Re: [PATCH] introduce the walk_process_tree() helper

[Oleg Nesterov <oleg@redhat.com>]

On 01/23, Oleg Nesterov wrote:
>
> Add the new helper to walk the process tree, the next patch adds a user.
> Note that it visits the group leaders only, proc_visitor can do
> for_each_thread itself or we can trivially extend walk_process_tree() to
> do this.

Please consider this patch as a preparation for your change, or feel free
to fold this code into your patch.

Now you can simply do

	int xxx(struct task_struct *p, void *data)
	{
		if (p->signal->has_child_subreaper ||
		    is_child_reaper(task_pid(p))
			return 0;
		p->signal->has_child_subreaper = 1;
		return 1;
	}

	walk_process_tree(xxx, NULL);

walk_process_tree() handles the sub-threads correctly, but "p" is always the
leader so is_child_reaper() is fine, but probably we need a new helper anyway.

Oleg.