From 6830ddb659270b59b5a310fdc0e581b09fae5326 Mon Sep 17 00:00:00 2001
From: obscuren <geffobscura@gmail.com>
Date: Sat, 18 Apr 2015 20:25:55 +0200
Subject: [PATCH] downloader: free up peers from work when the downloader
 resets

---
 eth/downloader/downloader.go |  4 +++-
 eth/downloader/peer.go       | 10 ++++++++++
 eth/downloader/queue.go      | 13 +++++++++----
 3 files changed, 22 insertions(+), 5 deletions(-)

diff --git a/eth/downloader/downloader.go b/eth/downloader/downloader.go
index 2b5dbe952..2f98a1414 100644
--- a/eth/downloader/downloader.go
+++ b/eth/downloader/downloader.go
@@ -297,8 +297,9 @@ out:
 
 				// make sure that we have peers available for fetching. If all peers have been tried
 				// and all failed throw an error
-				if len(availablePeers) > 0 && d.queue.fetchPool.Size() == 0 {
+				if len(d.queue.fetching) == 0 {
 					d.queue.reset()
+					d.peers.reset()
 
 					return errPeersUnavailable
 				}
@@ -337,6 +338,7 @@ out:
 					d.queue.deliver(pid, nil)
 					if peer := d.peers[pid]; peer != nil {
 						peer.demote()
+						peer.reset()
 					}
 				}
 
diff --git a/eth/downloader/peer.go b/eth/downloader/peer.go
index 5d5208e8e..ec2a61550 100644
--- a/eth/downloader/peer.go
+++ b/eth/downloader/peer.go
@@ -20,6 +20,12 @@ type blockFetcherFn func([]common.Hash) error
 // XXX make threadsafe!!!!
 type peers map[string]*peer
 
+func (p peers) reset() {
+	for _, peer := range p {
+		p.reset()
+	}
+}
+
 func (p peers) get(state int) []*peer {
 	var peers []*peer
 	for _, peer := range p {
@@ -128,3 +134,7 @@ func (p *peer) demote() {
 		p.rep = 0
 	}
 }
+
+func (p *peer) reset() {
+	p.state = idleState
+}
diff --git a/eth/downloader/queue.go b/eth/downloader/queue.go
index 5745bf1f8..ce3aa9850 100644
--- a/eth/downloader/queue.go
+++ b/eth/downloader/queue.go
@@ -60,13 +60,18 @@ func (c *queue) get(p *peer, max int) *chunk {
 			return false
 		}
 
-		hashes.Add(v)
-		i++
+		// Skip any hashes that have previously been requested from the peer
+		if !p.requested.Has(v) {
+			hashes.Add(v)
+			i++
+		}
 
 		return true
 	})
-	// remove hashes that have previously been fetched
-	hashes.Separate(p.requested)
+	// if no hashes can be requested return a nil chunk
+	if hashes.Size() == 0 {
+		return nil
+	}
 
 	// remove the fetchable hashes from hash pool
 	c.hashPool.Separate(hashes)