use rLock where can, part2 (#767)

file.go

@@ -156,9 +156,9 @@ func (f *File) SetPriority(prio piecePriority) {
 
 // Returns the priority per File.SetPriority.
 func (f *File) Priority() (prio piecePriority) {
-	f.t.cl.lock()
+	f.t.cl.rLock()
 	prio = f.prio
-	f.t.cl.unlock()
+	f.t.cl.rUnlock()
 	return
 }
 

peer-conn-msg-writer.go

@@ -27,8 +27,8 @@ func (pc *PeerConn) initMessageWriter() {
 		logger: pc.logger,
 		w:      pc.w,
 		keepAlive: func() bool {
-			pc.locker().Lock()
-			defer pc.locker().Unlock()
+			pc.locker().RLock()
+			defer pc.locker().RUnlock()
 			return pc.useful()
 		},
 		writeBuffer: new(bytes.Buffer),

peerconn.go

@@ -5,7 +5,6 @@ import (
 	"bytes"
 	"errors"
 	"fmt"
-	"golang.org/x/time/rate"
 	"io"
 	"math/rand"
 	"net"
@@ -27,6 +26,7 @@ import (
 	pp "github.com/anacrolix/torrent/peer_protocol"
 	request_strategy "github.com/anacrolix/torrent/request-strategy"
 	"github.com/anacrolix/torrent/typed-roaring"
+	"golang.org/x/time/rate"
 )
 
 type PeerSource string
@@ -356,8 +356,8 @@ func (cn *Peer) downloadRate() float64 {
 }
 
 func (cn *Peer) DownloadRate() float64 {
-	cn.locker().Lock()
-	defer cn.locker().Unlock()
+	cn.locker().RLock()
+	defer cn.locker().RUnlock()
 
 	return cn.downloadRate()
 }

t.go

@@ -86,8 +86,8 @@ func (t *Torrent) NumPieces() pieceIndex {
 
 // Get missing bytes count for specific piece.
 func (t *Torrent) PieceBytesMissing(piece int) int64 {
-	t.cl.lock()
-	defer t.cl.unlock()
+	t.cl.rLock()
+	defer t.cl.rUnlock()
 
 	return int64(t.pieces[piece].bytesLeft())
 }
@@ -122,9 +122,9 @@ func (t *Torrent) SubscribePieceStateChanges() *pubsub.Subscription[PieceStateCh
 // Returns true if the torrent is currently being seeded. This occurs when the
 // client is willing to upload without wanting anything in return.
 func (t *Torrent) Seeding() (ret bool) {
-	t.cl.lock()
+	t.cl.rLock()
 	ret = t.seeding()
-	t.cl.unlock()
+	t.cl.rUnlock()
 	return
 }
 
@@ -153,8 +153,8 @@ func (t *Torrent) Length() int64 {
 // Returns a run-time generated metainfo for the torrent that includes the
 // info bytes and announce-list as currently known to the client.
 func (t *Torrent) Metainfo() metainfo.MetaInfo {
-	t.cl.lock()
-	defer t.cl.unlock()
+	t.cl.rLock()
+	defer t.cl.rUnlock()
 	return t.newMetaInfo()
 }