fix(root): drop sparse trie tx sender when state updates finished

[shekhirin]

If StateRootMessage::FinishedStateUpdates is received after the last StateRootMessage::ProofCalculated is processed, we never drop the sparse_trie_tx.

To fix that, we need to do the same checks for dropping the sender in StateRootMessage::FinishedStateUpdates, as we do in StateRootMessage::ProofCalculated.

[mattsse]

why is this necessary?

not obvious why we need to do this, I assume because there is some internal wiring that will only close the channel if this sender is dropped, but unclear why the loop here doesn't just break naturally

[shekhirin]

@mattsse we can't just break the loop, because we're still waiting on the RootCalculated message to be received

reth/crates/engine/tree/src/tree/root.rs

Lines 684 to 704 in fa29d98

	StateRootMessage::RootCalculated { state_root, trie_updates, iterations } => {
	trace!(target: "engine::root", "processing StateRootMessage::RootCalculated");
	let total_time =
	first_update_time.expect("first update time should be set").elapsed();
	let time_from_last_update =
	last_update_time.expect("last update time should be set").elapsed();
	debug!(
	target: "engine::root",
	total_updates = updates_received,
	total_proofs = proofs_processed,
	roots_calculated = iterations,
	?total_time,
	?time_from_last_update,
	"All proofs processed, ending calculation"
	);
	return Ok(StateRootComputeOutcome {
	state_root: (state_root, trie_updates),
	total_time,
	time_from_last_update,
	});
	}

, and it will be only be sent once this loop exits

reth/crates/engine/tree/src/tree/root.rs

Line 759 in fa29d98

while let Ok(mut update) = update_rx.recv() {

and we send the result on the channel

reth/crates/engine/tree/src/tree/root.rs

Lines 524 to 529 in fa29d98

	let result = match run_sparse_trie(config, rx) {
	Ok((state_root, trie_updates, iterations)) => {
	StateRootMessage::RootCalculated { state_root, trie_updates, iterations }
	}
	Err(error) => StateRootMessage::RootCalculationError(error),
	};

[mattsse]

ah okay, I get this now

lgtm