Make feature gate threadsafe

staging/src/k8s.io/apiserver/pkg/util/feature/feature_gate.go

@@ -21,6 +21,7 @@ import (
 	"sort"
 	"strconv"
 	"strings"
+	"sync"
 
 	"github.com/golang/glog"
 	"github.com/spf13/pflag"
@@ -85,6 +86,8 @@ type FeatureGate interface {
 
 // featureGate implements FeatureGate as well as pflag.Value for flag parsing.
 type featureGate struct {
+	lock sync.RWMutex
+
 	known   map[Feature]FeatureSpec
 	special map[Feature]func(*featureGate, bool)
 	enabled map[Feature]bool
@@ -121,6 +124,9 @@ func NewFeatureGate() *featureGate {
 // Set Parses a string of the form "key1=value1,key2=value2,..." into a
 // map[string]bool of known keys or returns an error.
 func (f *featureGate) Set(value string) error {
+	f.lock.Lock()
+	defer f.lock.Unlock()
+
 	for _, s := range strings.Split(value, ",") {
 		if len(s) == 0 {
 			continue
@@ -153,6 +159,9 @@ func (f *featureGate) Set(value string) error {
 
 // String returns a string containing all enabled feature gates, formatted as "key1=value1,key2=value2,...".
 func (f *featureGate) String() string {
+	f.lock.RLock()
+	defer f.lock.RUnlock()
+
 	pairs := []string{}
 	for k, v := range f.enabled {
 		pairs = append(pairs, fmt.Sprintf("%s=%t", k, v))
@@ -167,6 +176,9 @@ func (f *featureGate) Type() string {
 
 // Add adds features to the featureGate.
 func (f *featureGate) Add(features map[Feature]FeatureSpec) error {
+	f.lock.Lock()
+	defer f.lock.Unlock()
+
 	if f.closed {
 		return fmt.Errorf("cannot add a feature gate after adding it to the flag set")
 	}
@@ -186,6 +198,9 @@ func (f *featureGate) Add(features map[Feature]FeatureSpec) error {
 
 // Enabled returns true if the key is enabled.
 func (f *featureGate) Enabled(key Feature) bool {
+	f.lock.RLock()
+	defer f.lock.RUnlock()
+
 	defaultValue := f.known[key].Default
 	if f.enabled != nil {
 		if v, ok := f.enabled[key]; ok {
@@ -197,7 +212,9 @@ func (f *featureGate) Enabled(key Feature) bool {
 
 // AddFlag adds a flag for setting global feature gates to the specified FlagSet.
 func (f *featureGate) AddFlag(fs *pflag.FlagSet) {
+	f.lock.Lock()
 	f.closed = true
+	f.lock.Unlock()
 
 	known := f.KnownFeatures()
 	fs.Var(f, flagName, ""+
@@ -207,6 +224,8 @@ func (f *featureGate) AddFlag(fs *pflag.FlagSet) {
 
 // KnownFeatures returns a slice of strings describing the FeatureGate's known features.
 func (f *featureGate) KnownFeatures() []string {
+	f.lock.RLock()
+	defer f.lock.RUnlock()
 	var known []string
 	for k, v := range f.known {
 		pre := ""