Merge pull request #4114 from filecoin-project/fix/fork-after-cron

Run fork function after cron for null block safety

chain/stmgr/stmgr.go

@@ -209,6 +209,18 @@ func (sm *StateManager) ApplyBlocks(ctx context.Context, parentEpoch abi.ChainEp
 	}
 
 	for i := parentEpoch; i < epoch; i++ {
+		if i > parentEpoch {
+			// run cron for null rounds if any
+			if err := runCron(); err != nil {
+				return cid.Undef, cid.Undef, err
+			}
+
+			pstate, err = vmi.Flush(ctx)
+			if err != nil {
+				return cid.Undef, cid.Undef, xerrors.Errorf("flushing vm: %w", err)
+			}
+		}
+
 		// handle state forks
 		// XXX: The state tree
 		newState, err := sm.handleStateForks(ctx, pstate, i, cb, ts)
@@ -223,18 +235,6 @@ func (sm *StateManager) ApplyBlocks(ctx context.Context, parentEpoch abi.ChainEp
 			}
 		}
 
-		if i > parentEpoch {
-			// run cron for null rounds if any
-			if err := runCron(); err != nil {
-				return cid.Cid{}, cid.Cid{}, err
-			}
-
-			newState, err = vmi.Flush(ctx)
-			if err != nil {
-				return cid.Undef, cid.Undef, xerrors.Errorf("flushing vm: %w", err)
-			}
-		}
-
 		vmi.SetBlockHeight(i + 1)
 		pstate = newState
 	}