Add PersistenceNotifier to ChannelManager
authorValentine Wallace <vwallace@protonmail.com>
Thu, 19 Nov 2020 17:53:16 +0000 (12:53 -0500)
committerValentine Wallace <vwallace@protonmail.com>
Fri, 19 Feb 2021 20:00:43 +0000 (15:00 -0500)
This will allow the ChannelManager to signal when it has new
updates to persist, and adds a way for ChannelManager persisters
to be notified when they should re-persist the ChannelManager
to disk/backups.

Feature-gate the wait_timeout function because the core
lightning crate shouldn't depend on wallclock time unless
users opt into it.

lightning/Cargo.toml
lightning/src/ln/channelmanager.rs

index 883aee4a1fc6a0970699a7423855ff981559f7ac..0b51a3992731636736917d3ebcde7e37215d5b38 100644 (file)
@@ -11,6 +11,7 @@ Still missing tons of error-handling. See GitHub issues for suggested projects i
 """
 
 [features]
+allow_wallclock_use = []
 fuzztarget = ["bitcoin/fuzztarget", "regex"]
 # Internal test utilities exposed to other repo crates
 _test_utils = ["hex", "regex"]
@@ -38,3 +39,6 @@ features = ["bitcoinconsensus"]
 [dev-dependencies]
 hex = "0.3"
 regex = "0.1.80"
+
+[package.metadata.docs.rs]
+features = ["allow_wallclock_use"] # When https://github.com/rust-lang/rust/issues/43781 complies with our MSVR, we can add nice banners in the docs for the methods behind this feature-gate.
index 3dcc74f905269a7f8a58978a529f96b6e48a5851..84dc486c9035f8ba094336771b29c1ee4ccbd52b 100644 (file)
@@ -58,9 +58,11 @@ use util::errors::APIError;
 use std::{cmp, mem};
 use std::collections::{HashMap, hash_map, HashSet};
 use std::io::{Cursor, Read};
-use std::sync::{Arc, Mutex, MutexGuard, RwLock};
+use std::sync::{Arc, Condvar, Mutex, MutexGuard, RwLock, RwLockReadGuard};
 use std::sync::atomic::{AtomicUsize, Ordering};
 use std::time::Duration;
+#[cfg(any(test, feature = "allow_wallclock_use"))]
+use std::time::Instant;
 use std::marker::{Sync, Send};
 use std::ops::Deref;
 use bitcoin::hashes::hex::ToHex;
@@ -437,13 +439,46 @@ pub struct ChannelManager<ChanSigner: ChannelKeys, M: Deref, T: Deref, K: Deref,
        /// Used when we have to take a BIG lock to make sure everything is self-consistent.
        /// Essentially just when we're serializing ourselves out.
        /// Taken first everywhere where we are making changes before any other locks.
+       /// When acquiring this lock in read mode, rather than acquiring it directly, call
+       /// `PersistenceNotifierGuard::new(..)` and pass the lock to it, to ensure the PersistenceNotifier
+       /// the lock contains sends out a notification when the lock is released.
        total_consistency_lock: RwLock<()>,
 
+       persistence_notifier: PersistenceNotifier,
+
        keys_manager: K,
 
        logger: L,
 }
 
+/// Whenever we release the `ChannelManager`'s `total_consistency_lock`, from read mode, it is
+/// desirable to notify any listeners on `wait_timeout`/`wait` that new updates are available for
+/// persistence. Therefore, this struct is responsible for locking the total consistency lock and,
+/// upon going out of scope, sending the aforementioned notification (since the lock being released
+/// indicates that the updates are ready for persistence).
+struct PersistenceNotifierGuard<'a> {
+       persistence_notifier: &'a PersistenceNotifier,
+       // We hold onto this result so the lock doesn't get released immediately.
+       _read_guard: RwLockReadGuard<'a, ()>,
+}
+
+impl<'a> PersistenceNotifierGuard<'a> {
+       fn new(lock: &'a RwLock<()>, notifier: &'a PersistenceNotifier) -> Self {
+               let read_guard = lock.read().unwrap();
+
+               Self {
+                       persistence_notifier: notifier,
+                       _read_guard: read_guard,
+               }
+       }
+}
+
+impl<'a> Drop for PersistenceNotifierGuard<'a> {
+       fn drop(&mut self) {
+               self.persistence_notifier.notify();
+       }
+}
+
 /// The amount of time we require our counterparty wait to claim their money (ie time between when
 /// we, or our watchtower, must check for them having broadcast a theft transaction).
 pub(crate) const BREAKDOWN_TIMEOUT: u16 = 6 * 24;
@@ -759,6 +794,7 @@ impl<ChanSigner: ChannelKeys, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref>
 
