progress: fix possible race in Stop(); fixes #322 (#332)

Author: jedib0t

progress/progress.go

@@ -23,37 +23,38 @@ var (
 
 // Progress helps track progress for one or more tasks.
 type Progress struct {
-autoStop bool
-lengthMessage int
-lengthProgress int
-lengthProgressOverall int
-lengthTracker int
-logsToRender []string
-logsToRenderMutex sync.RWMutex
-numTrackersExpected int64
-outputWriter io.Writer
-overallTracker *Tracker
-overallTrackerMutex sync.RWMutex
-pinnedMessages []string
-pinnedMessageMutex sync.RWMutex
-pinnedMessageNumLines int
-renderContext context.Context
-renderContextCancel context.CancelFunc
-renderInProgress bool
-renderInProgressMutex sync.RWMutex
-sortBy SortBy
-style *Style
-terminalWidth int
-terminalWidthMutex sync.RWMutex
-terminalWidthOverride int
-trackerPosition Position
-trackersActive []*Tracker
-trackersActiveMutex sync.RWMutex
-trackersDone []*Tracker
-trackersDoneMutex sync.RWMutex
-trackersInQueue []*Tracker
-trackersInQueueMutex sync.RWMutex
-updateFrequency time.Duration
+autoStop bool
+lengthMessage int
+lengthProgress int
+lengthProgressOverall int
+lengthTracker int
+logsToRender []string
+logsToRenderMutex sync.RWMutex
+numTrackersExpected int64
+outputWriter io.Writer
+overallTracker *Tracker
+overallTrackerMutex sync.RWMutex
+pinnedMessages []string
+pinnedMessageMutex sync.RWMutex
+pinnedMessageNumLines int
+renderContext context.Context
+renderContextCancel context.CancelFunc
+renderContextCancelMutex sync.Mutex
+renderInProgress bool
+renderInProgressMutex sync.RWMutex
+sortBy SortBy
+style *Style
+terminalWidth int
+terminalWidthMutex sync.RWMutex
+terminalWidthOverride int
+trackerPosition Position
+trackersActive []*Tracker
+trackersActiveMutex sync.RWMutex
+trackersDone []*Tracker
+trackersDoneMutex sync.RWMutex
+trackersInQueue []*Tracker
+trackersInQueueMutex sync.RWMutex
+updateFrequency time.Duration
 }
 
 // Position defines the position of the Tracker with respect to the Tracker's
@@ -284,7 +285,10 @@ func (p *Progress) ShowValue(show bool) {
 
 // Stop stops the Render() logic that is in progress.
 func (p *Progress) Stop() {
-if p.IsRenderInProgress() {
+p.renderContextCancelMutex.Lock()
+defer p.renderContextCancelMutex.Unlock()
+
+if p.renderContextCancel != nil {
 p.renderContextCancel()
 }
 }
@@ -309,15 +313,17 @@ func (p *Progress) getTerminalWidth() int {
 }
 
 func (p *Progress) initForRender() {
+// reset the signals
+p.renderContextCancelMutex.Lock()
+p.renderContext, p.renderContextCancel = context.WithCancel(context.Background())
+p.renderContextCancelMutex.Unlock()
+
 // pick a default style
 p.Style()
 if p.style.Options.SpeedOverallFormatter == nil {
 p.style.Options.SpeedOverallFormatter = FormatNumber
 }
 
-// reset the signals
-p.renderContext, p.renderContextCancel = context.WithCancel(context.Background())
-
 // pick default lengths if no valid ones set
 if p.lengthTracker <= 0 {
 p.lengthTracker = DefaultLengthTracker