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[4.8] libct/cg/fs/freezer: make sure to thaw on failure #51

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merged 1 commit into from
Jul 1, 2022
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[4.8] libct/cg/fs/freezer: make sure to thaw on failure #51

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14 changes: 10 additions & 4 deletions libcontainer/cgroups/fs/freezer.go
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Original file line number Diff line number Diff line change
Expand Up @@ -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
Expand Down Expand Up @@ -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))
Expand Down