From 0d4b58978ccd5423f8026a8436215c14279abff4 Mon Sep 17 00:00:00 2001
From: Paul Hauner <paul@paulhauner.com>
Date: Sat, 10 Aug 2019 17:19:27 +1000
Subject: [PATCH] Make fork choice write lock in to read lock

---
 eth2/lmd_ghost/src/reduced_tree.rs | 18 +++++++++++++-----
 1 file changed, 13 insertions(+), 5 deletions(-)

diff --git a/eth2/lmd_ghost/src/reduced_tree.rs b/eth2/lmd_ghost/src/reduced_tree.rs
index 9668620b79..822c388f6a 100644
--- a/eth2/lmd_ghost/src/reduced_tree.rs
+++ b/eth2/lmd_ghost/src/reduced_tree.rs
@@ -111,7 +111,7 @@ where
     }
 
     fn latest_message(&self, validator_index: usize) -> Option<(Hash256, Slot)> {
-        self.core.write().latest_message(validator_index)
+        self.core.read().latest_message(validator_index)
     }
 }
 
@@ -258,10 +258,10 @@ where
         Ok(head_node.block_hash)
     }
 
-    pub fn latest_message(&mut self, validator_index: usize) -> Option<(Hash256, Slot)> {
-        match self.latest_votes.get(validator_index) {
-            Some(v) => Some((v.hash.clone(), v.slot.clone())),
-            None => None,
+    pub fn latest_message(&self, validator_index: usize) -> Option<(Hash256, Slot)> {
+        match self.latest_votes.get_ref(validator_index) {
+            Some(Some(v)) => Some((v.hash.clone(), v.slot.clone())),
+            _ => None,
         }
     }
 
@@ -776,6 +776,14 @@ where
         &self.0[i]
     }
 
+    pub fn get_ref(&self, i: usize) -> Option<&T> {
+        if i < self.0.len() {
+            Some(&self.0[i])
+        } else {
+            None
+        }
+    }
+
     pub fn insert(&mut self, i: usize, element: T) {
         self.ensure(i);
         self.0[i] = element;