mirror of
https://gitlab.freedesktop.org/gstreamer/gst-plugins-rs.git
synced 2024-09-26 14:00:12 +00:00
1be30b8ecc
A strong handle reference was held in the `block_on_priv` `Result` handler in the thread for the `Scheduler::start` code path, which lead to the `Handler` strong count not dropping to 0 when it should, leading to the shutdown request not being triggered. Use an Arc<AtomicBool> instead of a oneshot channel for shutdown. The main Future is always polled and never relies on a waker, a `poll_fn` is cheap and does the job. Unpark the scheduler after posting a request to shutdown.
516 lines
16 KiB
Rust
516 lines
16 KiB
Rust
// Copyright (C) 2018-2020 Sebastian Dröge <sebastian@centricular.com>
|
|
// Copyright (C) 2019-2022 François Laignel <fengalin@free.fr>
|
|
//
|
|
// Take a look at the license at the top of the repository in the LICENSE file.
|
|
|
|
use futures::future::poll_fn;
|
|
use futures::pin_mut;
|
|
|
|
use gio::glib::clone::Downgrade;
|
|
|
|
use std::cell::RefCell;
|
|
use std::future::Future;
|
|
use std::panic;
|
|
#[cfg(feature = "tuning")]
|
|
use std::sync::atomic::AtomicU64;
|
|
use std::sync::atomic::{AtomicBool, Ordering};
|
|
use std::sync::mpsc as sync_mpsc;
|
|
use std::sync::{Arc, Condvar, Mutex, Weak};
|
|
use std::task::Poll;
|
|
use std::thread;
|
|
use std::time::{Duration, Instant};
|
|
|
|
use waker_fn::waker_fn;
|
|
|
|
use super::task::{SubTaskOutput, TaskId, TaskQueue};
|
|
use super::{CallOnDrop, JoinHandle, Reactor};
|
|
use crate::runtime::RUNTIME_CAT;
|
|
|
|
thread_local! {
|
|
static CURRENT_SCHEDULER: RefCell<Option<HandleWeak>> = RefCell::new(None);
|
|
}
|
|
|
|
#[derive(Debug)]
|
|
pub(super) struct Scheduler {
|
|
context_name: Arc<str>,
|
|
max_throttling: Duration,
|
|
tasks: TaskQueue,
|
|
must_unpark: Mutex<bool>,
|
|
must_unpark_cvar: Condvar,
|
|
#[cfg(feature = "tuning")]
|
|
parked_duration: AtomicU64,
|
|
}
|
|
|
|
impl Scheduler {
|
|
pub const DUMMY_NAME: &'static str = "DUMMY";
|
|
const MAX_SUCCESSIVE_TASKS: usize = 64;
|
|
|
|
pub fn start(context_name: &str, max_throttling: Duration) -> Handle {
|
|
// Name the thread so that it appears in panic messages.
|
|
let thread = thread::Builder::new().name(context_name.to_string());
|
|
|
|
let (handle_sender, handle_receiver) = sync_mpsc::channel();
|
|
let context_name = Arc::from(context_name);
|
|
let thread_ctx_name = Arc::clone(&context_name);
|
|
let join = thread
|
|
.spawn(move || {
|
|
gst::debug!(
|
|
RUNTIME_CAT,
|
|
"Started Scheduler thread for Context {}",
|
|
thread_ctx_name
|
|
);
|
|
|
|
let handle = Scheduler::init(Arc::clone(&thread_ctx_name), max_throttling);
|
|
let this = Arc::clone(&handle.0.scheduler);
|
|
let must_shutdown = handle.0.must_shutdown.clone();
|
|
let handle_weak = handle.downgrade();
|
|
handle_sender.send(handle).unwrap();
|
|
|
|
let shutdown_fut = poll_fn(move |_| {
|
|
if must_shutdown.load(Ordering::SeqCst) {
|
|
Poll::Ready(())
|
|
} else {
|
|
Poll::Pending
|
|
}
|
|
});
|
|
|
|
// Blocking on `shutdown_fut` which is cheap to `poll`.
