Merge pull request #26980 from hongchaodeng/fix

Automatic merge from submit-queue

processor listener: fix locking in pop()

Currently the lock in processorListener is used to guard pendingNotifications. But in pop, it also locks around on select chan. This will block the goroutine with lock acquired.

This PR changes the lock to guard the correct section only.

pkg/controller/framework/processor_listener_test.go

@@ -0,0 +1,48 @@
+/*
+Copyright 2016 The Kubernetes Authors All rights reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package framework
+
+import (
+	"testing"
+	"time"
+
+	"k8s.io/kubernetes/pkg/util/wait"
+)
+
+// TestPopReleaseLock tests that when processor listener blocks on chan,
+// it should release the lock for pendingNotifications.
+func TestPopReleaseLock(t *testing.T) {
+	pl := newProcessListener(nil)
+	stopCh := make(chan struct{})
+	defer close(stopCh)
+	// make pop() block on nextCh: waiting for receiver to get notification.
+	pl.add(1)
+	go pl.pop(stopCh)
+
+	resultCh := make(chan struct{})
+	go func() {
+		pl.lock.Lock()
+		close(resultCh)
+	}()
+
+	select {
+	case <-resultCh:
+	case <-time.After(wait.ForeverTestTimeout):
+		t.Errorf("Timeout after %v", wait.ForeverTestTimeout)
+	}
+	pl.lock.Unlock()
+}

pkg/controller/framework/shared_informer.go

@@ -279,21 +279,30 @@ func (p *processorListener) add(notification interface{}) {
 func (p *processorListener) pop(stopCh <-chan struct{}) {
 	defer utilruntime.HandleCrash()
 
-	p.lock.Lock()
-	defer p.lock.Unlock()
 	for {
-		for len(p.pendingNotifications) == 0 {
-			// check if we're shutdown
-			select {
-			case <-stopCh:
-				return
-			default:
+		blockingGet := func() (interface{}, bool) {
+			p.lock.Lock()
+			defer p.lock.Unlock()
+
+			for len(p.pendingNotifications) == 0 {
+				// check if we're shutdown
+				select {
+				case <-stopCh:
+					return nil, true
+				default:
+				}
+				p.cond.Wait()
 			}
 
-			p.cond.Wait()
+			nt := p.pendingNotifications[0]
+			p.pendingNotifications = p.pendingNotifications[1:]
+			return nt, false
+		}
+
+		notification, stopped := blockingGet()
+		if stopped {
+			return
 		}
-		notification := p.pendingNotifications[0]
-		p.pendingNotifications = p.pendingNotifications[1:]
 
 		select {
 		case <-stopCh: