On Thu, 2015-11-26 at 20:32 -0200, Marcelo Tosatti wrote:
> Move PF_NO_SETAFFINITY and kthreadd_task checks to cpuset cgroups,
> where they belong. This makes it possible to attach PF_NO_SETAFFINITY
> tasks to Intel CAT cgroup.
>
> Reported-by: Luiz Capitulino <[email protected]>
> Signed-off-by: Marcelo Tosatti <[email protected]>
> Reviewed-by: Chao Peng <[email protected]>
>
> v2: "PF_NO_SETAFFINITY check" -> "PF_NO_SETAFFINITY and kthreadd_task
> checks"
>
> diff --git a/kernel/cgroup.c b/kernel/cgroup.c
> index f89d929..0603652 100644
> --- a/kernel/cgroup.c
> +++ b/kernel/cgroup.c
> @@ -2466,16 +2466,6 @@ static ssize_t __cgroup_procs_write(struct
> kernfs_open_file *of, char *buf,
> if (threadgroup)
> tsk = tsk->group_leader;
>
> - /*
> - * Workqueue threads may acquire PF_NO_SETAFFINITY 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_NO_SETAFFINITY)) {
> - ret = -EINVAL;
> - goto out_unlock_rcu;
> - }
> -
> get_task_struct(tsk);
> rcu_read_unlock();
>
> diff --git a/kernel/cpuset.c b/kernel/cpuset.c
> index f0acff0..9fff4d6 100644
> --- a/kernel/cpuset.c
> +++ b/kernel/cpuset.c
> @@ -53,6 +53,7 @@
> #include <linux/time.h>
> #include <linux/backing-dev.h>
> #include <linux/sort.h>
> +#include <linux/kthread.h>
>
> #include <asm/uaccess.h>
> #include <linux/atomic.h>
> @@ -1445,6 +1446,17 @@ static int cpuset_can_attach(struct
> cgroup_subsys_state *css,
> goto out_unlock;
>
> cgroup_taskset_for_each(task, tset) {
> + /*
> + * Workqueue threads may acquire PF_NO_SETAFFINITY and become
> + * trapped in a cpuset, or RT worker may be born in a cgroup
> + * with no rt_runtime allocated. Just say no.
> + */
> + if (task == kthreadd_task ||
> + (task->flags & PF_NO_SETAFFINITY)) {
> + ret = -EINVAL;
> + goto out_unlock;
> + }
> +
> ret = task_can_attach(task, cs->cpus_allowed);
> if (ret)
> goto out_unlock;
Note the rt_runtime reference in the comment, that wasn't about cpuset.
The kthreadd wants to remain immune to all fiddlings methinks.
-Mike
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