                        pending_events: Mutex::new(Vec::new()),
                        total_consistency_lock: RwLock::new(()),
+                       persistence_notifier: PersistenceNotifier::new(),
 
                        keys_manager,
 
@@ -787,7 +823,10 @@ impl<ChanSigner: ChannelKeys, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref>
                let channel = Channel::new_outbound(&self.fee_estimator, &self.keys_manager, their_network_key, channel_value_satoshis, push_msat, user_id, config)?;
                let res = channel.get_open_channel(self.genesis_hash.clone());
 
-               let _consistency_lock = self.total_consistency_lock.read().unwrap();
+               let _persistence_guard = PersistenceNotifierGuard::new(&self.total_consistency_lock, &self.persistence_notifier);
+               // We want to make sure the lock is actually acquired by PersistenceNotifierGuard.
+               debug_assert!(&self.total_consistency_lock.try_write().is_err());
+
                let mut channel_state = self.channel_state.lock().unwrap();
                match channel_state.by_id.entry(channel.channel_id()) {
                        hash_map::Entry::Occupied(_) => {
@@ -859,7 +898,7 @@ impl<ChanSigner: ChannelKeys, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref>
        ///
        /// May generate a SendShutdown message event on success, which should be relayed.
        pub fn close_channel(&self, channel_id: &[u8; 32]) -> Result<(), APIError> {
-               let _consistency_lock = self.total_consistency_lock.read().unwrap();
+               let _persistence_guard = PersistenceNotifierGuard::new(&self.total_consistency_lock, &self.persistence_notifier);
 
                let (mut failed_htlcs, chan_option) = {
                        let mut channel_state_lock = self.channel_state.lock().unwrap();
@@ -951,7 +990,7 @@ impl<ChanSigner: ChannelKeys, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref>
        /// Force closes a channel, immediately broadcasting the latest local commitment transaction to
        /// the chain and rejecting new HTLCs on the given channel. Fails if channel_id is unknown to the manager.
        pub fn force_close_channel(&self, channel_id: &[u8; 32]) -> Result<(), APIError> {
-               let _consistency_lock = self.total_consistency_lock.read().unwrap();
+               let _persistence_guard = PersistenceNotifierGuard::new(&self.total_consistency_lock, &self.persistence_notifier);
                self.force_close_channel_with_peer(channel_id, None)
        }
 
@@ -1279,7 +1318,7 @@ impl<ChanSigner: ChannelKeys, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref>
                }
                let onion_packet = onion_utils::construct_onion_packet(onion_payloads, onion_keys, prng_seed, payment_hash);
 
-               let _consistency_lock = self.total_consistency_lock.read().unwrap();
+               let _persistence_guard = PersistenceNotifierGuard::new(&self.total_consistency_lock, &self.persistence_notifier);
 
                let err: Result<(), _> = loop {
                        let mut channel_lock = self.channel_state.lock().unwrap();
@@ -1447,7 +1486,7 @@ impl<ChanSigner: ChannelKeys, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref>
        /// May panic if the funding_txo is duplicative with some other channel (note that this should
        /// be trivially prevented by using unique funding transaction keys per-channel).
        pub fn funding_transaction_generated(&self, temporary_channel_id: &[u8; 32], funding_txo: OutPoint) {
-               let _consistency_lock = self.total_consistency_lock.read().unwrap();
+               let _persistence_guard = PersistenceNotifierGuard::new(&self.total_consistency_lock, &self.persistence_notifier);
 
                let (chan, msg) = {
                        let (res, chan) = match self.channel_state.lock().unwrap().by_id.remove(temporary_channel_id) {
@@ -1530,7 +1569,7 @@ impl<ChanSigner: ChannelKeys, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref>
        ///
        /// Panics if addresses is absurdly large (more than 500).
        pub fn broadcast_node_announcement(&self, rgb: [u8; 3], alias: [u8; 32], addresses: Vec<NetAddress>) {
-               let _consistency_lock = self.total_consistency_lock.read().unwrap();
+               let _persistence_guard = PersistenceNotifierGuard::new(&self.total_consistency_lock, &self.persistence_notifier);
 