|
|
match this.block_on_priv(shutdown_fut) {
|
|
Ok(_) => {
|
|
gst::debug!(
|
|
RUNTIME_CAT,
|
|
"Scheduler thread shut down for Context {}",
|
|
thread_ctx_name
|
|
);
|
|
}
|
|
Err(e) => {
|
|
gst::error!(
|
|
RUNTIME_CAT,
|
|
"Scheduler thread shut down due to an error within Context {}",
|
|
thread_ctx_name
|
|
);
|
|
|
|
if let Some(handle) = handle_weak.upgrade() {
|
|
handle.self_shutdown();
|
|
}
|
|
|
|
panic::resume_unwind(e);
|
|
}
|
|
}
|
|
})
|
|
.expect("Failed to spawn Scheduler thread");
|
|
|
|
let handle = handle_receiver.recv().expect("Context thread init failed");
|
|
handle.set_join_handle(join);
|
|
|
|
handle
|
|
}
|
|
|
|
fn init(context_name: Arc<str>, max_throttling: Duration) -> Handle {
|
|
let handle = CURRENT_SCHEDULER.with(|cur_scheduler| {
|
|
let mut cur_scheduler = cur_scheduler.borrow_mut();
|
|
if cur_scheduler.is_some() {
|
|
panic!("Attempt to initialize an Scheduler on thread where another Scheduler is running.");
|
|
}
|
|
|
|
let handle = Handle::new(Arc::new(Scheduler {
|
|
context_name: context_name.clone(),
|
|
max_throttling,
|
|
tasks: TaskQueue::new(context_name),
|
|
must_unpark: Mutex::new(false),
|
|
must_unpark_cvar: Condvar::new(),
|
|
#[cfg(feature = "tuning")]
|
|
parked_duration: AtomicU64::new(0),
|
|
}));
|
|
|
|
*cur_scheduler = Some(handle.downgrade());
|
|
|
|
handle
|
|
});
|
|
|
|
Reactor::init(handle.max_throttling());
|
|
|
|
handle
|
|
}
|
|
|
|
pub fn block_on<F>(future: F) -> F::Output
|
|
where
|
|
F: Future + Send + 'static,
|
|
F::Output: Send + 'static,
|
|
{
|
|
assert!(
|
|
!Scheduler::is_scheduler_thread(),
|
|
"Attempt to block within an existing Scheduler thread."
|
|
);
|
|
|
|
let handle = Scheduler::init(Scheduler::DUMMY_NAME.into(), Duration::ZERO);
|
|
let this = Arc::clone(&handle.0.scheduler);
|
|
|
|
// Move the (only) handle for this scheduler in the main task.
|
|
let (task_id, task) = this.tasks.add(async move {
|
|
let res = future.await;
|
|
|
|
let task_id = TaskId::current().unwrap();
|
|
let _ = handle.drain_sub_tasks(task_id).await;
|
|
|
|
res
|
|
});
|
|
|
|
gst::trace!(RUNTIME_CAT, "Blocking on current thread with {:?}", task_id);
|
|
|
|
let _guard = CallOnDrop::new(|| {
|
|
gst::trace!(
|
|
RUNTIME_CAT,
|
|
"Blocking on current thread with {:?} done",
|
|
task_id,
|
|
);
|
|
});
|
|
|
|
// Blocking on `task` which is cheap to `poll`.
|
|
match this.block_on_priv(task) {
|
|
Ok(res) => res,
|
|
Err(e) => {
|
|
gst::error!(
|
|
RUNTIME_CAT,
|
|
"Panic blocking on Context {}",
|
|
&Scheduler::DUMMY_NAME
|
|
);
|
|
|
|
panic::resume_unwind(e);
|
|
}
|
|
}
|
|
}
|
|
|
|
// Important: the `termination_future` MUST be cheap to poll.
|
|
//
|
|
// Examples of appropriate `termination_future` are:
|
|
//
|
|
// - an `executor::Task` returned by `self.tasks.add(..)`.
|
|
// - a `JoinHandle` returned by `Handle::spawn`.
