Re: [PATCH] cgroup: Don't expose dead tasks in cgroup

[Tejun Heo <tj@kernel.org>]

Hello,

On Wed, Mar 04, 2026 at 08:16:17PM +0100, Sebastian Andrzej Siewior wrote:
> --- a/kernel/cgroup/cgroup.c
> +++ b/kernel/cgroup/cgroup.c
> @@ -5108,6 +5108,8 @@ static void css_task_iter_advance(struct css_task_iter *it)
>  		return;
>  
>  	task = list_entry(it->task_pos, struct task_struct, cg_list);
> +	if ((task->flags & PF_EXITING) && !atomic_read(&task->signal->live))
> +		goto repeat;
>  
>  	if (it->flags & CSS_TASK_ITER_PROCS) {
>  		/* if PROCS, skip over tasks which aren't group leaders */
> 
> does work.
> So we delay the removal due to sched_ext and then hide due to userspace.
> Nice ;)

sched_ext made it more visible but the problem is shared in cgroup
controller in general. We don't want a cgroup to become empty while there's
active resource consumption going on and we tell userspace the task is dead
before it switches out for the last time, so...

> The signal check is to see the zombies, so you they pop up in the list
> until a waitpid()?
> Anyway, do you want me make a proper patch out of it?

Yes, please.

Thanks.

-- 
tejun