From be80588bceac2c5523b4e342783153f7715b6212 Mon Sep 17 00:00:00 2001
From: Martin Holst Swende <martin@swende.se>
Date: Fri, 24 Sep 2021 16:40:01 +0200
Subject: [PATCH] trie: check for derefs while committing

---
 trie/committer.go | 10 ++++++++++
 trie/database.go  |  7 +++++++
 2 files changed, 17 insertions(+)

diff --git a/trie/committer.go b/trie/committer.go
index 0721990a21799..ed461ba2e3f40 100644
--- a/trie/committer.go
+++ b/trie/committer.go
@@ -19,6 +19,8 @@ package trie
 import (
 	"errors"
 	"fmt"
+	"github.com/ethereum/go-ethereum/log"
+	"runtime/debug"
 	"sync"
 
 	"github.com/ethereum/go-ethereum/common"
@@ -77,7 +79,15 @@ func (c *committer) Commit(n node, db *Database) (hashNode, int, error) {
 	if db == nil {
 		return nil, 0, errors.New("no db provided")
 	}
+	derefcountA := db.DerefCount()
 	h, committed, err := c.commit(n, db)
+	derefcountB := db.DerefCount()
+	if derefcountA != derefcountB {
+		log.Warn("trie database dereference happened during commit.",
+			"before", derefcountA, "after", derefcountB)
+		log.Warn("Commit ended on error", "err", err)
+		debug.PrintStack()
+	}
 	if err != nil {
 		return nil, 0, err
 	}
diff --git a/trie/database.go b/trie/database.go
index f140a56642f55..78117dfceabed 100644
--- a/trie/database.go
+++ b/trie/database.go
@@ -23,6 +23,7 @@ import (
 	"reflect"
 	"runtime"
 	"sync"
+	"sync/atomic"
 	"time"
 
 	"github.com/VictoriaMetrics/fastcache"
@@ -76,6 +77,7 @@ type Database struct {
 
 	preimages map[common.Hash][]byte // Preimages of nodes from the secure trie
 
+	derefs  uint64             // counter on Dereference operations (accessed atomically)
 	gctime  time.Duration      // Time spent on garbage collection since last commit
 	gcnodes uint64             // Nodes garbage collected since last commit
 	gcsize  common.StorageSize // Data storage garbage collected since last commit
@@ -509,6 +511,10 @@ func (db *Database) reference(child common.Hash, parent common.Hash) {
 	}
 }
 
+func (db *Database) DerefCount() uint64 {
+	return atomic.LoadUint64(&db.derefs)
+}
+
 // Dereference removes an existing reference from a root node.
 func (db *Database) Dereference(root common.Hash) {
 	// Sanity check to ensure that the meta-root is not removed
@@ -518,6 +524,7 @@ func (db *Database) Dereference(root common.Hash) {
 	}
 	db.lock.Lock()
 	defer db.lock.Unlock()
+	atomic.AddUint64(&db.derefs, 1)
 
 	nodes, storage, start := len(db.dirties), db.dirtiesSize, time.Now()
 	db.dereference(root, common.Hash{})