|
|
// - a custom future with few cycles (ex. checking an `AtomicBool`).
|
|
fn block_on_priv<F>(&self, termination_future: F) -> std::thread::Result<F::Output>
|
|
where
|
|
F: Future + Send + 'static,
|
|
F::Output: Send + 'static,
|
|
{
|
|
let waker = waker_fn(|| ());
|
|
let cx = &mut std::task::Context::from_waker(&waker);
|
|
pin_mut!(termination_future);
|
|
|
|
let _guard = CallOnDrop::new(|| Scheduler::close(Arc::clone(&self.context_name)));
|
|
|
|
let mut now;
|
|
// This is to ensure reactor invocation on the first iteration.
|
|
let mut last_react = Instant::now() - self.max_throttling;
|
|
let mut tasks_checked;
|
|
'main: loop {
|
|
// Only check I/O and timers every `max_throttling`.
|
|
now = Instant::now();
|
|
if now - last_react >= self.max_throttling {
|
|
last_react = now;
|
|
Reactor::with_mut(|reactor| reactor.react(now).ok());
|
|
}
|
|
|
|
if let Poll::Ready(t) = termination_future.as_mut().poll(cx) {
|
|
return Ok(t);
|
|
}
|
|
|
|
tasks_checked = 0;
|
|
while tasks_checked < Self::MAX_SUCCESSIVE_TASKS {
|
|
if let Ok(runnable) = self.tasks.pop_runnable() {
|
|
panic::catch_unwind(|| runnable.run()).map_err(|err| {
|
|
gst::error!(
|
|
RUNTIME_CAT,
|
|
"A task has panicked within Context {}",
|
|
self.context_name
|
|
);
|
|
|
|
err
|
|
})?;
|
|
|
|
tasks_checked += 1;
|
|
} else {
|
|
let mut must_unpark = self.must_unpark.lock().unwrap();
|
|
loop {
|
|
if *must_unpark {
|
|
*must_unpark = false;
|
|
continue 'main;
|
|
}
|
|
|
|
if let Some(parking_duration) =
|
|
self.max_throttling.checked_sub(last_react.elapsed())
|
|
{
|
|
#[cfg(feature = "tuning")]
|
|
self.parked_duration.fetch_add(
|
|
parking_duration.subsec_nanos() as u64,
|
|
Ordering::Relaxed,
|
|
);
|
|
|
|
let result = self
|
|
.must_unpark_cvar
|
|
.wait_timeout(must_unpark, parking_duration)
|
|
.unwrap();
|
|
|
|
must_unpark = result.0;
|
|
} else {
|
|
*must_unpark = false;
|
|
continue 'main;
|
|
}
|
|
}
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
fn unpark(&self) {
|
|
let mut must_unpark = self.must_unpark.lock().unwrap();
|
|
*must_unpark = true;
|
|
self.must_unpark_cvar.notify_one();
|
|
}
|
|
|
|
fn close(context_name: Arc<str>) {
|
|
gst::trace!(
|
|
RUNTIME_CAT,
|
|
"Closing Scheduler for Context {}",
|
|
context_name,
|
|
);
|
|
|
|
Reactor::clear();
|
|
|
|
let _ = CURRENT_SCHEDULER.try_with(|cur_scheduler| {
|
|
*cur_scheduler.borrow_mut() = None;
|
|
});
|
|
}
|
|
|
|
pub fn is_scheduler_thread() -> bool {
|
|
CURRENT_SCHEDULER.with(|cur_scheduler| cur_scheduler.borrow().is_some())
|
|
}
|
|
|
|
pub fn current() -> Option<Handle> {
|
|
CURRENT_SCHEDULER.with(|cur_scheduler| {
|
|
cur_scheduler
|
|
.borrow()
|
|
.as_ref()
|
|
.and_then(HandleWeak::upgrade)
|
|
})
|
|
}
|
|
|
|
pub fn is_current(&self) -> bool {
|
|
CURRENT_SCHEDULER.with(|cur_scheduler| {
|
|
cur_scheduler
|
|
.borrow()
|
|
.as_ref()
|
|
.and_then(HandleWeak::upgrade)
|
|
.map_or(false, |cur| {
|
|
std::ptr::eq(self, Arc::as_ptr(&cur.0.scheduler))
|
|
})
|
|
})
|
|
}
|
|
}
|
|
|
|
#[derive(Debug)]
|
|
struct HandleInner {
|
|
scheduler: Arc<Scheduler>,
|
|
must_shutdown: Arc<AtomicBool>,
|
|
join: Mutex<Option<thread::JoinHandle<()>>>,
|
|
}
|
|
|
|
impl HandleInner {
|
|
fn new(scheduler: Arc<Scheduler>) -> Self {
|
|
HandleInner {
|
|
scheduler,
|
|
must_shutdown: Default::default(),
|
|
join: Default::default(),
|
|
}
|
|
}
|
|
}
|
|
|
|
impl Drop for HandleInner {
|
|
fn drop(&mut self) {
|
|
if !self.must_shutdown.fetch_or(true, Ordering::SeqCst) {
|
|
// Was not already shutting down.
