Add ParallelExecFailedError

Parallel execution can fail due to bad dependencies. In the case of bad
dependencies, the result of serial execution should be used.

core/blockchain.go

@@ -42,6 +42,7 @@ import (
 	"github.com/ethereum/go-ethereum/common/prque"
 	"github.com/ethereum/go-ethereum/common/tracing"
 	"github.com/ethereum/go-ethereum/consensus"
+	"github.com/ethereum/go-ethereum/core/blockstm"
 	"github.com/ethereum/go-ethereum/core/rawdb"
 	"github.com/ethereum/go-ethereum/core/state"
 	"github.com/ethereum/go-ethereum/core/state/snapshot"
@@ -500,6 +501,18 @@ func (bc *BlockChain) ProcessBlock(block *types.Block, parent *types.Header) (ty
 	}
 
 	result := <-resultChan
+
+	if _, ok := result.err.(blockstm.ParallelExecFailedError); ok {
+		log.Warn("Parallel state processor failed", "err", result.err)
+
+		// If the parallel processor failed, we will fallback to the serial processor if enabled
+		if processorCount == 2 {
+			result.statedb.StopPrefetcher()
+			result = <-resultChan
+			processorCount--
+		}
+	}
+
 	result.counter.Inc(1)
 
 	// Make sure we are not leaking any prefetchers

core/blockstm/executor.go

@@ -69,6 +69,14 @@ func (e ErrExecAbortError) Error() string {
 	}
 }
 
+type ParallelExecFailedError struct {
+	Msg string
+}
+
+func (e ParallelExecFailedError) Error() string {
+	return e.Msg
+}
+
 type IntHeap []int
 
 func (h IntHeap) Len() int           { return len(h) }
@@ -384,7 +392,7 @@ func (pe *ParallelExecutor) Prepare() error {
 	tx := pe.execTasks.takeNextPending()
 
 	if tx == -1 {
-		return fmt.Errorf("no transaction to execute")
+		return ParallelExecFailedError{"no executable transactions due to bad dependency"}
 	}
 
 	pe.cntExec++