Messages in this thread | | | From | "Michael Kerrisk (man-pages)" <> | Date | Tue, 20 Feb 2018 20:26:59 +0100 | Subject | A "domain invalid" cgroup *can* sometimes have member tasks |
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Hello Tejun
According to Documentation/cgroup-v2.txt, a "domain invalid" cgroup can't have member tasks. And indeed this is generally not permitted.
However, someone recently showed me a scenario where a "domain invalid" cgroup can have member processes. See the following example:
# mkdir -p /sys/fs/cgroup/unified/grp0/grp1 # sleep 1000 & [1] 10549 # echo 10549 > /sys/fs/cgroup/unified/grp0/grp1/cgroup.procs # echo threaded > /sys/fs/cgroup/unified/grp0/cgroup.type # cat /sys/fs/cgroup/unified/grp0/cgroup.type threaded # cat /sys/fs/cgroup/unified/grp0/grp1/cgroup.type domain invalid # cat /sys/fs/cgroup/unified/grp0/grp1/cgroup.threads 10549
From the above, we see that the cgroup grp0/grp1 is of type "domain invalid" and has a member thread. This seems to be a violation of the documented rules, and is I assume a bug, since in the above scenario, we are denied from adding further tasks to the grp0/grp1 cgroup:
# sleep 2000 & [2] 10553 # echo 10553 > /sys/fs/cgroup/unified/grp0/grp1/cgroup.procs sh: echo: write error: Operation not supported
Could you comment please?
Thanks,
Michael
-- Michael Kerrisk Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/ Linux/UNIX System Programming Training: http://man7.org/training/
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