From 7a8eba10b2b007b191776e9c0d9e63d160ff3245 Mon Sep 17 00:00:00 2001
From: Jeff Biseda <jbiseda@gmail.com>
Date: Thu, 2 Sep 2021 13:52:14 -0700
Subject: [PATCH] add synchronization comment to handle_new_root (#19571)

---
 core/src/replay_stage.rs | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/core/src/replay_stage.rs b/core/src/replay_stage.rs
index 72b3a08eea..af2ea5cc39 100644
--- a/core/src/replay_stage.rs
+++ b/core/src/replay_stage.rs
@@ -2703,6 +2703,8 @@ impl ReplayStage {
             accounts_background_request_sender,
             highest_confirmed_root,
         );
+        // Dropping the bank_forks write lock and reacquiring as a read lock is
+        // safe because updates to bank_forks are only made by a single thread.
         let r_bank_forks = bank_forks.read().unwrap();
         let new_root_bank = &r_bank_forks[new_root];
         if !*has_new_vote_been_rooted {