Rework Reader waiting

client.go

@@ -1097,12 +1097,12 @@ func (cl *Client) newTorrent(ih metainfo.Hash, specStorage storage.ClientImpl) (
 		storageOpener:       storageClient,
 		maxEstablishedConns: cl.config.EstablishedConnsPerTorrent,
 
-		networkingEnabled: true,
 		metadataChanged: sync.Cond{
 			L: cl.locker(),
 		},
 		webSeeds: make(map[string]*Peer),
 	}
+	t.networkingEnabled.Set()
 	t._pendingPieces.NewSet = priorityBitmapStableNewSet
 	t.logger = cl.logger.WithContextValue(t)
 	t.setChunkSize(defaultChunkSize)
@@ -1198,7 +1198,7 @@ func (t *Torrent) MergeSpec(spec *TorrentSpec) error {
 	}
 	t.addTrackers(spec.Trackers)
 	t.maybeNewConns()
-	t.dataDownloadDisallowed = spec.DisallowDataDownload
+	t.dataDownloadDisallowed.SetBool(spec.DisallowDataDownload)
 	t.dataUploadDisallowed = spec.DisallowDataUpload
 	return nil
 }

misc.go

@@ -52,8 +52,11 @@ func metadataPieceSize(totalSize int, piece int) int {
 }
 
 // Return the request that would include the given offset into the torrent data.
-func torrentOffsetRequest(torrentLength, pieceSize, chunkSize, offset int64) (
-	r Request, ok bool) {
+func torrentOffsetRequest(
+	torrentLength, pieceSize, chunkSize, offset int64,
+) (
+	r Request, ok bool,
+) {
 	if offset < 0 || offset >= torrentLength {
 		return
 	}

piece.go

@@ -4,6 +4,7 @@ import (
 	"fmt"
 	"sync"
 
+	"github.com/anacrolix/chansync"
 	"github.com/anacrolix/missinggo/v2/bitmap"
 
 	"github.com/anacrolix/torrent/metainfo"
@@ -21,6 +22,8 @@ type Piece struct {
 	// length can be determined by the request chunkSize in use.
 	_dirtyChunks bitmap.Bitmap
 
+	readerCond chansync.BroadcastCond
+
 	numVerifies         int64
 	hashing             bool
 	marking             bool
@@ -70,7 +73,7 @@ func (p *Piece) numDirtyChunks() pp.Integer {
 
 func (p *Piece) unpendChunkIndex(i int) {
 	p._dirtyChunks.Add(bitmap.BitIndex(i))
-	p.t.tickleReaders()
+	p.readerCond.Broadcast()
 }
 
 func (p *Piece) pendChunkIndex(i int) {

reader.go

@@ -97,11 +97,6 @@ func (r *reader) available(off, max int64) (ret int64) {
 	return
 }
 
-func (r *reader) waitReadable(off int64) {
-	// We may have been sent back here because we were told we could read but it failed.
-	r.t.cl.event.Wait()
-}
-
 // Calculates the pieces this reader wants downloaded, ignoring the cached value at r.pieces.
 func (r *reader) piecesUncached() (ret pieceRange) {
 	ra := r.readahead
@@ -122,27 +117,11 @@ func (r *reader) Read(b []byte) (n int, err error) {
 }
 
 func (r *reader) ReadContext(ctx context.Context, b []byte) (n int, err error) {
-	// This is set under the Client lock if the Context is canceled. I think we coordinate on a
-	// separate variable so as to avoid false negatives with race conditions due to Contexts being
-	// synchronized.
-	var ctxErr error
-	if ctx.Done() != nil {
-		ctx, cancel := context.WithCancel(ctx)
-		// Abort the goroutine when the function returns.
-		defer cancel()
-		go func() {
-			<-ctx.Done()
-			r.t.cl.lock()
-			ctxErr = ctx.Err()
-			r.t.tickleReaders()
-			r.t.cl.unlock()
-		}()
-	}
 	// Hmmm, if a Read gets stuck, this means you can't change position for other purposes. That
 	// seems reasonable, but unusual.
 	r.opMu.Lock()
 	defer r.opMu.Unlock()
-	n, err = r.readOnceAt(b, r.pos, &ctxErr)
+	n, err = r.readOnceAt(ctx, b, r.pos)
 	if n == 0 {
 		if err == nil && len(b) > 0 {
 			panic("expected error")
@@ -163,32 +142,44 @@ func (r *reader) ReadContext(ctx context.Context, b []byte) (n int, err error) {
 	return
 }
 