                if addresses.len() > 500 {
                        panic!("More than half the message size was taken up by public addresses!");
@@ -1560,7 +1599,7 @@ impl<ChanSigner: ChannelKeys, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref>
        /// Should only really ever be called in response to a PendingHTLCsForwardable event.
        /// Will likely generate further events.
        pub fn process_pending_htlc_forwards(&self) {
-               let _consistency_lock = self.total_consistency_lock.read().unwrap();
+               let _persistence_guard = PersistenceNotifierGuard::new(&self.total_consistency_lock, &self.persistence_notifier);
 
                let mut new_events = Vec::new();
                let mut failed_forwards = Vec::new();
@@ -1820,7 +1859,7 @@ impl<ChanSigner: ChannelKeys, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref>
        ///
        /// This method handles all the details, and must be called roughly once per minute.
        pub fn timer_chan_freshness_every_min(&self) {
-               let _consistency_lock = self.total_consistency_lock.read().unwrap();
+               let _persistence_guard = PersistenceNotifierGuard::new(&self.total_consistency_lock, &self.persistence_notifier);
                let mut channel_state_lock = self.channel_state.lock().unwrap();
                let channel_state = &mut *channel_state_lock;
                for (_, chan) in channel_state.by_id.iter_mut() {
@@ -1845,7 +1884,7 @@ impl<ChanSigner: ChannelKeys, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref>
        /// Returns false if no payment was found to fail backwards, true if the process of failing the
        /// HTLC backwards has been started.
        pub fn fail_htlc_backwards(&self, payment_hash: &PaymentHash, payment_secret: &Option<PaymentSecret>) -> bool {
-               let _consistency_lock = self.total_consistency_lock.read().unwrap();
+               let _persistence_guard = PersistenceNotifierGuard::new(&self.total_consistency_lock, &self.persistence_notifier);
 
                let mut channel_state = Some(self.channel_state.lock().unwrap());
                let removed_source = channel_state.as_mut().unwrap().claimable_htlcs.remove(&(*payment_hash, *payment_secret));
@@ -2024,7 +2063,7 @@ impl<ChanSigner: ChannelKeys, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref>
        pub fn claim_funds(&self, payment_preimage: PaymentPreimage, payment_secret: &Option<PaymentSecret>, expected_amount: u64) -> bool {
                let payment_hash = PaymentHash(Sha256::hash(&payment_preimage.0).into_inner());
 
-               let _consistency_lock = self.total_consistency_lock.read().unwrap();
+               let _persistence_guard = PersistenceNotifierGuard::new(&self.total_consistency_lock, &self.persistence_notifier);
 
                let mut channel_state = Some(self.channel_state.lock().unwrap());
                let removed_source = channel_state.as_mut().unwrap().claimable_htlcs.remove(&(payment_hash, *payment_secret));
@@ -2220,7 +2259,7 @@ impl<ChanSigner: ChannelKeys, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref>
        ///  4) once all remote copies are updated, you call this function with the update_id that
        ///     completed, and once it is the latest the Channel will be re-enabled.
        pub fn channel_monitor_updated(&self, funding_txo: &OutPoint, highest_applied_update_id: u64) {
-               let _consistency_lock = self.total_consistency_lock.read().unwrap();
+               let _persistence_guard = PersistenceNotifierGuard::new(&self.total_consistency_lock, &self.persistence_notifier);
 
