--- /dev/null
+// This file is Copyright its original authors, visible in version control
+// history.
+//
+// This file is licensed under the Apache License, Version 2.0 <LICENSE-APACHE
+// or http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your option.
+// You may not use this file except in accordance with one or both of these
+// licenses.
+
+//! Utilities which allow users to block on some future notification from LDK. These are
+//! specifically used by [`ChannelManager`] to allow waiting until the [`ChannelManager`] needs to
+//! be re-persisted.
+//!
+//! [`ChannelManager`]: crate::ln::channelmanager::ChannelManager
+
+use core::mem;
+use core::time::Duration;
+use sync::{Condvar, Mutex};
+
+#[cfg(any(test, feature = "std"))]
+use std::time::Instant;
+
+/// Used to signal to the ChannelManager persister that the manager needs to be re-persisted to
+/// disk/backups, through `await_persistable_update_timeout` and `await_persistable_update`.
+pub(crate) struct PersistenceNotifier {
+ /// Users won't access the persistence_lock directly, but rather wait on its bool using
+ /// `wait_timeout` and `wait`.
+ persistence_lock: (Mutex<bool>, Condvar),
+}
+
+impl PersistenceNotifier {
+ pub(crate) fn new() -> Self {
+ Self {
+ persistence_lock: (Mutex::new(false), Condvar::new()),
+ }
+ }
+
+ pub(crate) fn wait(&self) {
+ loop {
+ let &(ref mtx, ref cvar) = &self.persistence_lock;
+ let mut guard = mtx.lock().unwrap();
+ if *guard {
+ *guard = false;
+ return;
+ }
+ guard = cvar.wait(guard).unwrap();
+ let result = *guard;
+ if result {
+ *guard = false;
+ return
+ }
+ }
+ }
+
+ #[cfg(any(test, feature = "std"))]
+ pub(crate) fn wait_timeout(&self, max_wait: Duration) -> bool {
+ let current_time = Instant::now();
+ loop {
+ let &(ref mtx, ref cvar) = &self.persistence_lock;
+ let mut guard = mtx.lock().unwrap();
+ if *guard {
+ *guard = false;
+ return true;
+ }
+ guard = cvar.wait_timeout(guard, max_wait).unwrap().0;
+ // 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();
+ let result = *guard;
+ if result || elapsed >= max_wait {
+ *guard = false;
+ return result;
+ }
+ match max_wait.checked_sub(elapsed) {
+ None => return result,
+ Some(_) => continue
+ }
+ }
+ }
+
+ /// Wake waiters, tracking that persistence needs to occur.
+ pub(crate) fn notify(&self) {
+ let &(ref persist_mtx, ref cnd) = &self.persistence_lock;
+ let mut persistence_lock = persist_mtx.lock().unwrap();
+ *persistence_lock = true;
+ mem::drop(persistence_lock);
+ cnd.notify_all();
+ }
+
+ #[cfg(any(test, feature = "_test_utils"))]
+ pub fn needs_persist(&self) -> bool {
+ let &(ref mtx, _) = &self.persistence_lock;
+ let guard = mtx.lock().unwrap();
+ *guard
+ }
+}
+
+#[cfg(test)]
+mod tests {
+ #[cfg(feature = "std")]
+ #[test]
+ fn test_wait_timeout() {
+ use super::*;
+ use sync::Arc;
+ use core::sync::atomic::{AtomicBool, Ordering};
+ use std::thread;
+
+ let persistence_notifier = Arc::new(PersistenceNotifier::new());
+ let thread_notifier = Arc::clone(&persistence_notifier);
+
+ let exit_thread = Arc::new(AtomicBool::new(false));
+ let exit_thread_clone = exit_thread.clone();
+ thread::spawn(move || {
+ loop {
+ let &(ref persist_mtx, ref cnd) = &thread_notifier.persistence_lock;
+ let mut persistence_lock = persist_mtx.lock().unwrap();
+ *persistence_lock = true;
+ cnd.notify_all();
+
+ if exit_thread_clone.load(Ordering::SeqCst) {
+ break
+ }
+ }
+ });
+
+ // Check that we can block indefinitely until updates are available.
+ let _ = persistence_notifier.wait();
+
+ // Check that the PersistenceNotifier will return after the given duration if updates are
+ // available.
+ loop {
+ if persistence_notifier.wait_timeout(Duration::from_millis(100)) {
+ break
+ }
+ }
+
+ exit_thread.store(true, Ordering::SeqCst);
+
+ // Check that the PersistenceNotifier will return after the given duration even if no updates
+ // are available.
+ loop {
+ if !persistence_notifier.wait_timeout(Duration::from_millis(100)) {
+ break
+ }
+ }
+ }
+}
projects / rust-lightning / blobdiff