Expose method to force statedb to use singlethreaded mode even when m…

…ultiple CPUs are available. (ethereum-optimism#373)

core/state/statedb.go

@@ -42,7 +42,6 @@ import (
 	"github.com/ethereum/go-ethereum/trie/triestate"
 	"github.com/ethereum/go-ethereum/trie/utils"
 	"github.com/holiman/uint256"
-	"golang.org/x/sync/errgroup"
 )
 
 // TriesInMemory represents the number of layers that are kept in RAM.
@@ -167,6 +166,9 @@ type StateDB struct {
 	StorageUpdated atomic.Int64
 	AccountDeleted int
 	StorageDeleted atomic.Int64
+
+	// singlethreaded avoids creation of additional threads when set to true for compatibility with cannon.
+	singlethreaded bool
 }
 
 // New creates a new state from a given trie.
@@ -196,6 +198,10 @@ func New(root common.Hash, db Database, snaps *snapshot.Tree) (*StateDB, error)
 	return sdb, nil
 }
 
+func (s *StateDB) MakeSinglethreaded() {
+	s.singlethreaded = true
+}
+
 // SetLogger sets the logger for account update hooks.
 func (s *StateDB) SetLogger(l *tracing.Hooks) {
 	s.logger = l
@@ -852,7 +858,7 @@ func (s *StateDB) IntermediateRoot(deleteEmptyObjects bool) common.Hash {
 	// so there's no need to explicitly wait for the prefetchers to finish.
 	var (
 		start   = time.Now()
-		workers errgroup.Group
+		workers = newWorkerGroup(s.singlethreaded)
 	)
 	if s.db.TrieDB().IsVerkle() {
 		// Whilst MPT storage tries are independent, Verkle has one single trie
@@ -1227,7 +1233,7 @@ func (s *StateDB) commit(deleteEmptyObjects bool) (*stateUpdate, error) {
 	var (
 		start   = time.Now()
 		root    common.Hash
-		workers errgroup.Group
+		workers = newWorkerGroup(s.singlethreaded)
 	)
 	// Schedule the account trie first since that will be the biggest, so give
 	// it the most time to crunch.

core/state/workers.go

@@ -0,0 +1,37 @@
+package state
+
+import (
+	"errors"
+
+	"golang.org/x/sync/errgroup"
+)
+
+type workerGroup interface {
+	Go(func() error)
+	SetLimit(int)
+	Wait() error
+}
+
+func newWorkerGroup(singlethreaded bool) workerGroup {
+	if singlethreaded {
+		return &inlineWorkerGroup{}
+	} else {
+		var grp errgroup.Group
+		return &grp
+	}
+}
+
+type inlineWorkerGroup struct {
+	err error
+}
+
+func (i *inlineWorkerGroup) Go(action func() error) {
+	i.err = errors.Join(i.err, action())
+}
+
+func (i *inlineWorkerGroup) SetLimit(_ int) {
+}
+
+func (i *inlineWorkerGroup) Wait() error {
+	return i.err
+}