use alloc::sync::Arc;
use core::mem;
-use crate::sync::{Condvar, Mutex, MutexGuard};
+use crate::sync::{Condvar, Mutex};
use crate::prelude::*;
#[cfg(any(test, feature = "std"))]
-use std::time::{Duration, Instant};
+use std::time::Duration;
use core::future::Future as StdFuture;
use core::task::{Context, Poll};
/// Used to signal to one of many waiters that the condition they're waiting on has happened.
pub(crate) struct Notifier {
notify_pending: Mutex<(bool, Option<Arc<Mutex<FutureState>>>)>,
- condvar: Condvar,
-}
-
-macro_rules! check_woken {
- ($guard: expr, $retval: expr) => { {
- if $guard.0 {
- $guard.0 = false;
- if $guard.1.as_ref().map(|l| l.lock().unwrap().complete).unwrap_or(false) {
- // If we're about to return as woken, and the future state is marked complete, wipe
- // the future state and let the next future wait until we get a new notify.
- $guard.1.take();
- }
- return $retval;
- }
- } }
}
impl Notifier {
pub(crate) fn new() -> Self {
Self {
notify_pending: Mutex::new((false, None)),
- condvar: Condvar::new(),
- }
- }
-
- fn propagate_future_state_to_notify_flag(&self) -> MutexGuard<(bool, Option<Arc<Mutex<FutureState>>>)> {
- let mut lock = self.notify_pending.lock().unwrap();
- if let Some(existing_state) = &lock.1 {
- if existing_state.lock().unwrap().callbacks_made {
- // If the existing `FutureState` has completed and actually made callbacks,
- // consider the notification flag to have been cleared and reset the future state.
- lock.1.take();
- lock.0 = false;
- }
}
- lock
}
pub(crate) fn wait(&self) {
- loop {
- let mut guard = self.propagate_future_state_to_notify_flag();
- check_woken!(guard, ());
- guard = self.condvar.wait(guard).unwrap();
- check_woken!(guard, ());
- }
+ Sleeper::from_single_future(self.get_future()).wait();
}
#[cfg(any(test, feature = "std"))]
pub(crate) fn wait_timeout(&self, max_wait: Duration) -> bool {
- let current_time = Instant::now();
- loop {
- let mut guard = self.propagate_future_state_to_notify_flag();
- check_woken!(guard, true);
- guard = self.condvar.wait_timeout(guard, max_wait).unwrap().0;
- check_woken!(guard, true);
- // Due to spurious wakeups that can happen on `wait_timeout`, here we need to check if the
- // desired wait time has actually passed, and if not then restart the loop with a reduced wait
- // time. Note that this logic can be highly simplified through the use of
- // `Condvar::wait_while` and `Condvar::wait_timeout_while`, if and when our MSRV is raised to
- // 1.42.0.
- let elapsed = current_time.elapsed();
- if elapsed >= max_wait {
- return false;
- }
- match max_wait.checked_sub(elapsed) {
- None => return false,
- Some(_) => continue
- }
- }
+ Sleeper::from_single_future(self.get_future()).wait_timeout(max_wait)
}
/// Wake waiters, tracking that wake needs to occur even if there are currently no waiters.
}
}
lock.0 = true;
- mem::drop(lock);
- self.condvar.notify_all();
}
/// Gets a [`Future`] that will get woken up with any waiters
pub(crate) fn get_future(&self) -> Future {
- let mut lock = self.propagate_future_state_to_notify_flag();
+ let mut lock = self.notify_pending.lock().unwrap();
+ if let Some(existing_state) = &lock.1 {
+ if existing_state.lock().unwrap().callbacks_made {
+ // If the existing `FutureState` has completed and actually made callbacks,
+ // consider the notification flag to have been cleared and reset the future state.
+ lock.1.take();
+ lock.0 = false;
+ }
+ }
if let Some(existing_state) = &lock.1 {
Future { state: Arc::clone(&existing_state) }
} else {
}
/// A simple future which can complete once, and calls some callback(s) when it does so.
