From c3e5927d166a383227f26ebdcc1c6843e47ee247 Mon Sep 17 00:00:00 2001
From: Brooks Prumo <brooks@solana.com>
Date: Wed, 17 Nov 2021 07:11:16 -0600
Subject: [PATCH] Constrain memory ordering on AccountsDb::write_version
 (#21312)

---
 runtime/src/accounts_db.rs           | 6 +++---
 runtime/src/serde_snapshot.rs        | 2 +-
 runtime/src/serde_snapshot/future.rs | 2 +-
 3 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/runtime/src/accounts_db.rs b/runtime/src/accounts_db.rs
index b8874f49fe..8a9e1c17f3 100644
--- a/runtime/src/accounts_db.rs
+++ b/runtime/src/accounts_db.rs
@@ -4391,7 +4391,7 @@ impl AccountsDb {
 
     fn bulk_assign_write_version(&self, count: usize) -> StoredMetaWriteVersion {
         self.write_version
-            .fetch_add(count as StoredMetaWriteVersion, Ordering::Relaxed)
+            .fetch_add(count as StoredMetaWriteVersion, Ordering::AcqRel)
     }
 
     fn write_accounts_to_storage<F: FnMut(Slot, usize) -> Arc<AccountStorageEntry>>(
@@ -9193,8 +9193,8 @@ pub mod tests {
         let daccounts = reconstruct_accounts_db_via_serialization(&accounts, latest_slot);
 
         assert_eq!(
-            daccounts.write_version.load(Ordering::Relaxed),
-            accounts.write_version.load(Ordering::Relaxed)
+            daccounts.write_version.load(Ordering::Acquire),
+            accounts.write_version.load(Ordering::Acquire)
         );
 
         // Get the hash for the latest slot, which should be the only hash in the
diff --git a/runtime/src/serde_snapshot.rs b/runtime/src/serde_snapshot.rs
index 825b806d9e..ef0ea8e5ac 100644
--- a/runtime/src/serde_snapshot.rs
+++ b/runtime/src/serde_snapshot.rs
@@ -536,7 +536,7 @@ where
         .store(next_append_vec_id, Ordering::Relaxed);
     accounts_db
         .write_version
-        .fetch_add(snapshot_version, Ordering::Relaxed);
+        .fetch_add(snapshot_version, Ordering::Release);
 
     let mut measure_notify = Measure::start("accounts_notify");
 
diff --git a/runtime/src/serde_snapshot/future.rs b/runtime/src/serde_snapshot/future.rs
index c358235577..0a951f0628 100644
--- a/runtime/src/serde_snapshot/future.rs
+++ b/runtime/src/serde_snapshot/future.rs
@@ -242,7 +242,7 @@ impl<'a> TypeContext<'a> for Context {
         let version = serializable_db
             .accounts_db
             .write_version
-            .load(Ordering::Relaxed);
+            .load(Ordering::Acquire);
 
         // (1st of 3 elements) write the list of account storage entry lists out as a map
         let entry_count = RefCell::<usize>::new(0);