Any idea or feedback for the person to contact? Thanks br rb
On Wed, Sep 14, 2016 at 5:21 PM, Rahul Bhattacharya <[email protected]> wrote: > When I try to move a RT task to a different cgroup(shown below) I get a > EINVAL error. > > However I can change the cgroup first and then change the sched policy. > > After looking into kernel source code(*I dont use CONFIG_RT_GROUP_SCHED > config*) I was able to extract this piece of logic > > > > *chrt -p 777* > pid 777's current scheduling policy: SCHED_OTHER > pid 777's current scheduling priority: 0 > *cat /proc/777/cgroup* > 2:cpu,cpuacct:/system.slice > 1:name=systemd:/system.slice/d.service > *chrt -f -p 50 777* > > root@mgu-high:~# chrt -p 777 > pid 777's current scheduling policy: SCHED_FIFO > pid 777's current scheduling priority: 50 > */bin/echo 777>/sys/fs/cgroup/cpu,cpuacct/interaction.slice/tasks**echo: > write error: Invalid argument* > > > After browsing kernel sources I was able to find out the reason of failure. > > > static int cpu_cgroup_can_attach(struct cgroup_subsys_state *css, > struct cgroup_taskset *tset) > { > struct task_struct *task; > > > cgroup_taskset_for_each(task, tset) { > #ifdef CONFIG_RT_GROUP_SCHED > if (!sched_rt_can_attach(css_tg(css), task)) > return -EINVAL; > #else > > > > > */* We don't support RT-tasks being in separate groups */ if > (task->sched_class != &fair_sched_class) { > return -EINVAL; }* > #endif > } > return 0; > } > > My question is why is this check required? Also, changing cgroups first and > then the policy of FIFO works without issue(?) for the task. > > Thanks > > > br > > rb > >
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