Messages in this thread | | | From | "Michael Kerrisk (man-pages)" <> | Subject | Cgroup v2 thread mode oddity: "domain invalid" cgroup with threaded controller enabled | Date | Thu, 4 Oct 2018 21:40:57 +0200 |
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Hello Tejun,
Suppose we have the following scenario:
x [d] (pids) y [dt] (pids) p [t] q [t] r [t] z [d]
Here, x/y is a "domain threaded root" with a threaded controller (the 'pids' controller) enabled. (In this scenario, there are no member processes in any of the cgroups.)
Suppose we now convert x/z to "threaded" type:
# echo threaded > x/z/cgroup.type
Now we end up in the following state:
x [dt] (pids) y [inv] (pids) p [t] q [t] r [t] z [t]
This seems odd. x/y is now of "domain invalid" type with a controller enabled! This feels like a violation of the rules, since we can't in other circumstances do anything with a "domain invalid" cgroup except convert it to "threaded". In particular, we can't create child cgroups under a "domain invalid" cgroup, or add member processes to the cgroup, or *enable controllers in the cgroup*. In fact, when doing the
# echo threaded > x/z/cgroup.type
I had expected a write(2) error because the state of x/y should (I thought) not be permitted.
Your thoughts?
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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