                let mut close_results = Vec::new();
                let mut htlc_forwards = Vec::new();
@@ -2971,7 +3010,7 @@ impl<ChanSigner: ChannelKeys, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref>
        /// (C-not exported) Cause its doc(hidden) anyway
        #[doc(hidden)]
        pub fn update_fee(&self, channel_id: [u8;32], feerate_per_kw: u32) -> Result<(), APIError> {
-               let _consistency_lock = self.total_consistency_lock.read().unwrap();
+               let _persistence_guard = PersistenceNotifierGuard::new(&self.total_consistency_lock, &self.persistence_notifier);
                let counterparty_node_id;
                let err: Result<(), _> = loop {
                        let mut channel_state_lock = self.channel_state.lock().unwrap();
@@ -3111,7 +3150,7 @@ impl<ChanSigner: ChannelKeys, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref>
        pub fn block_connected(&self, header: &BlockHeader, txdata: &TransactionData, height: u32) {
                let header_hash = header.block_hash();
                log_trace!(self.logger, "Block {} at height {} connected", header_hash, height);
-               let _consistency_lock = self.total_consistency_lock.read().unwrap();
+               let _persistence_guard = PersistenceNotifierGuard::new(&self.total_consistency_lock, &self.persistence_notifier);
                let mut failed_channels = Vec::new();
                let mut timed_out_htlcs = Vec::new();
                {
@@ -3224,7 +3263,7 @@ impl<ChanSigner: ChannelKeys, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref>
        /// If necessary, the channel may be force-closed without letting the counterparty participate
        /// in the shutdown.
        pub fn block_disconnected(&self, header: &BlockHeader) {
-               let _consistency_lock = self.total_consistency_lock.read().unwrap();
+               let _persistence_guard = PersistenceNotifierGuard::new(&self.total_consistency_lock, &self.persistence_notifier);
                let mut failed_channels = Vec::new();
                {
                        let mut channel_lock = self.channel_state.lock().unwrap();
@@ -3254,6 +3293,29 @@ impl<ChanSigner: ChannelKeys, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref>
                self.latest_block_height.fetch_sub(1, Ordering::AcqRel);
                *self.last_block_hash.try_lock().expect("block_(dis)connected must not be called in parallel") = header.block_hash();
        }
+
+       /// Blocks until ChannelManager needs to be persisted or a timeout is reached. It returns a bool
+       /// indicating whether persistence is necessary. Only one listener on `wait_timeout` is
+       /// guaranteed to be woken up.
+       /// Note that the feature `allow_wallclock_use` must be enabled to use this function.
+       #[cfg(any(test, feature = "allow_wallclock_use"))]
+       pub fn wait_timeout(&self, max_wait: Duration) -> bool {
+               self.persistence_notifier.wait_timeout(max_wait)
+       }
+
+       /// Blocks until ChannelManager needs to be persisted. Only one listener on `wait` is
+       /// guaranteed to be woken up.
+       pub fn wait(&self) {
+               self.persistence_notifier.wait()
+       }
+
+       #[cfg(any(test, feature = "_test_utils"))]
+       pub fn get_persistence_condvar_value(&self) -> bool {
+               let mutcond = &self.persistence_notifier.persistence_lock;
+               let &(ref mtx, _) = mutcond;
+               let guard = mtx.lock().unwrap();
+               *guard
+       }
 }
 
 impl<ChanSigner: ChannelKeys, M: Deref + Sync + Send, T: Deref + Sync + Send, K: Deref + Sync + Send, F: Deref + Sync + Send, L: Deref + Sync + Send>
@@ -3265,87 +3327,87 @@ impl<ChanSigner: ChannelKeys, M: Deref + Sync + Send, T: Deref + Sync + Send, K:
         L::Target: Logger,
 {
        fn handle_open_channel(&self, counterparty_node_id: &PublicKey, their_features: InitFeatures, msg: &msgs::OpenChannel) {
-               let _consistency_lock = self.total_consistency_lock.read().unwrap();
+               let _persistence_guard = PersistenceNotifierGuard::new(&self.total_consistency_lock, &self.persistence_notifier);
                let _ = handle_error!(self, self.internal_open_channel(counterparty_node_id, their_features, msg), *counterparty_node_id);
        }
 
        fn handle_accept_channel(&self, counterparty_node_id: &PublicKey, their_features: InitFeatures, msg: &msgs::AcceptChannel) {
-               let _consistency_lock = self.total_consistency_lock.read().unwrap();
+               let _persistence_guard = PersistenceNotifierGuard::new(&self.total_consistency_lock, &self.persistence_notifier);
                let _ = handle_error!(self, self.internal_accept_channel(counterparty_node_id, their_features, msg), *counterparty_node_id);
        }
 
        fn handle_funding_created(&self, counterparty_node_id: &PublicKey, msg: &msgs::FundingCreated) {
-               let _consistency_lock = self.total_consistency_lock.read().unwrap();
+               let _persistence_guard = PersistenceNotifierGuard::new(&self.total_consistency_lock, &self.persistence_notifier);
                let _ = handle_error!(self, self.internal_funding_created(counterparty_node_id, msg), *counterparty_node_id);
        }
 
        fn handle_funding_signed(&self, counterparty_node_id: &PublicKey, msg: &msgs::FundingSigned) {
-               let _consistency_lock = self.total_consistency_lock.read().unwrap();
+               let _persistence_guard = PersistenceNotifierGuard::new(&self.total_consistency_lock, &self.persistence_notifier);
                let _ = handle_error!(self, self.internal_funding_signed(counterparty_node_id, msg), *counterparty_node_id);
        }
 
