Quoting Avinash Chiganmi (avinash.ca@xxxxxxxxx):
> Hi,
>
> I created a "cpu" cgroup:
> mkdir /dev/cgroup
> mkdir /dev/cgroup/cpu
> mount -t cgroup -o cpu cpu /dev/cgroup/cpu
> cd /dev/cgroup/cpu/
> mkdir low
>
> Now, I try to move tasks to the sub-cgroup "low":
> for task in `cat /dev/cgroup/cpu/tasks`; do /bin/echo $task >
> /dev/cgroup/cpu/low/tasks || echo "Failed to move PID $task"; done
>
> /bin/echo: write error: Invalid argument
> Failed to move PID 3
> /bin/echo: write error: Invalid argument
> Failed to move PID 4
> /bin/echo: write error: Invalid argument
> Failed to move PID 5
> /bin/echo: write error: Invalid argument
> Failed to move PID 6
> /bin/echo: write error: Invalid argument
> Failed to move PID 7
> /bin/echo: write error: Invalid argument
> Failed to move PID 8
> /bin/echo: write error: Invalid argument
> .
> .
> .
> /bin/echo: write error: Invalid argument
> Failed to move PID 58
>
> I was able to move the "init" process itself. However, I failed to move
> specific kernel threads:
>
> root 3 2 0 18:16 ? 00:00:00 [migration/0]
> root 4 2 0 18:16 ? 00:00:00 [sirq-high/0]
> root 5 2 0 18:16 ? 00:00:04 [sirq-timer/0]
> root 6 2 0 18:16 ? 00:00:00 [sirq-net-tx/0]
> root 7 2 0 18:16 ? 00:00:00 [sirq-net-rx/0]
> root 8 2 0 18:16 ? 00:00:00 [sirq-block/0]
> root 9 2 0 18:16 ? 00:00:00 [sirq-block-iopo]
> root 10 2 0 18:16 ? 00:00:00 [sirq-tasklet/0]
> root 11 2 0 18:16 ? 00:00:00 [sirq-sched/0]
> root 12 2 0 18:16 ? 00:00:00 [sirq-hrtimer/0]
> root 13 2 0 18:16 ? 00:00:04 [sirq-rcu/0]
> root 14 2 0 18:16 ? 00:00:00 [watchdog/0]
> root 15 2 0 18:16 ? 00:00:00 [desched/0]
> root 16 2 0 18:16 ? 00:00:00 [migration/1]
> root 17 2 0 18:16 ? 00:00:00 [sirq-high/1]
> root 18 2 0 18:16 ? 00:00:03 [sirq-timer/1]
> root 19 2 0 18:16 ? 00:00:00 [sirq-net-tx/1]
> root 20 2 0 18:16 ? 00:00:00 [sirq-net-rx/1]
> root 21 2 0 18:16 ? 00:00:00 [sirq-block/1]
>
>
> Is there something special about these threads that prevents them from
> being moved to a different cgroup? Is there something I am missing?
>
> Thanks!
> Avi.
I'm guessing:
kernel/cgroup.c:attach_task_by_pid():
/*
* Workqueue threads may acquire PF_THREAD_BOUND and become
* trapped in a cpuset, or RT worker may be born in a cgroup
* with no rt_runtime allocated. Just say no.
*/
if (tsk == kthreadd_task || (tsk->flags & PF_THREAD_BOUND)) {
ret = -EINVAL;
rcu_read_unlock();
goto out_unlock_cgroup;
}
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