add StaleOrGenerating in Snapshot and avoid using parallel process wh…

core/state/snapshot/difflayer.go

@@ -379,6 +379,18 @@ func (dl *diffLayer) accountRLP(hash common.Hash, depth int) ([]byte, error) {
 	return dl.parent.AccountRLP(hash)
 }
 
+// StaleOrGenerating returns whether the snapshot is stale or generating
+func (dl *diffLayer) StaleOrGenerating() bool {
+	dl.lock.RLock()
+	defer dl.lock.RUnlock()
+
+	if dl.Stale() {
+		return true
+	}
+
+	return dl.parent.Stale()
+}
+
 // Storage directly retrieves the storage data associated with a particular hash,
 // within a particular account. If the slot is unknown to this diff, it's parent
 // is consulted.

core/state/snapshot/disklayer.go

@@ -128,6 +128,18 @@ func (dl *diskLayer) AccountRLP(hash common.Hash) ([]byte, error) {
 	return blob, nil
 }
 
+// StaleOrGenerating returns whether the snapshot is stale or generating
+func (dl *diskLayer) StaleOrGenerating() bool {
+	dl.lock.RLock()
+	defer dl.lock.RUnlock()
+
+	if dl.Stale() || dl.genMarker != nil {
+		return true
+	}
+
+	return false
+}
+
 // Storage directly retrieves the storage data associated with a particular hash,
 // within a particular account.
 func (dl *diskLayer) Storage(accountHash, storageHash common.Hash) ([]byte, error) {

core/state/snapshot/snapshot.go

@@ -121,6 +121,9 @@ type Snapshot interface {
 	// Storage directly retrieves the storage data associated with a particular hash,
 	// within a particular account.
 	Storage(accountHash, storageHash common.Hash) ([]byte, error)
+
+	// StaleOrGenerating returns whether the snapshot is stale or generating
+	StaleOrGenerating() bool
 }
 
 // snapshot is the internal version of the snapshot data layer that supports some

core/state/statedb.go

@@ -311,6 +311,14 @@ func newStateDB(root common.Hash, db Database, snaps *snapshot.Tree) (*StateDB,
 	return sdb, nil
 }
 
+func (s *StateDB) SnapshotAvailable() bool {
+	if s.snap == nil {
+		return false
+	}
+
+	return !s.snap.StaleOrGenerating()
+}
+
 func (s *StateDB) getBaseStateDB() *StateDB {
 	return s
 }

core/state_processor.go

@@ -948,6 +948,11 @@ func (p *ParallelStateProcessor) doCleanUp() {
 
 // Implement BEP-130: Parallel Transaction Execution.
 func (p *ParallelStateProcessor) Process(block *types.Block, statedb *state.StateDB, cfg vm.Config) (*state.StateDB, types.Receipts, []*types.Log, uint64, error) {
+	// if snapshot is nil or generating, fall back to sequential process
+	if !statedb.SnapshotAvailable() {
+		return p.StateProcessor.Process(block, statedb, cfg)
+	}
+
 	var (
 		usedGas = new(uint64)
 		header  = block.Header()