Messages in this thread | | | Date | Tue, 20 Feb 2018 11:35:47 -0800 | From | Tejun Heo <> | Subject | Re: A "domain invalid" cgroup *can* sometimes have member tasks |
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On Tue, Feb 20, 2018 at 08:26:59PM +0100, Michael Kerrisk (man-pages) wrote: > 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?
Hmm... nr_populated_domain_children check should have caught that condition and rejected it. Will look into what's going on.
Thanks.
-- tejun
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