Propagate dead slots up to replay (#17227)

ledger/src/blockstore.rs

@@ -2755,17 +2755,7 @@ impl Blockstore {
         let result: HashMap<u64, Vec<u64>> = slots
             .iter()
             .zip(slot_metas)
-            .filter_map(|(height, meta)| {
+            .filter_map(|(height, meta)| meta.map(|meta| (*height, meta.next_slots.to_vec())))
-                meta.map(|meta| {
-                    let valid_next_slots: Vec<u64> = meta
-                        .next_slots
-                        .iter()
-                        .cloned()
-                        .filter(|s| !self.is_dead(*s))
-                        .collect();
-                    (*height, valid_next_slots)
-                })
-            })
             .collect();
 
         Ok(result)

local-cluster/tests/local_cluster.rs

@@ -2123,9 +2123,14 @@ fn test_optimistic_confirmation_violation_detection() {
             "Setting slot: {} on main fork as dead, should cause fork",
             prev_voted_slot
         );
-        // marking this voted slot as dead makes the saved tower garbage
+        // Necessary otherwise tower will inform this validator that it's latest
-        // effectively. That's because its stray last vote becomes stale (= no
+        // vote is on slot `prev_voted_slot`. This will then prevent this validator
-        // ancestor in bank forks).
+        // from resetting to the parent of `prev_voted_slot` to create an alternative fork because
+        // 1) Validator can't vote on earlier ancestor of last vote due to switch threshold (can't vote
+        // on ancestors of last vote)
+        // 2) Won't reset to this earlier ancestor becasue reset can only happen on same voted fork if
+        // it's for the last vote slot or later
+        remove_tower(&exited_validator_info.info.ledger_path, &entry_point_id);
         blockstore.set_dead_slot(prev_voted_slot).unwrap();
     }