Reopen cgroupRootHandle if it was unexpectedly opened to another file

[sctb512]

Try to address opencontainers/runc#3026

[lifubang]

Thank you for your PR. It would be greatly appreciated if you could provide some failure logs and help us analyze the root cause of this issue. For instance, could it be related to the Go stdlib’s file descriptor shuffling bug (issue opencontainers/runc#4452)?

I believe it's worth investing time to identify the underlying cause. Reopening the cgroup root file descriptor should be considered a last resort.

[kolyshkin]

@sctb512 can you reply to the comment above?

[sctb512]

Reopening the cgroup root file descriptor should be considered a last resort.

Yes, I agree with you. Unfortunately, it’s hard to reproduce this issue. We have restarted the kubelet service since the machine is in a production environment. I don’t think it’s related to https://github.com/opencontainers/runc/pull/4452, because the file descriptor pointing to /sys/fs/cgroup does not exist.