Re: [PATCH] cgroup: Move cgroup_task_dead() to task_struct clean up

[Sebastian Andrzej Siewior <bigeasy@linutronix.de>]

On 2026-03-13 18:33:14 [+0100], Michal Koutný wrote:
> Hello.
> 
> On Wed, Mar 11, 2026 at 01:08:29PM +0100, Sebastian Andrzej Siewior <bigeasy@linutronix.de> wrote:
> > @@ -7084,6 +7031,7 @@ void cgroup_task_free(struct task_struct *task)
> >  {
> >  	struct css_set *cset = task_css_set(task);
> >  
> > +	cgroup_task_dead(task);
> >  	if (!list_empty(&task->cg_list)) {
> >  		spin_lock_irq(&css_set_lock);
> >  		css_set_skip_task_iters(task_css_set(task), task);
> 
> Erm, isn't this way too late?

My understanding is that the point is that the cgroup must not be
exposed to userland once the task is about to die. This has been moved
after the fine schedule() which is too late because the parent is
signaled before that and the removal happens after that.
So now we hide the tasks in the iterator once the task is PF_EXITING.

> I see that cset->dying_tasks is appended in do_cgroup_task_dead() (which
> I was used to find in cgroup_exit()).

So this could be probably removed later on if this is the only purpose.

> (Also, whole cgroup_task_dead() becomes single use thing so it could be
> open-coded in the place where it belongs.)

If this what we want, I could inline it there.

> Thanks,
> Michal

Sebastian