        fn handle_funding_locked(&self, counterparty_node_id: &PublicKey, msg: &msgs::FundingLocked) {
-               let _consistency_lock = self.total_consistency_lock.read().unwrap();
+               let _persistence_guard = PersistenceNotifierGuard::new(&self.total_consistency_lock, &self.persistence_notifier);
                let _ = handle_error!(self, self.internal_funding_locked(counterparty_node_id, msg), *counterparty_node_id);
        }
 
        fn handle_shutdown(&self, counterparty_node_id: &PublicKey, msg: &msgs::Shutdown) {
-               let _consistency_lock = self.total_consistency_lock.read().unwrap();
+               let _persistence_guard = PersistenceNotifierGuard::new(&self.total_consistency_lock, &self.persistence_notifier);
                let _ = handle_error!(self, self.internal_shutdown(counterparty_node_id, msg), *counterparty_node_id);
        }
 
        fn handle_closing_signed(&self, counterparty_node_id: &PublicKey, msg: &msgs::ClosingSigned) {
-               let _consistency_lock = self.total_consistency_lock.read().unwrap();
+               let _persistence_guard = PersistenceNotifierGuard::new(&self.total_consistency_lock, &self.persistence_notifier);
                let _ = handle_error!(self, self.internal_closing_signed(counterparty_node_id, msg), *counterparty_node_id);
        }
 
        fn handle_update_add_htlc(&self, counterparty_node_id: &PublicKey, msg: &msgs::UpdateAddHTLC) {
-               let _consistency_lock = self.total_consistency_lock.read().unwrap();
+               let _persistence_guard = PersistenceNotifierGuard::new(&self.total_consistency_lock, &self.persistence_notifier);
                let _ = handle_error!(self, self.internal_update_add_htlc(counterparty_node_id, msg), *counterparty_node_id);
        }
 
        fn handle_update_fulfill_htlc(&self, counterparty_node_id: &PublicKey, msg: &msgs::UpdateFulfillHTLC) {
-               let _consistency_lock = self.total_consistency_lock.read().unwrap();
+               let _persistence_guard = PersistenceNotifierGuard::new(&self.total_consistency_lock, &self.persistence_notifier);
                let _ = handle_error!(self, self.internal_update_fulfill_htlc(counterparty_node_id, msg), *counterparty_node_id);
        }
 
        fn handle_update_fail_htlc(&self, counterparty_node_id: &PublicKey, msg: &msgs::UpdateFailHTLC) {
-               let _consistency_lock = self.total_consistency_lock.read().unwrap();
+               let _persistence_guard = PersistenceNotifierGuard::new(&self.total_consistency_lock, &self.persistence_notifier);
                let _ = handle_error!(self, self.internal_update_fail_htlc(counterparty_node_id, msg), *counterparty_node_id);
        }
 
        fn handle_update_fail_malformed_htlc(&self, counterparty_node_id: &PublicKey, msg: &msgs::UpdateFailMalformedHTLC) {
-               let _consistency_lock = self.total_consistency_lock.read().unwrap();
+               let _persistence_guard = PersistenceNotifierGuard::new(&self.total_consistency_lock, &self.persistence_notifier);
                let _ = handle_error!(self, self.internal_update_fail_malformed_htlc(counterparty_node_id, msg), *counterparty_node_id);
        }
 
        fn handle_commitment_signed(&self, counterparty_node_id: &PublicKey, msg: &msgs::CommitmentSigned) {
-               let _consistency_lock = self.total_consistency_lock.read().unwrap();
+               let _persistence_guard = PersistenceNotifierGuard::new(&self.total_consistency_lock, &self.persistence_notifier);
                let _ = handle_error!(self, self.internal_commitment_signed(counterparty_node_id, msg), *counterparty_node_id);
        }
 
        fn handle_revoke_and_ack(&self, counterparty_node_id: &PublicKey, msg: &msgs::RevokeAndACK) {
-               let _consistency_lock = self.total_consistency_lock.read().unwrap();
+               let _persistence_guard = PersistenceNotifierGuard::new(&self.total_consistency_lock, &self.persistence_notifier);
                let _ = handle_error!(self, self.internal_revoke_and_ack(counterparty_node_id, msg), *counterparty_node_id);
        }
 
