Remove unncessary mutex usage in the secondary network CNI cache (#3232)

The cache itself uses cache.Indexer which is thread-safe, and so needs
not the mutex to protect cache accesses. The mutex should be  used just
for protecting CNIConfigInfo.PodCNIDeleted, which is written by
CNIServer and read by the secondary network Pod controller.

Signed-off-by: Jianjun Shen <[email protected]>

pkg/agent/secondarynetwork/cnipodcache/cache.go

@@ -28,21 +28,19 @@ const (
 )
 
 type CNIPodInfoCache struct {
+	// Mutex to protect CNIConfigInfo.PodCNIDeleted which is written by CNIServer, and read by
+	// the secondary network Pod controller.
 	sync.RWMutex
 	cache cache.Indexer
 }
 
 // Add CNIPodInfo to local cache store.
 func (c *CNIPodInfoCache) AddCNIConfigInfo(CNIConfig *CNIConfigInfo) {
-	c.Lock()
-	defer c.Unlock()
 	c.cache.Add(CNIConfig)
 }
 
 // Delete CNIPodInfo from local cache store.
 func (c *CNIPodInfoCache) DeleteCNIConfigInfo(CNIConfig *CNIConfigInfo) {
-	c.Lock()
-	defer c.Unlock()
 	c.cache.Delete(CNIConfig)
 }
 
@@ -54,9 +52,9 @@ func (c *CNIPodInfoCache) SetPodCNIDeleted(CNIConfig *CNIConfigInfo) {
 
 // Retrieve a valid CNI cache (PodCNIDeleted is not true) entry for the given Pod name and namespace.
 func (c *CNIPodInfoCache) GetValidCNIConfigInfoPerPod(podName, podNamespace string) *CNIConfigInfo {
+	podObjs, _ := c.cache.ByIndex(podIndex, k8s.NamespacedName(podNamespace, podName))
 	c.RLock()
 	defer c.RUnlock()
-	podObjs, _ := c.cache.ByIndex(podIndex, k8s.NamespacedName(podNamespace, podName))
 	for i := range podObjs {
 		var cniPodConfig *CNIConfigInfo
 		cniPodConfig = podObjs[i].(*CNIConfigInfo)
@@ -70,8 +68,6 @@ func (c *CNIPodInfoCache) GetValidCNIConfigInfoPerPod(podName, podNamespace stri
 // Retrieve all CNIConfigInfo from cacheStore for the given podName and its Namespace
 // NOTE: In an ideal scenario, there should be one cache entry per Pod name and namespace.
 func (c *CNIPodInfoCache) GetAllCNIConfigInfoPerPod(podName, podNamespace string) []*CNIConfigInfo {
-	c.RLock()
-	defer c.RUnlock()
 	podObjs, _ := c.cache.ByIndex(podIndex, k8s.NamespacedName(podNamespace, podName))
 	CNIPodConfigs := make([]*CNIConfigInfo, len(podObjs))
 	for i := range podObjs {
@@ -81,8 +77,6 @@ func (c *CNIPodInfoCache) GetAllCNIConfigInfoPerPod(podName, podNamespace string
 }
 
 func (c *CNIPodInfoCache) GetCNIConfigInfoByContainerID(podName, podNamespace, containerID string) *CNIConfigInfo {
-	c.RLock()
-	defer c.RUnlock()
 	podObjs, _ := c.cache.ByIndex(podIndex, k8s.NamespacedName(podNamespace, podName))
 	for i := range podObjs {
 		var cniPodConfig *CNIConfigInfo