Merge pull request #2963 from MichaelEischer/fix-status-deadlock

backup: Fix possible deadlock of scanner goroutine

changelog/unreleased/issue-2834

@@ -0,0 +1,7 @@
+Bugfix: Fix rare cases of backup command hanging forever
+
+We've fixed an issue with the backup progress reporting which could cause
+restic to hang forever right before finishing a backup.
+
+https://github.com/restic/restic/issues/2834
+https://github.com/restic/restic/pull/2963

internal/ui/backup.go

@@ -41,6 +41,7 @@ type Backup struct {
 	errCh       chan struct{}
 	workerCh    chan fileWorkerMessage
 	finished    chan struct{}
+	closed      chan struct{}
 
 	summary struct {
 		sync.Mutex
@@ -71,6 +72,7 @@ func NewBackup(term *termstatus.Terminal, verbosity uint) *Backup {
 		errCh:       make(chan struct{}),
 		workerCh:    make(chan fileWorkerMessage),
 		finished:    make(chan struct{}),
+		closed:      make(chan struct{}),
 	}
 }
 
@@ -88,6 +90,9 @@ func (b *Backup) Run(ctx context.Context) error {
 
 	t := time.NewTicker(time.Second)
 	defer t.Stop()
+	defer close(b.closed)
+	// Reset status when finished
+	defer b.term.SetStatus([]string{""})
 
 	for {
 		select {
@@ -192,20 +197,27 @@ func (b *Backup) ScannerError(item string, fi os.FileInfo, err error) error {
 // Error is the error callback function for the archiver, it prints the error and returns nil.
 func (b *Backup) Error(item string, fi os.FileInfo, err error) error {
 	b.E("error: %v\n", err)
-	b.errCh <- struct{}{}
+	select {
+	case b.errCh <- struct{}{}:
+	case <-b.closed:
+	}
 	return nil
 }
 
 // StartFile is called when a file is being processed by a worker.
 func (b *Backup) StartFile(filename string) {
-	b.workerCh <- fileWorkerMessage{
-		filename: filename,
+	select {
+	case b.workerCh <- fileWorkerMessage{filename: filename}:
+	case <-b.closed:
 	}
 }
 
 // CompleteBlob is called for all saved blobs for files.
 func (b *Backup) CompleteBlob(filename string, bytes uint64) {
-	b.processedCh <- counter{Bytes: bytes}
+	select {
+	case b.processedCh <- counter{Bytes: bytes}:
+	case <-b.closed:
+	}
 }
 
 func formatPercent(numerator uint64, denominator uint64) string {
@@ -270,22 +282,28 @@ func (b *Backup) CompleteItem(item string, previous, current *restic.Node, s arc
 
 	if current == nil {
 		// error occurred, tell the status display to remove the line
-		b.workerCh <- fileWorkerMessage{
-			filename: item,
-			done:     true,
+		select {
+		case b.workerCh <- fileWorkerMessage{filename: item, done: true}:
+		case <-b.closed:
 		}
 		return
 	}
 
 	switch current.Type {
 	case "file":
-		b.processedCh <- counter{Files: 1}
-		b.workerCh <- fileWorkerMessage{
-			filename: item,
-			done:     true,
+		select {
+		case b.processedCh <- counter{Files: 1}:
+		case <-b.closed:
+		}
+		select {
+		case b.workerCh <- fileWorkerMessage{filename: item, done: true}:
+		case <-b.closed:
 		}
 	case "dir":
-		b.processedCh <- counter{Dirs: 1}
+		select {
+		case b.processedCh <- counter{Dirs: 1}:
+		case <-b.closed:
+		}
 	}
 
 	if current.Type == "dir" {
@@ -310,10 +328,9 @@ func (b *Backup) CompleteItem(item string, previous, current *restic.Node, s arc
 		}
 
 	} else if current.Type == "file" {
-
-		b.workerCh <- fileWorkerMessage{
-			done:     true,
-			filename: item,
+		select {
+		case b.workerCh <- fileWorkerMessage{done: true, filename: item}:
+		case <-b.closed:
 		}
 
 		if previous == nil {
@@ -342,7 +359,7 @@ func (b *Backup) CompleteItem(item string, previous, current *restic.Node, s arc
 func (b *Backup) ReportTotal(item string, s archiver.ScanStats) {
 	select {
 	case b.totalCh <- counter{Files: s.Files, Dirs: s.Dirs, Bytes: s.Bytes}:
-	case <-b.finished:
+	case <-b.closed:
 	}
 
 	if item == "" {
@@ -357,7 +374,10 @@ func (b *Backup) ReportTotal(item string, s archiver.ScanStats) {
 