        fn handle_update_fee(&self, counterparty_node_id: &PublicKey, msg: &msgs::UpdateFee) {
-               let _consistency_lock = self.total_consistency_lock.read().unwrap();
+               let _persistence_guard = PersistenceNotifierGuard::new(&self.total_consistency_lock, &self.persistence_notifier);
                let _ = handle_error!(self, self.internal_update_fee(counterparty_node_id, msg), *counterparty_node_id);
        }
 
        fn handle_announcement_signatures(&self, counterparty_node_id: &PublicKey, msg: &msgs::AnnouncementSignatures) {
-               let _consistency_lock = self.total_consistency_lock.read().unwrap();
+               let _persistence_guard = PersistenceNotifierGuard::new(&self.total_consistency_lock, &self.persistence_notifier);
                let _ = handle_error!(self, self.internal_announcement_signatures(counterparty_node_id, msg), *counterparty_node_id);
        }
 
        fn handle_channel_reestablish(&self, counterparty_node_id: &PublicKey, msg: &msgs::ChannelReestablish) {
-               let _consistency_lock = self.total_consistency_lock.read().unwrap();
+               let _persistence_guard = PersistenceNotifierGuard::new(&self.total_consistency_lock, &self.persistence_notifier);
                let _ = handle_error!(self, self.internal_channel_reestablish(counterparty_node_id, msg), *counterparty_node_id);
        }
 
        fn peer_disconnected(&self, counterparty_node_id: &PublicKey, no_connection_possible: bool) {
-               let _consistency_lock = self.total_consistency_lock.read().unwrap();
+               let _persistence_guard = PersistenceNotifierGuard::new(&self.total_consistency_lock, &self.persistence_notifier);
                let mut failed_channels = Vec::new();
                let mut failed_payments = Vec::new();
                let mut no_channels_remain = true;
@@ -3438,7 +3500,7 @@ impl<ChanSigner: ChannelKeys, M: Deref + Sync + Send, T: Deref + Sync + Send, K:
        fn peer_connected(&self, counterparty_node_id: &PublicKey, init_msg: &msgs::Init) {
                log_debug!(self.logger, "Generating channel_reestablish events for {}", log_pubkey!(counterparty_node_id));
 
-               let _consistency_lock = self.total_consistency_lock.read().unwrap();
+               let _persistence_guard = PersistenceNotifierGuard::new(&self.total_consistency_lock, &self.persistence_notifier);
 
                {
                        let mut peer_state_lock = self.per_peer_state.write().unwrap();
@@ -3478,7 +3540,7 @@ impl<ChanSigner: ChannelKeys, M: Deref + Sync + Send, T: Deref + Sync + Send, K:
        }
 
        fn handle_error(&self, counterparty_node_id: &PublicKey, msg: &msgs::ErrorMessage) {
-               let _consistency_lock = self.total_consistency_lock.read().unwrap();
+               let _persistence_guard = PersistenceNotifierGuard::new(&self.total_consistency_lock, &self.persistence_notifier);
 
                if msg.channel_id == [0; 32] {
                        for chan in self.list_channels() {
@@ -3494,6 +3556,69 @@ impl<ChanSigner: ChannelKeys, M: Deref + Sync + Send, T: Deref + Sync + Send, K:
        }
 }
 
+/// 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();
+       }
+}
+
 const SERIALIZATION_VERSION: u8 = 1;
 const MIN_SERIALIZATION_VERSION: u8 = 1;
 
@@ -4011,6 +4136,8 @@ impl<'a, ChanSigner: ChannelKeys, M: Deref, T: Deref, K: Deref, F: Deref, L: Der
 
                        pending_events: Mutex::new(pending_events_read),
                        total_consistency_lock: RwLock::new(()),
+                       persistence_notifier: PersistenceNotifier::new(),
+
                        keys_manager: args.keys_manager,
                        logger: args.logger,
                        default_configuration: args.default_config,
@@ -4026,3 +4153,54 @@ impl<'a, ChanSigner: ChannelKeys, M: Deref, T: Deref, K: Deref, F: Deref, L: Der
                Ok((last_block_hash.clone(), channel_manager))
        }
 }
+
+#[cfg(test)]
+mod tests {
+       use ln::channelmanager::PersistenceNotifier;
+       use std::sync::Arc;
+       use std::sync::atomic::{AtomicBool, Ordering};
+       use std::thread;
+       use std::time::Duration;
+
+       #[test]
+       fn test_wait_timeout() {
+               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
+                       }
+               }
+       }
+}