|
|
self.scheduler.unpark();
|
|
|
|
gst::trace!(
|
|
RUNTIME_CAT,
|
|
"Shutting down Scheduler thread for Context {}",
|
|
self.scheduler.context_name
|
|
);
|
|
|
|
// Don't block shutting down itself
|
|
if !self.scheduler.is_current() {
|
|
if let Some(join_handler) = self.join.lock().unwrap().take() {
|
|
gst::trace!(
|
|
RUNTIME_CAT,
|
|
"Waiting for Scheduler thread to shutdown for Context {}",
|
|
self.scheduler.context_name
|
|
);
|
|
|
|
let _ = join_handler.join();
|
|
}
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
#[derive(Clone, Debug)]
|
|
pub(super) struct HandleWeak(Weak<HandleInner>);
|
|
|
|
impl HandleWeak {
|
|
pub(super) fn upgrade(&self) -> Option<Handle> {
|
|
self.0.upgrade().map(Handle)
|
|
}
|
|
}
|
|
|
|
#[derive(Clone, Debug)]
|
|
pub(super) struct Handle(Arc<HandleInner>);
|
|
|
|
impl Handle {
|
|
fn new(scheduler: Arc<Scheduler>) -> Self {
|
|
Handle(Arc::new(HandleInner::new(scheduler)))
|
|
}
|
|
|
|
fn set_join_handle(&self, join: thread::JoinHandle<()>) {
|
|
*self.0.join.lock().unwrap() = Some(join);
|
|
}
|
|
|
|
fn self_shutdown(self) {
|
|
self.0.must_shutdown.store(true, Ordering::SeqCst);
|
|
*self.0.join.lock().unwrap() = None;
|
|
}
|
|
|
|
pub fn context_name(&self) -> &str {
|
|
&self.0.scheduler.context_name
|
|
}
|
|
|
|
pub fn max_throttling(&self) -> Duration {
|
|
self.0.scheduler.max_throttling
|
|
}
|
|
|
|
#[cfg(feature = "tuning")]
|
|
pub fn parked_duration(&self) -> Duration {
|
|
Duration::from_nanos(self.0.scheduler.parked_duration.load(Ordering::Relaxed))
|
|
}
|
|
|
|
/// Executes the provided function relatively to this [`Scheduler`]'s [`Reactor`].
|
|
///
|
|
/// Usefull to initialze i/o sources and timers from outside
|
|
/// of a [`Scheduler`].
|
|
///
|
|
/// # Panic
|
|
///
|
|
/// This will block current thread and would panic if run
|
|
/// from the [`Scheduler`].
|
|
pub fn enter<'a, F, O>(&'a self, f: F) -> O
|
|
where
|
|
F: FnOnce() -> O + Send + 'a,
|
|
O: Send + 'a,
|
|
{
|
|
assert!(!self.0.scheduler.is_current());
|
|
|
|
// Safety: bounding `self` to `'a` and blocking on the task
|
|
// ensures that the lifetime bounds satisfy the safety
|
|
// requirements for `TaskQueue::add_sync`.
