Comment 10 for bug 1791246

I've added a fix to backoff when the sysfs stressor detects heavier spamming of the kmsg log,

http://kernel.ubuntu.com/git/cking/stress-ng.git/commit/?id=339c9f99030be84489b3c448750bec338030cf49

This has been run through the ADT testing manually and no longer blocks testing to completion. So I think this final fix nails the bug.