From 9c42a41ed81c0f138236b4ee6490a63092bea3fa Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?P=C3=A9ter=20Szil=C3=A1gyi?= <peterke@gmail.com>
Date: Tue, 2 Jan 2018 12:38:26 +0200
Subject: [PATCH] eth/downloader: avoid hidden reference to finished statesync
 request (#15545)

---
 eth/downloader/statesync.go | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/eth/downloader/statesync.go b/eth/downloader/statesync.go
index a0b05c9be6..937828b949 100644
--- a/eth/downloader/statesync.go
+++ b/eth/downloader/statesync.go
@@ -132,7 +132,10 @@ func (d *Downloader) runStateSync(s *stateSync) *stateSync {
 
 		// Send the next finished request to the current sync:
 		case deliverReqCh <- deliverReq:
-			finished = append(finished[:0], finished[1:]...)
+			// Shift out the first request, but also set the emptied slot to nil for GC
+			copy(finished, finished[1:])
+			finished[len(finished)-1] = nil
+			finished = finished[:len(finished)-1]
 
 		// Handle incoming state packs:
 		case pack := <-d.stateCh: