
})));
|
||||||
|
|
||||||
|
// Replace the tail with the new entry.
|
||||||
|
match mem::replace(&mut self.tail, Some(entry)) {
|
||||||
|
None => self.head = Some(entry),
|
||||||
|
Some(t) => t.as_ref().next.set(Some(entry)),
|
||||||
|
}
|
||||||
|
|
||||||
|
// Bump the total count and the count of notifiable entries.
|
||||||
|
self.len += 1;
|
||||||
|
self.notifiable += 1;
|
||||||
|
|
||||||
|
entry
|
||||||
|
}
|
||||||
|
}
|
||||||
|
|
||||||
|
/// Removes an entry from the list and returns its state.
|
||||||
|
fn remove(&mut self, entry: NonNull<Entry>) -> State {
|
||||||
|
unsafe {
|
||||||
|
let prev = entry.as_ref().prev.get();
|
||||||
|
let next = entry.as_ref().next.get();
|
||||||
|
|
||||||
|
// Unlink from the previous entry.
|
||||||
|
match prev {
|
||||||
|
None => self.head = next,
|
||||||
|
Some(p) => p.as_ref().next.set(next),
|
||||||
|
}
|
||||||
|
|
||||||
|
// Unlink from the next entry.
|
||||||
|
match next {
|
||||||
|
None => self.tail = prev,
|
||||||
|
Some(n) => n.as_ref().prev.set(prev),
|
||||||
|
}
|
||||||
|
|
||||||
|
// Deallocate and extract the state.
|
||||||
|
let entry = Box::from_raw(entry.as_ptr());
|
||||||
|
let state = entry.state.into_inner();
|
||||||
|
|
||||||
|
// Update the counters.
|
||||||
|
if !state.is_notified() {
|
||||||
|
self.notifiable -= 1;
|
||||||
|
}
|
||||||
|
self.len -= 1;
|
||||||
|
|
||||||
|
state
|
||||||
|
}
|
||||||
|
}
|
||||||
|
|
||||||
|
/// Notifies an entry.
|
||||||
|
#[cold]
|
||||||
|
fn notify(&mut self, notify_all: bool) {
|
||||||
|
let mut entry = self.tail;
|
||||||
|
|
||||||
|
// Iterate over the entries in the list.
|
||||||
|
while let Some(e) = entry {
|
||||||
|
let e = unsafe { e.as_ref() };
|
||||||
|
|
||||||
|
// Set the state of this entry to `Notified`.
|
||||||
|
let state = e.state.replace(State::Notified);
|
||||||
|
let is_notified = state.is_notified();
|
||||||
|
|
||||||
|
// Wake the task or unpark the thread.
|
||||||
|
match state {
|
||||||
|
State::Notified => {}
|
||||||
|
State::Created => {}
|
||||||
|
State::Polling(w) => w.wake(),
|
||||||
|
State::Waiting(t) => t.unpark(),
|
||||||
|
}
|
||||||
|
|
||||||
|
// Update the count of notifiable entries.
|
||||||
|
if !is_notified {
|
||||||
|
self.notifiable -= 1;
|
||||||
|
}
|
||||||
|
|
||||||
|
// If all entries need to be notified, go to the next one.
|
||||||
|
if notify_all {
|
||||||
|
entry = e.prev.get();
|
||||||
|
} else {
|
||||||
|
break;
|
||||||
|
}
|
||||||
|
}
|
||||||
|
}
|
||||||
|
}
|
||||||
|
|
||||||
|
/// Equivalent to `atomic::fence(Ordering::SeqCst)`, but in some cases faster.
|
||||||
|
#[inline]
|
||||||
|
fn full_fence() {
|
||||||
|
if cfg!(any(target_arch = "x86", target_arch = "x86_64")) {
|
||||||
|
// HACK(stjepang): On x86 architectures there are two different ways of executing
|
||||||
|
// a `SeqCst` fence.
|
||||||
|
//
|
||||||
|
// 1. `atomic::fence(SeqCst)`, which compiles into a `mfence` instruction.
|
||||||
|
// 2. `_.compare_and_swap(_, _, SeqCst)`, which compiles into a `lock cmpxchg` instruction.
|
||||||
|
//
|
||||||
|
// Both instructions have the effect of a full barrier, but empirical benchmarks have shown
|
||||||
|
// that the second one is sometimes a bit faster.
|
||||||
|
//
|
||||||
|
// The ideal solution here would be to use inline assembly, but we're instead creating a
|
||||||
|
// temporary atomic variable and compare-and-exchanging its value. No sane compiler to
|
||||||
|
// x86 platforms is going to optimize this away.
|
||||||
|
let a = AtomicUsize::new(0);
|
||||||
|
a.compare_and_swap(0, 1, Ordering::SeqCst);
|
||||||
|
} else {
|
||||||
|
atomic::fence(Ordering::SeqCst);
|
||||||
|
}
|
||||||
|
}
|
Loading…
Reference in New Issue