From 0167b4b4a3bf120224a7c71e4c387fb058d939b8 Mon Sep 17 00:00:00 2001
From: Jakob Borg <jakob@nym.se>
Date: Tue, 17 Nov 2015 12:03:18 +0100
Subject: [PATCH] Don't cause rare spurious event timeout

Correctly resetting timers is surprisingly tricky.
---
 lib/events/events.go | 22 +++++++++++++++-------
 1 file changed, 15 insertions(+), 7 deletions(-)

diff --git a/lib/events/events.go b/lib/events/events.go
index 29391fec..5ad94e33 100644
--- a/lib/events/events.go
+++ b/lib/events/events.go
@@ -164,11 +164,20 @@ func (l *Logger) Log(t EventType, data interface{}) {
 func (l *Logger) Subscribe(mask EventType) *Subscription {
 	l.mutex.Lock()
 	dl.Debugln("subscribe", mask)
+
 	s := &Subscription{
 		mask:    mask,
 		events:  make(chan Event, BufferSize),
 		timeout: time.NewTimer(0),
 	}
+
+	// We need to create the timeout timer in the stopped, non-fired state so
+	// that Subscription.Poll() can safely reset it and select on the timeout
+	// channel. This ensures the timer is stopped and the channel drained.
+	if !s.timeout.Stop() {
+		<-s.timeout.C
+	}
+
 	l.subs = append(l.subs, s)
 	l.mutex.Unlock()
 	return s
@@ -196,19 +205,18 @@ func (l *Logger) Unsubscribe(s *Subscription) {
 func (s *Subscription) Poll(timeout time.Duration) (Event, error) {
 	dl.Debugln("poll", timeout)
 
-	if !s.timeout.Reset(timeout) {
-		select {
-		case <-s.timeout.C:
-		default:
-		}
-	}
+	s.timeout.Reset(timeout)
 
 	select {
 	case e, ok := <-s.events:
 		if !ok {
 			return e, ErrClosed
 		}
-		s.timeout.Stop()
+		if !s.timeout.Stop() {
+			// The timeout must be stopped and possibly drained to be ready
+			// for reuse in the next call.
+			<-s.timeout.C
+		}
 		return e, nil
 	case <-s.timeout.C:
 		return Event{}, ErrTimeout