don't enable threaded mode by default

Because in threaded mode, we can't enable the memory controller -- it isn't thread-aware.

Signed-off-by: lifubang <[email protected]>

libcontainer/cgroups/fs2/create.go

@@ -63,6 +63,25 @@ func neededControllers(cgroup *configs.Cgroup) ([]string, error) {
 	return list, nil
 }
 
+// containsDomainController returns whether the current config contains domain controller or not.
+// Refer to: http://man7.org/linux/man-pages/man7/cgroups.7.html
+// As at Linux 4.19, the following controllers are threaded: cpu, perf_event, and pids.
+func containsDomainController(cgroup *configs.Cgroup) bool {
+	if isMemorySet(cgroup) {
+		return true
+	}
+	if isIoSet(cgroup) {
+		return true
+	}
+	if isCpuSet(cgroup) {
+		return true
+	}
+	if isHugeTlbSet(cgroup) {
+		return true
+	}
+	return false
+}
+
 // CreateCgroupPath creates cgroupv2 path, enabling all the
 // needed controllers in the process.
 func CreateCgroupPath(path string, c *configs.Cgroup) (Err error) {
@@ -95,10 +114,18 @@ func CreateCgroupPath(path string, c *configs.Cgroup) (Err error) {
 					}
 				}()
 			}
-			// Write cgroup.type explicitly.
-			// Otherwise ENOTSUP may happen.
-			cgType := filepath.Join(current, "cgroup.type")
-			_ = ioutil.WriteFile(cgType, []byte("threaded"), 0644)
+			// There are 4 types: 'domain', 'threaded', 'domain threaded', and 'domain invalid'.
+			// If got 'domain invalid', we should check whether the current config contains domain controller or not.
+			// When does not contain domain controller, we can write "threaded" without retuning erro.
+			cgTypeFile := filepath.Join(current, "cgroup.type")
+			cgType, _ := ioutil.ReadFile(cgTypeFile)
+			if strings.TrimSpace(string(cgType)) == "domain invalid" {
+				if containsDomainController(c) {
+					return fmt.Errorf("Can't enter cgroup path %s, the cgroup type is 'domain invalid.", current)
+				} else {
+					_ = ioutil.WriteFile(cgTypeFile, []byte("threaded"), 0644)
+				}
+			}
 		}
 		// enable needed controllers
 		if i < len(elements)-1 {