Remove `forward_htlc` after `channel_state` lock order

The `forward_htlc` was prior to this commit only held at the same time
as the `channel_state` lock during the write process of the
`ChannelManager`. This commit removes the lock order dependency, by
taking the `channel_state`lock temporarily during the write process.

diff --git a/lightning/src/ln/channelmanager.rs b/lightning/src/ln/channelmanager.rs
index cce6a7f97c8b0ae376fcd05871961538427730a0..85602f3bb37c5fb85e752db8a55063bd7247d43e 100644 (file)
--- a/lightning/src/ln/channelmanager.rs
+++ b/lightning/src/ln/channelmanager.rs
@@ -6548,30 +6548,37 @@ impl<Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref> Writeable f
                        best_block.block_hash().write(writer)?;
                }
 
-               let channel_state = self.channel_state.lock().unwrap();
-               let mut unfunded_channels = 0;
-               for (_, channel) in channel_state.by_id.iter() {
-                       if !channel.is_funding_initiated() {
-                               unfunded_channels += 1;
+               {
+                       // Take `channel_state` lock temporarily to avoid creating a lock order that requires
+                       // that the `forward_htlcs` lock is taken after `channel_state`
+                       let channel_state = self.channel_state.lock().unwrap();
+                       let mut unfunded_channels = 0;
+                       for (_, channel) in channel_state.by_id.iter() {
+                               if !channel.is_funding_initiated() {
+                                       unfunded_channels += 1;
+                               }
                        }
-               }
-               ((channel_state.by_id.len() - unfunded_channels) as u64).write(writer)?;
-               for (_, channel) in channel_state.by_id.iter() {
-                       if channel.is_funding_initiated() {
-                               channel.write(writer)?;
+                       ((channel_state.by_id.len() - unfunded_channels) as u64).write(writer)?;
+                       for (_, channel) in channel_state.by_id.iter() {
+                               if channel.is_funding_initiated() {
+                                       channel.write(writer)?;
+                               }
                        }
                }
 
-               let forward_htlcs = self.forward_htlcs.lock().unwrap();
-               (forward_htlcs.len() as u64).write(writer)?;
-               for (short_channel_id, pending_forwards) in forward_htlcs.iter() {
-                       short_channel_id.write(writer)?;
-                       (pending_forwards.len() as u64).write(writer)?;
-                       for forward in pending_forwards {
-                               forward.write(writer)?;
+               {
+                       let forward_htlcs = self.forward_htlcs.lock().unwrap();
+                       (forward_htlcs.len() as u64).write(writer)?;
+                       for (short_channel_id, pending_forwards) in forward_htlcs.iter() {
+                               short_channel_id.write(writer)?;
+                               (pending_forwards.len() as u64).write(writer)?;
+                               for forward in pending_forwards {
+                                       forward.write(writer)?;
+                               }
                        }
                }
 
+               let channel_state = self.channel_state.lock().unwrap();
                let mut htlc_purposes: Vec<&events::PaymentPurpose> = Vec::new();
                (channel_state.claimable_htlcs.len() as u64).write(writer)?;
                for (payment_hash, (purpose, previous_hops)) in channel_state.claimable_htlcs.iter() {