From 89b123473774248fc3a0356dd3ce5b116cc69b29 Mon Sep 17 00:00:00 2001
From: Tonis Tiigi <tonistiigi@gmail.com>
Date: Tue, 15 Nov 2016 18:02:26 -0800
Subject: [PATCH] Fix deadlock on cancelling healthcheck

Signed-off-by: Tonis Tiigi <tonistiigi@gmail.com>
---
 container/health.go   |  5 +----
 daemon/health.go      | 13 ++++++++++---
 daemon/health_test.go |  2 +-
 3 files changed, 12 insertions(+), 8 deletions(-)

diff --git a/container/health.go b/container/health.go
index 81fae50456..6e3cd12f3b 100644
--- a/container/health.go
+++ b/container/health.go
@@ -42,10 +42,7 @@ func (s *Health) OpenMonitorChannel() chan struct{} {
 func (s *Health) CloseMonitorChannel() {
 	if s.stop != nil {
 		logrus.Debug("CloseMonitorChannel: waiting for probe to stop")
-		// This channel does not buffer. Once the write succeeds, the monitor
-		// has read the stop request and will not make any further updates
-		// to c.State.Health.
-		s.stop <- struct{}{}
+		close(s.stop)
 		s.stop = nil
 		logrus.Debug("CloseMonitorChannel done")
 	}
diff --git a/daemon/health.go b/daemon/health.go
index f191472df6..ff8742613d 100644
--- a/daemon/health.go
+++ b/daemon/health.go
@@ -107,10 +107,17 @@ func (p *cmdProbe) run(ctx context.Context, d *Daemon, container *container.Cont
 }
 
 // Update the container's Status.Health struct based on the latest probe's result.
-func handleProbeResult(d *Daemon, c *container.Container, result *types.HealthcheckResult) {
+func handleProbeResult(d *Daemon, c *container.Container, result *types.HealthcheckResult, done chan struct{}) {
 	c.Lock()
 	defer c.Unlock()
 
+	// probe may have been cancelled while waiting on lock. Ignore result then
+	select {
+	case <-done:
+		return
+	default:
+	}
+
 	retries := c.Config.Healthcheck.Retries
 	if retries <= 0 {
 		retries = defaultProbeRetries
@@ -183,7 +190,7 @@ func monitor(d *Daemon, c *container.Container, stop chan struct{}, probe probe)
 				cancelProbe()
 				return
 			case result := <-results:
-				handleProbeResult(d, c, result)
+				handleProbeResult(d, c, result, stop)
 				// Stop timeout
 				cancelProbe()
 			case <-ctx.Done():
@@ -193,7 +200,7 @@ func monitor(d *Daemon, c *container.Container, stop chan struct{}, probe probe)
 					Output:   fmt.Sprintf("Health check exceeded timeout (%v)", probeTimeout),
 					Start:    startTime,
 					End:      time.Now(),
-				})
+				}, stop)
 				cancelProbe()
 				// Wait for probe to exit (it might take a while to respond to the TERM
 				// signal and we don't want dying probes to pile up).
diff --git a/daemon/health_test.go b/daemon/health_test.go
index bd221aa4d6..545b57beb7 100644
--- a/daemon/health_test.go
+++ b/daemon/health_test.go
@@ -80,7 +80,7 @@ func TestHealthStates(t *testing.T) {
 			Start:    startTime,
 			End:      startTime,
 			ExitCode: exitCode,
-		})
+		}, nil)
 	}
 
 	// starting -> failed -> success -> failed