+var closedChan = make(chan struct{})
+
+func init() {
+	close(closedChan)
+}
+
 // Wait until some data should be available to read. Tickles the client if it isn't. Returns how
 // much should be readable without blocking.
-func (r *reader) waitAvailable(pos, wanted int64, ctxErr *error, wait bool) (avail int64, err error) {
-	r.t.cl.lock()
-	defer r.t.cl.unlock()
+func (r *reader) waitAvailable(ctx context.Context, pos, wanted int64, wait bool) (avail int64, err error) {
+	t := r.t
 	for {
+		r.t.cl.rLock()
 		avail = r.available(pos, wanted)
+		readerCond := t.piece(int((r.offset + pos) / t.info.PieceLength)).readerCond.Signaled()
+		r.t.cl.rUnlock()
 		if avail != 0 {
 			return
 		}
-		if r.t.closed.IsSet() {
+		var dontWait <-chan struct{}
+		if !wait || wanted == 0 {
+			dontWait = closedChan
+		}
+		select {
+		case <-r.t.closed.Done():
 			err = errors.New("torrent closed")
 			return
-		}
-		if *ctxErr != nil {
-			err = *ctxErr
+		case <-ctx.Done():
+			err = ctx.Err()
 			return
-		}
-		if r.t.dataDownloadDisallowed || !r.t.networkingEnabled {
-			err = errors.New("downloading disabled and data not already available")
+		case <-r.t.dataDownloadDisallowed.On():
+			err = errors.New("torrent data downloading disabled")
+		case <-r.t.networkingEnabled.Off():
+			err = errors.New("torrent networking disabled")
 			return
-		}
-		if !wait || wanted == 0 {
+		case <-dontWait:
 			return
+		case <-readerCond:
 		}
-		r.waitReadable(pos)
 	}
 }
 
@@ -199,14 +190,14 @@ func (r *reader) torrentOffset(readerPos int64) int64 {
 }
 
 // Performs at most one successful read to torrent storage.
-func (r *reader) readOnceAt(b []byte, pos int64, ctxErr *error) (n int, err error) {
+func (r *reader) readOnceAt(ctx context.Context, b []byte, pos int64) (n int, err error) {
 	if pos >= r.length {
 		err = io.EOF
 		return
 	}
 	for {
 		var avail int64
-		avail, err = r.waitAvailable(pos, int64(len(b)), ctxErr, n == 0)
+		avail, err = r.waitAvailable(ctx, pos, int64(len(b)), n == 0)
 		if avail == 0 {
 			return
 		}

torrent.go

@@ -13,12 +13,12 @@ import (
 	"net/url"
 	"sort"
 	"strings"
-	"sync"
 	"text/tabwriter"
 	"time"
 	"unsafe"
 
 	"github.com/RoaringBitmap/roaring"
+	"github.com/anacrolix/chansync"
 	"github.com/anacrolix/dht/v2"
 	"github.com/anacrolix/log"
 	"github.com/anacrolix/missinggo/iter"
@@ -29,6 +29,7 @@ import (
 	"github.com/anacrolix/missinggo/v2/bitmap"
 	"github.com/anacrolix/missinggo/v2/prioritybitmap"
 	"github.com/anacrolix/multiless"
+	"github.com/anacrolix/sync"
 	"github.com/davecgh/go-spew/spew"
 	"github.com/pion/datachannel"
 
@@ -52,12 +53,12 @@ type Torrent struct {
 	cl     *Client
 	logger log.Logger
 
-	networkingEnabled      bool
-	dataDownloadDisallowed bool
+	networkingEnabled      chansync.Flag
+	dataDownloadDisallowed chansync.Flag
 	dataUploadDisallowed   bool
 	userOnWriteChunkErr    func(error)
 
-	closed   missinggo.Event
+	closed   chansync.SetOnce
 	infoHash metainfo.Hash
 	pieces   []Piece
 	// Values are the piece indices that changed.
@@ -192,13 +193,9 @@ func (t *Torrent) pendingPieces() *prioritybitmap.PriorityBitmap {
 	return &t._pendingPieces
 }
 
