From 4f0d88cb023d51bdc5f38cdb54dd11c51765c98b Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?P=C3=A9ter=20Szil=C3=A1gyi?= <peterke@gmail.com>
Date: Fri, 15 May 2015 19:43:42 +0300
Subject: [PATCH] eth/downloader: fix cancel channel double close

---
 eth/downloader/downloader.go | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/eth/downloader/downloader.go b/eth/downloader/downloader.go
index f9bd5a6353..a0a5b20a20 100644
--- a/eth/downloader/downloader.go
+++ b/eth/downloader/downloader.go
@@ -212,9 +212,14 @@ func (d *Downloader) Cancel() bool {
 		return false
 	}
 	// Close the current cancel channel
-	d.cancelLock.RLock()
-	close(d.cancelCh)
-	d.cancelLock.RUnlock()
+	d.cancelLock.Lock()
+	select {
+	case <-d.cancelCh:
+		// Channel was already closed
+	default:
+		close(d.cancelCh)
+	}
+	d.cancelLock.Unlock()
 
 	// reset the queue
 	d.queue.Reset()