 // Finish prints the finishing messages.
 func (b *Backup) Finish(snapshotID restic.ID) {
-	close(b.finished)
+	select {
+	case b.finished <- struct{}{}:
+	case <-b.closed:
+	}
 
 	b.P("\n")
 	b.P("Files:       %5d new, %5d changed, %5d unmodified\n", b.summary.Files.New, b.summary.Files.Changed, b.summary.Files.Unchanged)

internal/ui/json/backup.go

@@ -42,6 +42,7 @@ type Backup struct {
 	errCh       chan struct{}
 	workerCh    chan fileWorkerMessage
 	finished    chan struct{}
+	closed      chan struct{}
 
 	summary struct {
 		sync.Mutex
@@ -72,6 +73,7 @@ func NewBackup(term *termstatus.Terminal, verbosity uint) *Backup {
 		errCh:       make(chan struct{}),
 		workerCh:    make(chan fileWorkerMessage),
 		finished:    make(chan struct{}),
+		closed:      make(chan struct{}),
 	}
 }
 
@@ -103,6 +105,7 @@ func (b *Backup) Run(ctx context.Context) error {
 
 	t := time.NewTicker(time.Second)
 	defer t.Stop()
+	defer close(b.closed)
 
 	for {
 		select {
@@ -200,20 +203,27 @@ func (b *Backup) Error(item string, fi os.FileInfo, err error) error {
 		During:      "archival",
 		Item:        item,
 	})
-	b.errCh <- struct{}{}
+	select {
+	case b.errCh <- struct{}{}:
+	case <-b.closed:
+	}
 	return nil
 }
 
 // StartFile is called when a file is being processed by a worker.
 func (b *Backup) StartFile(filename string) {
-	b.workerCh <- fileWorkerMessage{
-		filename: filename,
+	select {
+	case b.workerCh <- fileWorkerMessage{filename: filename}:
+	case <-b.closed:
 	}
 }
 
 // CompleteBlob is called for all saved blobs for files.
 func (b *Backup) CompleteBlob(filename string, bytes uint64) {
-	b.processedCh <- counter{Bytes: bytes}
+	select {
+	case b.processedCh <- counter{Bytes: bytes}:
+	case <-b.closed:
+	}
 }
 
 // CompleteItem is the status callback function for the archiver when a
@@ -225,9 +235,9 @@ func (b *Backup) CompleteItem(item string, previous, current *restic.Node, s arc
 
 	if current == nil {
 		// error occurred, tell the status display to remove the line
-		b.workerCh <- fileWorkerMessage{
-			filename: item,
-			done:     true,
+		select {
+		case b.workerCh <- fileWorkerMessage{filename: item, done: true}:
+		case <-b.closed:
 		}
 		return
 	}
@@ -236,13 +246,19 @@ func (b *Backup) CompleteItem(item string, previous, current *restic.Node, s arc
 
 	switch current.Type {
 	case "file":
-		b.processedCh <- counter{Files: 1}
-		b.workerCh <- fileWorkerMessage{
-			filename: item,
-			done:     true,
+		select {
+		case b.processedCh <- counter{Files: 1}:
+		case <-b.closed:
+		}
+		select {
+		case b.workerCh <- fileWorkerMessage{filename: item, done: true}:
+		case <-b.closed:
 		}
 	case "dir":
-		b.processedCh <- counter{Dirs: 1}
+		select {
+		case b.processedCh <- counter{Dirs: 1}:
+		case <-b.closed:
+		}
 	}
 
 	if current.Type == "dir" {
@@ -291,10 +307,9 @@ func (b *Backup) CompleteItem(item string, previous, current *restic.Node, s arc
 		}
 
 	} else if current.Type == "file" {
-
-		b.workerCh <- fileWorkerMessage{
-			done:     true,
-			filename: item,
+		select {
+		case b.workerCh <- fileWorkerMessage{done: true, filename: item}:
+		case <-b.closed:
 		}
 
 		if previous == nil {
@@ -345,7 +360,7 @@ func (b *Backup) CompleteItem(item string, previous, current *restic.Node, s arc
 func (b *Backup) ReportTotal(item string, s archiver.ScanStats) {
 	select {
 	case b.totalCh <- counter{Files: uint64(s.Files), Dirs: uint64(s.Dirs), Bytes: s.Bytes}:
-	case <-b.finished:
+	case <-b.closed:
 	}
 
 	if item == "" {
@@ -365,7 +380,11 @@ func (b *Backup) ReportTotal(item string, s archiver.ScanStats) {
 
 // Finish prints the finishing messages.
 func (b *Backup) Finish(snapshotID restic.ID) {
-	close(b.finished)
+	select {
+	case b.finished <- struct{}{}:
+	case <-b.closed:
+	}
+
 	b.print(summaryOutput{
 		MessageType:         "summary",
 		FilesNew:            b.summary.Files.New,