-func (t *Torrent) tickleReaders() {
-	t.cl.event.Broadcast()
-}
-
 // Returns a channel that is closed when the Torrent is closed.
-func (t *Torrent) Closed() <-chan struct{} {
-	return t.closed.LockedChan(t.cl.locker())
+func (t *Torrent) Closed() chansync.Done {
+	return t.closed.Done()
 }
 
 // KnownSwarm returns the known subset of the peers in the Torrent's swarm, including active,
@@ -794,7 +791,6 @@ func (t *Torrent) numPiecesCompleted() (num pieceIndex) {
 
 func (t *Torrent) close() (err error) {
 	t.closed.Set()
-	t.tickleReaders()
 	if t.storage != nil {
 		go func() {
 			t.storageLock.Lock()
@@ -1162,7 +1158,6 @@ func (t *Torrent) pendRequest(req Request) {
 }
 
 func (t *Torrent) pieceCompletionChanged(piece pieceIndex) {
-	t.tickleReaders()
 	t.cl.event.Broadcast()
 	if t.pieceComplete(piece) {
 		t.onPieceCompleted(piece)
@@ -1501,7 +1496,7 @@ func (t *Torrent) runHandshookConnLoggingErr(pc *PeerConn) {
 func (t *Torrent) startWebsocketAnnouncer(u url.URL) torrentTrackerAnnouncer {
 	wtc, release := t.cl.websocketTrackers.Get(u.String())
 	go func() {
-		<-t.closed.LockedChan(t.cl.locker())
+		<-t.closed.Done()
 		release()
 	}()
 	wst := websocketTrackerStatus{u, wtc}
@@ -1664,7 +1659,7 @@ func (t *Torrent) timeboxedAnnounceToDht(s DhtServer) error {
 		return err
 	}
 	select {
-	case <-t.closed.LockedChan(t.cl.locker()):
+	case <-t.closed.Done():
 	case <-time.After(5 * time.Minute):
 	}
 	stop()
@@ -1815,7 +1810,7 @@ func (t *Torrent) addPeerConn(c *PeerConn) (err error) {
 }
 
 func (t *Torrent) wantConns() bool {
-	if !t.networkingEnabled {
+	if !t.networkingEnabled.Bool() {
 		return false
 	}
 	if t.closed.IsSet() {
@@ -1949,6 +1944,7 @@ func (t *Torrent) cancelRequestsForPiece(piece pieceIndex) {
 func (t *Torrent) onPieceCompleted(piece pieceIndex) {
 	t.pendAllChunkSpecs(piece)
 	t.cancelRequestsForPiece(piece)
+	t.piece(piece).readerCond.Broadcast()
 	for conn := range t.conns {
 		conn.have(piece)
 		t.maybeDropMutuallyCompletePeer(&conn.Peer)
@@ -2137,27 +2133,15 @@ func (t *Torrent) onWriteChunkErr(err error) {
 }
 
 func (t *Torrent) DisallowDataDownload() {
-	t.cl.lock()
-	defer t.cl.unlock()
 	t.disallowDataDownloadLocked()
 }
 
 func (t *Torrent) disallowDataDownloadLocked() {
-	t.dataDownloadDisallowed = true
-	t.iterPeers(func(c *Peer) {
-		c.updateRequests()
-	})
-	t.tickleReaders()
+	t.dataDownloadDisallowed.Set()
 }
 
 func (t *Torrent) AllowDataDownload() {
-	t.cl.lock()
-	defer t.cl.unlock()
-	t.dataDownloadDisallowed = false
-	t.tickleReaders()
-	t.iterPeers(func(c *Peer) {
-		c.updateRequests()
-	})
+	t.dataDownloadDisallowed.Clear()
 }
 
 // Enables uploading data, if it was disabled.

tracker_scraper.go

@@ -216,7 +216,6 @@ func (me *trackerScraper) Run() {
 
 		me.t.cl.lock()
 		wantPeers := me.t.wantPeersEvent.C()
-		closed := me.t.closed.C()
 		me.t.cl.unlock()
 
 		// If we want peers, reduce the interval to the minimum if it's appropriate.
@@ -234,7 +233,7 @@ func (me *trackerScraper) Run() {
 		}
 
 		select {
-		case <-closed:
+		case <-me.t.closed.Done():
 			return
 		case <-reconsider:
 			// Recalculate the interval.