lkml.org 
[lkml]   [2018]   [Oct]   [4]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
SubjectCgroup v2 thread mode oddity: "domain invalid" cgroup with threaded controller enabled
Date
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/

\
 
 \ /
  Last update: 2018-10-04 21:41    [W:0.212 / U:0.168 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site