+/// Used to signal to the ChannelManager persister that the manager needs to be re-persisted to
+/// disk/backups, through `wait_timeout` and `wait`.
+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 {
+ fn new() -> Self {
+ Self {
+ persistence_lock: (Mutex::new(false), Condvar::new()),
+ }
+ }
+
+ fn wait(&self) {
+ loop {
+ let &(ref mtx, ref cvar) = &self.persistence_lock;
+ let mut guard = mtx.lock().unwrap();
+ guard = cvar.wait(guard).unwrap();
+ let result = *guard;
+ if result {
+ *guard = false;
+ return
+ }
+ }
+ }
+
+ #[cfg(any(test, feature = "allow_wallclock_use"))]
+ 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();
+ 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
+ }
+ }
+ }
+
+ // Signal to the ChannelManager persister that there are updates necessitating persisting to disk.
+ 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();
+ }
+}
+