+///
+/// Clones can be made and all futures cloned from the same source will complete at the same time.
+#[derive(Clone)]
pub struct Future {
state: Arc<Mutex<FutureState>>,
}
}
}
+/// A struct which can be used to select across many [`Future`]s at once without relying on a full
+/// async context.
+pub struct Sleeper {
+ notifiers: Vec<Arc<Mutex<FutureState>>>,
+}
+
+impl Sleeper {
+ /// Constructs a new sleeper from one future, allowing blocking on it.
+ pub fn from_single_future(future: Future) -> Self {
+ Self { notifiers: vec![future.state] }
+ }
+ /// Constructs a new sleeper from two futures, allowing blocking on both at once.
+ // Note that this is the common case - a ChannelManager and ChainMonitor.
+ pub fn from_two_futures(fut_a: Future, fut_b: Future) -> Self {
+ Self { notifiers: vec![fut_a.state, fut_b.state] }
+ }
+ /// Constructs a new sleeper on many futures, allowing blocking on all at once.
+ pub fn new(futures: Vec<Future>) -> Self {
+ Self { notifiers: futures.into_iter().map(|f| f.state).collect() }
+ }
+ /// Prepares to go into a wait loop body, creating a condition variable which we can block on
+ /// and an `Arc<Mutex<Option<_>>>` which gets set to the waking `Future`'s state prior to the
+ /// condition variable being woken.
+ fn setup_wait(&self) -> (Arc<Condvar>, Arc<Mutex<Option<Arc<Mutex<FutureState>>>>>) {
+ let cv = Arc::new(Condvar::new());
+ let notified_fut_mtx = Arc::new(Mutex::new(None));
+ {
+ for notifier_mtx in self.notifiers.iter() {
+ let cv_ref = Arc::clone(&cv);
+ let notified_fut_ref = Arc::clone(¬ified_fut_mtx);
+ let notifier_ref = Arc::clone(¬ifier_mtx);
+ let mut notifier = notifier_mtx.lock().unwrap();
+ if notifier.complete {
+ *notified_fut_mtx.lock().unwrap() = Some(notifier_ref);
+ break;
+ }
+ notifier.callbacks.push((false, Box::new(move || {
+ *notified_fut_ref.lock().unwrap() = Some(Arc::clone(¬ifier_ref));
+ cv_ref.notify_all();
+ })));
+ }
+ }
+ (cv, notified_fut_mtx)
+ }
+
+ /// Wait until one of the [`Future`]s registered with this [`Sleeper`] has completed.
+ pub fn wait(&self) {
+ let (cv, notified_fut_mtx) = self.setup_wait();
+ let notified_fut = cv.wait_while(notified_fut_mtx.lock().unwrap(), |fut_opt| fut_opt.is_none())
+ .unwrap().take().expect("CV wait shouldn't have returned until the notifying future was set");
+ notified_fut.lock().unwrap().callbacks_made = true;
+ }
+
+ /// Wait until one of the [`Future`]s registered with this [`Sleeper`] has completed or the
+ /// given amount of time has elapsed. Returns true if a [`Future`] completed, false if the time
+ /// elapsed.
