Merge pull request #1610 from sboeuf/fix_freezer_state

libcontainer: cgroups: Write freezer state after every state check

libcontainer/cgroups/fs/freezer.go

@@ -29,18 +29,23 @@ func (s *FreezerGroup) Apply(d *cgroupData) error {
 func (s *FreezerGroup) Set(path string, cgroup *configs.Cgroup) error {
 	switch cgroup.Resources.Freezer {
 	case configs.Frozen, configs.Thawed:
-		if err := writeFile(path, "freezer.state", string(cgroup.Resources.Freezer)); err != nil {
-			return err
-		}
-
 		for {
+			// In case this loop does not exit because it doesn't get the expected
+			// state, let's write again this state, hoping it's going to be properly
+			// set this time. Otherwise, this loop could run infinitely, waiting for
+			// a state change that would never happen.
+			if err := writeFile(path, "freezer.state", string(cgroup.Resources.Freezer)); err != nil {
+				return err
+			}
+
 			state, err := readFile(path, "freezer.state")
 			if err != nil {
 				return err
 			}
 			if strings.TrimSpace(state) == string(cgroup.Resources.Freezer) {
 				break
 			}
+
 			time.Sleep(1 * time.Millisecond)
 		}
 	case configs.Undefined: