From 5c752466dd19b0a2bf3f71ec0d4def949b8855bd Mon Sep 17 00:00:00 2001
From: Martin Holst Swende <martin@swende.se>
Date: Mon, 24 Jan 2022 17:28:20 +0100
Subject: [PATCH] eth/tracers: use non-threaded tracechain, fixes #23205

---
 eth/tracers/api.go | 51 +++++++++++-----------------------------------
 1 file changed, 12 insertions(+), 39 deletions(-)

diff --git a/eth/tracers/api.go b/eth/tracers/api.go
index b16b68c1fa043..59c20c50e059d 100644
--- a/eth/tracers/api.go
+++ b/eth/tracers/api.go
@@ -584,58 +584,31 @@ func (api *API) traceBlock(ctx context.Context, block *types.Block, config *Trac
 		signer  = types.MakeSigner(api.backend.ChainConfig(), block.Number())
 		txs     = block.Transactions()
 		results = make([]*txTraceResult, len(txs))
-
-		pend = new(sync.WaitGroup)
-		jobs = make(chan *txTraceTask, len(txs))
 	)
-	threads := runtime.NumCPU()
-	if threads > len(txs) {
-		threads = len(txs)
-	}
+	blockCtx := core.NewEVMBlockContext(block.Header(), api.chainContext(ctx), nil)
 	blockHash := block.Hash()
-	for th := 0; th < threads; th++ {
-		pend.Add(1)
-		go func() {
-			blockCtx := core.NewEVMBlockContext(block.Header(), api.chainContext(ctx), nil)
-			defer pend.Done()
-			// Fetch and execute the next transaction trace tasks
-			for task := range jobs {
-				msg, _ := txs[task.index].AsMessage(signer, block.BaseFee())
-				txctx := &Context{
-					BlockHash: blockHash,
-					TxIndex:   task.index,
-					TxHash:    txs[task.index].Hash(),
-				}
-				res, err := api.traceTx(ctx, msg, txctx, blockCtx, task.statedb, config)
-				if err != nil {
-					results[task.index] = &txTraceResult{Error: err.Error()}
-					continue
-				}
-				results[task.index] = &txTraceResult{Result: res}
-			}
-		}()
-	}
 	// Feed the transactions into the tracers and return
 	var failed error
-	blockCtx := core.NewEVMBlockContext(block.Header(), api.chainContext(ctx), nil)
+	is158 := api.backend.ChainConfig().IsEIP158(block.Number())
 	for i, tx := range txs {
-		// Send the trace task over for execution
-		jobs <- &txTraceTask{statedb: statedb.Copy(), index: i}
-
 		// Generate the next state snapshot fast without tracing
 		msg, _ := tx.AsMessage(signer, block.BaseFee())
-		statedb.Prepare(tx.Hash(), i)
-		vmenv := vm.NewEVM(blockCtx, core.NewEVMTxContext(msg), statedb, api.backend.ChainConfig(), vm.Config{})
-		if _, err := core.ApplyMessage(vmenv, msg, new(core.GasPool).AddGas(msg.Gas())); err != nil {
+		txctx := &Context{
+			BlockHash: blockHash,
+			TxIndex:   i,
+			TxHash:    tx.Hash(),
+		}
+		res, err := api.traceTx(ctx, msg, txctx, blockCtx, statedb, config)
+		if err != nil {
+			results[i] = &txTraceResult{Error: err.Error()}
 			failed = err
 			break
 		}
+		results[i] = &txTraceResult{Result: res}
 		// Finalize the state so any modifications are written to the trie
 		// Only delete empty objects if EIP158/161 (a.k.a Spurious Dragon) is in effect
-		statedb.Finalise(vmenv.ChainConfig().IsEIP158(block.Number()))
+		statedb.Finalise(is158)
 	}
-	close(jobs)
-	pend.Wait()
 
 	// If execution failed in between, abort
 	if failed != nil {