+ #[cfg(any(test, feature = "std"))]
+ pub fn wait_timeout(&self, max_wait: Duration) -> bool {
+ let (cv, notified_fut_mtx) = self.setup_wait();
+ let notified_fut =
+ match cv.wait_timeout_while(notified_fut_mtx.lock().unwrap(), max_wait, |fut_opt| fut_opt.is_none()) {
+ Ok((_, e)) if e.timed_out() => return false,
+ Ok((mut notified_fut, _)) =>
+ notified_fut.take().expect("CV wait shouldn't have returned until the notifying future was set"),
+ Err(_) => panic!("Previous panic while a lock was held led to a lock panic"),
+ };
+ notified_fut.lock().unwrap().callbacks_made = true;
+ true
+ }
+}
+
#[cfg(test)]
mod tests {
use super::*;
let exit_thread_clone = exit_thread.clone();
thread::spawn(move || {
loop {
- let mut lock = thread_notifier.notify_pending.lock().unwrap();
- lock.0 = true;
- thread_notifier.condvar.notify_all();
-
+ thread_notifier.notify();
if exit_thread_clone.load(Ordering::SeqCst) {
break
}
assert!(woken.load(Ordering::SeqCst));
assert_eq!(Pin::new(&mut future).poll(&mut Context::from_waker(&waker)), Poll::Ready(()));
}
+
+ #[test]
+ fn test_multi_future_sleep() {
+ // Tests the `Sleeper` with multiple futures.
+ let notifier_a = Notifier::new();
+ let notifier_b = Notifier::new();
+
+ // Set both notifiers as woken without sleeping yet.
+ notifier_a.notify();
+ notifier_b.notify();
+ Sleeper::from_two_futures(notifier_a.get_future(), notifier_b.get_future()).wait();
+
+ // One future has woken us up, but the other should still have a pending notification.
+ Sleeper::from_two_futures(notifier_a.get_future(), notifier_b.get_future()).wait();
+
+ // However once we've slept twice, we should no longer have any pending notifications
+ assert!(!Sleeper::from_two_futures(notifier_a.get_future(), notifier_b.get_future())
+ .wait_timeout(Duration::from_millis(10)));
+
+ // Test ordering somewhat more.
+ notifier_a.notify();
+ Sleeper::from_two_futures(notifier_a.get_future(), notifier_b.get_future()).wait();
+ }
+
+ #[test]
+ #[cfg(feature = "std")]
+ fn sleeper_with_pending_callbacks() {
+ // This is similar to the above `test_multi_future_sleep` test, but in addition registers
+ // "normal" callbacks which will cause the futures to assume notification has occurred,
+ // rather than waiting for a woken sleeper.
+ let notifier_a = Notifier::new();
+ let notifier_b = Notifier::new();
+
+ // Set both notifiers as woken without sleeping yet.
+ notifier_a.notify();
+ notifier_b.notify();
+
+ // After sleeping one future (not guaranteed which one, however) will have its notification
+ // bit cleared.
+ Sleeper::from_two_futures(notifier_a.get_future(), notifier_b.get_future()).wait();
+
+ // By registering a callback on the futures for both notifiers, one will complete
+ // immediately, but one will remain tied to the notifier, and will complete once the
+ // notifier is next woken, which will be considered the completion of the notification.
+ let callback_a = Arc::new(AtomicBool::new(false));
+ let callback_b = Arc::new(AtomicBool::new(false));
+ let callback_a_ref = Arc::clone(&callback_a);
+ let callback_b_ref = Arc::clone(&callback_b);
+ notifier_a.get_future().register_callback(Box::new(move || assert!(!callback_a_ref.fetch_or(true, Ordering::SeqCst))));
+ notifier_b.get_future().register_callback(Box::new(move || assert!(!callback_b_ref.fetch_or(true, Ordering::SeqCst))));
+ assert!(callback_a.load(Ordering::SeqCst) ^ callback_b.load(Ordering::SeqCst));
+
+ // If we now notify both notifiers again, the other callback will fire, completing the
+ // notification, and we'll be back to one pending notification.
+ notifier_a.notify();
+ notifier_b.notify();
+
+ assert!(callback_a.load(Ordering::SeqCst) && callback_b.load(Ordering::SeqCst));
+ Sleeper::from_two_futures(notifier_a.get_future(), notifier_b.get_future()).wait();
+ assert!(!Sleeper::from_two_futures(notifier_a.get_future(), notifier_b.get_future())
+ .wait_timeout(Duration::from_millis(10)));
+ }
}
projects / rust-lightning / commitdiff