libcontainer: intelrdt: use init() to avoid race condition

This is the follow-up PR of opencontainers#1279 to fix remaining issues:

Use init() to avoid race condition in IsIntelRdtEnabled().
Add also rename some variables and functions.

Signed-off-by: Xiaochen Shen <xiaochen.shen@intel.com>

libcontainer/configs/validate/validator.go

@@ -159,7 +159,7 @@ func (v *ConfigValidator) sysctl(config *configs.Config) error {
 
 func (v *ConfigValidator) intelrdt(config *configs.Config) error {
 	if config.IntelRdt != nil {
-		if !intelrdt.IsIntelRdtEnabled() {
+		if !intelrdt.IsEnabled() {
 			return fmt.Errorf("intelRdt is specified in config, but Intel RDT feature is not supported or enabled")
 		}
 		if config.IntelRdt.L3CacheSchema == "" {

libcontainer/container_linux_test.go

@@ -160,7 +160,7 @@ func TestGetContainerStats(t *testing.T) {
 	if stats.CgroupStats.MemoryStats.Usage.Usage != 1024 {
 		t.Fatalf("expected memory usage 1024 but recevied %d", stats.CgroupStats.MemoryStats.Usage.Usage)
 	}
-	if intelrdt.IsIntelRdtEnabled() {
+	if intelrdt.IsEnabled() {
 		if stats.IntelRdtStats == nil {
 			t.Fatal("intel rdt stats are nil")
 		}
@@ -231,7 +231,7 @@ func TestGetContainerState(t *testing.T) {
 	if memPath := paths["memory"]; memPath != expectedMemoryPath {
 		t.Fatalf("expected memory path %q but received %q", expectedMemoryPath, memPath)
 	}
-	if intelrdt.IsIntelRdtEnabled() {
+	if intelrdt.IsEnabled() {
 		intelRdtPath := state.IntelRdtPath
 		if intelRdtPath == "" {
 			t.Fatal("intel rdt path should not be empty")

libcontainer/factory_linux.go

@@ -204,7 +204,7 @@ func (l *LinuxFactory) Create(id string, config *configs.Config) (Container, err
 		cgroupManager: l.NewCgroupsManager(config.Cgroups, nil),
 	}
 	c.intelRdtManager = nil
-	if intelrdt.IsIntelRdtEnabled() && c.config.IntelRdt != nil {
+	if intelrdt.IsEnabled() && c.config.IntelRdt != nil {
 		c.intelRdtManager = l.NewIntelRdtManager(config, id, "")
 	}
 	c.state = &stoppedState{c: c}
@@ -245,7 +245,7 @@ func (l *LinuxFactory) Load(id string) (Container, error) {
 		return nil, err
 	}
 	c.intelRdtManager = nil
-	if intelrdt.IsIntelRdtEnabled() && c.config.IntelRdt != nil {
+	if intelrdt.IsEnabled() && c.config.IntelRdt != nil {
 		c.intelRdtManager = l.NewIntelRdtManager(&state.Config, id, state.IntelRdtPath)
 	}
 	return c, nil

libcontainer/intelrdt/intelrdt.go

@@ -130,7 +130,7 @@ var (
 	intelRdtRootLock sync.Mutex
 
 	// The flag to indicate if Intel RDT is supported
-	isIntelRdtEnabled bool
+	isEnabled bool
 )
 
 type intelRdtData struct {
@@ -139,6 +139,21 @@ type intelRdtData struct {
 	pid    int
 }
 
+// Check if Intel RDT is enabled in init()
+func init() {
+	// 1. Check if hardware and kernel support Intel RDT/CAT feature
+	// "cat_l3" flag is set if supported
+	isFlagSet, err := parseCpuInfoFile("/proc/cpuinfo")
+	if !isFlagSet || err != nil {
+		isEnabled = false
+		return
+	}
+
+	// 2. Check if Intel RDT "resource control" filesystem is mounted
+	// The user guarantees to mount the filesystem
+	isEnabled = isIntelRdtMounted()
+}
+
 // Return the mount point path of Intel RDT "resource control" filesysem
 func findIntelRdtMountpointDir() (string, error) {
 	f, err := os.Open("/proc/self/mountinfo")
@@ -369,24 +384,8 @@ func WriteIntelRdtTasks(dir string, pid int) error {
 }
 
 // Check if Intel RDT is enabled
-func IsIntelRdtEnabled() bool {
-	// We have checked the flag before
-	if isIntelRdtEnabled {
-		return true
-	}
-
-	// 1. Check if hardware and kernel support Intel RDT/CAT feature
-	// "cat_l3" flag is set if supported
-	isFlagSet, err := parseCpuInfoFile("/proc/cpuinfo")
-	if !isFlagSet || err != nil {
-		isIntelRdtEnabled = false
-		return false
-	}
-
-	// 2. Check if Intel RDT "resource control" filesystem is mounted
-	// The user guarantees to mount the filesystem
-	isIntelRdtEnabled = isIntelRdtMounted()
-	return isIntelRdtEnabled
+func IsEnabled() bool {
+	return isEnabled
 }
 
 // Get the 'container_id' path in Intel RDT "resource control" filesystem

libcontainer/intelrdt/intelrdt_test.go

@@ -8,7 +8,7 @@ import (
 )
 
 func TestIntelRdtSetL3CacheSchema(t *testing.T) {
-	if !IsIntelRdtEnabled() {
+	if !IsEnabled() {
 		return
 	}
 

utils_linux.go

@@ -43,7 +43,7 @@ func loadFactory(context *cli.Context) (libcontainer.Factory, error) {
 			return nil, fmt.Errorf("systemd cgroup flag passed, but systemd support for managing cgroups is not available")
 		}
 	}
-	if intelrdt.IsIntelRdtEnabled() {
+	if intelrdt.IsEnabled() {
 		intelRdtManager := libcontainer.IntelRdtFs
 		return libcontainer.New(abs, cgroupManager, intelRdtManager, libcontainer.CriuPath(context.GlobalString("criu")))
 	}