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//! Threadpool
mod atomic_cell;
use atomic_cell::AtomicCell;
mod idle;
use self::idle::Idle;
mod worker;
pub(crate) use worker::Launch;
pub(crate) use worker::block_in_place;
use crate::loom::sync::Arc;
use crate::runtime::task::{self, JoinHandle};
use crate::runtime::Parker;
use std::fmt;
use std::future::Future;
/// Work-stealing based thread pool for executing futures.
pub(crate) struct ThreadPool {
spawner: Spawner,
}
/// Submit futures to the associated thread pool for execution.
///
/// A `Spawner` instance is a handle to a single thread pool that allows the owner
/// of the handle to spawn futures onto the thread pool.
///
/// The `Spawner` handle is *only* used for spawning new futures. It does not
/// impact the lifecycle of the thread pool in any way. The thread pool may
/// shutdown while there are outstanding `Spawner` instances.
///
/// `Spawner` instances are obtained by calling [`ThreadPool::spawner`].
///
/// [`ThreadPool::spawner`]: method@ThreadPool::spawner
#[derive(Clone)]
pub(crate) struct Spawner {
shared: Arc<worker::Shared>,
}
// ===== impl ThreadPool =====
impl ThreadPool {
pub(crate) fn new(size: usize, parker: Parker) -> (ThreadPool, Launch) {
let (shared, launch) = worker::create(size, parker);
let spawner = Spawner { shared };
let thread_pool = ThreadPool { spawner };
(thread_pool, launch)
}
/// Returns reference to `Spawner`.
///
/// The `Spawner` handle can be cloned and enables spawning tasks from other
/// threads.
pub(crate) fn spawner(&self) -> &Spawner {
&self.spawner
}
/// Spawns a task
pub(crate) fn spawn<F>(&self, future: F) -> JoinHandle<F::Output>
where
F: Future + Send + 'static,
F::Output: Send + 'static,
{
self.spawner.spawn(future)
}
/// Blocks the current thread waiting for the future to complete.
///
/// The future will execute on the current thread, but all spawned tasks
/// will be executed on the thread pool.
pub(crate) fn block_on<F>(&self, future: F) -> F::Output
where
F: Future,
{
let mut enter = crate::runtime::enter(true);
enter.block_on(future).expect("failed to park thread")
}
}
impl fmt::Debug for ThreadPool {
fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
fmt.debug_struct("ThreadPool").finish()
}
}
impl Drop for ThreadPool {
fn drop(&mut self) {
self.spawner.shutdown();
}
}
// ==== impl Spawner =====
impl Spawner {
/// Spawns a future onto the thread pool
pub(crate) fn spawn<F>(&self, future: F) -> JoinHandle<F::Output>
where
F: Future + Send + 'static,
F::Output: Send + 'static,
{
let (task, handle) = task::joinable(future);
self.shared.schedule(task, false);
handle
}
pub(crate) fn shutdown(&mut self) {
self.shared.close();
}
}
impl fmt::Debug for Spawner {
fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
fmt.debug_struct("Spawner").finish()
}
}
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