use OnceCell instead of RwLock for rent_paying_accounts_by_partition (#26601)

runtime/src/accounts_index.rs

@@ -13,6 +13,7 @@ use {
         secondary_index::*,
     },
     log::*,
+    once_cell::sync::OnceCell,
     ouroboros::self_referencing,
     rand::{thread_rng, Rng},
     rayon::{
@@ -697,7 +698,7 @@ pub struct AccountsIndex<T: IndexValue> {
     pub max_distance_to_min_scan_slot: AtomicU64,
 
     /// populated at generate_index time - accounts that could possibly be rent paying
-    pub rent_paying_accounts_by_partition: RwLock<RentPayingAccountsByPartition>,
+    pub rent_paying_accounts_by_partition: OnceCell<RentPayingAccountsByPartition>,
 }
 
 impl<T: IndexValue> AccountsIndex<T> {
@@ -731,7 +732,7 @@ impl<T: IndexValue> AccountsIndex<T> {
             roots_removed: AtomicUsize::default(),
             active_scans: AtomicUsize::default(),
             max_distance_to_min_scan_slot: AtomicU64::default(),
-            rent_paying_accounts_by_partition: RwLock::default(),
+            rent_paying_accounts_by_partition: OnceCell::default(),
         }
     }
 

runtime/src/bank.rs

@@ -5456,23 +5456,23 @@ impl Bank {
 
     /// get all pubkeys that we expect to be rent-paying or None, if this was not initialized at load time (that should only exist in test cases)
     fn get_rent_paying_pubkeys(&self, partition: &Partition) -> Option<HashSet<Pubkey>> {
-        let rent_paying_accounts = &self
-            .rc
+        self.rc
             .accounts
             .accounts_db
             .accounts_index
             .rent_paying_accounts_by_partition
-            .read()
-            .unwrap();
-        rent_paying_accounts.is_initialized().then(|| {
-            Self::get_partition_end_indexes(partition)
-                .into_iter()
-                .flat_map(|end_index| {
-                    rent_paying_accounts.get_pubkeys_in_partition_index(end_index)
+            .get()
+            .and_then(|rent_paying_accounts| {
+                rent_paying_accounts.is_initialized().then(|| {
+                    Self::get_partition_end_indexes(partition)
+                        .into_iter()
+                        .flat_map(|end_index| {
+                            rent_paying_accounts.get_pubkeys_in_partition_index(end_index)
+                        })
+                        .cloned()
+                        .collect::<HashSet<_>>()
                 })
-                .cloned()
-                .collect::<HashSet<_>>()
-        })
+            })
     }
 
     /// load accounts with pubkeys in 'subrange_full'
@@ -19322,14 +19322,13 @@ pub(crate) mod tests {
         rent_paying_accounts_by_partition.add_account(&pk1);
         rent_paying_accounts_by_partition.add_account(&pk2);
 
-        *bank
-            .rc
+        bank.rc
             .accounts
             .accounts_db
             .accounts_index
             .rent_paying_accounts_by_partition
-            .write()
-            .unwrap() = rent_paying_accounts_by_partition;
+            .set(rent_paying_accounts_by_partition)
+            .unwrap();
 
         assert_eq!(
             bank.get_rent_paying_pubkeys(&(0, 1, n)),

runtime/src/serde_snapshot.rs

@@ -722,11 +722,11 @@ where
         verify_index,
         genesis_config,
     );
-    *accounts_db
+    accounts_db
         .accounts_index
         .rent_paying_accounts_by_partition
-        .write()
-        .unwrap() = rent_paying_accounts_by_partition;
+        .set(rent_paying_accounts_by_partition)
+        .unwrap();
 
     accounts_db.maybe_add_filler_accounts(
         &genesis_config.epoch_schedule,