Merge pull request #2918 from kolyshkin/freeze-3

libct/cg/fs/freezer: make sure to thaw on failure

libcontainer/cgroups/fs/freezer.go

@@ -27,9 +27,18 @@ func (s *FreezerGroup) Apply(path string, d *cgroupData) error {
  return join(path, d.pid)
 }
 
-func (s *FreezerGroup) Set(path string, cgroup *configs.Cgroup) error {
+func (s *FreezerGroup) Set(path string, cgroup *configs.Cgroup) (Err error) {
  switch cgroup.Resources.Freezer {
  case configs.Frozen:
+ defer func() {
+ if Err != nil {
+ // Freezing failed, and it is bad and dangerous
+ // to leave the cgroup in FROZEN or FREEZING
+ // state, so (try to) thaw it back.
+ _ = fscommon.WriteFile(path, "freezer.state", string(configs.Thawed))
+ }
+ }()
+
  // As per older kernel docs (freezer-subsystem.txt before
  // kernel commit ef9fe980c6fcc1821), if FREEZING is seen,
  // userspace should either retry or thaw. While current
@@ -75,9 +84,6 @@ func (s *FreezerGroup) Set(path string, cgroup *configs.Cgroup) error {
  }
  }
  // Despite our best efforts, it got stuck in FREEZING.
- // Leaving it in this state is bad and dangerous, so
- // let's (try to) thaw it back and error out.
- _ = fscommon.WriteFile(path, "freezer.state", string(configs.Thawed))
  return errors.New("unable to freeze")
  case configs.Thawed:
  return fscommon.WriteFile(path, "freezer.state", string(configs.Thawed))