From 7de7bddba9d9a8b0b7490931e346e8f10d0bdb7f Mon Sep 17 00:00:00 2001
From: David Hill <dhill@mindcry.org>
Date: Mon, 20 Jun 2016 15:34:21 -0400
Subject: [PATCH] peer: use atomics instead of mutexes (#670)

---
 peer/peer.go | 34 ++++++++++++----------------------
 1 file changed, 12 insertions(+), 22 deletions(-)

diff --git a/peer/peer.go b/peer/peer.go
index cf773c94..259371f1 100644
--- a/peer/peer.go
+++ b/peer/peer.go
@@ -392,10 +392,12 @@ type HostToNetAddrFunc func(host string, port uint16,
 // provided as a convenience.
 type Peer struct {
 	// The following variables must only be used atomically.
-	connected     int32
-	disconnect    int32
 	bytesReceived uint64
 	bytesSent     uint64
+	lastRecv      int64
+	lastSend      int64
+	connected     int32
+	disconnect    int32
 
 	conn net.Conn
 
@@ -429,8 +431,6 @@ type Peer struct {
 	statsMtx           sync.RWMutex
 	timeOffset         int64
 	timeConnected      time.Time
-	lastSend           time.Time
-	lastRecv           time.Time
 	startingHeight     int32
 	lastBlock          int32
 	lastAnnouncedBlock *wire.ShaHash
@@ -509,10 +509,10 @@ func (p *Peer) StatsSnapshot() *StatsSnap {
 		Addr:           addr,
 		UserAgent:      userAgent,
 		Services:       services,
-		LastSend:       p.lastSend,
-		LastRecv:       p.lastRecv,
-		BytesSent:      atomic.LoadUint64(&p.bytesSent),
-		BytesRecv:      atomic.LoadUint64(&p.bytesReceived),
+		LastSend:       p.LastSend(),
+		LastRecv:       p.LastRecv(),
+		BytesSent:      p.BytesSent(),
+		BytesRecv:      p.BytesReceived(),
 		ConnTime:       p.timeConnected,
 		TimeOffset:     p.timeOffset,
 		Version:        protocolVersion,
@@ -667,20 +667,14 @@ func (p *Peer) LastBlock() int32 {
 //
 // This function is safe for concurrent access.
 func (p *Peer) LastSend() time.Time {
-	p.statsMtx.RLock()
-	defer p.statsMtx.RUnlock()
-
-	return p.lastSend
+	return time.Unix(atomic.LoadInt64(&p.lastSend), 0)
 }
 
 // LastRecv returns the last recv time of the peer.
 //
 // This function is safe for concurrent access.
 func (p *Peer) LastRecv() time.Time {
-	p.statsMtx.RLock()
-	defer p.statsMtx.RUnlock()
-
-	return p.lastRecv
+	return time.Unix(atomic.LoadInt64(&p.lastRecv), 0)
 }
 
 // BytesSent returns the total number of bytes sent by the peer.
@@ -1496,9 +1490,7 @@ out:
 			}
 			break out
 		}
-		p.statsMtx.Lock()
-		p.lastRecv = time.Now()
-		p.statsMtx.Unlock()
+		atomic.StoreInt64(&p.lastRecv, time.Now().Unix())
 		p.stallControl <- stallControlMsg{sccReceiveMessage, rmsg}
 
 		// Ensure version message comes first.
@@ -1876,9 +1868,7 @@ out:
 			// message that it has been sent (if requested), and
 			// signal the send queue to the deliver the next queued
 			// message.
-			p.statsMtx.Lock()
-			p.lastSend = time.Now()
-			p.statsMtx.Unlock()
+			atomic.StoreInt64(&p.lastSend, time.Now().Unix())
 			if msg.doneChan != nil {
 				msg.doneChan <- struct{}{}
 			}