Clean headers pointers when removing links (#4222)

* Clean headers pointers when removing links

* Replace the lock

Co-authored-by: Alexey Sharp <alexeysharp@Alexeys-iMac.local>

turbo/stages/headerdownload/header_algos.go

@@ -102,16 +102,7 @@ func (hd *HeaderDownload) ReportBadHeader(headerHash common.Hash) {
 	hd.badHeaders[headerHash] = struct{}{}
 	// Find the link, remove it and all its descendands from all the queues
 	if link, ok := hd.links[headerHash]; ok {
-		removeList := []*Link{link}
-		for len(removeList) > 0 {
-			removal := removeList[len(removeList)-1]
-			removeList = removeList[:len(removeList)-1]
-			hd.moveLinkToQueue(removal, NoQueue)
-			delete(hd.links, removal.hash)
-			for child := removal.fChild; child != nil; child = child.next {
-				removeList = append(removeList, child)
-			}
-		}
+		hd.removeUpwards(link)
 	}
 }
 
@@ -146,16 +137,16 @@ func (hd *HeaderDownload) IsBadHeaderPoS(tipHash common.Hash) (bad bool, lastVal
 }
 
 func (hd *HeaderDownload) removeUpwards(link *Link) {
-	var toRemove []*Link
-	for child := link; child != nil; child = child.next {
-		toRemove = append(toRemove, child)
+	if link == nil {
+		return
 	}
+	var toRemove []*Link = []*Link{link}
 	for len(toRemove) > 0 {
 		removal := toRemove[len(toRemove)-1]
 		toRemove = toRemove[:len(toRemove)-1]
 		delete(hd.links, removal.hash)
 		hd.moveLinkToQueue(removal, NoQueue)
-		for child := removal.fChild; child != nil; child = child.next {
+		for child := removal.fChild; child != nil; child, child.next = child.next, nil {
 			toRemove = append(toRemove, child)
 		}
 	}
@@ -185,6 +176,8 @@ func (hd *HeaderDownload) removeAnchor(anchor *Anchor) {
 	// Anchor is removed from the map, and from the priority queue
 	delete(hd.anchors, anchor.parentHash)
 	heap.Remove(hd.anchorQueue, anchor.idx)
+	for child := anchor.fLink; child != nil; child, child.next = child.next, nil {
+	}
 	anchor.idx = -1
 }
 
@@ -192,6 +185,8 @@ func (hd *HeaderDownload) pruneLinkQueue() {
 	for hd.linkQueue.Len() > hd.linkLimit {
 		link := heap.Pop(&hd.linkQueue).(*Link)
 		delete(hd.links, link.hash)
+		for child := link.fChild; child != nil; child, child.next = child.next, nil {
+		}
 		if parentLink, ok := hd.links[link.header.ParentHash]; ok {
 			var prevChild *Link
 			for child := parentLink.fChild; child != nil && child != link; child = child.next {
@@ -295,6 +290,8 @@ func (hd *HeaderDownload) RecoverFromDb(db kv.RoDB) error {
 	for hd.persistedLinkQueue.Len() > 0 {
 		link := heap.Pop(&hd.persistedLinkQueue).(*Link)
 		delete(hd.links, link.hash)
+		for child := link.fChild; child != nil; child, child.next = child.next, nil {
+		}
 	}
 	err := db.View(context.Background(), func(tx kv.Tx) error {
 		c, err := tx.Cursor(kv.Headers)
@@ -461,6 +458,7 @@ func (hd *HeaderDownload) InsertHeader(hf FeedHeaderFunc, terminalTotalDifficult
 			// If the link or its parent is marked bad, throw it out
 			hd.moveLinkToQueue(link, NoQueue)
 			delete(hd.links, link.hash)
+			hd.removeUpwards(link)
 			return true, false, nil
 		}
 		if !link.verified {
@@ -473,6 +471,7 @@ func (hd *HeaderDownload) InsertHeader(hf FeedHeaderFunc, terminalTotalDifficult
 					log.Debug("Verification failed for header", "hash", link.hash, "height", link.blockHeight, "err", err)
 					hd.moveLinkToQueue(link, NoQueue)
 					delete(hd.links, link.hash)
+					hd.removeUpwards(link)
 					return true, false, nil
 				}
 			}
@@ -519,6 +518,8 @@ func (hd *HeaderDownload) InsertHeader(hf FeedHeaderFunc, terminalTotalDifficult
 	for hd.persistedLinkQueue.Len() > hd.persistedLinkLimit {
 		link := heap.Pop(&hd.persistedLinkQueue).(*Link)
 		delete(hd.links, link.hash)
+		for child := link.fChild; child != nil; child, child.next = child.next, nil {
+		}
 	}
 	return hd.insertQueue.Len() > 0 && hd.insertQueue[0].blockHeight <= hd.highestInDb+1, false, nil
 }
@@ -930,6 +931,8 @@ func (hd *HeaderDownload) ProcessHeaders(csHeaders []ChainSegmentHeader, newBloc
 			requestMore = true
 		}
 	}
+	hd.lock.Lock()
+	defer hd.lock.Unlock()
 	log.Trace("Link queue", "size", hd.linkQueue.Len())
 	if hd.linkQueue.Len() > hd.linkLimit {
 		log.Trace("Too many links, cutting down", "count", hd.linkQueue.Len(), "tried to add", len(csHeaders), "limit", hd.linkLimit)