|
|
let task = unsafe { self.0.scheduler.tasks.add_sync(f) };
|
|
self.0.scheduler.unpark();
|
|
futures::executor::block_on(task)
|
|
}
|
|
|
|
pub fn spawn<F>(&self, future: F) -> JoinHandle<F::Output>
|
|
where
|
|
F: Future + Send + 'static,
|
|
F::Output: Send + 'static,
|
|
{
|
|
let (task_id, task) = self.0.scheduler.tasks.add(future);
|
|
JoinHandle::new(task_id, task, self)
|
|
}
|
|
|
|
pub fn spawn_and_unpark<F>(&self, future: F) -> JoinHandle<F::Output>
|
|
where
|
|
F: Future + Send + 'static,
|
|
F::Output: Send + 'static,
|
|
{
|
|
let (task_id, task) = self.0.scheduler.tasks.add(future);
|
|
self.0.scheduler.unpark();
|
|
JoinHandle::new(task_id, task, self)
|
|
}
|
|
|
|
pub(super) fn unpark(&self) {
|
|
self.0.scheduler.unpark();
|
|
}
|
|
|
|
pub fn add_sub_task<T>(&self, task_id: TaskId, sub_task: T) -> Result<(), T>
|
|
where
|
|
T: Future<Output = SubTaskOutput> + Send + 'static,
|
|
{
|
|
self.0.scheduler.tasks.add_sub_task(task_id, sub_task)
|
|
}
|
|
|
|
pub fn downgrade(&self) -> HandleWeak {
|
|
HandleWeak(self.0.downgrade())
|
|
}
|
|
|
|
pub async fn drain_sub_tasks(&self, task_id: TaskId) -> SubTaskOutput {
|
|
let sub_tasks_fut = self.0.scheduler.tasks.drain_sub_tasks(task_id);
|
|
sub_tasks_fut.await
|
|
}
|
|
}
|
|
|
|
impl PartialEq for Handle {
|
|
fn eq(&self, other: &Self) -> bool {
|
|
Arc::ptr_eq(&self.0, &other.0)
|
|
}
|
|
}
|
|
|
|
#[cfg(test)]
|
|
mod tests {
|
|
use super::super::*;
|
|
use std::time::Duration;
|
|
|
|
#[test]
|
|
fn block_on_task_join_handle() {
|
|
use futures::channel::oneshot;
|
|
use std::sync::mpsc;
|
|
|
|
let (join_sender, join_receiver) = mpsc::channel();
|
|
let (shutdown_sender, shutdown_receiver) = oneshot::channel();
|
|
|
|
std::thread::spawn(move || {
|
|
let handle =
|
|
Scheduler::init("block_on_task_join_handle".into(), Duration::from_millis(2));
|
|
let join_handle = handle.spawn(async {
|
|
timer::delay_for(Duration::from_millis(5)).await;
|
|
42
|
|
});
|
|
|
|
let _ = join_sender.send(join_handle);
|
|
let _ = handle.0.scheduler.block_on_priv(shutdown_receiver);
|
|
});
|
|
|
|
let task_join_handle = join_receiver.recv().unwrap();
|
|
let res = Scheduler::block_on(task_join_handle).unwrap();
|
|
|
|
let _ = shutdown_sender.send(());
|
|
|
|
assert_eq!(res, 42);
|
|
}
|
|
|
|
#[test]
|
|
fn block_on_timer() {
|
|
let res = Scheduler::block_on(async {
|
|
timer::delay_for(Duration::from_millis(5)).await;
|
|
42
|
|
});
|
|
|
|
assert_eq!(res, 42);
|
|
}
|
|
|
|
#[test]
|
|
fn enter_non_static() {
|
|
let handle = Scheduler::start("enter_non_static", Duration::from_millis(2));
|
|
|
|
let mut flag = false;
|
|
handle.enter(|| flag = true);
|
|
assert!(flag);
|
|
}
|
|
}
|