Re: memcg creates an unkillable task in 3.2-rc2

From: Li Zefan
Date: Mon Jul 29 2013 - 22:00:27 EST

> I am also seeing what looks like a leak somewhere in the cgroup code as
> well. After some runs of the same reproducer I get into a state where
> after everything is clean up. All of the control groups have been
> removed and the cgroup filesystem is unmounted, I can mount a cgroup
> filesystem with that same combindation of subsystems, but I can't mount
> a cgroup filesystem with any of those subsystems in any other
> combination. So I am guessing that the superblock is from the original
> mounting is still lingering for some reason.

If this happens again, you can check /proc/cgroups,

#subsys_name hierarchy num_cgroups enabled
cpuset 0 1 1
debug 0 1 1
cpu 0 1 1
cpuacct 0 1 1
memory 0 1 1
devices 0 1 1
freezer 0 1 1
blkio 0 1 1

If "hierachy" is not 0, then it didn't really unmounted. If "num_cgroups"
is not 1, then there're some cgroups not really destroyed though they've
been rmdired.

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